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Diffstat (limited to 'sys/dev/hwt/hwt.c')
| -rw-r--r-- | sys/dev/hwt/hwt.c | 242 |
1 files changed, 242 insertions, 0 deletions
diff --git a/sys/dev/hwt/hwt.c b/sys/dev/hwt/hwt.c new file mode 100644 index 000000000000..c476e6031ba8 --- /dev/null +++ b/sys/dev/hwt/hwt.c @@ -0,0 +1,242 @@ +/*- + * SPDX-License-Identifier: BSD-2-Clause + * + * Copyright (c) 2023-2025 Ruslan Bukin <br@bsdpad.com> + * + * This work was supported by Innovate UK project 105694, "Digital Security + * by Design (DSbD) Technology Platform Prototype". + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions + * are met: + * 1. Redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer. + * 2. Redistributions in binary form must reproduce the above copyright + * notice, this list of conditions and the following disclaimer in the + * documentation and/or other materials provided with the distribution. + * + * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND + * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE + * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE + * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE + * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL + * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS + * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) + * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT + * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY + * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF + * SUCH DAMAGE. + */ + +/* + * Hardware Tracing framework. + * + * The framework manages hardware tracing units that collect information + * about software execution and store it as events in highly compressed format + * into DRAM. The events cover information about control flow changes of a + * program, whether branches taken or not, exceptions taken, timing information, + * cycles elapsed and more. That allows us to restore entire program flow of a + * given application without performance impact. + * + * Design overview. + * + * The framework provides character devices for mmap(2) and ioctl(2) system + * calls to allow user to manage CPU (hardware) tracing units. + * + * /dev/hwt: + * .ioctl: + * hwt_ioctl(): + * a) HWT_IOC_ALLOC + * Allocates kernel tracing context CTX based on requested mode + * of operation. Verifies the information that comes with the + * request (pid, cpus), allocates unique ID for the context. + * Creates a new character device for CTX management. + * + * /dev/hwt_%d[_%d], ident[, thread_id] + * .mmap + * Maps tracing buffers of the corresponding thread to userspace. + * .ioctl + * hwt_thread_ioctl(): + * a) HWT_IOC_START + * Enables tracing unit for a given context. + * b) HWT_IOC_RECORD_GET + * Transfers (small) record entries collected during program + * execution for a given context to userspace, such as mmaping + * tables of executable and dynamic libraries, interpreter, + * kernel mappings, tid of threads created, etc. + * c) HWT_IOC_SET_CONFIG + * Allows to specify backend-specific configuration of the + * trace unit. + * d) HWT_IOC_WAKEUP + * Wakes up a thread that is currently sleeping. + * e) HWT_IOC_BUFPTR_GET + * Transfers current hardware pointer in the filling buffer + * to the userspace. + * f) HWT_IOC_SVC_BUF + * To avoid data loss, userspace may notify kernel it has + * copied out the given buffer, so kernel is ok to overwrite + * + * HWT context lifecycle in THREAD mode of operation: + * 1. User invokes HWT_IOC_ALLOC ioctl with information about pid to trace and + * size of the buffers for the trace data to allocate. + * Some architectures may have different tracing units supported, so user + * also provides backend name to use for this context, e.g. "coresight". + * 2. Kernel allocates context, lookups the proc for the given pid. Then it + * creates first hwt_thread in the context and allocates trace buffers for + * it. Immediately, kernel initializes tracing backend. + * Kernel creates character device and returns unique identificator of + * trace context to the user. + * 3. To manage the new context, user opens the character device created. + * User invokes HWT_IOC_START ioctl, kernel marks context as RUNNING. + * At this point any HWT hook invocation by scheduler enables/disables + * tracing for threads associated with the context (threads of the proc). + * Any new threads creation (of the target proc) procedures will be invoking + * corresponding hooks in HWT framework, so that new hwt_thread and buffers + * allocated, character device for mmap(2) created on the fly. + * 4. User issues HWT_IOC_RECORD_GET ioctl to fetch information about mmaping + * tables and threads created during application startup. + * 5. User mmaps tracing buffers of each thread to userspace (using + * /dev/hwt_%d_%d % (ident, thread_id) character devices). + * 6. User can repeat 4 if expected thread is not yet created during target + * application execution. + * 7. User issues HWT_IOC_BUFPTR_GET ioctl to get current filling level of the + * hardware buffer of a given thread. + * 8. User invokes trace decoder library to process available data and see the + * results in human readable form. + * 9. User repeats 7 if needed. + * + * HWT context lifecycle in CPU mode of operation: + * 1. User invokes HWT_IOC_ALLOC ioctl providing a set of CPU to trace within + * single CTX. + * 2. Kernel verifies the set of CPU and allocates tracing context, creates + * a buffer for each CPU. + * Kernel creates a character device for every CPU provided in the request. + * Kernel initialized tracing backend. + * 3. User opens character devices of interest to map the buffers to userspace. + * User can start tracing by invoking HWT_IOC_START on any of character + * device within the context, entire context will be marked as RUNNING. + * 4. The rest is similar to the THREAD mode. + * + */ + +#include <sys/param.h> +#include <sys/conf.h> +#include <sys/eventhandler.h> +#include <sys/kernel.h> +#include <sys/module.h> + +#include <dev/hwt/hwt_context.h> +#include <dev/hwt/hwt_contexthash.h> +#include <dev/hwt/hwt_thread.h> +#include <dev/hwt/hwt_owner.h> +#include <dev/hwt/hwt_ownerhash.h> +#include <dev/hwt/hwt_backend.h> +#include <dev/hwt/hwt_record.h> +#include <dev/hwt/hwt_ioctl.h> +#include <dev/hwt/hwt_hook.h> + +#define HWT_DEBUG +#undef HWT_DEBUG + +#ifdef HWT_DEBUG +#define dprintf(fmt, ...) printf(fmt, ##__VA_ARGS__) +#else +#define dprintf(fmt, ...) +#endif + +static eventhandler_tag hwt_exit_tag; +static struct cdev *hwt_cdev; +static struct cdevsw hwt_cdevsw = { + .d_version = D_VERSION, + .d_name = "hwt", + .d_mmap_single = NULL, + .d_ioctl = hwt_ioctl +}; + +static void +hwt_process_exit(void *arg __unused, struct proc *p) +{ + struct hwt_owner *ho; + + /* Stop HWTs associated with exiting owner, if any. */ + ho = hwt_ownerhash_lookup(p); + if (ho) + hwt_owner_shutdown(ho); +} + +static int +hwt_load(void) +{ + struct make_dev_args args; + int error; + + make_dev_args_init(&args); + args.mda_devsw = &hwt_cdevsw; + args.mda_flags = MAKEDEV_CHECKNAME | MAKEDEV_WAITOK; + args.mda_uid = UID_ROOT; + args.mda_gid = GID_WHEEL; + args.mda_mode = 0660; + args.mda_si_drv1 = NULL; + + hwt_backend_load(); + hwt_ctx_load(); + hwt_contexthash_load(); + hwt_ownerhash_load(); + hwt_record_load(); + + error = make_dev_s(&args, &hwt_cdev, "hwt"); + if (error != 0) + return (error); + + hwt_exit_tag = EVENTHANDLER_REGISTER(process_exit, hwt_process_exit, + NULL, EVENTHANDLER_PRI_ANY); + + hwt_hook_load(); + + return (0); +} + +static int +hwt_unload(void) +{ + + hwt_hook_unload(); + EVENTHANDLER_DEREGISTER(process_exit, hwt_exit_tag); + destroy_dev(hwt_cdev); + hwt_record_unload(); + hwt_ownerhash_unload(); + hwt_contexthash_unload(); + hwt_ctx_unload(); + hwt_backend_unload(); + + return (0); +} + +static int +hwt_modevent(module_t mod, int type, void *data) +{ + int error; + + switch (type) { + case MOD_LOAD: + error = hwt_load(); + break; + case MOD_UNLOAD: + error = hwt_unload(); + break; + default: + error = 0; + break; + } + + return (error); +} + +static moduledata_t hwt_mod = { + "hwt", + hwt_modevent, + NULL +}; + +DECLARE_MODULE(hwt, hwt_mod, SI_SUB_DRIVERS, SI_ORDER_FIRST); +MODULE_VERSION(hwt, 1); |