2 * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
4 * Copyright (C) 2018 The FreeBSD Foundation. All rights reserved.
5 * Copyright (C) 2018, 2019 Andrew Turner
7 * This software was developed by Mitchell Horne under sponsorship of
8 * the FreeBSD Foundation.
10 * This software was developed by SRI International and the University of
11 * Cambridge Computer Laboratory under DARPA/AFRL contract FA8750-10-C-0237
12 * ("CTSRD"), as part of the DARPA CRASH research programme.
14 * Redistribution and use in source and binary forms, with or without
15 * modification, are permitted provided that the following conditions
17 * 1. Redistributions of source code must retain the above copyright
18 * notice, this list of conditions and the following disclaimer.
19 * 2. Redistributions in binary form must reproduce the above copyright
20 * notice, this list of conditions and the following disclaimer in the
21 * documentation and/or other materials provided with the distribution.
23 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
24 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
25 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
26 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
27 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
28 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
29 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
30 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
31 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
32 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
40 #include <sys/cdefs.h>
41 __FBSDID("$FreeBSD$");
43 #include <sys/param.h>
44 #include <sys/systm.h>
46 #include <sys/eventhandler.h>
48 #include <sys/kernel.h>
49 #include <sys/limits.h>
51 #include <sys/malloc.h>
53 #include <sys/mutex.h>
55 #include <sys/rwlock.h>
56 #include <sys/sysctl.h>
60 #include <vm/vm_extern.h>
61 #include <vm/vm_object.h>
62 #include <vm/vm_page.h>
63 #include <vm/vm_pager.h>
64 #include <vm/vm_param.h>
66 MALLOC_DEFINE(M_KCOV_INFO, "kcovinfo", "KCOV info type");
68 #define KCOV_ELEMENT_SIZE sizeof(uint64_t)
71 * To know what the code can safely perform at any point in time we use a
72 * state machine. In the normal case the state transitions are:
74 * OPEN -> READY -> RUNNING -> DYING
77 * | +-------------------+ |
78 * +-----------------------------+
81 * OPEN: The kcov fd has been opened, but no buffer is available to store
83 * READY: The buffer to store coverage data has been allocated. Userspace
84 * can set this by using ioctl(fd, KIOSETBUFSIZE, entries);. When
85 * this has been set the buffer can be written to by the kernel,
86 * and mmaped by userspace.
87 * RUNNING: The coverage probes are able to store coverage data in the buffer.
88 * This is entered with ioctl(fd, KIOENABLE, mode);. The READY state
89 * can be exited by ioctl(fd, KIODISABLE); or exiting the thread to
90 * return to the READY state to allow tracing to be reused, or by
91 * closing the kcov fd to enter the DYING state.
92 * DYING: The fd has been closed. All states can enter into this state when
93 * userspace closes the kcov fd.
95 * We need to be careful when moving into and out of the RUNNING state. As
96 * an interrupt may happen while this is happening the ordering of memory
97 * operations is important so struct kcov_info is valid for the tracing
100 * When moving into the RUNNING state prior stores to struct kcov_info need
101 * to be observed before the state is set. This allows for interrupts that
102 * may call into one of the coverage functions to fire at any point while
103 * being enabled and see a consistent struct kcov_info.
105 * When moving out of the RUNNING state any later stores to struct kcov_info
106 * need to be observed after the state is set. As with entering this is to
107 * present a consistent struct kcov_info to interrupts.
111 KCOV_STATE_OPEN, /* The device is open, but with no buffer */
112 KCOV_STATE_READY, /* The buffer has been allocated */
113 KCOV_STATE_RUNNING, /* Recording trace data */
114 KCOV_STATE_DYING, /* The fd was closed */
118 * (l) Set while holding the kcov_lock mutex and not in the RUNNING state.
119 * (o) Only set once while in the OPEN state. Cleaned up while in the DYING
120 * state, and with no thread associated with the struct kcov_info.
121 * (s) Set atomically to enter or exit the RUNNING state, non-atomically
122 * otherwise. See above for a description of the other constraints while
123 * moving into or out of the RUNNING state.
126 struct thread *thread; /* (l) */
127 vm_object_t bufobj; /* (o) */
128 vm_offset_t kvaddr; /* (o) */
129 size_t entries; /* (o) */
130 size_t bufsize; /* (o) */
131 kcov_state_t state; /* (s) */
136 static d_open_t kcov_open;
137 static d_close_t kcov_close;
138 static d_mmap_single_t kcov_mmap_single;
139 static d_ioctl_t kcov_ioctl;
141 static int kcov_alloc(struct kcov_info *info, size_t entries);
142 static void kcov_free(struct kcov_info *info);
143 static void kcov_init(const void *unused);
145 static struct cdevsw kcov_cdevsw = {
146 .d_version = D_VERSION,
148 .d_close = kcov_close,
149 .d_mmap_single = kcov_mmap_single,
150 .d_ioctl = kcov_ioctl,
154 SYSCTL_NODE(_kern, OID_AUTO, kcov, CTLFLAG_RW | CTLFLAG_MPSAFE, 0,
157 static u_int kcov_max_entries = KCOV_MAXENTRIES;
158 SYSCTL_UINT(_kern_kcov, OID_AUTO, max_entries, CTLFLAG_RW,
159 &kcov_max_entries, 0,
160 "Maximum number of entries in the kcov buffer");
162 static struct mtx kcov_lock;
163 static int active_count;
165 static struct kcov_info *
166 get_kinfo(struct thread *td)
168 struct kcov_info *info;
170 /* We might have a NULL thread when releasing the secondary CPUs */
175 * We are in an interrupt, stop tracing as it is not explicitly
178 if (td->td_intr_nesting_level > 0 || td->td_intr_frame != NULL)
182 * If info is NULL or the state is not running we are not tracing.
184 info = td->td_kcov_info;
186 atomic_load_acq_int(&info->state) != KCOV_STATE_RUNNING)
193 trace_pc(uintptr_t ret)
196 struct kcov_info *info;
197 uint64_t *buf, index;
200 info = get_kinfo(td);
205 * Check we are in the PC-trace mode.
207 if (info->mode != KCOV_MODE_TRACE_PC)
210 KASSERT(info->kvaddr != 0,
211 ("__sanitizer_cov_trace_pc: NULL buf while running"));
213 buf = (uint64_t *)info->kvaddr;
215 /* The first entry of the buffer holds the index */
217 if (index + 2 > info->entries)
220 buf[index + 1] = ret;
225 trace_cmp(uint64_t type, uint64_t arg1, uint64_t arg2, uint64_t ret)
228 struct kcov_info *info;
229 uint64_t *buf, index;
232 info = get_kinfo(td);
237 * Check we are in the comparison-trace mode.
239 if (info->mode != KCOV_MODE_TRACE_CMP)
242 KASSERT(info->kvaddr != 0,
243 ("__sanitizer_cov_trace_pc: NULL buf while running"));
245 buf = (uint64_t *)info->kvaddr;
247 /* The first entry of the buffer holds the index */
250 /* Check we have space to store all elements */
251 if (index * 4 + 4 + 1 > info->entries)
255 buf[index * 4 + 1] = type;
256 buf[index * 4 + 2] = arg1;
257 buf[index * 4 + 3] = arg2;
258 buf[index * 4 + 4] = ret;
260 if (atomic_cmpset_64(&buf[0], index, index + 1))
269 * The fd is being closed, cleanup everything we can.
272 kcov_mmap_cleanup(void *arg)
274 struct kcov_info *info = arg;
275 struct thread *thread;
277 mtx_lock_spin(&kcov_lock);
279 * Move to KCOV_STATE_DYING to stop adding new entries.
281 * If the thread is running we need to wait until thread exit to
282 * clean up as it may currently be adding a new entry. If this is
283 * the case being in KCOV_STATE_DYING will signal that the buffer
284 * needs to be cleaned up.
286 atomic_store_int(&info->state, KCOV_STATE_DYING);
287 atomic_thread_fence_seq_cst();
288 thread = info->thread;
289 mtx_unlock_spin(&kcov_lock);
295 * We can safely clean up the info struct as it is in the
296 * KCOV_STATE_DYING state with no thread associated.
298 * The KCOV_STATE_DYING stops new threads from using it.
299 * The lack of a thread means nothing is currently using the buffers.
305 kcov_open(struct cdev *dev, int oflags, int devtype, struct thread *td)
307 struct kcov_info *info;
310 info = malloc(sizeof(struct kcov_info), M_KCOV_INFO, M_ZERO | M_WAITOK);
311 info->state = KCOV_STATE_OPEN;
315 if ((error = devfs_set_cdevpriv(info, kcov_mmap_cleanup)) != 0)
316 kcov_mmap_cleanup(info);
322 kcov_close(struct cdev *dev, int fflag, int devtype, struct thread *td)
324 struct kcov_info *info;
327 if ((error = devfs_get_cdevpriv((void **)&info)) != 0)
330 KASSERT(info != NULL, ("kcov_close with no kcov_info structure"));
332 /* Trying to close, but haven't disabled */
333 if (info->state == KCOV_STATE_RUNNING)
340 kcov_mmap_single(struct cdev *dev, vm_ooffset_t *offset, vm_size_t size,
341 struct vm_object **object, int nprot)
343 struct kcov_info *info;
346 if ((nprot & (PROT_EXEC | PROT_READ | PROT_WRITE)) !=
347 (PROT_READ | PROT_WRITE))
350 if ((error = devfs_get_cdevpriv((void **)&info)) != 0)
353 if (info->kvaddr == 0 || size / KCOV_ELEMENT_SIZE != info->entries)
356 vm_object_reference(info->bufobj);
358 *object = info->bufobj;
363 kcov_alloc(struct kcov_info *info, size_t entries)
368 KASSERT(info->kvaddr == 0, ("kcov_alloc: Already have a buffer"));
369 KASSERT(info->state == KCOV_STATE_OPEN,
370 ("kcov_alloc: Not in open state (%x)", info->state));
372 if (entries < 2 || entries > kcov_max_entries)
375 /* Align to page size so mmap can't access other kernel memory */
376 info->bufsize = roundup2(entries * KCOV_ELEMENT_SIZE, PAGE_SIZE);
377 pages = info->bufsize / PAGE_SIZE;
379 if ((info->kvaddr = kva_alloc(info->bufsize)) == 0)
382 info->bufobj = vm_pager_allocate(OBJT_PHYS, 0, info->bufsize,
383 PROT_READ | PROT_WRITE, 0, curthread->td_ucred);
385 VM_OBJECT_WLOCK(info->bufobj);
386 for (n = 0; n < pages; n++) {
387 m = vm_page_grab(info->bufobj, n,
388 VM_ALLOC_ZERO | VM_ALLOC_WIRED);
391 pmap_qenter(info->kvaddr + n * PAGE_SIZE, &m, 1);
393 VM_OBJECT_WUNLOCK(info->bufobj);
395 info->entries = entries;
401 kcov_free(struct kcov_info *info)
406 if (info->kvaddr != 0) {
407 pmap_qremove(info->kvaddr, info->bufsize / PAGE_SIZE);
408 kva_free(info->kvaddr, info->bufsize);
410 if (info->bufobj != NULL) {
411 VM_OBJECT_WLOCK(info->bufobj);
412 m = vm_page_lookup(info->bufobj, 0);
413 for (i = 0; i < info->bufsize / PAGE_SIZE; i++) {
414 vm_page_unwire_noq(m);
417 VM_OBJECT_WUNLOCK(info->bufobj);
418 vm_object_deallocate(info->bufobj);
420 free(info, M_KCOV_INFO);
424 kcov_ioctl(struct cdev *dev, u_long cmd, caddr_t data, int fflag __unused,
427 struct kcov_info *info;
430 if ((error = devfs_get_cdevpriv((void **)&info)) != 0)
433 if (cmd == KIOSETBUFSIZE) {
435 * Set the size of the coverage buffer. Should be called
436 * before enabling coverage collection for that thread.
438 if (info->state != KCOV_STATE_OPEN) {
441 error = kcov_alloc(info, *(u_int *)data);
443 info->state = KCOV_STATE_READY;
447 mtx_lock_spin(&kcov_lock);
450 if (info->state != KCOV_STATE_READY) {
454 if (td->td_kcov_info != NULL) {
459 if (mode != KCOV_MODE_TRACE_PC && mode != KCOV_MODE_TRACE_CMP) {
464 /* Lets hope nobody opens this 2 billion times */
465 KASSERT(active_count < INT_MAX,
466 ("%s: Open too many times", __func__));
468 if (active_count == 1) {
469 cov_register_pc(&trace_pc);
470 cov_register_cmp(&trace_cmp);
473 KASSERT(info->thread == NULL,
474 ("Enabling kcov when already enabled"));
478 * Ensure the mode has been set before starting coverage
481 atomic_store_rel_int(&info->state, KCOV_STATE_RUNNING);
482 td->td_kcov_info = info;
485 /* Only the currently enabled thread may disable itself */
486 if (info->state != KCOV_STATE_RUNNING ||
487 info != td->td_kcov_info) {
491 KASSERT(active_count > 0, ("%s: Open count is zero", __func__));
493 if (active_count == 0) {
495 cov_unregister_cmp();
498 td->td_kcov_info = NULL;
499 atomic_store_int(&info->state, KCOV_STATE_READY);
501 * Ensure we have exited the READY state before clearing the
502 * rest of the info struct.
504 atomic_thread_fence_rel();
512 mtx_unlock_spin(&kcov_lock);
518 kcov_thread_dtor(void *arg __unused, struct thread *td)
520 struct kcov_info *info;
522 info = td->td_kcov_info;
526 mtx_lock_spin(&kcov_lock);
527 KASSERT(active_count > 0, ("%s: Open count is zero", __func__));
529 if (active_count == 0) {
531 cov_unregister_cmp();
533 td->td_kcov_info = NULL;
534 if (info->state != KCOV_STATE_DYING) {
536 * The kcov file is still open. Mark it as unused and
537 * wait for it to be closed before cleaning up.
539 atomic_store_int(&info->state, KCOV_STATE_READY);
540 atomic_thread_fence_seq_cst();
541 /* This info struct is unused */
543 mtx_unlock_spin(&kcov_lock);
546 mtx_unlock_spin(&kcov_lock);
549 * We can safely clean up the info struct as it is in the
550 * KCOV_STATE_DYING state where the info struct is associated with
551 * the current thread that's about to exit.
553 * The KCOV_STATE_DYING stops new threads from using it.
554 * It also stops the current thread from trying to use the info struct.
560 kcov_init(const void *unused)
562 struct make_dev_args args;
565 mtx_init(&kcov_lock, "kcov lock", NULL, MTX_SPIN);
567 make_dev_args_init(&args);
568 args.mda_devsw = &kcov_cdevsw;
569 args.mda_uid = UID_ROOT;
570 args.mda_gid = GID_WHEEL;
571 args.mda_mode = 0600;
572 if (make_dev_s(&args, &dev, "kcov") != 0) {
573 printf("%s", "Failed to create kcov device");
577 EVENTHANDLER_REGISTER(thread_dtor, kcov_thread_dtor, NULL,
578 EVENTHANDLER_PRI_ANY);
581 SYSINIT(kcovdev, SI_SUB_LAST, SI_ORDER_ANY, kcov_init, NULL);