1 files changed, 133 insertions, 0 deletions
diff --git a/lib/esan/working_set_posix.cpp b/lib/esan/working_set_posix.cpp
new file mode 100644
index 0000000000000..fcfa87128857f
--- /dev/null
+++ b/lib/esan/working_set_posix.cpp
@@ -0,0 +1,133 @@
+//===-- working_set_posix.cpp -----------------------------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file is a part of EfficiencySanitizer, a family of performance tuners.
+//
+// POSIX-specific working set tool code.
+//===----------------------------------------------------------------------===//
+
+#include "working_set.h"
+#include "esan_flags.h"
+#include "esan_shadow.h"
+#include "sanitizer_common/sanitizer_common.h"
+#include "sanitizer_common/sanitizer_linux.h"
+#include <signal.h>
+#include <sys/mman.h>
+
+namespace __esan {
+
+// We only support regular POSIX threads with a single signal handler
+// for the whole process == thread group.
+// Thus we only need to store one app signal handler.
+// FIXME: Store and use any alternate stack and signal flags set by
+// the app.  For now we just call the app handler from our handler.
+static __sanitizer_sigaction AppSigAct;
+
+bool processWorkingSetSignal(int SigNum, void (*Handler)(int),
+                             void (**Result)(int)) {
+  VPrintf(2, "%s: %d\n", __FUNCTION__, SigNum);
+  if (SigNum == SIGSEGV) {
+    *Result = AppSigAct.handler;
+    AppSigAct.sigaction = (void (*)(int, void*, void*))Handler;
+    return false; // Skip real call.
+  }
+  return true;
+}
+
+bool processWorkingSetSigaction(int SigNum, const void *ActVoid,
+                                void *OldActVoid) {
+  VPrintf(2, "%s: %d\n", __FUNCTION__, SigNum);
+  if (SigNum == SIGSEGV) {
+    const struct sigaction *Act = (const struct sigaction *) ActVoid;
+    struct sigaction *OldAct = (struct sigaction *) OldActVoid;
+    if (OldAct)
+      internal_memcpy(OldAct, &AppSigAct, sizeof(OldAct));
+    if (Act)
+      internal_memcpy(&AppSigAct, Act, sizeof(AppSigAct));
+    return false; // Skip real call.
+  }
+  return true;
+}
+
+bool processWorkingSetSigprocmask(int How, void *Set, void *OldSet) {
+  VPrintf(2, "%s\n", __FUNCTION__);
+  // All we need to do is ensure that SIGSEGV is not blocked.
+  // FIXME: we are not fully transparent as we do not pretend that
+  // SIGSEGV is still blocked on app queries: that would require
+  // per-thread mask tracking.
+  if (Set && (How == SIG_BLOCK || How == SIG_SETMASK)) {
+    if (internal_sigismember((__sanitizer_sigset_t *)Set, SIGSEGV)) {
+      VPrintf(1, "%s: removing SIGSEGV from the blocked set\n", __FUNCTION__);
+      internal_sigdelset((__sanitizer_sigset_t *)Set, SIGSEGV);
+    }
+  }
+  return true;
+}
+
+static void reinstateDefaultHandler(int SigNum) {
+  __sanitizer_sigaction SigAct;
+  internal_memset(&SigAct, 0, sizeof(SigAct));
+  SigAct.sigaction = (void (*)(int, void*, void*)) SIG_DFL;
+  int Res = internal_sigaction(SigNum, &SigAct, nullptr);
+  CHECK(Res == 0);
+  VPrintf(1, "Unregistered for %d handler\n", SigNum);
+}
+
+// If this is a shadow fault, we handle it here; otherwise, we pass it to the
+// app to handle it just as the app would do without our tool in place.
+static void handleMemoryFault(int SigNum, void *Info, void *Ctx) {
+  if (SigNum == SIGSEGV) {
+    // We rely on si_addr being filled in (thus we do not support old kernels).
+    siginfo_t *SigInfo = (siginfo_t *)Info;
+    uptr Addr = (uptr)SigInfo->si_addr;
+    if (isShadowMem(Addr)) {
+      VPrintf(3, "Shadow fault @%p\n", Addr);
+      uptr PageSize = GetPageSizeCached();
+      int Res = internal_mprotect((void *)RoundDownTo(Addr, PageSize),
+                                  PageSize, PROT_READ|PROT_WRITE);
+      CHECK(Res == 0);
+    } else if (AppSigAct.sigaction) {
+      // FIXME: For simplicity we ignore app options including its signal stack
+      // (we just use ours) and all the delivery flags.
+      AppSigAct.sigaction(SigNum, Info, Ctx);
+    } else {
+      // Crash instead of spinning with infinite faults.
+      reinstateDefaultHandler(SigNum);
+    }
+  } else
+    UNREACHABLE("signal not registered");
+}
+
+void registerMemoryFaultHandler() {
+  // We do not use an alternate signal stack, as doing so would require
+  // setting it up for each app thread.
+  // FIXME: This could result in problems with emulating the app's signal
+  // handling if the app relies on an alternate stack for SIGSEGV.
+
+  // We require that SIGSEGV is not blocked.  We use a sigprocmask
+  // interceptor to ensure that in the future.  Here we ensure it for
+  // the current thread.  We assume there are no other threads at this
+  // point during initialization, or that at least they do not block
+  // SIGSEGV.
+  __sanitizer_sigset_t SigSet;
+  internal_sigemptyset(&SigSet);
+  internal_sigprocmask(SIG_BLOCK, &SigSet, nullptr);
+
+  __sanitizer_sigaction SigAct;
+  internal_memset(&SigAct, 0, sizeof(SigAct));
+  SigAct.sigaction = handleMemoryFault;
+  // We want to handle nested signals b/c we need to handle a
+  // shadow fault in an app signal handler.
+  SigAct.sa_flags = SA_SIGINFO | SA_NODEFER;
+  int Res = internal_sigaction(SIGSEGV, &SigAct, &AppSigAct);
+  CHECK(Res == 0);
+  VPrintf(1, "Registered for SIGSEGV handler\n");
+}
+
+} // namespace __esan