vendor/lldb/lldb-trunk-r256945

1 files changed, 3189 insertions, 0 deletions

diff --git a/source/Plugins/Process/Linux/NativeProcessLinux.cpp b/source/Plugins/Process/Linux/NativeProcessLinux.cpp
new file mode 100644
index 0000000000000..87c76f57830c5
--- /dev/null
+++ b/source/Plugins/Process/Linux/NativeProcessLinux.cpp
@@ -0,0 +1,3189 @@
+//===-- NativeProcessLinux.cpp -------------------------------- -*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "NativeProcessLinux.h"
+
+// C Includes
+#include <errno.h>
+#include <string.h>
+#include <stdint.h>
+#include <unistd.h>
+
+// C++ Includes
+#include <fstream>
+#include <mutex>
+#include <sstream>
+#include <string>
+#include <unordered_map>
+
+// Other libraries and framework includes
+#include "lldb/Core/EmulateInstruction.h"
+#include "lldb/Core/Error.h"
+#include "lldb/Core/Module.h"
+#include "lldb/Core/ModuleSpec.h"
+#include "lldb/Core/RegisterValue.h"
+#include "lldb/Core/State.h"
+#include "lldb/Host/common/NativeBreakpoint.h"
+#include "lldb/Host/common/NativeRegisterContext.h"
+#include "lldb/Host/Host.h"
+#include "lldb/Host/ThreadLauncher.h"
+#include "lldb/Target/Platform.h"
+#include "lldb/Target/Process.h"
+#include "lldb/Target/ProcessLaunchInfo.h"
+#include "lldb/Target/Target.h"
+#include "lldb/Utility/LLDBAssert.h"
+#include "lldb/Utility/PseudoTerminal.h"
+#include "lldb/Utility/StringExtractor.h"
+
+#include "Plugins/Process/POSIX/ProcessPOSIXLog.h"
+#include "NativeThreadLinux.h"
+#include "ProcFileReader.h"
+#include "Procfs.h"
+
+// System includes - They have to be included after framework includes because they define some
+// macros which collide with variable names in other modules
+#include <linux/unistd.h>
+#include <sys/socket.h>
+
+#include <sys/syscall.h>
+#include <sys/types.h>
+#include <sys/user.h>
+#include <sys/wait.h>
+
+#include "lldb/Host/linux/Personality.h"
+#include "lldb/Host/linux/Ptrace.h"
+#include "lldb/Host/linux/Signalfd.h"
+#include "lldb/Host/linux/Uio.h"
+#include "lldb/Host/android/Android.h"
+
+#define LLDB_PERSONALITY_GET_CURRENT_SETTINGS  0xffffffff
+
+// Support hardware breakpoints in case it has not been defined
+#ifndef TRAP_HWBKPT
+  #define TRAP_HWBKPT 4
+#endif
+
+using namespace lldb;
+using namespace lldb_private;
+using namespace lldb_private::process_linux;
+using namespace llvm;
+
+// Private bits we only need internally.
+
+static bool ProcessVmReadvSupported()
+{
+    static bool is_supported;
+    static std::once_flag flag;
+
+    std::call_once(flag, [] {
+        Log *log(GetLogIfAllCategoriesSet (LIBLLDB_LOG_PROCESS));
+
+        uint32_t source = 0x47424742;
+        uint32_t dest = 0;
+
+        struct iovec local, remote;
+        remote.iov_base = &source;
+        local.iov_base = &dest;
+        remote.iov_len = local.iov_len = sizeof source;
+
+        // We shall try if cross-process-memory reads work by attempting to read a value from our own process.
+        ssize_t res = process_vm_readv(getpid(), &local, 1, &remote, 1, 0);
+        is_supported = (res == sizeof(source) && source == dest);
+        if (log)
+        {
+            if (is_supported)
+                log->Printf("%s: Detected kernel support for process_vm_readv syscall. Fast memory reads enabled.",
+                        __FUNCTION__);
+            else
+                log->Printf("%s: syscall process_vm_readv failed (error: %s). Fast memory reads disabled.",
+                        __FUNCTION__, strerror(errno));
+        }
+    });
+
+    return is_supported;
+}
+
+namespace
+{
+    Error
+    ResolveProcessArchitecture (lldb::pid_t pid, Platform &platform, ArchSpec &arch)
+    {
+        // Grab process info for the running process.
+        ProcessInstanceInfo process_info;
+        if (!platform.GetProcessInfo (pid, process_info))
+            return Error("failed to get process info");
+
+        // Resolve the executable module.
+        ModuleSP exe_module_sp;
+        ModuleSpec exe_module_spec(process_info.GetExecutableFile(), process_info.GetArchitecture());
+        FileSpecList executable_search_paths (Target::GetDefaultExecutableSearchPaths ());
+        Error error = platform.ResolveExecutable(
+            exe_module_spec,
+            exe_module_sp,
+            executable_search_paths.GetSize () ? &executable_search_paths : NULL);
+
+        if (!error.Success ())
+            return error;
+
+        // Check if we've got our architecture from the exe_module.
+        arch = exe_module_sp->GetArchitecture ();
+        if (arch.IsValid ())
+            return Error();
+        else
+            return Error("failed to retrieve a valid architecture from the exe module");
+    }
+
+    void
+    DisplayBytes (StreamString &s, void *bytes, uint32_t count)
+    {
+        uint8_t *ptr = (uint8_t *)bytes;
+        const uint32_t loop_count = std::min<uint32_t>(DEBUG_PTRACE_MAXBYTES, count);
+        for(uint32_t i=0; i<loop_count; i++)
+        {
+            s.Printf ("[%x]", *ptr);
+            ptr++;
+        }
+    }
+
+    void
+    PtraceDisplayBytes(int &req, void *data, size_t data_size)
+    {
+        StreamString buf;
+        Log *verbose_log (ProcessPOSIXLog::GetLogIfAllCategoriesSet (
+                    POSIX_LOG_PTRACE | POSIX_LOG_VERBOSE));
+
+        if (verbose_log)
+        {
+            switch(req)
+            {
+            case PTRACE_POKETEXT:
+            {
+                DisplayBytes(buf, &data, 8);
+                verbose_log->Printf("PTRACE_POKETEXT %s", buf.GetData());
+                break;
+            }
+            case PTRACE_POKEDATA:
+            {
+                DisplayBytes(buf, &data, 8);
+                verbose_log->Printf("PTRACE_POKEDATA %s", buf.GetData());
+                break;
+            }
+            case PTRACE_POKEUSER:
+            {
+                DisplayBytes(buf, &data, 8);
+                verbose_log->Printf("PTRACE_POKEUSER %s", buf.GetData());
+                break;
+            }
+            case PTRACE_SETREGS:
+            {
+                DisplayBytes(buf, data, data_size);
+                verbose_log->Printf("PTRACE_SETREGS %s", buf.GetData());
+                break;
+            }
+            case PTRACE_SETFPREGS:
+            {
+                DisplayBytes(buf, data, data_size);
+                verbose_log->Printf("PTRACE_SETFPREGS %s", buf.GetData());
+                break;
+            }
+            case PTRACE_SETSIGINFO:
+            {
+                DisplayBytes(buf, data, sizeof(siginfo_t));
+                verbose_log->Printf("PTRACE_SETSIGINFO %s", buf.GetData());
+                break;
+            }
+            case PTRACE_SETREGSET:
+            {
+                // Extract iov_base from data, which is a pointer to the struct IOVEC
+                DisplayBytes(buf, *(void **)data, data_size);
+                verbose_log->Printf("PTRACE_SETREGSET %s", buf.GetData());
+                break;
+            }
+            default:
+            {
+            }
+            }
+        }
+    }
+
+    static constexpr unsigned k_ptrace_word_size = sizeof(void*);
+    static_assert(sizeof(long) >= k_ptrace_word_size, "Size of long must be larger than ptrace word size");
+} // end of anonymous namespace
+
+// Simple helper function to ensure flags are enabled on the given file
+// descriptor.
+static Error
+EnsureFDFlags(int fd, int flags)
+{
+    Error error;
+
+    int status = fcntl(fd, F_GETFL);
+    if (status == -1)
+    {
+        error.SetErrorToErrno();
+        return error;
+    }
+
+    if (fcntl(fd, F_SETFL, status | flags) == -1)
+    {
+        error.SetErrorToErrno();
+        return error;
+    }
+
+    return error;
+}
+
+NativeProcessLinux::LaunchArgs::LaunchArgs(Module *module,
+                                       char const **argv,
+                                       char const **envp,
+                                       const FileSpec &stdin_file_spec,
+                                       const FileSpec &stdout_file_spec,
+                                       const FileSpec &stderr_file_spec,
+                                       const FileSpec &working_dir,
+                                       const ProcessLaunchInfo &launch_info)
+    : m_module(module),
+      m_argv(argv),
+      m_envp(envp),
+      m_stdin_file_spec(stdin_file_spec),
+      m_stdout_file_spec(stdout_file_spec),
+      m_stderr_file_spec(stderr_file_spec),
+      m_working_dir(working_dir),
+      m_launch_info(launch_info)
+{
+}
+
+NativeProcessLinux::LaunchArgs::~LaunchArgs()
+{ }
+
+// -----------------------------------------------------------------------------
+// Public Static Methods
+// -----------------------------------------------------------------------------
+
+Error
+NativeProcessProtocol::Launch (
+    ProcessLaunchInfo &launch_info,
+    NativeProcessProtocol::NativeDelegate &native_delegate,
+    MainLoop &mainloop,
+    NativeProcessProtocolSP &native_process_sp)
+{
+    Log *log (GetLogIfAllCategoriesSet (LIBLLDB_LOG_PROCESS));
+
+    lldb::ModuleSP exe_module_sp;
+    PlatformSP platform_sp (Platform::GetHostPlatform ());
+    Error error = platform_sp->ResolveExecutable(
+            ModuleSpec(launch_info.GetExecutableFile(), launch_info.GetArchitecture()),
+            exe_module_sp,
+            nullptr);
+
+    if (! error.Success())
+        return error;
+
+    // Verify the working directory is valid if one was specified.
+    FileSpec working_dir{launch_info.GetWorkingDirectory()};
+    if (working_dir &&
+            (!working_dir.ResolvePath() ||
+             working_dir.GetFileType() != FileSpec::eFileTypeDirectory))
+    {
+        error.SetErrorStringWithFormat ("No such file or directory: %s",
+                working_dir.GetCString());
+        return error;
+    }
+
+    const FileAction *file_action;
+
+    // Default of empty will mean to use existing open file descriptors.
+    FileSpec stdin_file_spec{};
+    FileSpec stdout_file_spec{};
+    FileSpec stderr_file_spec{};
+
+    file_action = launch_info.GetFileActionForFD (STDIN_FILENO);
+    if (file_action)
+        stdin_file_spec = file_action->GetFileSpec();
+
+    file_action = launch_info.GetFileActionForFD (STDOUT_FILENO);
+    if (file_action)
+        stdout_file_spec = file_action->GetFileSpec();
+
+    file_action = launch_info.GetFileActionForFD (STDERR_FILENO);
+    if (file_action)
+        stderr_file_spec = file_action->GetFileSpec();
+
+    if (log)
+    {
+        if (stdin_file_spec)
+            log->Printf ("NativeProcessLinux::%s setting STDIN to '%s'",
+                    __FUNCTION__, stdin_file_spec.GetCString());
+        else
+            log->Printf ("NativeProcessLinux::%s leaving STDIN as is", __FUNCTION__);
+
+        if (stdout_file_spec)
+            log->Printf ("NativeProcessLinux::%s setting STDOUT to '%s'",
+                    __FUNCTION__, stdout_file_spec.GetCString());
+        else
+            log->Printf ("NativeProcessLinux::%s leaving STDOUT as is", __FUNCTION__);
+
+        if (stderr_file_spec)
+            log->Printf ("NativeProcessLinux::%s setting STDERR to '%s'",
+                    __FUNCTION__, stderr_file_spec.GetCString());
+        else
+            log->Printf ("NativeProcessLinux::%s leaving STDERR as is", __FUNCTION__);
+    }
+
+    // Create the NativeProcessLinux in launch mode.
+    native_process_sp.reset (new NativeProcessLinux ());
+
+    if (log)
+    {
+        int i = 0;
+        for (const char **args = launch_info.GetArguments ().GetConstArgumentVector (); *args; ++args, ++i)
+        {
+            log->Printf ("NativeProcessLinux::%s arg %d: \"%s\"", __FUNCTION__, i, *args ? *args : "nullptr");
+            ++i;
+        }
+    }
+
+    if (!native_process_sp->RegisterNativeDelegate (native_delegate))
+    {
+        native_process_sp.reset ();
+        error.SetErrorStringWithFormat ("failed to register the native delegate");
+        return error;
+    }
+
+    std::static_pointer_cast<NativeProcessLinux> (native_process_sp)->LaunchInferior (
+            mainloop,
+            exe_module_sp.get(),
+            launch_info.GetArguments ().GetConstArgumentVector (),
+            launch_info.GetEnvironmentEntries ().GetConstArgumentVector (),
+            stdin_file_spec,
+            stdout_file_spec,
+            stderr_file_spec,
+            working_dir,
+            launch_info,
+            error);
+
+    if (error.Fail ())
+    {
+        native_process_sp.reset ();
+        if (log)
+            log->Printf ("NativeProcessLinux::%s failed to launch process: %s", __FUNCTION__, error.AsCString ());
+        return error;
+    }
+
+    launch_info.SetProcessID (native_process_sp->GetID ());
+
+    return error;
+}
+
+Error
+NativeProcessProtocol::Attach (
+    lldb::pid_t pid,
+    NativeProcessProtocol::NativeDelegate &native_delegate,
+    MainLoop &mainloop,
+    NativeProcessProtocolSP &native_process_sp)
+{
+    Log *log (GetLogIfAllCategoriesSet (LIBLLDB_LOG_PROCESS));
+    if (log && log->GetMask ().Test (POSIX_LOG_VERBOSE))
+        log->Printf ("NativeProcessLinux::%s(pid = %" PRIi64 ")", __FUNCTION__, pid);
+
+    // Grab the current platform architecture.  This should be Linux,
+    // since this code is only intended to run on a Linux host.
+    PlatformSP platform_sp (Platform::GetHostPlatform ());
+    if (!platform_sp)
+        return Error("failed to get a valid default platform");
+
+    // Retrieve the architecture for the running process.
+    ArchSpec process_arch;
+    Error error = ResolveProcessArchitecture (pid, *platform_sp.get (), process_arch);
+    if (!error.Success ())
+        return error;
+
+    std::shared_ptr<NativeProcessLinux> native_process_linux_sp (new NativeProcessLinux ());
+
+    if (!native_process_linux_sp->RegisterNativeDelegate (native_delegate))
+    {
+        error.SetErrorStringWithFormat ("failed to register the native delegate");
+        return error;
+    }
+
+    native_process_linux_sp->AttachToInferior (mainloop, pid, error);
+    if (!error.Success ())
+        return error;
+
+    native_process_sp = native_process_linux_sp;
+    return error;
+}
+
+// -----------------------------------------------------------------------------
+// Public Instance Methods
+// -----------------------------------------------------------------------------
+
+NativeProcessLinux::NativeProcessLinux () :
+    NativeProcessProtocol (LLDB_INVALID_PROCESS_ID),
+    m_arch (),
+    m_supports_mem_region (eLazyBoolCalculate),
+    m_mem_region_cache (),
+    m_mem_region_cache_mutex(),
+    m_pending_notification_tid(LLDB_INVALID_THREAD_ID)
+{
+}
+
+void
+NativeProcessLinux::LaunchInferior (
+    MainLoop &mainloop,
+    Module *module,
+    const char *argv[],
+    const char *envp[],
+    const FileSpec &stdin_file_spec,
+    const FileSpec &stdout_file_spec,
+    const FileSpec &stderr_file_spec,
+    const FileSpec &working_dir,
+    const ProcessLaunchInfo &launch_info,
+    Error &error)
+{
+    m_sigchld_handle = mainloop.RegisterSignal(SIGCHLD,
+            [this] (MainLoopBase &) { SigchldHandler(); }, error);
+    if (! m_sigchld_handle)
+        return;
+
+    if (module)
+        m_arch = module->GetArchitecture ();
+
+    SetState (eStateLaunching);
+
+    std::unique_ptr<LaunchArgs> args(
+        new LaunchArgs(module, argv, envp,
+                       stdin_file_spec,
+                       stdout_file_spec,
+                       stderr_file_spec,
+                       working_dir,
+                       launch_info));
+
+    Launch(args.get(), error);
+}
+
+void
+NativeProcessLinux::AttachToInferior (MainLoop &mainloop, lldb::pid_t pid, Error &error)
+{
+    Log *log (GetLogIfAllCategoriesSet (LIBLLDB_LOG_PROCESS));
+    if (log)
+        log->Printf ("NativeProcessLinux::%s (pid = %" PRIi64 ")", __FUNCTION__, pid);
+
+    m_sigchld_handle = mainloop.RegisterSignal(SIGCHLD,
+            [this] (MainLoopBase &) { SigchldHandler(); }, error);
+    if (! m_sigchld_handle)
+        return;
+
+    // We can use the Host for everything except the ResolveExecutable portion.
+    PlatformSP platform_sp = Platform::GetHostPlatform ();
+    if (!platform_sp)
+    {
+        if (log)
+            log->Printf ("NativeProcessLinux::%s (pid = %" PRIi64 "): no default platform set", __FUNCTION__, pid);
+        error.SetErrorString ("no default platform available");
+        return;
+    }
+
+    // Gather info about the process.
+    ProcessInstanceInfo process_info;
+    if (!platform_sp->GetProcessInfo (pid, process_info))
+    {
+        if (log)
+            log->Printf ("NativeProcessLinux::%s (pid = %" PRIi64 "): failed to get process info", __FUNCTION__, pid);
+        error.SetErrorString ("failed to get process info");
+        return;
+    }
+
+    // Resolve the executable module
+    ModuleSP exe_module_sp;
+    FileSpecList executable_search_paths (Target::GetDefaultExecutableSearchPaths());
+    ModuleSpec exe_module_spec(process_info.GetExecutableFile(), process_info.GetArchitecture());
+    error = platform_sp->ResolveExecutable(exe_module_spec, exe_module_sp,
+                                           executable_search_paths.GetSize() ? &executable_search_paths : NULL);
+    if (!error.Success())
+        return;
+
+    // Set the architecture to the exe architecture.
+    m_arch = exe_module_sp->GetArchitecture();
+    if (log)
+        log->Printf ("NativeProcessLinux::%s (pid = %" PRIi64 ") detected architecture %s", __FUNCTION__, pid, m_arch.GetArchitectureName ());
+
+    m_pid = pid;
+    SetState(eStateAttaching);
+
+    Attach(pid, error);
+}
+
+::pid_t
+NativeProcessLinux::Launch(LaunchArgs *args, Error &error)
+{
+    assert (args && "null args");
+
+    const char **argv = args->m_argv;
+    const char **envp = args->m_envp;
+    const FileSpec working_dir = args->m_working_dir;
+
+    lldb_utility::PseudoTerminal terminal;
+    const size_t err_len = 1024;
+    char err_str[err_len];
+    lldb::pid_t pid;
+
+    // Propagate the environment if one is not supplied.
+    if (envp == NULL || envp[0] == NULL)
+        envp = const_cast<const char **>(environ);
+
+    if ((pid = terminal.Fork(err_str, err_len)) == static_cast<lldb::pid_t> (-1))
+    {
+        error.SetErrorToGenericError();
+        error.SetErrorStringWithFormat("Process fork failed: %s", err_str);
+        return -1;
+    }
+
+    // Recognized child exit status codes.
+    enum {
+        ePtraceFailed = 1,
+        eDupStdinFailed,
+        eDupStdoutFailed,
+        eDupStderrFailed,
+        eChdirFailed,
+        eExecFailed,
+        eSetGidFailed,
+        eSetSigMaskFailed
+    };
+
+    // Child process.
+    if (pid == 0)
+    {
+        // First, make sure we disable all logging. If we are logging to stdout, our logs can be
+        // mistaken for inferior output.
+        Log::DisableAllLogChannels(nullptr);
+        // FIXME consider opening a pipe between parent/child and have this forked child
+        // send log info to parent re: launch status.
+
+        // Start tracing this child that is about to exec.
+        error = PtraceWrapper(PTRACE_TRACEME, 0);
+        if (error.Fail())
+            exit(ePtraceFailed);
+
+        // terminal has already dupped the tty descriptors to stdin/out/err.
+        // This closes original fd from which they were copied (and avoids
+        // leaking descriptors to the debugged process.
+        terminal.CloseSlaveFileDescriptor();
+
+        // Do not inherit setgid powers.
+        if (setgid(getgid()) != 0)
+            exit(eSetGidFailed);
+
+        // Attempt to have our own process group.
+        if (setpgid(0, 0) != 0)
+        {
+            // FIXME log that this failed. This is common.
+            // Don't allow this to prevent an inferior exec.
+        }
+
+        // Dup file descriptors if needed.
+        if (args->m_stdin_file_spec)
+            if (!DupDescriptor(args->m_stdin_file_spec, STDIN_FILENO, O_RDONLY))
+                exit(eDupStdinFailed);
+
+        if (args->m_stdout_file_spec)
+            if (!DupDescriptor(args->m_stdout_file_spec, STDOUT_FILENO, O_WRONLY | O_CREAT | O_TRUNC))
+                exit(eDupStdoutFailed);
+
+        if (args->m_stderr_file_spec)
+            if (!DupDescriptor(args->m_stderr_file_spec, STDERR_FILENO, O_WRONLY | O_CREAT | O_TRUNC))
+                exit(eDupStderrFailed);
+
+        // Close everything besides stdin, stdout, and stderr that has no file
+        // action to avoid leaking
+        for (int fd = 3; fd < sysconf(_SC_OPEN_MAX); ++fd)
+            if (!args->m_launch_info.GetFileActionForFD(fd))
+                close(fd);
+
+        // Change working directory
+        if (working_dir && 0 != ::chdir(working_dir.GetCString()))
+              exit(eChdirFailed);
+
+        // Disable ASLR if requested.
+        if (args->m_launch_info.GetFlags ().Test (lldb::eLaunchFlagDisableASLR))
+        {
+            const int old_personality = personality (LLDB_PERSONALITY_GET_CURRENT_SETTINGS);
+            if (old_personality == -1)
+            {
+                // Can't retrieve Linux personality.  Cannot disable ASLR.
+            }
+            else
+            {
+                const int new_personality = personality (ADDR_NO_RANDOMIZE | old_personality);
+                if (new_personality == -1)
+                {
+                    // Disabling ASLR failed.
+                }
+                else
+                {
+                    // Disabling ASLR succeeded.
+                }
+            }
+        }
+
+        // Clear the signal mask to prevent the child from being affected by
+        // any masking done by the parent.
+        sigset_t set;
+        if (sigemptyset(&set) != 0 || pthread_sigmask(SIG_SETMASK, &set, nullptr) != 0)
+            exit(eSetSigMaskFailed);
+
+        // Execute.  We should never return...
+        execve(argv[0],
+               const_cast<char *const *>(argv),
+               const_cast<char *const *>(envp));
+
+        // ...unless exec fails.  In which case we definitely need to end the child here.
+        exit(eExecFailed);
+    }
+
+    //
+    // This is the parent code here.
+    //
+    Log *log (GetLogIfAllCategoriesSet (LIBLLDB_LOG_PROCESS));
+
+    // Wait for the child process to trap on its call to execve.
+    ::pid_t wpid;
+    int status;
+    if ((wpid = waitpid(pid, &status, 0)) < 0)
+    {
+        error.SetErrorToErrno();
+        if (log)
+            log->Printf ("NativeProcessLinux::%s waitpid for inferior failed with %s",
+                    __FUNCTION__, error.AsCString ());
+
+        // Mark the inferior as invalid.
+        // FIXME this could really use a new state - eStateLaunchFailure.  For now, using eStateInvalid.
+        SetState (StateType::eStateInvalid);
+
+        return -1;
+    }
+    else if (WIFEXITED(status))
+    {
+        // open, dup or execve likely failed for some reason.
+        error.SetErrorToGenericError();
+        switch (WEXITSTATUS(status))
+        {
+            case ePtraceFailed:
+                error.SetErrorString("Child ptrace failed.");
+                break;
+            case eDupStdinFailed:
+                error.SetErrorString("Child open stdin failed.");
+                break;
+            case eDupStdoutFailed:
+                error.SetErrorString("Child open stdout failed.");
+                break;
+            case eDupStderrFailed:
+                error.SetErrorString("Child open stderr failed.");
+                break;
+            case eChdirFailed:
+                error.SetErrorString("Child failed to set working directory.");
+                break;
+            case eExecFailed:
+                error.SetErrorString("Child exec failed.");
+                break;
+            case eSetGidFailed:
+                error.SetErrorString("Child setgid failed.");
+                break;
+            case eSetSigMaskFailed:
+                error.SetErrorString("Child failed to set signal mask.");
+                break;
+            default:
+                error.SetErrorString("Child returned unknown exit status.");
+                break;
+        }
+
+        if (log)
+        {
+            log->Printf ("NativeProcessLinux::%s inferior exited with status %d before issuing a STOP",
+                    __FUNCTION__,
+                    WEXITSTATUS(status));
+        }
+
+        // Mark the inferior as invalid.
+        // FIXME this could really use a new state - eStateLaunchFailure.  For now, using eStateInvalid.
+        SetState (StateType::eStateInvalid);
+
+        return -1;
+    }
+    assert(WIFSTOPPED(status) && (wpid == static_cast< ::pid_t> (pid)) &&
+           "Could not sync with inferior process.");
+
+    if (log)
+        log->Printf ("NativeProcessLinux::%s inferior started, now in stopped state", __FUNCTION__);
+
+    error = SetDefaultPtraceOpts(pid);
+    if (error.Fail())
+    {
+        if (log)
+            log->Printf ("NativeProcessLinux::%s inferior failed to set default ptrace options: %s",
+                    __FUNCTION__, error.AsCString ());
+
+        // Mark the inferior as invalid.
+        // FIXME this could really use a new state - eStateLaunchFailure.  For now, using eStateInvalid.
+        SetState (StateType::eStateInvalid);
+
+        return -1;
+    }
+
+    // Release the master terminal descriptor and pass it off to the
+    // NativeProcessLinux instance.  Similarly stash the inferior pid.
+    m_terminal_fd = terminal.ReleaseMasterFileDescriptor();
+    m_pid = pid;
+
+    // Set the terminal fd to be in non blocking mode (it simplifies the
+    // implementation of ProcessLinux::GetSTDOUT to have a non-blocking
+    // descriptor to read from).
+    error = EnsureFDFlags(m_terminal_fd, O_NONBLOCK);
+    if (error.Fail())
+    {
+        if (log)
+            log->Printf ("NativeProcessLinux::%s inferior EnsureFDFlags failed for ensuring terminal O_NONBLOCK setting: %s",
+                    __FUNCTION__, error.AsCString ());
+
+        // Mark the inferior as invalid.
+        // FIXME this could really use a new state - eStateLaunchFailure.  For now, using eStateInvalid.
+        SetState (StateType::eStateInvalid);
+
+        return -1;
+    }
+
+    if (log)
+        log->Printf ("NativeProcessLinux::%s() adding pid = %" PRIu64, __FUNCTION__, pid);
+
+    NativeThreadLinuxSP thread_sp = AddThread(pid);
+    assert (thread_sp && "AddThread() returned a nullptr thread");
+    thread_sp->SetStoppedBySignal(SIGSTOP);
+    ThreadWasCreated(*thread_sp);
+
+    // Let our process instance know the thread has stopped.
+    SetCurrentThreadID (thread_sp->GetID ());
+    SetState (StateType::eStateStopped);
+
+    if (log)
+    {
+        if (error.Success ())
+        {
+            log->Printf ("NativeProcessLinux::%s inferior launching succeeded", __FUNCTION__);
+        }
+        else
+        {
+            log->Printf ("NativeProcessLinux::%s inferior launching failed: %s",
+                __FUNCTION__, error.AsCString ());
+            return -1;
+        }
+    }
+    return pid;
+}
+
+::pid_t
+NativeProcessLinux::Attach(lldb::pid_t pid, Error &error)
+{
+    Log *log (GetLogIfAllCategoriesSet (LIBLLDB_LOG_PROCESS));
+
+    // Use a map to keep track of the threads which we have attached/need to attach.
+    Host::TidMap tids_to_attach;
+    if (pid <= 1)
+    {
+        error.SetErrorToGenericError();
+        error.SetErrorString("Attaching to process 1 is not allowed.");
+        return -1;
+    }
+
+    while (Host::FindProcessThreads(pid, tids_to_attach))
+    {
+        for (Host::TidMap::iterator it = tids_to_attach.begin();
+             it != tids_to_attach.end();)
+        {
+            if (it->second == false)
+            {
+                lldb::tid_t tid = it->first;
+
+                // Attach to the requested process.
+                // An attach will cause the thread to stop with a SIGSTOP.
+                error = PtraceWrapper(PTRACE_ATTACH, tid);
+                if (error.Fail())
+                {
+                    // No such thread. The thread may have exited.
+                    // More error handling may be needed.
+                    if (error.GetError() == ESRCH)
+                    {
+                        it = tids_to_attach.erase(it);
+                        continue;
+                    }
+                    else
+                        return -1;
+                }
+
+                int status;
+                // Need to use __WALL otherwise we receive an error with errno=ECHLD
+                // At this point we should have a thread stopped if waitpid succeeds.
+                if ((status = waitpid(tid, NULL, __WALL)) < 0)
+                {
+                    // No such thread. The thread may have exited.
+                    // More error handling may be needed.
+                    if (errno == ESRCH)
+                    {
+                        it = tids_to_attach.erase(it);
+                        continue;
+                    }
+                    else
+                    {
+                        error.SetErrorToErrno();
+                        return -1;
+                    }
+                }
+
+                error = SetDefaultPtraceOpts(tid);
+                if (error.Fail())
+                    return -1;
+
+                if (log)
+                    log->Printf ("NativeProcessLinux::%s() adding tid = %" PRIu64, __FUNCTION__, tid);
+
+                it->second = true;
+
+                // Create the thread, mark it as stopped.
+                NativeThreadLinuxSP thread_sp (AddThread(static_cast<lldb::tid_t>(tid)));
+                assert (thread_sp && "AddThread() returned a nullptr");
+
+                // This will notify this is a new thread and tell the system it is stopped.
+                thread_sp->SetStoppedBySignal(SIGSTOP);
+                ThreadWasCreated(*thread_sp);
+                SetCurrentThreadID (thread_sp->GetID ());
+            }
+
+            // move the loop forward
+            ++it;
+        }
+    }
+
+    if (tids_to_attach.size() > 0)
+    {
+        m_pid = pid;
+        // Let our process instance know the thread has stopped.
+        SetState (StateType::eStateStopped);
+    }
+    else
+    {
+        error.SetErrorToGenericError();
+        error.SetErrorString("No such process.");
+        return -1;
+    }
+
+    return pid;
+}
+
+Error
+NativeProcessLinux::SetDefaultPtraceOpts(lldb::pid_t pid)
+{
+    long ptrace_opts = 0;
+
+    // Have the child raise an event on exit.  This is used to keep the child in
+    // limbo until it is destroyed.
+    ptrace_opts |= PTRACE_O_TRACEEXIT;
+
+    // Have the tracer trace threads which spawn in the inferior process.
+    // TODO: if we want to support tracing the inferiors' child, add the
+    // appropriate ptrace flags here (PTRACE_O_TRACEFORK, PTRACE_O_TRACEVFORK)
+    ptrace_opts |= PTRACE_O_TRACECLONE;
+
+    // Have the tracer notify us before execve returns
+    // (needed to disable legacy SIGTRAP generation)
+    ptrace_opts |= PTRACE_O_TRACEEXEC;
+
+    return PtraceWrapper(PTRACE_SETOPTIONS, pid, nullptr, (void*)ptrace_opts);
+}
+
+static ExitType convert_pid_status_to_exit_type (int status)
+{
+    if (WIFEXITED (status))
+        return ExitType::eExitTypeExit;
+    else if (WIFSIGNALED (status))
+        return ExitType::eExitTypeSignal;
+    else if (WIFSTOPPED (status))
+        return ExitType::eExitTypeStop;
+    else
+    {
+        // We don't know what this is.
+        return ExitType::eExitTypeInvalid;
+    }
+}
+
+static int convert_pid_status_to_return_code (int status)
+{
+    if (WIFEXITED (status))
+        return WEXITSTATUS (status);
+    else if (WIFSIGNALED (status))
+        return WTERMSIG (status);
+    else if (WIFSTOPPED (status))
+        return WSTOPSIG (status);
+    else
+    {
+        // We don't know what this is.
+        return ExitType::eExitTypeInvalid;
+    }
+}
+
+// Handles all waitpid events from the inferior process.
+void
+NativeProcessLinux::MonitorCallback(lldb::pid_t pid,
+                                    bool exited,
+                                    int signal,
+                                    int status)
+{
+    Log *log (GetLogIfAnyCategoriesSet (LIBLLDB_LOG_PROCESS));
+
+    // Certain activities differ based on whether the pid is the tid of the main thread.
+    const bool is_main_thread = (pid == GetID ());
+
+    // Handle when the thread exits.
+    if (exited)
+    {
+        if (log)
+            log->Printf ("NativeProcessLinux::%s() got exit signal(%d) , tid = %"  PRIu64 " (%s main thread)", __FUNCTION__, signal, pid, is_main_thread ? "is" : "is not");
+
+        // This is a thread that exited.  Ensure we're not tracking it anymore.
+        const bool thread_found = StopTrackingThread (pid);
+
+        if (is_main_thread)
+        {
+            // We only set the exit status and notify the delegate if we haven't already set the process
+            // state to an exited state.  We normally should have received a SIGTRAP | (PTRACE_EVENT_EXIT << 8)
+            // for the main thread.
+            const bool already_notified = (GetState() == StateType::eStateExited) || (GetState () == StateType::eStateCrashed);
+            if (!already_notified)
+            {
+                if (log)
+                    log->Printf ("NativeProcessLinux::%s() tid = %"  PRIu64 " handling main thread exit (%s), expected exit state already set but state was %s instead, setting exit state now", __FUNCTION__, pid, thread_found ? "stopped tracking thread metadata" : "thread metadata not found", StateAsCString (GetState ()));
+                // The main thread exited.  We're done monitoring.  Report to delegate.
+                SetExitStatus (convert_pid_status_to_exit_type (status), convert_pid_status_to_return_code (status), nullptr, true);
+
+                // Notify delegate that our process has exited.
+                SetState (StateType::eStateExited, true);
+            }
+            else
+            {
+                if (log)
+                    log->Printf ("NativeProcessLinux::%s() tid = %"  PRIu64 " main thread now exited (%s)", __FUNCTION__, pid, thread_found ? "stopped tracking thread metadata" : "thread metadata not found");
+            }
+        }
+        else
+        {
+            // Do we want to report to the delegate in this case?  I think not.  If this was an orderly
+            // thread exit, we would already have received the SIGTRAP | (PTRACE_EVENT_EXIT << 8) signal,
+            // and we would have done an all-stop then.
+            if (log)
+                log->Printf ("NativeProcessLinux::%s() tid = %"  PRIu64 " handling non-main thread exit (%s)", __FUNCTION__, pid, thread_found ? "stopped tracking thread metadata" : "thread metadata not found");
+        }
+        return;
+    }
+
+    siginfo_t info;
+    const auto info_err = GetSignalInfo(pid, &info);
+    auto thread_sp = GetThreadByID(pid);
+
+    if (! thread_sp)
+    {
+        // Normally, the only situation when we cannot find the thread is if we have just
+        // received a new thread notification. This is indicated by GetSignalInfo() returning
+        // si_code == SI_USER and si_pid == 0
+        if (log)
+            log->Printf("NativeProcessLinux::%s received notification about an unknown tid %" PRIu64 ".", __FUNCTION__, pid);
+
+        if (info_err.Fail())
+        {
+            if (log)
+                log->Printf("NativeProcessLinux::%s (tid %" PRIu64 ") GetSignalInfo failed (%s). Ingoring this notification.", __FUNCTION__, pid, info_err.AsCString());
+            return;
+        }
+
+        if (log && (info.si_code != SI_USER || info.si_pid != 0))
+            log->Printf("NativeProcessLinux::%s (tid %" PRIu64 ") unexpected signal info (si_code: %d, si_pid: %d). Treating as a new thread notification anyway.", __FUNCTION__, pid, info.si_code, info.si_pid);
+
+        auto thread_sp = AddThread(pid);
+        // Resume the newly created thread.
+        ResumeThread(*thread_sp, eStateRunning, LLDB_INVALID_SIGNAL_NUMBER);
+        ThreadWasCreated(*thread_sp);
+        return;
+    }
+
+    // Get details on the signal raised.
+    if (info_err.Success())
+    {
+        // We have retrieved the signal info.  Dispatch appropriately.
+        if (info.si_signo == SIGTRAP)
+            MonitorSIGTRAP(info, *thread_sp);
+        else
+            MonitorSignal(info, *thread_sp, exited);
+    }
+    else
+    {
+        if (info_err.GetError() == EINVAL)
+        {
+            // This is a group stop reception for this tid.
+            // We can reach here if we reinject SIGSTOP, SIGSTP, SIGTTIN or SIGTTOU into the
+            // tracee, triggering the group-stop mechanism. Normally receiving these would stop
+            // the process, pending a SIGCONT. Simulating this state in a debugger is hard and is
+            // generally not needed (one use case is debugging background task being managed by a
+            // shell). For general use, it is sufficient to stop the process in a signal-delivery
+            // stop which happens before the group stop. This done by MonitorSignal and works
+            // correctly for all signals.
+            if (log)
+                log->Printf("NativeProcessLinux::%s received a group stop for pid %" PRIu64 " tid %" PRIu64 ". Transparent handling of group stops not supported, resuming the thread.", __FUNCTION__, GetID (), pid);
+            ResumeThread(*thread_sp, thread_sp->GetState(), LLDB_INVALID_SIGNAL_NUMBER);
+        }
+        else
+        {
+            // ptrace(GETSIGINFO) failed (but not due to group-stop).
+
+            // A return value of ESRCH means the thread/process is no longer on the system,
+            // so it was killed somehow outside of our control.  Either way, we can't do anything
+            // with it anymore.
+
+            // Stop tracking the metadata for the thread since it's entirely off the system now.
+            const bool thread_found = StopTrackingThread (pid);
+
+            if (log)
+                log->Printf ("NativeProcessLinux::%s GetSignalInfo failed: %s, tid = %" PRIu64 ", signal = %d, status = %d (%s, %s, %s)",
+                             __FUNCTION__, info_err.AsCString(), pid, signal, status, info_err.GetError() == ESRCH ? "thread/process killed" : "unknown reason", is_main_thread ? "is main thread" : "is not main thread", thread_found ? "thread metadata removed" : "thread metadata not found");
+
+            if (is_main_thread)
+            {
+                // Notify the delegate - our process is not available but appears to have been killed outside
+                // our control.  Is eStateExited the right exit state in this case?
+                SetExitStatus (convert_pid_status_to_exit_type (status), convert_pid_status_to_return_code (status), nullptr, true);
+                SetState (StateType::eStateExited, true);
+            }
+            else
+            {
+                // This thread was pulled out from underneath us.  Anything to do here? Do we want to do an all stop?
+                if (log)
+                    log->Printf ("NativeProcessLinux::%s pid %" PRIu64 " tid %" PRIu64 " non-main thread exit occurred, didn't tell delegate anything since thread disappeared out from underneath us", __FUNCTION__, GetID (), pid);
+            }
+        }
+    }
+}
+
+void
+NativeProcessLinux::WaitForNewThread(::pid_t tid)
+{
+    Log *log (GetLogIfAllCategoriesSet (LIBLLDB_LOG_PROCESS));
+
+    NativeThreadLinuxSP new_thread_sp = GetThreadByID(tid);
+
+    if (new_thread_sp)
+    {
+        // We are already tracking the thread - we got the event on the new thread (see
+        // MonitorSignal) before this one. We are done.
+        return;
+    }
+
+    // The thread is not tracked yet, let's wait for it to appear.
+    int status = -1;
+    ::pid_t wait_pid;
+    do
+    {
+        if (log)
+            log->Printf ("NativeProcessLinux::%s() received thread creation event for tid %" PRIu32 ". tid not tracked yet, waiting for thread to appear...", __FUNCTION__, tid);
+        wait_pid = waitpid(tid, &status, __WALL);
+    }
+    while (wait_pid == -1 && errno == EINTR);
+    // Since we are waiting on a specific tid, this must be the creation event. But let's do
+    // some checks just in case.
+    if (wait_pid != tid) {
+        if (log)
+            log->Printf ("NativeProcessLinux::%s() waiting for tid %" PRIu32 " failed. Assuming the thread has disappeared in the meantime", __FUNCTION__, tid);
+        // The only way I know of this could happen is if the whole process was
+        // SIGKILLed in the mean time. In any case, we can't do anything about that now.
+        return;
+    }
+    if (WIFEXITED(status))
+    {
+        if (log)
+            log->Printf ("NativeProcessLinux::%s() waiting for tid %" PRIu32 " returned an 'exited' event. Not tracking the thread.", __FUNCTION__, tid);
+        // Also a very improbable event.
+        return;
+    }
+
+    siginfo_t info;
+    Error error = GetSignalInfo(tid, &info);
+    if (error.Fail())
+    {
+        if (log)
+            log->Printf ("NativeProcessLinux::%s() GetSignalInfo for tid %" PRIu32 " failed. Assuming the thread has disappeared in the meantime.", __FUNCTION__, tid);
+        return;
+    }
+
+    if (((info.si_pid != 0) || (info.si_code != SI_USER)) && log)
+    {
+        // We should be getting a thread creation signal here, but we received something
+        // else. There isn't much we can do about it now, so we will just log that. Since the
+        // thread is alive and we are receiving events from it, we shall pretend that it was
+        // created properly.
+        log->Printf ("NativeProcessLinux::%s() GetSignalInfo for tid %" PRIu32 " received unexpected signal with code %d from pid %d.", __FUNCTION__, tid, info.si_code, info.si_pid);
+    }
+
+    if (log)
+        log->Printf ("NativeProcessLinux::%s() pid = %" PRIu64 ": tracking new thread tid %" PRIu32,
+                 __FUNCTION__, GetID (), tid);
+
+    new_thread_sp = AddThread(tid);
+    ResumeThread(*new_thread_sp, eStateRunning, LLDB_INVALID_SIGNAL_NUMBER);
+    ThreadWasCreated(*new_thread_sp);
+}
+
+void
+NativeProcessLinux::MonitorSIGTRAP(const siginfo_t &info, NativeThreadLinux &thread)
+{
+    Log *log (GetLogIfAllCategoriesSet (LIBLLDB_LOG_PROCESS));
+    const bool is_main_thread = (thread.GetID() == GetID ());
+
+    assert(info.si_signo == SIGTRAP && "Unexpected child signal!");
+
+    Mutex::Locker locker (m_threads_mutex);
+
+    switch (info.si_code)
+    {
+    // TODO: these two cases are required if we want to support tracing of the inferiors' children.  We'd need this to debug a monitor.
+    // case (SIGTRAP | (PTRACE_EVENT_FORK << 8)):
+    // case (SIGTRAP | (PTRACE_EVENT_VFORK << 8)):
+
+    case (SIGTRAP | (PTRACE_EVENT_CLONE << 8)):
+    {
+        // This is the notification on the parent thread which informs us of new thread
+        // creation.
+        // We don't want to do anything with the parent thread so we just resume it. In case we
+        // want to implement "break on thread creation" functionality, we would need to stop
+        // here.
+
+        unsigned long event_message = 0;
+        if (GetEventMessage(thread.GetID(), &event_message).Fail())
+        {
+            if (log)
+                log->Printf ("NativeProcessLinux::%s() pid %" PRIu64 " received thread creation event but GetEventMessage failed so we don't know the new tid", __FUNCTION__, thread.GetID());
+        } else 
+            WaitForNewThread(event_message);
+
+        ResumeThread(thread, thread.GetState(), LLDB_INVALID_SIGNAL_NUMBER);
+        break;
+    }
+
+    case (SIGTRAP | (PTRACE_EVENT_EXEC << 8)):
+    {
+        NativeThreadLinuxSP main_thread_sp;
+        if (log)
+            log->Printf ("NativeProcessLinux::%s() received exec event, code = %d", __FUNCTION__, info.si_code ^ SIGTRAP);
+
+        // Exec clears any pending notifications.
+        m_pending_notification_tid = LLDB_INVALID_THREAD_ID;
+
+        // Remove all but the main thread here.  Linux fork creates a new process which only copies the main thread.  Mutexes are in undefined state.
+        if (log)
+            log->Printf ("NativeProcessLinux::%s exec received, stop tracking all but main thread", __FUNCTION__);
+
+        for (auto thread_sp : m_threads)
+        {
+            const bool is_main_thread = thread_sp && thread_sp->GetID () == GetID ();
+            if (is_main_thread)
+            {
+                main_thread_sp = std::static_pointer_cast<NativeThreadLinux>(thread_sp);
+                if (log)
+                    log->Printf ("NativeProcessLinux::%s found main thread with tid %" PRIu64 ", keeping", __FUNCTION__, main_thread_sp->GetID ());
+            }
+            else
+            {
+                if (log)
+                    log->Printf ("NativeProcessLinux::%s discarding non-main-thread tid %" PRIu64 " due to exec", __FUNCTION__, thread_sp->GetID ());
+            }
+        }
+
+        m_threads.clear ();
+
+        if (main_thread_sp)
+        {
+            m_threads.push_back (main_thread_sp);
+            SetCurrentThreadID (main_thread_sp->GetID ());
+            main_thread_sp->SetStoppedByExec();
+        }
+        else
+        {
+            SetCurrentThreadID (LLDB_INVALID_THREAD_ID);
+            if (log)
+                log->Printf ("NativeProcessLinux::%s pid %" PRIu64 "no main thread found, discarded all threads, we're in a no-thread state!", __FUNCTION__, GetID ());
+        }
+
+        // Tell coordinator about about the "new" (since exec) stopped main thread.
+        ThreadWasCreated(*main_thread_sp);
+
+        // Let our delegate know we have just exec'd.
+        NotifyDidExec ();
+
+        // If we have a main thread, indicate we are stopped.
+        assert (main_thread_sp && "exec called during ptraced process but no main thread metadata tracked");
+
+        // Let the process know we're stopped.
+        StopRunningThreads(main_thread_sp->GetID());
+
+        break;
+    }
+
+    case (SIGTRAP | (PTRACE_EVENT_EXIT << 8)):
+    {
+        // The inferior process or one of its threads is about to exit.
+        // We don't want to do anything with the thread so we just resume it. In case we
+        // want to implement "break on thread exit" functionality, we would need to stop
+        // here.
+
+        unsigned long data = 0;
+        if (GetEventMessage(thread.GetID(), &data).Fail())
+            data = -1;
+
+        if (log)
+        {
+            log->Printf ("NativeProcessLinux::%s() received PTRACE_EVENT_EXIT, data = %lx (WIFEXITED=%s,WIFSIGNALED=%s), pid = %" PRIu64 " (%s)",
+                         __FUNCTION__,
+                         data, WIFEXITED (data) ? "true" : "false", WIFSIGNALED (data) ? "true" : "false",
+                         thread.GetID(),
+                    is_main_thread ? "is main thread" : "not main thread");
+        }
+
+        if (is_main_thread)
+        {
+            SetExitStatus (convert_pid_status_to_exit_type (data), convert_pid_status_to_return_code (data), nullptr, true);
+        }
+
+        StateType state = thread.GetState();
+        if (! StateIsRunningState(state))
+        {
+            // Due to a kernel bug, we may sometimes get this stop after the inferior gets a
+            // SIGKILL. This confuses our state tracking logic in ResumeThread(), since normally,
+            // we should not be receiving any ptrace events while the inferior is stopped. This
+            // makes sure that the inferior is resumed and exits normally.
+            state = eStateRunning;
+        }
+        ResumeThread(thread, state, LLDB_INVALID_SIGNAL_NUMBER);
+
+        break;
+    }
+
+    case 0:
+    case TRAP_TRACE:  // We receive this on single stepping.
+    case TRAP_HWBKPT: // We receive this on watchpoint hit
+    {
+        // If a watchpoint was hit, report it
+        uint32_t wp_index;
+        Error error = thread.GetRegisterContext()->GetWatchpointHitIndex(wp_index, (uintptr_t)info.si_addr);
+        if (error.Fail() && log)
+            log->Printf("NativeProcessLinux::%s() "
+                        "received error while checking for watchpoint hits, "
+                        "pid = %" PRIu64 " error = %s",
+                        __FUNCTION__, thread.GetID(), error.AsCString());
+        if (wp_index != LLDB_INVALID_INDEX32)
+        {
+            MonitorWatchpoint(thread, wp_index);
+            break;
+        }
+
+        // Otherwise, report step over
+        MonitorTrace(thread);
+        break;
+    }
+
+    case SI_KERNEL:
+#if defined __mips__
+        // For mips there is no special signal for watchpoint
+        // So we check for watchpoint in kernel trap
+    {
+        // If a watchpoint was hit, report it
+        uint32_t wp_index;
+        Error error = thread.GetRegisterContext()->GetWatchpointHitIndex(wp_index, LLDB_INVALID_ADDRESS);
+        if (error.Fail() && log)
+            log->Printf("NativeProcessLinux::%s() "
+                        "received error while checking for watchpoint hits, "
+                        "pid = %" PRIu64 " error = %s",
+                        __FUNCTION__, thread.GetID(), error.AsCString());
+        if (wp_index != LLDB_INVALID_INDEX32)
+        {
+            MonitorWatchpoint(thread, wp_index);
+            break;
+        }
+    }
+        // NO BREAK
+#endif
+    case TRAP_BRKPT:
+        MonitorBreakpoint(thread);
+        break;
+
+    case SIGTRAP:
+    case (SIGTRAP | 0x80):
+        if (log)
+            log->Printf ("NativeProcessLinux::%s() received unknown SIGTRAP system call stop event, pid %" PRIu64 "tid %" PRIu64 ", resuming", __FUNCTION__, GetID (), thread.GetID());
+
+        // Ignore these signals until we know more about them.
+        ResumeThread(thread, thread.GetState(), LLDB_INVALID_SIGNAL_NUMBER);
+        break;
+
+    default:
+        assert(false && "Unexpected SIGTRAP code!");
+        if (log)
+            log->Printf ("NativeProcessLinux::%s() pid %" PRIu64 "tid %" PRIu64 " received unhandled SIGTRAP code: 0x%d",
+                    __FUNCTION__, GetID(), thread.GetID(), info.si_code);
+        break;
+        
+    }
+}
+
+void
+NativeProcessLinux::MonitorTrace(NativeThreadLinux &thread)
+{
+    Log *log(GetLogIfAllCategoriesSet(LIBLLDB_LOG_PROCESS));
+    if (log)
+        log->Printf("NativeProcessLinux::%s() received trace event, pid = %" PRIu64 " (single stepping)",
+                __FUNCTION__, thread.GetID());
+
+    // This thread is currently stopped.
+    thread.SetStoppedByTrace();
+
+    StopRunningThreads(thread.GetID());
+}
+
+void
+NativeProcessLinux::MonitorBreakpoint(NativeThreadLinux &thread)
+{
+    Log *log(GetLogIfAnyCategoriesSet(LIBLLDB_LOG_PROCESS | LIBLLDB_LOG_BREAKPOINTS));
+    if (log)
+        log->Printf("NativeProcessLinux::%s() received breakpoint event, pid = %" PRIu64,
+                __FUNCTION__, thread.GetID());
+
+    // Mark the thread as stopped at breakpoint.
+    thread.SetStoppedByBreakpoint();
+    Error error = FixupBreakpointPCAsNeeded(thread);
+    if (error.Fail())
+        if (log)
+            log->Printf("NativeProcessLinux::%s() pid = %" PRIu64 " fixup: %s",
+                    __FUNCTION__, thread.GetID(), error.AsCString());
+
+    if (m_threads_stepping_with_breakpoint.find(thread.GetID()) != m_threads_stepping_with_breakpoint.end())
+        thread.SetStoppedByTrace();
+
+    StopRunningThreads(thread.GetID());
+}
+
+void
+NativeProcessLinux::MonitorWatchpoint(NativeThreadLinux &thread, uint32_t wp_index)
+{
+    Log *log(GetLogIfAnyCategoriesSet(LIBLLDB_LOG_PROCESS | LIBLLDB_LOG_WATCHPOINTS));
+    if (log)
+        log->Printf("NativeProcessLinux::%s() received watchpoint event, "
+                    "pid = %" PRIu64 ", wp_index = %" PRIu32,
+                    __FUNCTION__, thread.GetID(), wp_index);
+
+    // Mark the thread as stopped at watchpoint.
+    // The address is at (lldb::addr_t)info->si_addr if we need it.
+    thread.SetStoppedByWatchpoint(wp_index);
+
+    // We need to tell all other running threads before we notify the delegate about this stop.
+    StopRunningThreads(thread.GetID());
+}
+
+void
+NativeProcessLinux::MonitorSignal(const siginfo_t &info, NativeThreadLinux &thread, bool exited)
+{
+    const int signo = info.si_signo;
+    const bool is_from_llgs = info.si_pid == getpid ();
+
+    Log *log (GetLogIfAllCategoriesSet (LIBLLDB_LOG_PROCESS));
+
+    // POSIX says that process behaviour is undefined after it ignores a SIGFPE,
+    // SIGILL, SIGSEGV, or SIGBUS *unless* that signal was generated by a
+    // kill(2) or raise(3).  Similarly for tgkill(2) on Linux.
+    //
+    // IOW, user generated signals never generate what we consider to be a
+    // "crash".
+    //
+    // Similarly, ACK signals generated by this monitor.
+
+    Mutex::Locker locker (m_threads_mutex);
+
+    // Handle the signal.
+    if (info.si_code == SI_TKILL || info.si_code == SI_USER)
+    {
+        if (log)
+            log->Printf ("NativeProcessLinux::%s() received signal %s (%d) with code %s, (siginfo pid = %d (%s), waitpid pid = %" PRIu64 ")",
+                            __FUNCTION__,
+                            Host::GetSignalAsCString(signo),
+                            signo,
+                            (info.si_code == SI_TKILL ? "SI_TKILL" : "SI_USER"),
+                            info.si_pid,
+                            is_from_llgs ? "from llgs" : "not from llgs",
+                            thread.GetID());
+    }
+
+    // Check for thread stop notification.
+    if (is_from_llgs && (info.si_code == SI_TKILL) && (signo == SIGSTOP))
+    {
+        // This is a tgkill()-based stop.
+        if (log)
+            log->Printf ("NativeProcessLinux::%s() pid %" PRIu64 " tid %" PRIu64 ", thread stopped",
+                         __FUNCTION__,
+                         GetID (),
+                         thread.GetID());
+
+        // Check that we're not already marked with a stop reason.
+        // Note this thread really shouldn't already be marked as stopped - if we were, that would imply that
+        // the kernel signaled us with the thread stopping which we handled and marked as stopped,
+        // and that, without an intervening resume, we received another stop.  It is more likely
+        // that we are missing the marking of a run state somewhere if we find that the thread was
+        // marked as stopped.
+        const StateType thread_state = thread.GetState();
+        if (!StateIsStoppedState (thread_state, false))
+        {
+            // An inferior thread has stopped because of a SIGSTOP we have sent it.
+            // Generally, these are not important stops and we don't want to report them as
+            // they are just used to stop other threads when one thread (the one with the
+            // *real* stop reason) hits a breakpoint (watchpoint, etc...). However, in the
+            // case of an asynchronous Interrupt(), this *is* the real stop reason, so we
+            // leave the signal intact if this is the thread that was chosen as the
+            // triggering thread.
+            if (m_pending_notification_tid != LLDB_INVALID_THREAD_ID)
+            {
+                if (m_pending_notification_tid == thread.GetID())
+                    thread.SetStoppedBySignal(SIGSTOP, &info);
+                else
+                    thread.SetStoppedWithNoReason();
+
+                SetCurrentThreadID (thread.GetID ());
+                SignalIfAllThreadsStopped();
+            }
+            else
+            {
+                // We can end up here if stop was initiated by LLGS but by this time a
+                // thread stop has occurred - maybe initiated by another event.
+                Error error = ResumeThread(thread, thread.GetState(), 0);
+                if (error.Fail() && log)
+                {
+                    log->Printf("NativeProcessLinux::%s failed to resume thread tid  %" PRIu64 ": %s",
+                            __FUNCTION__, thread.GetID(), error.AsCString());
+                }
+            }
+        }
+        else
+        {
+            if (log)
+            {
+                // Retrieve the signal name if the thread was stopped by a signal.
+                int stop_signo = 0;
+                const bool stopped_by_signal = thread.IsStopped(&stop_signo);
+                const char *signal_name = stopped_by_signal ? Host::GetSignalAsCString(stop_signo) : "<not stopped by signal>";
+                if (!signal_name)
+                    signal_name = "<no-signal-name>";
+
+                log->Printf ("NativeProcessLinux::%s() pid %" PRIu64 " tid %" PRIu64 ", thread was already marked as a stopped state (state=%s, signal=%d (%s)), leaving stop signal as is",
+                             __FUNCTION__,
+                             GetID (),
+                             thread.GetID(),
+                             StateAsCString (thread_state),
+                             stop_signo,
+                             signal_name);
+            }
+            SignalIfAllThreadsStopped();
+        }
+
+        // Done handling.
+        return;
+    }
+
+    if (log)
+        log->Printf ("NativeProcessLinux::%s() received signal %s", __FUNCTION__, Host::GetSignalAsCString(signo));
+
+    // This thread is stopped.
+    thread.SetStoppedBySignal(signo, &info);
+
+    // Send a stop to the debugger after we get all other threads to stop.
+    StopRunningThreads(thread.GetID());
+}
+
+namespace {
+
+struct EmulatorBaton
+{
+    NativeProcessLinux* m_process;
+    NativeRegisterContext* m_reg_context;
+
+    // eRegisterKindDWARF -> RegsiterValue
+    std::unordered_map<uint32_t, RegisterValue> m_register_values;
+
+    EmulatorBaton(NativeProcessLinux* process, NativeRegisterContext* reg_context) :
+            m_process(process), m_reg_context(reg_context) {}
+};
+
+} // anonymous namespace
+
+static size_t
+ReadMemoryCallback (EmulateInstruction *instruction,
+                    void *baton,
+                    const EmulateInstruction::Context &context, 
+                    lldb::addr_t addr, 
+                    void *dst,
+                    size_t length)
+{
+    EmulatorBaton* emulator_baton = static_cast<EmulatorBaton*>(baton);
+
+    size_t bytes_read;
+    emulator_baton->m_process->ReadMemory(addr, dst, length, bytes_read);
+    return bytes_read;
+}
+
+static bool
+ReadRegisterCallback (EmulateInstruction *instruction,
+                      void *baton,
+                      const RegisterInfo *reg_info,
+                      RegisterValue &reg_value)
+{
+    EmulatorBaton* emulator_baton = static_cast<EmulatorBaton*>(baton);
+
+    auto it = emulator_baton->m_register_values.find(reg_info->kinds[eRegisterKindDWARF]);
+    if (it != emulator_baton->m_register_values.end())
+    {
+        reg_value = it->second;
+        return true;
+    }
+
+    // The emulator only fill in the dwarf regsiter numbers (and in some case
+    // the generic register numbers). Get the full register info from the
+    // register context based on the dwarf register numbers.
+    const RegisterInfo* full_reg_info = emulator_baton->m_reg_context->GetRegisterInfo(
+            eRegisterKindDWARF, reg_info->kinds[eRegisterKindDWARF]);
+
+    Error error = emulator_baton->m_reg_context->ReadRegister(full_reg_info, reg_value);
+    if (error.Success())
+        return true;
+
+    return false;
+}
+
+static bool
+WriteRegisterCallback (EmulateInstruction *instruction,
+                       void *baton,
+                       const EmulateInstruction::Context &context,
+                       const RegisterInfo *reg_info,
+                       const RegisterValue &reg_value)
+{
+    EmulatorBaton* emulator_baton = static_cast<EmulatorBaton*>(baton);
+    emulator_baton->m_register_values[reg_info->kinds[eRegisterKindDWARF]] = reg_value;
+    return true;
+}
+
+static size_t
+WriteMemoryCallback (EmulateInstruction *instruction,
+                     void *baton,
+                     const EmulateInstruction::Context &context, 
+                     lldb::addr_t addr, 
+                     const void *dst,
+                     size_t length)
+{
+    return length;
+}
+
+static lldb::addr_t
+ReadFlags (NativeRegisterContext* regsiter_context)
+{
+    const RegisterInfo* flags_info = regsiter_context->GetRegisterInfo(
+            eRegisterKindGeneric, LLDB_REGNUM_GENERIC_FLAGS);
+    return regsiter_context->ReadRegisterAsUnsigned(flags_info, LLDB_INVALID_ADDRESS);
+}
+
+Error
+NativeProcessLinux::SetupSoftwareSingleStepping(NativeThreadLinux &thread)
+{
+    Error error;
+    NativeRegisterContextSP register_context_sp = thread.GetRegisterContext();
+
+    std::unique_ptr<EmulateInstruction> emulator_ap(
+        EmulateInstruction::FindPlugin(m_arch, eInstructionTypePCModifying, nullptr));
+
+    if (emulator_ap == nullptr)
+        return Error("Instruction emulator not found!");
+
+    EmulatorBaton baton(this, register_context_sp.get());
+    emulator_ap->SetBaton(&baton);
+    emulator_ap->SetReadMemCallback(&ReadMemoryCallback);
+    emulator_ap->SetReadRegCallback(&ReadRegisterCallback);
+    emulator_ap->SetWriteMemCallback(&WriteMemoryCallback);
+    emulator_ap->SetWriteRegCallback(&WriteRegisterCallback);
+
+    if (!emulator_ap->ReadInstruction())
+        return Error("Read instruction failed!");
+
+    bool emulation_result = emulator_ap->EvaluateInstruction(eEmulateInstructionOptionAutoAdvancePC);
+
+    const RegisterInfo* reg_info_pc = register_context_sp->GetRegisterInfo(eRegisterKindGeneric, LLDB_REGNUM_GENERIC_PC);
+    const RegisterInfo* reg_info_flags = register_context_sp->GetRegisterInfo(eRegisterKindGeneric, LLDB_REGNUM_GENERIC_FLAGS);
+
+    auto pc_it = baton.m_register_values.find(reg_info_pc->kinds[eRegisterKindDWARF]);
+    auto flags_it = baton.m_register_values.find(reg_info_flags->kinds[eRegisterKindDWARF]);
+
+    lldb::addr_t next_pc;
+    lldb::addr_t next_flags;
+    if (emulation_result)
+    {
+        assert(pc_it != baton.m_register_values.end() && "Emulation was successfull but PC wasn't updated");
+        next_pc = pc_it->second.GetAsUInt64();
+
+        if (flags_it != baton.m_register_values.end())
+            next_flags = flags_it->second.GetAsUInt64();
+        else
+            next_flags = ReadFlags (register_context_sp.get());
+    }
+    else if (pc_it == baton.m_register_values.end())
+    {
+        // Emulate instruction failed and it haven't changed PC. Advance PC
+        // with the size of the current opcode because the emulation of all
+        // PC modifying instruction should be successful. The failure most
+        // likely caused by a not supported instruction which don't modify PC.
+        next_pc = register_context_sp->GetPC() + emulator_ap->GetOpcode().GetByteSize();
+        next_flags = ReadFlags (register_context_sp.get());
+    }
+    else
+    {
+        // The instruction emulation failed after it modified the PC. It is an
+        // unknown error where we can't continue because the next instruction is
+        // modifying the PC but we don't  know how.
+        return Error ("Instruction emulation failed unexpectedly.");
+    }
+
+    if (m_arch.GetMachine() == llvm::Triple::arm)
+    {
+        if (next_flags & 0x20)
+        {
+            // Thumb mode
+            error = SetSoftwareBreakpoint(next_pc, 2);
+        }
+        else
+        {
+            // Arm mode
+            error = SetSoftwareBreakpoint(next_pc, 4);
+        }
+    }
+    else if (m_arch.GetMachine() == llvm::Triple::mips64
+            || m_arch.GetMachine() == llvm::Triple::mips64el
+            || m_arch.GetMachine() == llvm::Triple::mips
+            || m_arch.GetMachine() == llvm::Triple::mipsel)
+        error = SetSoftwareBreakpoint(next_pc, 4);
+    else
+    {
+        // No size hint is given for the next breakpoint
+        error = SetSoftwareBreakpoint(next_pc, 0);
+    }
+
+    if (error.Fail())
+        return error;
+
+    m_threads_stepping_with_breakpoint.insert({thread.GetID(), next_pc});
+
+    return Error();
+}
+
+bool
+NativeProcessLinux::SupportHardwareSingleStepping() const
+{
+    if (m_arch.GetMachine() == llvm::Triple::arm
+        || m_arch.GetMachine() == llvm::Triple::mips64 || m_arch.GetMachine() == llvm::Triple::mips64el
+        || m_arch.GetMachine() == llvm::Triple::mips || m_arch.GetMachine() == llvm::Triple::mipsel)
+        return false;
+    return true;
+}
+
+Error
+NativeProcessLinux::Resume (const ResumeActionList &resume_actions)
+{
+    Log *log (GetLogIfAllCategoriesSet (LIBLLDB_LOG_PROCESS | LIBLLDB_LOG_THREAD));
+    if (log)
+        log->Printf ("NativeProcessLinux::%s called: pid %" PRIu64, __FUNCTION__, GetID ());
+
+    bool software_single_step = !SupportHardwareSingleStepping();
+
+    Mutex::Locker locker (m_threads_mutex);
+
+    if (software_single_step)
+    {
+        for (auto thread_sp : m_threads)
+        {
+            assert (thread_sp && "thread list should not contain NULL threads");
+
+            const ResumeAction *const action = resume_actions.GetActionForThread (thread_sp->GetID (), true);
+            if (action == nullptr)
+                continue;
+
+            if (action->state == eStateStepping)
+            {
+                Error error = SetupSoftwareSingleStepping(static_cast<NativeThreadLinux &>(*thread_sp));
+                if (error.Fail())
+                    return error;
+            }
+        }
+    }
+
+    for (auto thread_sp : m_threads)
+    {
+        assert (thread_sp && "thread list should not contain NULL threads");
+
+        const ResumeAction *const action = resume_actions.GetActionForThread (thread_sp->GetID (), true);
+
+        if (action == nullptr)
+        {
+            if (log)
+                log->Printf ("NativeProcessLinux::%s no action specified for pid %" PRIu64 " tid %" PRIu64,
+                    __FUNCTION__, GetID (), thread_sp->GetID ());
+            continue;
+        }
+
+        if (log)
+        {
+            log->Printf ("NativeProcessLinux::%s processing resume action state %s for pid %" PRIu64 " tid %" PRIu64, 
+                    __FUNCTION__, StateAsCString (action->state), GetID (), thread_sp->GetID ());
+        }
+
+        switch (action->state)
+        {
+        case eStateRunning:
+        case eStateStepping:
+        {
+            // Run the thread, possibly feeding it the signal.
+            const int signo = action->signal;
+            ResumeThread(static_cast<NativeThreadLinux &>(*thread_sp), action->state, signo);
+            break;
+        }
+
+        case eStateSuspended:
+        case eStateStopped:
+            lldbassert(0 && "Unexpected state");
+
+        default:
+            return Error ("NativeProcessLinux::%s (): unexpected state %s specified for pid %" PRIu64 ", tid %" PRIu64,
+                    __FUNCTION__, StateAsCString (action->state), GetID (), thread_sp->GetID ());
+        }
+    }
+
+    return Error();
+}
+
+Error
+NativeProcessLinux::Halt ()
+{
+    Error error;
+
+    if (kill (GetID (), SIGSTOP) != 0)
+        error.SetErrorToErrno ();
+
+    return error;
+}
+
+Error
+NativeProcessLinux::Detach ()
+{
+    Error error;
+
+    // Stop monitoring the inferior.
+    m_sigchld_handle.reset();
+
+    // Tell ptrace to detach from the process.
+    if (GetID () == LLDB_INVALID_PROCESS_ID)
+        return error;
+
+    for (auto thread_sp : m_threads)
+    {
+        Error e = Detach(thread_sp->GetID());
+        if (e.Fail())
+            error = e; // Save the error, but still attempt to detach from other threads.
+    }
+
+    return error;
+}
+
+Error
+NativeProcessLinux::Signal (int signo)
+{
+    Error error;
+
+    Log *log (GetLogIfAllCategoriesSet (LIBLLDB_LOG_PROCESS));
+    if (log)
+        log->Printf ("NativeProcessLinux::%s: sending signal %d (%s) to pid %" PRIu64,
+                __FUNCTION__, signo, Host::GetSignalAsCString(signo), GetID());
+
+    if (kill(GetID(), signo))
+        error.SetErrorToErrno();
+
+    return error;
+}
+
+Error
+NativeProcessLinux::Interrupt ()
+{
+    // Pick a running thread (or if none, a not-dead stopped thread) as
+    // the chosen thread that will be the stop-reason thread.
+    Log *log (GetLogIfAllCategoriesSet (LIBLLDB_LOG_PROCESS));
+
+    NativeThreadProtocolSP running_thread_sp;
+    NativeThreadProtocolSP stopped_thread_sp;
+        
+    if (log)
+        log->Printf ("NativeProcessLinux::%s selecting running thread for interrupt target", __FUNCTION__);
+
+    Mutex::Locker locker (m_threads_mutex);
+
+    for (auto thread_sp : m_threads)
+    {
+        // The thread shouldn't be null but lets just cover that here.
+        if (!thread_sp)
+            continue;
+
+        // If we have a running or stepping thread, we'll call that the
+        // target of the interrupt.
+        const auto thread_state = thread_sp->GetState ();
+        if (thread_state == eStateRunning ||
+            thread_state == eStateStepping)
+        {
+            running_thread_sp = thread_sp;
+            break;
+        }
+        else if (!stopped_thread_sp && StateIsStoppedState (thread_state, true))
+        {
+            // Remember the first non-dead stopped thread.  We'll use that as a backup if there are no running threads.
+            stopped_thread_sp = thread_sp;
+        }
+    }
+
+    if (!running_thread_sp && !stopped_thread_sp)
+    {
+        Error error("found no running/stepping or live stopped threads as target for interrupt");
+        if (log)
+            log->Printf ("NativeProcessLinux::%s skipping due to error: %s", __FUNCTION__, error.AsCString ());
+
+        return error;
+    }
+
+    NativeThreadProtocolSP deferred_signal_thread_sp = running_thread_sp ? running_thread_sp : stopped_thread_sp;
+
+    if (log)
+        log->Printf ("NativeProcessLinux::%s pid %" PRIu64 " %s tid %" PRIu64 " chosen for interrupt target",
+                     __FUNCTION__,
+                     GetID (),
+                     running_thread_sp ? "running" : "stopped",
+                     deferred_signal_thread_sp->GetID ());
+
+    StopRunningThreads(deferred_signal_thread_sp->GetID());
+
+    return Error();
+}
+
+Error
+NativeProcessLinux::Kill ()
+{
+    Log *log (GetLogIfAllCategoriesSet (LIBLLDB_LOG_PROCESS));
+    if (log)
+        log->Printf ("NativeProcessLinux::%s called for PID %" PRIu64, __FUNCTION__, GetID ());
+
+    Error error;
+
+    switch (m_state)
+    {
+        case StateType::eStateInvalid:
+        case StateType::eStateExited:
+        case StateType::eStateCrashed:
+        case StateType::eStateDetached:
+        case StateType::eStateUnloaded:
+            // Nothing to do - the process is already dead.
+            if (log)
+                log->Printf ("NativeProcessLinux::%s ignored for PID %" PRIu64 " due to current state: %s", __FUNCTION__, GetID (), StateAsCString (m_state));
+            return error;
+
+        case StateType::eStateConnected:
+        case StateType::eStateAttaching:
+        case StateType::eStateLaunching:
+        case StateType::eStateStopped:
+        case StateType::eStateRunning:
+        case StateType::eStateStepping:
+        case StateType::eStateSuspended:
+            // We can try to kill a process in these states.
+            break;
+    }
+
+    if (kill (GetID (), SIGKILL) != 0)
+    {
+        error.SetErrorToErrno ();
+        return error;
+    }
+
+    return error;
+}
+
+static Error
+ParseMemoryRegionInfoFromProcMapsLine (const std::string &maps_line, MemoryRegionInfo &memory_region_info)
+{
+    memory_region_info.Clear();
+
+    StringExtractor line_extractor (maps_line.c_str ());
+
+    // Format: {address_start_hex}-{address_end_hex} perms offset  dev   inode   pathname
+    // perms: rwxp   (letter is present if set, '-' if not, final character is p=private, s=shared).
+
+    // Parse out the starting address
+    lldb::addr_t start_address = line_extractor.GetHexMaxU64 (false, 0);
+
+    // Parse out hyphen separating start and end address from range.
+    if (!line_extractor.GetBytesLeft () || (line_extractor.GetChar () != '-'))
+        return Error ("malformed /proc/{pid}/maps entry, missing dash between address range");
+
+    // Parse out the ending address
+    lldb::addr_t end_address = line_extractor.GetHexMaxU64 (false, start_address);
+
+    // Parse out the space after the address.
+    if (!line_extractor.GetBytesLeft () || (line_extractor.GetChar () != ' '))
+        return Error ("malformed /proc/{pid}/maps entry, missing space after range");
+
+    // Save the range.
+    memory_region_info.GetRange ().SetRangeBase (start_address);
+    memory_region_info.GetRange ().SetRangeEnd (end_address);
+
+    // Parse out each permission entry.
+    if (line_extractor.GetBytesLeft () < 4)
+        return Error ("malformed /proc/{pid}/maps entry, missing some portion of permissions");
+
+    // Handle read permission.
+    const char read_perm_char = line_extractor.GetChar ();
+    if (read_perm_char == 'r')
+        memory_region_info.SetReadable (MemoryRegionInfo::OptionalBool::eYes);
+    else
+    {
+        assert ( (read_perm_char == '-') && "unexpected /proc/{pid}/maps read permission char" );
+        memory_region_info.SetReadable (MemoryRegionInfo::OptionalBool::eNo);
+    }
+
+    // Handle write permission.
+    const char write_perm_char = line_extractor.GetChar ();
+    if (write_perm_char == 'w')
+        memory_region_info.SetWritable (MemoryRegionInfo::OptionalBool::eYes);
+    else
+    {
+        assert ( (write_perm_char == '-') && "unexpected /proc/{pid}/maps write permission char" );
+        memory_region_info.SetWritable (MemoryRegionInfo::OptionalBool::eNo);
+    }
+
+    // Handle execute permission.
+    const char exec_perm_char = line_extractor.GetChar ();
+    if (exec_perm_char == 'x')
+        memory_region_info.SetExecutable (MemoryRegionInfo::OptionalBool::eYes);
+    else
+    {
+        assert ( (exec_perm_char == '-') && "unexpected /proc/{pid}/maps exec permission char" );
+        memory_region_info.SetExecutable (MemoryRegionInfo::OptionalBool::eNo);
+    }
+
+    return Error ();
+}
+
+Error
+NativeProcessLinux::GetMemoryRegionInfo (lldb::addr_t load_addr, MemoryRegionInfo &range_info)
+{
+    // FIXME review that the final memory region returned extends to the end of the virtual address space,
+    // with no perms if it is not mapped.
+
+    // Use an approach that reads memory regions from /proc/{pid}/maps.
+    // Assume proc maps entries are in ascending order.
+    // FIXME assert if we find differently.
+    Mutex::Locker locker (m_mem_region_cache_mutex);
+
+    Log *log (GetLogIfAllCategoriesSet (LIBLLDB_LOG_PROCESS));
+    Error error;
+
+    if (m_supports_mem_region == LazyBool::eLazyBoolNo)
+    {
+        // We're done.
+        error.SetErrorString ("unsupported");
+        return error;
+    }
+
+    // If our cache is empty, pull the latest.  There should always be at least one memory region
+    // if memory region handling is supported.
+    if (m_mem_region_cache.empty ())
+    {
+        error = ProcFileReader::ProcessLineByLine (GetID (), "maps",
+             [&] (const std::string &line) -> bool
+             {
+                 MemoryRegionInfo info;
+                 const Error parse_error = ParseMemoryRegionInfoFromProcMapsLine (line, info);
+                 if (parse_error.Success ())
+                 {
+                     m_mem_region_cache.push_back (info);
+                     return true;
+                 }
+                 else
+                 {
+                     if (log)
+                         log->Printf ("NativeProcessLinux::%s failed to parse proc maps line '%s': %s", __FUNCTION__, line.c_str (), error.AsCString ());
+                     return false;
+                 }
+             });
+
+        // If we had an error, we'll mark unsupported.
+        if (error.Fail ())
+        {
+            m_supports_mem_region = LazyBool::eLazyBoolNo;
+            return error;
+        }
+        else if (m_mem_region_cache.empty ())
+        {
+            // No entries after attempting to read them.  This shouldn't happen if /proc/{pid}/maps
+            // is supported.  Assume we don't support map entries via procfs.
+            if (log)
+                log->Printf ("NativeProcessLinux::%s failed to find any procfs maps entries, assuming no support for memory region metadata retrieval", __FUNCTION__);
+            m_supports_mem_region = LazyBool::eLazyBoolNo;
+            error.SetErrorString ("not supported");
+            return error;
+        }
+
+        if (log)
+            log->Printf ("NativeProcessLinux::%s read %" PRIu64 " memory region entries from /proc/%" PRIu64 "/maps", __FUNCTION__, static_cast<uint64_t> (m_mem_region_cache.size ()), GetID ());
+
+        // We support memory retrieval, remember that.
+        m_supports_mem_region = LazyBool::eLazyBoolYes;
+    }
+    else
+    {
+        if (log)
+            log->Printf ("NativeProcessLinux::%s reusing %" PRIu64 " cached memory region entries", __FUNCTION__, static_cast<uint64_t> (m_mem_region_cache.size ()));
+    }
+
+    lldb::addr_t prev_base_address = 0;
+
+    // FIXME start by finding the last region that is <= target address using binary search.  Data is sorted.
+    // There can be a ton of regions on pthreads apps with lots of threads.
+    for (auto it = m_mem_region_cache.begin(); it != m_mem_region_cache.end (); ++it)
+    {
+        MemoryRegionInfo &proc_entry_info = *it;
+
+        // Sanity check assumption that /proc/{pid}/maps entries are ascending.
+        assert ((proc_entry_info.GetRange ().GetRangeBase () >= prev_base_address) && "descending /proc/pid/maps entries detected, unexpected");
+        prev_base_address = proc_entry_info.GetRange ().GetRangeBase ();
+
+        // If the target address comes before this entry, indicate distance to next region.
+        if (load_addr < proc_entry_info.GetRange ().GetRangeBase ())
+        {
+            range_info.GetRange ().SetRangeBase (load_addr);
+            range_info.GetRange ().SetByteSize (proc_entry_info.GetRange ().GetRangeBase () - load_addr);
+            range_info.SetReadable (MemoryRegionInfo::OptionalBool::eNo);
+            range_info.SetWritable (MemoryRegionInfo::OptionalBool::eNo);
+            range_info.SetExecutable (MemoryRegionInfo::OptionalBool::eNo);
+
+            return error;
+        }
+        else if (proc_entry_info.GetRange ().Contains (load_addr))
+        {
+            // The target address is within the memory region we're processing here.
+            range_info = proc_entry_info;
+            return error;
+        }
+
+        // The target memory address comes somewhere after the region we just parsed.
+    }
+
+    // If we made it here, we didn't find an entry that contained the given address. Return the
+    // load_addr as start and the amount of bytes betwwen load address and the end of the memory as
+    // size.
+    range_info.GetRange ().SetRangeBase (load_addr);
+    switch (m_arch.GetAddressByteSize())
+    {
+        case 4:
+            range_info.GetRange ().SetByteSize (0x100000000ull - load_addr);
+            break;
+        case 8:
+            range_info.GetRange ().SetByteSize (0ull - load_addr);
+            break;
+        default:
+            assert(false && "Unrecognized data byte size");
+            break;
+    }
+    range_info.SetReadable (MemoryRegionInfo::OptionalBool::eNo);
+    range_info.SetWritable (MemoryRegionInfo::OptionalBool::eNo);
+    range_info.SetExecutable (MemoryRegionInfo::OptionalBool::eNo);
+    return error;
+}
+
+void
+NativeProcessLinux::DoStopIDBumped (uint32_t newBumpId)
+{
+    Log *log (GetLogIfAllCategoriesSet (LIBLLDB_LOG_PROCESS));
+    if (log)
+        log->Printf ("NativeProcessLinux::%s(newBumpId=%" PRIu32 ") called", __FUNCTION__, newBumpId);
+
+    {
+        Mutex::Locker locker (m_mem_region_cache_mutex);
+        if (log)
+            log->Printf ("NativeProcessLinux::%s clearing %" PRIu64 " entries from the cache", __FUNCTION__, static_cast<uint64_t> (m_mem_region_cache.size ()));
+        m_mem_region_cache.clear ();
+    }
+}
+
+Error
+NativeProcessLinux::AllocateMemory(size_t size, uint32_t permissions, lldb::addr_t &addr)
+{
+    // FIXME implementing this requires the equivalent of
+    // InferiorCallPOSIX::InferiorCallMmap, which depends on
+    // functional ThreadPlans working with Native*Protocol.
+#if 1
+    return Error ("not implemented yet");
+#else
+    addr = LLDB_INVALID_ADDRESS;
+
+    unsigned prot = 0;
+    if (permissions & lldb::ePermissionsReadable)
+        prot |= eMmapProtRead;
+    if (permissions & lldb::ePermissionsWritable)
+        prot |= eMmapProtWrite;
+    if (permissions & lldb::ePermissionsExecutable)
+        prot |= eMmapProtExec;
+
+    // TODO implement this directly in NativeProcessLinux
+    // (and lift to NativeProcessPOSIX if/when that class is
+    // refactored out).
+    if (InferiorCallMmap(this, addr, 0, size, prot,
+                         eMmapFlagsAnon | eMmapFlagsPrivate, -1, 0)) {
+        m_addr_to_mmap_size[addr] = size;
+        return Error ();
+    } else {
+        addr = LLDB_INVALID_ADDRESS;
+        return Error("unable to allocate %" PRIu64 " bytes of memory with permissions %s", size, GetPermissionsAsCString (permissions));
+    }
+#endif
+}
+
+Error
+NativeProcessLinux::DeallocateMemory (lldb::addr_t addr)
+{
+    // FIXME see comments in AllocateMemory - required lower-level
+    // bits not in place yet (ThreadPlans)
+    return Error ("not implemented");
+}
+
+lldb::addr_t
+NativeProcessLinux::GetSharedLibraryInfoAddress ()
+{
+#if 1
+    // punt on this for now
+    return LLDB_INVALID_ADDRESS;
+#else
+    // Return the image info address for the exe module
+#if 1
+    Log *log (GetLogIfAllCategoriesSet (LIBLLDB_LOG_PROCESS));
+
+    ModuleSP module_sp;
+    Error error = GetExeModuleSP (module_sp);
+    if (error.Fail ())
+    {
+         if (log)
+            log->Warning ("NativeProcessLinux::%s failed to retrieve exe module: %s", __FUNCTION__, error.AsCString ());
+        return LLDB_INVALID_ADDRESS;
+    }
+
+    if (module_sp == nullptr)
+    {
+         if (log)
+            log->Warning ("NativeProcessLinux::%s exe module returned was NULL", __FUNCTION__);
+         return LLDB_INVALID_ADDRESS;
+    }
+
+    ObjectFileSP object_file_sp = module_sp->GetObjectFile ();
+    if (object_file_sp == nullptr)
+    {
+         if (log)
+            log->Warning ("NativeProcessLinux::%s exe module returned a NULL object file", __FUNCTION__);
+         return LLDB_INVALID_ADDRESS;
+    }
+
+    return obj_file_sp->GetImageInfoAddress();
+#else
+    Target *target = &GetTarget();
+    ObjectFile *obj_file = target->GetExecutableModule()->GetObjectFile();
+    Address addr = obj_file->GetImageInfoAddress(target);
+
+    if (addr.IsValid())
+        return addr.GetLoadAddress(target);
+    return LLDB_INVALID_ADDRESS;
+#endif
+#endif // punt on this for now
+}
+
+size_t
+NativeProcessLinux::UpdateThreads ()
+{
+    // The NativeProcessLinux monitoring threads are always up to date
+    // with respect to thread state and they keep the thread list
+    // populated properly. All this method needs to do is return the
+    // thread count.
+    Mutex::Locker locker (m_threads_mutex);
+    return m_threads.size ();
+}
+
+bool
+NativeProcessLinux::GetArchitecture (ArchSpec &arch) const
+{
+    arch = m_arch;
+    return true;
+}
+
+Error
+NativeProcessLinux::GetSoftwareBreakpointPCOffset(uint32_t &actual_opcode_size)
+{
+    // FIXME put this behind a breakpoint protocol class that can be
+    // set per architecture.  Need ARM, MIPS support here.
+    static const uint8_t g_i386_opcode [] = { 0xCC };
+
+    switch (m_arch.GetMachine ())
+    {
+        case llvm::Triple::x86:
+        case llvm::Triple::x86_64:
+            actual_opcode_size = static_cast<uint32_t> (sizeof(g_i386_opcode));
+            return Error ();
+
+        case llvm::Triple::arm:
+        case llvm::Triple::aarch64:
+        case llvm::Triple::mips64:
+        case llvm::Triple::mips64el:
+        case llvm::Triple::mips:
+        case llvm::Triple::mipsel:
+            // On these architectures the PC don't get updated for breakpoint hits
+            actual_opcode_size = 0;
+            return Error ();
+        
+        default:
+            assert(false && "CPU type not supported!");
+            return Error ("CPU type not supported");
+    }
+}
+
+Error
+NativeProcessLinux::SetBreakpoint (lldb::addr_t addr, uint32_t size, bool hardware)
+{
+    if (hardware)
+        return Error ("NativeProcessLinux does not support hardware breakpoints");
+    else
+        return SetSoftwareBreakpoint (addr, size);
+}
+
+Error
+NativeProcessLinux::GetSoftwareBreakpointTrapOpcode (size_t trap_opcode_size_hint,
+                                                     size_t &actual_opcode_size,
+                                                     const uint8_t *&trap_opcode_bytes)
+{
+    // FIXME put this behind a breakpoint protocol class that can be set per
+    // architecture.  Need MIPS support here.
+    static const uint8_t g_aarch64_opcode[] = { 0x00, 0x00, 0x20, 0xd4 };
+    // The ARM reference recommends the use of 0xe7fddefe and 0xdefe but the
+    // linux kernel does otherwise.
+    static const uint8_t g_arm_breakpoint_opcode[] = { 0xf0, 0x01, 0xf0, 0xe7 };
+    static const uint8_t g_i386_opcode [] = { 0xCC };
+    static const uint8_t g_mips64_opcode[] = { 0x00, 0x00, 0x00, 0x0d };
+    static const uint8_t g_mips64el_opcode[] = { 0x0d, 0x00, 0x00, 0x00 };
+    static const uint8_t g_thumb_breakpoint_opcode[] = { 0x01, 0xde };
+
+    switch (m_arch.GetMachine ())
+    {
+    case llvm::Triple::aarch64:
+        trap_opcode_bytes = g_aarch64_opcode;
+        actual_opcode_size = sizeof(g_aarch64_opcode);
+        return Error ();
+
+    case llvm::Triple::arm:
+        switch (trap_opcode_size_hint)
+        {
+        case 2:
+            trap_opcode_bytes = g_thumb_breakpoint_opcode;
+            actual_opcode_size = sizeof(g_thumb_breakpoint_opcode);
+            return Error ();
+        case 4:
+            trap_opcode_bytes = g_arm_breakpoint_opcode;
+            actual_opcode_size = sizeof(g_arm_breakpoint_opcode);
+            return Error ();
+        default:
+            assert(false && "Unrecognised trap opcode size hint!");
+            return Error ("Unrecognised trap opcode size hint!");
+        }
+
+    case llvm::Triple::x86:
+    case llvm::Triple::x86_64:
+        trap_opcode_bytes = g_i386_opcode;
+        actual_opcode_size = sizeof(g_i386_opcode);
+        return Error ();
+
+    case llvm::Triple::mips:
+    case llvm::Triple::mips64:
+        trap_opcode_bytes = g_mips64_opcode;
+        actual_opcode_size = sizeof(g_mips64_opcode);
+        return Error ();
+
+    case llvm::Triple::mipsel:
+    case llvm::Triple::mips64el:
+        trap_opcode_bytes = g_mips64el_opcode;
+        actual_opcode_size = sizeof(g_mips64el_opcode);
+        return Error ();
+
+    default:
+        assert(false && "CPU type not supported!");
+        return Error ("CPU type not supported");
+    }
+}
+
+#if 0
+ProcessMessage::CrashReason
+NativeProcessLinux::GetCrashReasonForSIGSEGV(const siginfo_t *info)
+{
+    ProcessMessage::CrashReason reason;
+    assert(info->si_signo == SIGSEGV);
+
+    reason = ProcessMessage::eInvalidCrashReason;
+
+    switch (info->si_code)
+    {
+    default:
+        assert(false && "unexpected si_code for SIGSEGV");
+        break;
+    case SI_KERNEL:
+        // Linux will occasionally send spurious SI_KERNEL codes.
+        // (this is poorly documented in sigaction)
+        // One way to get this is via unaligned SIMD loads.
+        reason = ProcessMessage::eInvalidAddress; // for lack of anything better
+        break;
+    case SEGV_MAPERR:
+        reason = ProcessMessage::eInvalidAddress;
+        break;
+    case SEGV_ACCERR:
+        reason = ProcessMessage::ePrivilegedAddress;
+        break;
+    }
+
+    return reason;
+}
+#endif
+
+
+#if 0
+ProcessMessage::CrashReason
+NativeProcessLinux::GetCrashReasonForSIGILL(const siginfo_t *info)
+{
+    ProcessMessage::CrashReason reason;
+    assert(info->si_signo == SIGILL);
+
+    reason = ProcessMessage::eInvalidCrashReason;
+
+    switch (info->si_code)
+    {
+    default:
+        assert(false && "unexpected si_code for SIGILL");
+        break;
+    case ILL_ILLOPC:
+        reason = ProcessMessage::eIllegalOpcode;
+        break;
+    case ILL_ILLOPN:
+        reason = ProcessMessage::eIllegalOperand;
+        break;
+    case ILL_ILLADR:
+        reason = ProcessMessage::eIllegalAddressingMode;
+        break;
+    case ILL_ILLTRP:
+        reason = ProcessMessage::eIllegalTrap;
+        break;
+    case ILL_PRVOPC:
+        reason = ProcessMessage::ePrivilegedOpcode;
+        break;
+    case ILL_PRVREG:
+        reason = ProcessMessage::ePrivilegedRegister;
+        break;
+    case ILL_COPROC:
+        reason = ProcessMessage::eCoprocessorError;
+        break;
+    case ILL_BADSTK:
+        reason = ProcessMessage::eInternalStackError;
+        break;
+    }
+
+    return reason;
+}
+#endif
+
+#if 0
+ProcessMessage::CrashReason
+NativeProcessLinux::GetCrashReasonForSIGFPE(const siginfo_t *info)
+{
+    ProcessMessage::CrashReason reason;
+    assert(info->si_signo == SIGFPE);
+
+    reason = ProcessMessage::eInvalidCrashReason;
+
+    switch (info->si_code)
+    {
+    default:
+        assert(false && "unexpected si_code for SIGFPE");
+        break;
+    case FPE_INTDIV:
+        reason = ProcessMessage::eIntegerDivideByZero;
+        break;
+    case FPE_INTOVF:
+        reason = ProcessMessage::eIntegerOverflow;
+        break;
+    case FPE_FLTDIV:
+        reason = ProcessMessage::eFloatDivideByZero;
+        break;
+    case FPE_FLTOVF:
+        reason = ProcessMessage::eFloatOverflow;
+        break;
+    case FPE_FLTUND:
+        reason = ProcessMessage::eFloatUnderflow;
+        break;
+    case FPE_FLTRES:
+        reason = ProcessMessage::eFloatInexactResult;
+        break;
+    case FPE_FLTINV:
+        reason = ProcessMessage::eFloatInvalidOperation;
+        break;
+    case FPE_FLTSUB:
+        reason = ProcessMessage::eFloatSubscriptRange;
+        break;
+    }
+
+    return reason;
+}
+#endif
+
+#if 0
+ProcessMessage::CrashReason
+NativeProcessLinux::GetCrashReasonForSIGBUS(const siginfo_t *info)
+{
+    ProcessMessage::CrashReason reason;
+    assert(info->si_signo == SIGBUS);
+
+    reason = ProcessMessage::eInvalidCrashReason;
+
+    switch (info->si_code)
+    {
+    default:
+        assert(false && "unexpected si_code for SIGBUS");
+        break;
+    case BUS_ADRALN:
+        reason = ProcessMessage::eIllegalAlignment;
+        break;
+    case BUS_ADRERR:
+        reason = ProcessMessage::eIllegalAddress;
+        break;
+    case BUS_OBJERR:
+        reason = ProcessMessage::eHardwareError;
+        break;
+    }
+
+    return reason;
+}
+#endif
+
+Error
+NativeProcessLinux::ReadMemory (lldb::addr_t addr, void *buf, size_t size, size_t &bytes_read)
+{
+    if (ProcessVmReadvSupported()) {
+        // The process_vm_readv path is about 50 times faster than ptrace api. We want to use
+        // this syscall if it is supported.
+
+        const ::pid_t pid = GetID();
+
+        struct iovec local_iov, remote_iov;
+        local_iov.iov_base = buf;
+        local_iov.iov_len = size;
+        remote_iov.iov_base = reinterpret_cast<void *>(addr);
+        remote_iov.iov_len = size;
+
+        bytes_read = process_vm_readv(pid, &local_iov, 1, &remote_iov, 1, 0);
+        const bool success = bytes_read == size;
+
+        Log *log(GetLogIfAllCategoriesSet (LIBLLDB_LOG_PROCESS));
+        if (log)
+            log->Printf ("NativeProcessLinux::%s using process_vm_readv to read %zd bytes from inferior address 0x%" PRIx64": %s",
+                    __FUNCTION__, size, addr, success ? "Success" : strerror(errno));
+
+        if (success)
+            return Error();
+        // else
+        //     the call failed for some reason, let's retry the read using ptrace api.
+    }
+
+    unsigned char *dst = static_cast<unsigned char*>(buf);
+    size_t remainder;
+    long data;
+
+    Log *log (ProcessPOSIXLog::GetLogIfAllCategoriesSet (POSIX_LOG_ALL));
+    if (log)
+        ProcessPOSIXLog::IncNestLevel();
+    if (log && ProcessPOSIXLog::AtTopNestLevel() && log->GetMask().Test(POSIX_LOG_MEMORY))
+        log->Printf ("NativeProcessLinux::%s(%p, %p, %zd, _)", __FUNCTION__, (void*)addr, buf, size);
+
+    for (bytes_read = 0; bytes_read < size; bytes_read += remainder)
+    {
+        Error error = NativeProcessLinux::PtraceWrapper(PTRACE_PEEKDATA, GetID(), (void*)addr, nullptr, 0, &data);
+        if (error.Fail())
+        {
+            if (log)
+                ProcessPOSIXLog::DecNestLevel();
+            return error;
+        }
+
+        remainder = size - bytes_read;
+        remainder = remainder > k_ptrace_word_size ? k_ptrace_word_size : remainder;
+
+        // Copy the data into our buffer
+        memcpy(dst, &data, remainder);
+
+        if (log && ProcessPOSIXLog::AtTopNestLevel() &&
+                (log->GetMask().Test(POSIX_LOG_MEMORY_DATA_LONG) ||
+                        (log->GetMask().Test(POSIX_LOG_MEMORY_DATA_SHORT) &&
+                                size <= POSIX_LOG_MEMORY_SHORT_BYTES)))
+        {
+            uintptr_t print_dst = 0;
+            // Format bytes from data by moving into print_dst for log output
+            for (unsigned i = 0; i < remainder; ++i)
+                print_dst |= (((data >> i*8) & 0xFF) << i*8);
+            log->Printf ("NativeProcessLinux::%s() [0x%" PRIx64 "]:0x%" PRIx64 " (0x%" PRIx64 ")",
+                    __FUNCTION__, addr, uint64_t(print_dst), uint64_t(data));
+        }
+        addr += k_ptrace_word_size;
+        dst += k_ptrace_word_size;
+    }
+
+    if (log)
+        ProcessPOSIXLog::DecNestLevel();
+    return Error();
+}
+
+Error
+NativeProcessLinux::ReadMemoryWithoutTrap(lldb::addr_t addr, void *buf, size_t size, size_t &bytes_read)
+{
+    Error error = ReadMemory(addr, buf, size, bytes_read);
+    if (error.Fail()) return error;
+    return m_breakpoint_list.RemoveTrapsFromBuffer(addr, buf, size);
+}
+
+Error
+NativeProcessLinux::WriteMemory(lldb::addr_t addr, const void *buf, size_t size, size_t &bytes_written)
+{
+    const unsigned char *src = static_cast<const unsigned char*>(buf);
+    size_t remainder;
+    Error error;
+
+    Log *log (ProcessPOSIXLog::GetLogIfAllCategoriesSet (POSIX_LOG_ALL));
+    if (log)
+        ProcessPOSIXLog::IncNestLevel();
+    if (log && ProcessPOSIXLog::AtTopNestLevel() && log->GetMask().Test(POSIX_LOG_MEMORY))
+        log->Printf ("NativeProcessLinux::%s(0x%" PRIx64 ", %p, %zu)", __FUNCTION__, addr, buf, size);
+
+    for (bytes_written = 0; bytes_written < size; bytes_written += remainder)
+    {
+        remainder = size - bytes_written;
+        remainder = remainder > k_ptrace_word_size ? k_ptrace_word_size : remainder;
+
+        if (remainder == k_ptrace_word_size)
+        {
+            unsigned long data = 0;
+            memcpy(&data, src, k_ptrace_word_size);
+
+            if (log && ProcessPOSIXLog::AtTopNestLevel() &&
+                    (log->GetMask().Test(POSIX_LOG_MEMORY_DATA_LONG) ||
+                            (log->GetMask().Test(POSIX_LOG_MEMORY_DATA_SHORT) &&
+                                    size <= POSIX_LOG_MEMORY_SHORT_BYTES)))
+                log->Printf ("NativeProcessLinux::%s() [%p]:0x%lx (0x%lx)", __FUNCTION__,
+                        (void*)addr, *(const unsigned long*)src, data);
+
+            error = NativeProcessLinux::PtraceWrapper(PTRACE_POKEDATA, GetID(), (void*)addr, (void*)data);
+            if (error.Fail())
+            {
+                if (log)
+                    ProcessPOSIXLog::DecNestLevel();
+                return error;
+            }
+        }
+        else
+        {
+            unsigned char buff[8];
+            size_t bytes_read;
+            error = ReadMemory(addr, buff, k_ptrace_word_size, bytes_read);
+            if (error.Fail())
+            {
+                if (log)
+                    ProcessPOSIXLog::DecNestLevel();
+                return error;
+            }
+
+            memcpy(buff, src, remainder);
+
+            size_t bytes_written_rec;
+            error = WriteMemory(addr, buff, k_ptrace_word_size, bytes_written_rec);
+            if (error.Fail())
+            {
+                if (log)
+                    ProcessPOSIXLog::DecNestLevel();
+                return error;
+            }
+
+            if (log && ProcessPOSIXLog::AtTopNestLevel() &&
+                    (log->GetMask().Test(POSIX_LOG_MEMORY_DATA_LONG) ||
+                            (log->GetMask().Test(POSIX_LOG_MEMORY_DATA_SHORT) &&
+                                    size <= POSIX_LOG_MEMORY_SHORT_BYTES)))
+                log->Printf ("NativeProcessLinux::%s() [%p]:0x%lx (0x%lx)", __FUNCTION__,
+                        (void*)addr, *(const unsigned long*)src, *(unsigned long*)buff);
+        }
+
+        addr += k_ptrace_word_size;
+        src += k_ptrace_word_size;
+    }
+    if (log)
+        ProcessPOSIXLog::DecNestLevel();
+    return error;
+}
+
+Error
+NativeProcessLinux::Resume (lldb::tid_t tid, uint32_t signo)
+{
+    Log *log (GetLogIfAllCategoriesSet (LIBLLDB_LOG_PROCESS));
+
+    if (log)
+        log->Printf ("NativeProcessLinux::%s() resuming thread = %"  PRIu64 " with signal %s", __FUNCTION__, tid,
+                                 Host::GetSignalAsCString(signo));
+
+
+
+    intptr_t data = 0;
+
+    if (signo != LLDB_INVALID_SIGNAL_NUMBER)
+        data = signo;
+
+    Error error = PtraceWrapper(PTRACE_CONT, tid, nullptr, (void*)data);
+
+    if (log)
+        log->Printf ("NativeProcessLinux::%s() resuming thread = %"  PRIu64 " result = %s", __FUNCTION__, tid, error.Success() ? "true" : "false");
+    return error;
+}
+
+Error
+NativeProcessLinux::SingleStep(lldb::tid_t tid, uint32_t signo)
+{
+    intptr_t data = 0;
+
+    if (signo != LLDB_INVALID_SIGNAL_NUMBER)
+        data = signo;
+
+    // If hardware single-stepping is not supported, we just do a continue. The breakpoint on the
+    // next instruction has been setup in NativeProcessLinux::Resume.
+    return PtraceWrapper(SupportHardwareSingleStepping() ? PTRACE_SINGLESTEP : PTRACE_CONT,
+            tid, nullptr, (void*)data);
+}
+
+Error
+NativeProcessLinux::GetSignalInfo(lldb::tid_t tid, void *siginfo)
+{
+    return PtraceWrapper(PTRACE_GETSIGINFO, tid, nullptr, siginfo);
+}
+
+Error
+NativeProcessLinux::GetEventMessage(lldb::tid_t tid, unsigned long *message)
+{
+    return PtraceWrapper(PTRACE_GETEVENTMSG, tid, nullptr, message);
+}
+
+Error
+NativeProcessLinux::Detach(lldb::tid_t tid)
+{
+    if (tid == LLDB_INVALID_THREAD_ID)
+        return Error();
+
+    return PtraceWrapper(PTRACE_DETACH, tid);
+}
+
+bool
+NativeProcessLinux::DupDescriptor(const FileSpec &file_spec, int fd, int flags)
+{
+    int target_fd = open(file_spec.GetCString(), flags, 0666);
+
+    if (target_fd == -1)
+        return false;
+
+    if (dup2(target_fd, fd) == -1)
+        return false;
+
+    return (close(target_fd) == -1) ? false : true;
+}
+
+bool
+NativeProcessLinux::HasThreadNoLock (lldb::tid_t thread_id)
+{
+    for (auto thread_sp : m_threads)
+    {
+        assert (thread_sp && "thread list should not contain NULL threads");
+        if (thread_sp->GetID () == thread_id)
+        {
+            // We have this thread.
+            return true;
+        }
+    }
+
+    // We don't have this thread.
+    return false;
+}
+
+bool
+NativeProcessLinux::StopTrackingThread (lldb::tid_t thread_id)
+{
+    Log *const log = GetLogIfAllCategoriesSet (LIBLLDB_LOG_THREAD);
+
+    if (log)
+        log->Printf("NativeProcessLinux::%s (tid: %" PRIu64 ")", __FUNCTION__, thread_id);
+
+    bool found = false;
+
+    Mutex::Locker locker (m_threads_mutex);
+    for (auto it = m_threads.begin (); it != m_threads.end (); ++it)
+    {
+        if (*it && ((*it)->GetID () == thread_id))
+        {
+            m_threads.erase (it);
+            found = true;
+            break;
+        }
+    }
+
+    SignalIfAllThreadsStopped();
+
+    return found;
+}
+
+NativeThreadLinuxSP
+NativeProcessLinux::AddThread (lldb::tid_t thread_id)
+{
+    Log *log (GetLogIfAllCategoriesSet (LIBLLDB_LOG_THREAD));
+
+    Mutex::Locker locker (m_threads_mutex);
+
+    if (log)
+    {
+        log->Printf ("NativeProcessLinux::%s pid %" PRIu64 " adding thread with tid %" PRIu64,
+                __FUNCTION__,
+                GetID (),
+                thread_id);
+    }
+
+    assert (!HasThreadNoLock (thread_id) && "attempted to add a thread by id that already exists");
+
+    // If this is the first thread, save it as the current thread
+    if (m_threads.empty ())
+        SetCurrentThreadID (thread_id);
+
+    auto thread_sp = std::make_shared<NativeThreadLinux>(this, thread_id);
+    m_threads.push_back (thread_sp);
+    return thread_sp;
+}
+
+Error
+NativeProcessLinux::FixupBreakpointPCAsNeeded(NativeThreadLinux &thread)
+{
+    Log *log (GetLogIfAllCategoriesSet (LIBLLDB_LOG_BREAKPOINTS));
+
+    Error error;
+
+    // Find out the size of a breakpoint (might depend on where we are in the code).
+    NativeRegisterContextSP context_sp = thread.GetRegisterContext();
+    if (!context_sp)
+    {
+        error.SetErrorString ("cannot get a NativeRegisterContext for the thread");
+        if (log)
+            log->Printf ("NativeProcessLinux::%s failed: %s", __FUNCTION__, error.AsCString ());
+        return error;
+    }
+
+    uint32_t breakpoint_size = 0;
+    error = GetSoftwareBreakpointPCOffset(breakpoint_size);
+    if (error.Fail ())
+    {
+        if (log)
+            log->Printf ("NativeProcessLinux::%s GetBreakpointSize() failed: %s", __FUNCTION__, error.AsCString ());
+        return error;
+    }
+    else
+    {
+        if (log)
+            log->Printf ("NativeProcessLinux::%s breakpoint size: %" PRIu32, __FUNCTION__, breakpoint_size);
+    }
+
+    // First try probing for a breakpoint at a software breakpoint location: PC - breakpoint size.
+    const lldb::addr_t initial_pc_addr = context_sp->GetPCfromBreakpointLocation ();
+    lldb::addr_t breakpoint_addr = initial_pc_addr;
+    if (breakpoint_size > 0)
+    {
+        // Do not allow breakpoint probe to wrap around.
+        if (breakpoint_addr >= breakpoint_size)
+            breakpoint_addr -= breakpoint_size;
+    }
+
+    // Check if we stopped because of a breakpoint.
+    NativeBreakpointSP breakpoint_sp;
+    error = m_breakpoint_list.GetBreakpoint (breakpoint_addr, breakpoint_sp);
+    if (!error.Success () || !breakpoint_sp)
+    {
+        // We didn't find one at a software probe location.  Nothing to do.
+        if (log)
+            log->Printf ("NativeProcessLinux::%s pid %" PRIu64 " no lldb breakpoint found at current pc with adjustment: 0x%" PRIx64, __FUNCTION__, GetID (), breakpoint_addr);
+        return Error ();
+    }
+
+    // If the breakpoint is not a software breakpoint, nothing to do.
+    if (!breakpoint_sp->IsSoftwareBreakpoint ())
+    {
+        if (log)
+            log->Printf ("NativeProcessLinux::%s pid %" PRIu64 " breakpoint found at 0x%" PRIx64 ", not software, nothing to adjust", __FUNCTION__, GetID (), breakpoint_addr);
+        return Error ();
+    }
+
+    //
+    // We have a software breakpoint and need to adjust the PC.
+    //
+
+    // Sanity check.
+    if (breakpoint_size == 0)
+    {
+        // Nothing to do!  How did we get here?
+        if (log)
+            log->Printf ("NativeProcessLinux::%s pid %" PRIu64 " breakpoint found at 0x%" PRIx64 ", it is software, but the size is zero, nothing to do (unexpected)", __FUNCTION__, GetID (), breakpoint_addr);
+        return Error ();
+    }
+
+    // Change the program counter.
+    if (log)
+        log->Printf ("NativeProcessLinux::%s pid %" PRIu64 " tid %" PRIu64 ": changing PC from 0x%" PRIx64 " to 0x%" PRIx64, __FUNCTION__, GetID(), thread.GetID(), initial_pc_addr, breakpoint_addr);
+
+    error = context_sp->SetPC (breakpoint_addr);
+    if (error.Fail ())
+    {
+        if (log)
+            log->Printf ("NativeProcessLinux::%s pid %" PRIu64 " tid %" PRIu64 ": failed to set PC: %s", __FUNCTION__, GetID(), thread.GetID(), error.AsCString ());
+        return error;
+    }
+
+    return error;
+}
+
+Error
+NativeProcessLinux::GetLoadedModuleFileSpec(const char* module_path, FileSpec& file_spec)
+{
+    FileSpec module_file_spec(module_path, true);
+
+    bool found = false;
+    file_spec.Clear();
+    ProcFileReader::ProcessLineByLine(GetID(), "maps",
+        [&] (const std::string &line)
+        {
+            SmallVector<StringRef, 16> columns;
+            StringRef(line).split(columns, " ", -1, false);
+            if (columns.size() < 6)
+                return true; // continue searching
+
+            FileSpec this_file_spec(columns[5].str().c_str(), false);
+            if (this_file_spec.GetFilename() != module_file_spec.GetFilename())
+                return true; // continue searching
+
+            file_spec = this_file_spec;
+            found = true;
+            return false; // we are done
+        });
+
+    if (! found)
+        return Error("Module file (%s) not found in /proc/%" PRIu64 "/maps file!",
+                module_file_spec.GetFilename().AsCString(), GetID());
+
+    return Error();
+}
+
+Error
+NativeProcessLinux::GetFileLoadAddress(const llvm::StringRef& file_name, lldb::addr_t& load_addr)
+{
+    load_addr = LLDB_INVALID_ADDRESS;
+    Error error = ProcFileReader::ProcessLineByLine (GetID (), "maps",
+        [&] (const std::string &line) -> bool
+        {
+            StringRef maps_row(line);
+ 
+            SmallVector<StringRef, 16> maps_columns;
+            maps_row.split(maps_columns, StringRef(" "), -1, false);
+ 
+            if (maps_columns.size() < 6)
+            {
+                // Return true to continue reading the proc file
+                return true;
+            }
+
+            if (maps_columns[5] == file_name)
+            {
+                StringExtractor addr_extractor(maps_columns[0].str().c_str());
+                load_addr = addr_extractor.GetHexMaxU64(false, LLDB_INVALID_ADDRESS); 
+
+                // Return false to stop reading the proc file further
+                return false;
+            }
+ 
+            // Return true to continue reading the proc file
+            return true;
+        });
+    return error; 
+}
+
+NativeThreadLinuxSP
+NativeProcessLinux::GetThreadByID(lldb::tid_t tid)
+{
+    return std::static_pointer_cast<NativeThreadLinux>(NativeProcessProtocol::GetThreadByID(tid));
+}
+
+Error
+NativeProcessLinux::ResumeThread(NativeThreadLinux &thread, lldb::StateType state, int signo)
+{
+    Log *const log = GetLogIfAllCategoriesSet (LIBLLDB_LOG_THREAD);
+
+    if (log)
+        log->Printf("NativeProcessLinux::%s (tid: %" PRIu64 ")",
+                __FUNCTION__, thread.GetID());
+    
+    // Before we do the resume below, first check if we have a pending
+    // stop notification that is currently waiting for
+    // all threads to stop.  This is potentially a buggy situation since
+    // we're ostensibly waiting for threads to stop before we send out the
+    // pending notification, and here we are resuming one before we send
+    // out the pending stop notification.
+    if (m_pending_notification_tid != LLDB_INVALID_THREAD_ID && log)
+    {
+        log->Printf("NativeProcessLinux::%s about to resume tid %" PRIu64 " per explicit request but we have a pending stop notification (tid %" PRIu64 ") that is actively waiting for this thread to stop. Valid sequence of events?", __FUNCTION__, thread.GetID(), m_pending_notification_tid);
+    }
+
+    // Request a resume.  We expect this to be synchronous and the system
+    // to reflect it is running after this completes.
+    switch (state)
+    {
+    case eStateRunning:
+    {
+        thread.SetRunning();
+        const auto resume_result = Resume(thread.GetID(), signo);
+        if (resume_result.Success())
+            SetState(eStateRunning, true);
+        return resume_result;
+    }
+    case eStateStepping:
+    {
+        thread.SetStepping();
+        const auto step_result = SingleStep(thread.GetID(), signo);
+        if (step_result.Success())
+            SetState(eStateRunning, true);
+        return step_result;
+    }
+    default:
+        if (log)
+            log->Printf("NativeProcessLinux::%s Unhandled state %s.",
+                    __FUNCTION__, StateAsCString(state));
+        llvm_unreachable("Unhandled state for resume");
+    }
+}
+
+//===----------------------------------------------------------------------===//
+
+void
+NativeProcessLinux::StopRunningThreads(const lldb::tid_t triggering_tid)
+{
+    Log *const log = GetLogIfAllCategoriesSet (LIBLLDB_LOG_THREAD);
+
+    if (log)
+    {
+        log->Printf("NativeProcessLinux::%s about to process event: (triggering_tid: %" PRIu64 ")",
+                __FUNCTION__, triggering_tid);
+    }
+
+    m_pending_notification_tid = triggering_tid;
+
+    // Request a stop for all the thread stops that need to be stopped
+    // and are not already known to be stopped.
+    for (const auto &thread_sp: m_threads)
+    {
+        if (StateIsRunningState(thread_sp->GetState()))
+            static_pointer_cast<NativeThreadLinux>(thread_sp)->RequestStop();
+    }
+
+    SignalIfAllThreadsStopped();
+
+    if (log)
+    {
+        log->Printf("NativeProcessLinux::%s event processing done", __FUNCTION__);
+    }
+}
+
+void
+NativeProcessLinux::SignalIfAllThreadsStopped()
+{
+    if (m_pending_notification_tid == LLDB_INVALID_THREAD_ID)
+        return; // No pending notification. Nothing to do.
+
+    for (const auto &thread_sp: m_threads)
+    {
+        if (StateIsRunningState(thread_sp->GetState()))
+            return; // Some threads are still running. Don't signal yet.
+    }
+
+    // We have a pending notification and all threads have stopped.
+    Log *log(GetLogIfAnyCategoriesSet(LIBLLDB_LOG_PROCESS | LIBLLDB_LOG_BREAKPOINTS));
+
+    // Clear any temporary breakpoints we used to implement software single stepping.
+    for (const auto &thread_info: m_threads_stepping_with_breakpoint)
+    {
+        Error error = RemoveBreakpoint (thread_info.second);
+        if (error.Fail())
+            if (log)
+                log->Printf("NativeProcessLinux::%s() pid = %" PRIu64 " remove stepping breakpoint: %s",
+                        __FUNCTION__, thread_info.first, error.AsCString());
+    }
+    m_threads_stepping_with_breakpoint.clear();
+
+    // Notify the delegate about the stop
+    SetCurrentThreadID(m_pending_notification_tid);
+    SetState(StateType::eStateStopped, true);
+    m_pending_notification_tid = LLDB_INVALID_THREAD_ID;
+}
+
+void
+NativeProcessLinux::ThreadWasCreated(NativeThreadLinux &thread)
+{
+    Log *const log = GetLogIfAllCategoriesSet (LIBLLDB_LOG_THREAD);
+
+    if (log)
+        log->Printf("NativeProcessLinux::%s (tid: %" PRIu64 ")", __FUNCTION__, thread.GetID());
+
+    if (m_pending_notification_tid != LLDB_INVALID_THREAD_ID && StateIsRunningState(thread.GetState()))
+    {
+        // We will need to wait for this new thread to stop as well before firing the
+        // notification.
+        thread.RequestStop();
+    }
+}
+
+void
+NativeProcessLinux::SigchldHandler()
+{
+    Log *log(GetLogIfAllCategoriesSet(LIBLLDB_LOG_PROCESS));
+    // Process all pending waitpid notifications.
+    while (true)
+    {
+        int status = -1;
+        ::pid_t wait_pid = waitpid(-1, &status, __WALL | __WNOTHREAD | WNOHANG);
+
+        if (wait_pid == 0)
+            break; // We are done.
+
+        if (wait_pid == -1)
+        {
+            if (errno == EINTR)
+                continue;
+
+            Error error(errno, eErrorTypePOSIX);
+            if (log)
+                log->Printf("NativeProcessLinux::%s waitpid (-1, &status, __WALL | __WNOTHREAD | WNOHANG) failed: %s",
+                        __FUNCTION__, error.AsCString());
+            break;
+        }
+
+        bool exited = false;
+        int signal = 0;
+        int exit_status = 0;
+        const char *status_cstr = nullptr;
+        if (WIFSTOPPED(status))
+        {
+            signal = WSTOPSIG(status);
+            status_cstr = "STOPPED";
+        }
+        else if (WIFEXITED(status))
+        {
+            exit_status = WEXITSTATUS(status);
+            status_cstr = "EXITED";
+            exited = true;
+        }
+        else if (WIFSIGNALED(status))
+        {
+            signal = WTERMSIG(status);
+            status_cstr = "SIGNALED";
+            if (wait_pid == static_cast< ::pid_t>(GetID())) {
+                exited = true;
+                exit_status = -1;
+            }
+        }
+        else
+            status_cstr = "(\?\?\?)";
+
+        if (log)
+            log->Printf("NativeProcessLinux::%s: waitpid (-1, &status, __WALL | __WNOTHREAD | WNOHANG)"
+                "=> pid = %" PRIi32 ", status = 0x%8.8x (%s), signal = %i, exit_state = %i",
+                __FUNCTION__, wait_pid, status, status_cstr, signal, exit_status);
+
+        MonitorCallback (wait_pid, exited, signal, exit_status);
+    }
+}
+
+// Wrapper for ptrace to catch errors and log calls.
+// Note that ptrace sets errno on error because -1 can be a valid result (i.e. for PTRACE_PEEK*)
+Error
+NativeProcessLinux::PtraceWrapper(int req, lldb::pid_t pid, void *addr, void *data, size_t data_size, long *result)
+{
+    Error error;
+    long int ret;
+
+    Log *log (ProcessPOSIXLog::GetLogIfAllCategoriesSet (POSIX_LOG_PTRACE));
+
+    PtraceDisplayBytes(req, data, data_size);
+
+    errno = 0;
+    if (req == PTRACE_GETREGSET || req == PTRACE_SETREGSET)
+        ret = ptrace(static_cast<__ptrace_request>(req), static_cast< ::pid_t>(pid), *(unsigned int *)addr, data);
+    else
+        ret = ptrace(static_cast<__ptrace_request>(req), static_cast< ::pid_t>(pid), addr, data);
+
+    if (ret == -1)
+        error.SetErrorToErrno();
+
+    if (result)
+        *result = ret;
+
+    if (log)
+        log->Printf("ptrace(%d, %" PRIu64 ", %p, %p, %zu)=%lX", req, pid, addr, data, data_size, ret);
+
+    PtraceDisplayBytes(req, data, data_size);
+
+    if (log && error.GetError() != 0)
+    {
+        const char* str;
+        switch (error.GetError())
+        {
+        case ESRCH:  str = "ESRCH"; break;
+        case EINVAL: str = "EINVAL"; break;
+        case EBUSY:  str = "EBUSY"; break;
+        case EPERM:  str = "EPERM"; break;
+        default:     str = error.AsCString();
+        }
+        log->Printf("ptrace() failed; errno=%d (%s)", error.GetError(), str);
+    }
+
+    return error;
+}