/*
* Copyright (c) 2018-2021 Apple Inc. All rights reserved.
*
* @APPLE_OSREFERENCE_LICENSE_HEADER_START@
*
* This file contains Original Code and/or Modifications of Original Code
* as defined in and that are subject to the Apple Public Source License
* Version 2.0 (the 'License'). You may not use this file except in
* compliance with the License. The rights granted to you under the License
* may not be used to create, or enable the creation or redistribution of,
* unlawful or unlicensed copies of an Apple operating system, or to
* circumvent, violate, or enable the circumvention or violation of, any
* terms of an Apple operating system software license agreement.
*
* Please obtain a copy of the License at
* http://www.opensource.apple.com/apsl/ and read it before using this file.
*
* The Original Code and all software distributed under the License are
* distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
* EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
* INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
* Please see the License for the specific language governing rights and
* limitations under the License.
*
* @APPLE_OSREFERENCE_LICENSE_HEADER_END@
*/
#include <os/atomic_private.h>
#include <kern/cpu_data.h>
#include <kern/kalloc.h>
#include <kern/simple_lock.h> // hw_wait_while_equals
#include <libkern/libkern.h>
#include <sys/sysctl.h>
#include "ubsan.h"
/*
* To dump the violation log:
* $ sysctl kern.ubsan.log
*
* To reset:
* $ sysctl kern.ubsan.logentries=0
*/
static const size_t ubsan_log_size = 2048;
ubsan_violation_t ubsan_log[ubsan_log_size];
/*
* Implement a fixed-size buffer FIFO, similar to the Chase-Lev DeQueue.
*
* See https://fzn.fr/readings/ppopp13.pdf for explanations on barriers.
*/
_Atomic size_t ubsan_log_head = 0; /* first valid entry */
_Atomic size_t ubsan_log_tail = 0; /* next free slot (reader) */
_Atomic size_t ubsan_log_next = 0; /* next free slot (writer) */
static const bool ubsan_logging = true;
static inline size_t
next_entry(size_t x)
{
return (x + 1) % ubsan_log_size;
}
void
ubsan_log_append(ubsan_violation_t *violation)
{
if (!ubsan_logging) {
return;
}
/* reserve a slot */
size_t i, e, n;
disable_preemption();
os_atomic_rmw_loop(&ubsan_log_next, i, n, relaxed, {
n = next_entry(i);
if (n == os_atomic_load(&ubsan_log_tail, acquire)) {
enable_preemption();
return; /* full */
}
});
ubsan_log[i] = *violation;
os_atomic_thread_fence(release);
/* make the entry available */
again:
os_atomic_rmw_loop(&ubsan_log_head, e, n, relaxed, {
if (e != i) {
// we need to wait for another enqueuer
os_atomic_rmw_loop_give_up({
hw_wait_while_equals_long(&ubsan_log_head, e);
goto again;
});
}
});
enable_preemption();
}
static size_t
ubsan_log_recorded(size_t head, size_t tail)
{
if (head >= tail) {
return head - tail;
}
return ubsan_log_size - (tail - head + 1);
}
static int
sysctl_ubsan_log_dump SYSCTL_HANDLER_ARGS
{
#pragma unused(oidp, arg1, arg2)
const size_t buf_size = ubsan_log_size * 256;
size_t head, tail;
head = os_atomic_load(&ubsan_log_head, relaxed);
os_atomic_thread_fence(seq_cst);
tail = os_atomic_load(&ubsan_log_tail, relaxed);
size_t nentries = ubsan_log_recorded(head, tail);
if (nentries == 0) {
return 0; /* log is empty */
}
char *buf = kalloc_data(buf_size, Z_WAITOK | Z_ZERO);
if (!buf) {
return 0;
}
ubsan_buf_t ubsan_buf;
ubsan_json_init(&ubsan_buf, buf, buf_size);
ubsan_json_begin(&ubsan_buf, nentries);
for (size_t i = tail; i != head; i = next_entry(i)) {
if (!ubsan_json_format(&ubsan_log[i], &ubsan_buf)) {
break;
}
}
size_t buf_written = ubsan_json_finish(&ubsan_buf);
int err = SYSCTL_OUT(req, buf, buf_written);
kfree_data(buf, buf_size);
return err;
}
static int
sysctl_ubsan_log_entries SYSCTL_HANDLER_ARGS
{
#pragma unused(oidp, arg1, arg2)
size_t head, tail;
head = os_atomic_load(&ubsan_log_head, relaxed);
os_atomic_thread_fence(seq_cst);
tail = os_atomic_load(&ubsan_log_tail, relaxed);
size_t nentries = ubsan_log_recorded(head, tail);
int changed = 0;
int err = sysctl_io_number(req, nentries, sizeof(nentries), &nentries, &changed);
if (err || !changed) {
return err;
}
if (nentries != 0) {
return EINVAL;
}
os_atomic_store(&ubsan_log_tail, head, relaxed);
return 0;
}
SYSCTL_DECL(ubsan);
SYSCTL_NODE(_kern, OID_AUTO, ubsan, CTLFLAG_RW | CTLFLAG_LOCKED, 0, "");
SYSCTL_COMPAT_UINT(_kern_ubsan, OID_AUTO, logsize, CTLFLAG_RD, NULL, (unsigned)ubsan_log_size, "");
SYSCTL_PROC(_kern_ubsan, OID_AUTO, logentries,
CTLTYPE_INT | CTLFLAG_RW,
0, 0, sysctl_ubsan_log_entries, "I", "");
SYSCTL_PROC(_kern_ubsan, OID_AUTO, log,
CTLTYPE_STRING | CTLFLAG_RD | CTLFLAG_MASKED,
0, 0, sysctl_ubsan_log_dump, "A", "");