/*-
* SPDX-License-Identifier: BSD-2-Clause-FreeBSD
*
* Copyright (C) 2018 The FreeBSD Foundation. All rights reserved.
* Copyright (C) 2018, 2019 Andrew Turner
*
* This software was developed by Mitchell Horne under sponsorship of
* the FreeBSD Foundation.
*
* This software was developed by SRI International and the University of
* Cambridge Computer Laboratory under DARPA/AFRL contract FA8750-10-C-0237
* ("CTSRD"), as part of the DARPA CRASH research programme.
*
* 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.
*
* $FreeBSD$
*/
#define KCSAN_RUNTIME
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/conf.h>
#include <sys/eventhandler.h>
#include <sys/kcov.h>
#include <sys/kernel.h>
#include <sys/limits.h>
#include <sys/lock.h>
#include <sys/malloc.h>
#include <sys/mman.h>
#include <sys/mutex.h>
#include <sys/proc.h>
#include <sys/rwlock.h>
#include <sys/sysctl.h>
#include <vm/vm.h>
#include <vm/pmap.h>
#include <vm/vm_extern.h>
#include <vm/vm_object.h>
#include <vm/vm_page.h>
#include <vm/vm_pager.h>
#include <vm/vm_param.h>
MALLOC_DEFINE(M_KCOV_INFO, "kcovinfo", "KCOV info type");
#define KCOV_ELEMENT_SIZE sizeof(uint64_t)
/*
* To know what the code can safely perform at any point in time we use a
* state machine. In the normal case the state transitions are:
*
* OPEN -> READY -> RUNNING -> DYING
* | | ^ | ^ ^
* | | +--------+ | |
* | +-------------------+ |
* +-----------------------------+
*
* The states are:
* OPEN: The kcov fd has been opened, but no buffer is available to store
* coverage data.
* READY: The buffer to store coverage data has been allocated. Userspace
* can set this by using ioctl(fd, KIOSETBUFSIZE, entries);. When
* this has been set the buffer can be written to by the kernel,
* and mmaped by userspace.
* RUNNING: The coverage probes are able to store coverage data in the buffer.
* This is entered with ioctl(fd, KIOENABLE, mode);. The READY state
* can be exited by ioctl(fd, KIODISABLE); or exiting the thread to
* return to the READY state to allow tracing to be reused, or by
* closing the kcov fd to enter the DYING state.
* DYING: The fd has been closed. All states can enter into this state when
* userspace closes the kcov fd.
*
* We need to be careful when moving into and out of the RUNNING state. As
* an interrupt may happen while this is happening the ordering of memory
* operations is important so struct kcov_info is valid for the tracing
* functions.
*
* When moving into the RUNNING state prior stores to struct kcov_info need
* to be observed before the state is set. This allows for interrupts that
* may call into one of the coverage functions to fire at any point while
* being enabled and see a consistent struct kcov_info.
*
* When moving out of the RUNNING state any later stores to struct kcov_info
* need to be observed after the state is set. As with entering this is to
* present a consistent struct kcov_info to interrupts.
*/
typedef enum {
KCOV_STATE_INVALID,
KCOV_STATE_OPEN, /* The device is open, but with no buffer */
KCOV_STATE_READY, /* The buffer has been allocated */
KCOV_STATE_RUNNING, /* Recording trace data */
KCOV_STATE_DYING, /* The fd was closed */
} kcov_state_t;
/*
* (l) Set while holding the kcov_lock mutex and not in the RUNNING state.
* (o) Only set once while in the OPEN state. Cleaned up while in the DYING
* state, and with no thread associated with the struct kcov_info.
* (s) Set atomically to enter or exit the RUNNING state, non-atomically
* otherwise. See above for a description of the other constraints while
* moving into or out of the RUNNING state.
*/
struct kcov_info {
struct thread *thread; /* (l) */
vm_object_t bufobj; /* (o) */
vm_offset_t kvaddr; /* (o) */
size_t entries; /* (o) */
size_t bufsize; /* (o) */
kcov_state_t state; /* (s) */
int mode; /* (l) */
};
/* Prototypes */
static d_open_t kcov_open;
static d_close_t kcov_close;
static d_mmap_single_t kcov_mmap_single;
static d_ioctl_t kcov_ioctl;
static int kcov_alloc(struct kcov_info *info, size_t entries);
static void kcov_free(struct kcov_info *info);
static void kcov_init(const void *unused);
static struct cdevsw kcov_cdevsw = {
.d_version = D_VERSION,
.d_open = kcov_open,
.d_close = kcov_close,
.d_mmap_single = kcov_mmap_single,
.d_ioctl = kcov_ioctl,
.d_name = "kcov",
};
SYSCTL_NODE(_kern, OID_AUTO, kcov, CTLFLAG_RW | CTLFLAG_MPSAFE, 0,
"Kernel coverage");
static u_int kcov_max_entries = KCOV_MAXENTRIES;
SYSCTL_UINT(_kern_kcov, OID_AUTO, max_entries, CTLFLAG_RW,
&kcov_max_entries, 0,
"Maximum number of entries in the kcov buffer");
static struct mtx kcov_lock;
static int active_count;
static struct kcov_info *
get_kinfo(struct thread *td)
{
struct kcov_info *info;
/* We might have a NULL thread when releasing the secondary CPUs */
if (td == NULL)
return (NULL);
/*
* We are in an interrupt, stop tracing as it is not explicitly
* part of a syscall.
*/
if (td->td_intr_nesting_level > 0 || td->td_intr_frame != NULL)
return (NULL);
/*
* If info is NULL or the state is not running we are not tracing.
*/
info = td->td_kcov_info;
if (info == NULL ||
atomic_load_acq_int(&info->state) != KCOV_STATE_RUNNING)
return (NULL);
return (info);
}
static void
trace_pc(uintptr_t ret)
{
struct thread *td;
struct kcov_info *info;
uint64_t *buf, index;
td = curthread;
info = get_kinfo(td);
if (info == NULL)
return;
/*
* Check we are in the PC-trace mode.
*/
if (info->mode != KCOV_MODE_TRACE_PC)
return;
KASSERT(info->kvaddr != 0,
("__sanitizer_cov_trace_pc: NULL buf while running"));
buf = (uint64_t *)info->kvaddr;
/* The first entry of the buffer holds the index */
index = buf[0];
if (index + 2 > info->entries)
return;
buf[index + 1] = ret;
buf[0] = index + 1;
}
static bool
trace_cmp(uint64_t type, uint64_t arg1, uint64_t arg2, uint64_t ret)
{
struct thread *td;
struct kcov_info *info;
uint64_t *buf, index;
td = curthread;
info = get_kinfo(td);
if (info == NULL)
return (false);
/*
* Check we are in the comparison-trace mode.
*/
if (info->mode != KCOV_MODE_TRACE_CMP)
return (false);
KASSERT(info->kvaddr != 0,
("__sanitizer_cov_trace_pc: NULL buf while running"));
buf = (uint64_t *)info->kvaddr;
/* The first entry of the buffer holds the index */
index = buf[0];
/* Check we have space to store all elements */
if (index * 4 + 4 + 1 > info->entries)
return (false);
while (1) {
buf[index * 4 + 1] = type;
buf[index * 4 + 2] = arg1;
buf[index * 4 + 3] = arg2;
buf[index * 4 + 4] = ret;
if (atomic_cmpset_64(&buf[0], index, index + 1))
break;
buf[0] = index;
}
return (true);
}
/*
* The fd is being closed, cleanup everything we can.
*/
static void
kcov_mmap_cleanup(void *arg)
{
struct kcov_info *info = arg;
struct thread *thread;
mtx_lock_spin(&kcov_lock);
/*
* Move to KCOV_STATE_DYING to stop adding new entries.
*
* If the thread is running we need to wait until thread exit to
* clean up as it may currently be adding a new entry. If this is
* the case being in KCOV_STATE_DYING will signal that the buffer
* needs to be cleaned up.
*/
atomic_store_int(&info->state, KCOV_STATE_DYING);
atomic_thread_fence_seq_cst();
thread = info->thread;
mtx_unlock_spin(&kcov_lock);
if (thread != NULL)
return;
/*
* We can safely clean up the info struct as it is in the
* KCOV_STATE_DYING state with no thread associated.
*
* The KCOV_STATE_DYING stops new threads from using it.
* The lack of a thread means nothing is currently using the buffers.
*/
kcov_free(info);
}
static int
kcov_open(struct cdev *dev, int oflags, int devtype, struct thread *td)
{
struct kcov_info *info;
int error;
info = malloc(sizeof(struct kcov_info), M_KCOV_INFO, M_ZERO | M_WAITOK);
info->state = KCOV_STATE_OPEN;
info->thread = NULL;
info->mode = -1;
if ((error = devfs_set_cdevpriv(info, kcov_mmap_cleanup)) != 0)
kcov_mmap_cleanup(info);
return (error);
}
static int
kcov_close(struct cdev *dev, int fflag, int devtype, struct thread *td)
{
struct kcov_info *info;
int error;
if ((error = devfs_get_cdevpriv((void **)&info)) != 0)
return (error);
KASSERT(info != NULL, ("kcov_close with no kcov_info structure"));
/* Trying to close, but haven't disabled */
if (info->state == KCOV_STATE_RUNNING)
return (EBUSY);
return (0);
}
static int
kcov_mmap_single(struct cdev *dev, vm_ooffset_t *offset, vm_size_t size,
struct vm_object **object, int nprot)
{
struct kcov_info *info;
int error;
if ((nprot & (PROT_EXEC | PROT_READ | PROT_WRITE)) !=
(PROT_READ | PROT_WRITE))
return (EINVAL);
if ((error = devfs_get_cdevpriv((void **)&info)) != 0)
return (error);
if (info->kvaddr == 0 || size / KCOV_ELEMENT_SIZE != info->entries)
return (EINVAL);
vm_object_reference(info->bufobj);
*offset = 0;
*object = info->bufobj;
return (0);
}
static int
kcov_alloc(struct kcov_info *info, size_t entries)
{
size_t n, pages;
vm_page_t m;
KASSERT(info->kvaddr == 0, ("kcov_alloc: Already have a buffer"));
KASSERT(info->state == KCOV_STATE_OPEN,
("kcov_alloc: Not in open state (%x)", info->state));
if (entries < 2 || entries > kcov_max_entries)
return (EINVAL);
/* Align to page size so mmap can't access other kernel memory */
info->bufsize = roundup2(entries * KCOV_ELEMENT_SIZE, PAGE_SIZE);
pages = info->bufsize / PAGE_SIZE;
if ((info->kvaddr = kva_alloc(info->bufsize)) == 0)
return (ENOMEM);
info->bufobj = vm_pager_allocate(OBJT_PHYS, 0, info->bufsize,
PROT_READ | PROT_WRITE, 0, curthread->td_ucred);
VM_OBJECT_WLOCK(info->bufobj);
for (n = 0; n < pages; n++) {
m = vm_page_grab(info->bufobj, n,
VM_ALLOC_ZERO | VM_ALLOC_WIRED);
vm_page_valid(m);
vm_page_xunbusy(m);
pmap_qenter(info->kvaddr + n * PAGE_SIZE, &m, 1);
}
VM_OBJECT_WUNLOCK(info->bufobj);
info->entries = entries;
return (0);
}
static void
kcov_free(struct kcov_info *info)
{
vm_page_t m;
size_t i;
if (info->kvaddr != 0) {
pmap_qremove(info->kvaddr, info->bufsize / PAGE_SIZE);
kva_free(info->kvaddr, info->bufsize);
}
if (info->bufobj != NULL) {
VM_OBJECT_WLOCK(info->bufobj);
m = vm_page_lookup(info->bufobj, 0);
for (i = 0; i < info->bufsize / PAGE_SIZE; i++) {
vm_page_unwire_noq(m);
m = vm_page_next(m);
}
VM_OBJECT_WUNLOCK(info->bufobj);
vm_object_deallocate(info->bufobj);
}
free(info, M_KCOV_INFO);
}
static int
kcov_ioctl(struct cdev *dev, u_long cmd, caddr_t data, int fflag __unused,
struct thread *td)
{
struct kcov_info *info;
int mode, error;
if ((error = devfs_get_cdevpriv((void **)&info)) != 0)
return (error);
if (cmd == KIOSETBUFSIZE) {
/*
* Set the size of the coverage buffer. Should be called
* before enabling coverage collection for that thread.
*/
if (info->state != KCOV_STATE_OPEN) {
return (EBUSY);
}
error = kcov_alloc(info, *(u_int *)data);
if (error == 0)
info->state = KCOV_STATE_READY;
return (error);
}
mtx_lock_spin(&kcov_lock);
switch (cmd) {
case KIOENABLE:
if (info->state != KCOV_STATE_READY) {
error = EBUSY;
break;
}
if (td->td_kcov_info != NULL) {
error = EINVAL;
break;
}
mode = *(int *)data;
if (mode != KCOV_MODE_TRACE_PC && mode != KCOV_MODE_TRACE_CMP) {
error = EINVAL;
break;
}
/* Lets hope nobody opens this 2 billion times */
KASSERT(active_count < INT_MAX,
("%s: Open too many times", __func__));
active_count++;
if (active_count == 1) {
cov_register_pc(&trace_pc);
cov_register_cmp(&trace_cmp);
}
KASSERT(info->thread == NULL,
("Enabling kcov when already enabled"));
info->thread = td;
info->mode = mode;
/*
* Ensure the mode has been set before starting coverage
* tracing.
*/
atomic_store_rel_int(&info->state, KCOV_STATE_RUNNING);
td->td_kcov_info = info;
break;
case KIODISABLE:
/* Only the currently enabled thread may disable itself */
if (info->state != KCOV_STATE_RUNNING ||
info != td->td_kcov_info) {
error = EINVAL;
break;
}
KASSERT(active_count > 0, ("%s: Open count is zero", __func__));
active_count--;
if (active_count == 0) {
cov_unregister_pc();
cov_unregister_cmp();
}
td->td_kcov_info = NULL;
atomic_store_int(&info->state, KCOV_STATE_READY);
/*
* Ensure we have exited the READY state before clearing the
* rest of the info struct.
*/
atomic_thread_fence_rel();
info->mode = -1;
info->thread = NULL;
break;
default:
error = EINVAL;
break;
}
mtx_unlock_spin(&kcov_lock);
return (error);
}
static void
kcov_thread_dtor(void *arg __unused, struct thread *td)
{
struct kcov_info *info;
info = td->td_kcov_info;
if (info == NULL)
return;
mtx_lock_spin(&kcov_lock);
KASSERT(active_count > 0, ("%s: Open count is zero", __func__));
active_count--;
if (active_count == 0) {
cov_unregister_pc();
cov_unregister_cmp();
}
td->td_kcov_info = NULL;
if (info->state != KCOV_STATE_DYING) {
/*
* The kcov file is still open. Mark it as unused and
* wait for it to be closed before cleaning up.
*/
atomic_store_int(&info->state, KCOV_STATE_READY);
atomic_thread_fence_seq_cst();
/* This info struct is unused */
info->thread = NULL;
mtx_unlock_spin(&kcov_lock);
return;
}
mtx_unlock_spin(&kcov_lock);
/*
* We can safely clean up the info struct as it is in the
* KCOV_STATE_DYING state where the info struct is associated with
* the current thread that's about to exit.
*
* The KCOV_STATE_DYING stops new threads from using it.
* It also stops the current thread from trying to use the info struct.
*/
kcov_free(info);
}
static void
kcov_init(const void *unused)
{
struct make_dev_args args;
struct cdev *dev;
mtx_init(&kcov_lock, "kcov lock", NULL, MTX_SPIN);
make_dev_args_init(&args);
args.mda_devsw = &kcov_cdevsw;
args.mda_uid = UID_ROOT;
args.mda_gid = GID_WHEEL;
args.mda_mode = 0600;
if (make_dev_s(&args, &dev, "kcov") != 0) {
printf("%s", "Failed to create kcov device");
return;
}
EVENTHANDLER_REGISTER(thread_dtor, kcov_thread_dtor, NULL,
EVENTHANDLER_PRI_ANY);
}
SYSINIT(kcovdev, SI_SUB_LAST, SI_ORDER_ANY, kcov_init, NULL);
