// SPDX-License-Identifier: GPL-2.0
#include <linux/atomic.h>
#include <linux/bsearch.h>
#include <linux/bug.h>
#include <linux/debugfs.h>
#include <linux/init.h>
#include <linux/kallsyms.h>
#include <linux/seq_file.h>
#include <linux/slab.h>
#include <linux/sort.h>
#include <linux/string.h>
#include <linux/uaccess.h>
#include "kcsan.h"
/*
* Statistics counters.
*/
static atomic_long_t counters[KCSAN_COUNTER_COUNT];
/*
* Addresses for filtering functions from reporting. This list can be used as a
* whitelist or blacklist.
*/
static struct {
unsigned long *addrs; /* array of addresses */
size_t size; /* current size */
int used; /* number of elements used */
bool sorted; /* if elements are sorted */
bool whitelist; /* if list is a blacklist or whitelist */
} report_filterlist = {
.addrs = NULL,
.size = 8, /* small initial size */
.used = 0,
.sorted = false,
.whitelist = false, /* default is blacklist */
};
static DEFINE_SPINLOCK(report_filterlist_lock);
static const char *counter_to_name(enum kcsan_counter_id id)
{
switch (id) {
case KCSAN_COUNTER_USED_WATCHPOINTS:
return "used_watchpoints";
case KCSAN_COUNTER_SETUP_WATCHPOINTS:
return "setup_watchpoints";
case KCSAN_COUNTER_DATA_RACES:
return "data_races";
case KCSAN_COUNTER_NO_CAPACITY:
return "no_capacity";
case KCSAN_COUNTER_REPORT_RACES:
return "report_races";
case KCSAN_COUNTER_RACES_UNKNOWN_ORIGIN:
return "races_unknown_origin";
case KCSAN_COUNTER_UNENCODABLE_ACCESSES:
return "unencodable_accesses";
case KCSAN_COUNTER_ENCODING_FALSE_POSITIVES:
return "encoding_false_positives";
case KCSAN_COUNTER_COUNT:
BUG();
}
return NULL;
}
void kcsan_counter_inc(enum kcsan_counter_id id)
{
atomic_long_inc(&counters[id]);
}
void kcsan_counter_dec(enum kcsan_counter_id id)
{
atomic_long_dec(&counters[id]);
}
/*
* The microbenchmark allows benchmarking KCSAN core runtime only. To run
* multiple threads, pipe 'microbench=<iters>' from multiple tasks into the
* debugfs file.
*/
static void microbenchmark(unsigned long iters)
{
cycles_t cycles;
pr_info("KCSAN: %s begin | iters: %lu\n", __func__, iters);
cycles = get_cycles();
while (iters--) {
/*
* We can run this benchmark from multiple tasks; this address
* calculation increases likelyhood of some accesses overlapping
* (they still won't conflict because all are reads).
*/
unsigned long addr =
iters % (CONFIG_KCSAN_NUM_WATCHPOINTS * PAGE_SIZE);
__kcsan_check_read((void *)addr, sizeof(long));
}
cycles = get_cycles() - cycles;
pr_info("KCSAN: %s end | cycles: %llu\n", __func__, cycles);
}
static int cmp_filterlist_addrs(const void *rhs, const void *lhs)
{
const unsigned long a = *(const unsigned long *)rhs;
const unsigned long b = *(const unsigned long *)lhs;
return a < b ? -1 : a == b ? 0 : 1;
}
bool kcsan_skip_report_debugfs(unsigned long func_addr)
{
unsigned long symbolsize, offset;
unsigned long flags;
bool ret = false;
if (!kallsyms_lookup_size_offset(func_addr, &symbolsize, &offset))
return false;
func_addr -= offset; /* get function start */
spin_lock_irqsave(&report_filterlist_lock, flags);
if (report_filterlist.used == 0)
goto out;
/* Sort array if it is unsorted, and then do a binary search. */
if (!report_filterlist.sorted) {
sort(report_filterlist.addrs, report_filterlist.used,
sizeof(unsigned long), cmp_filterlist_addrs, NULL);
report_filterlist.sorted = true;
}
ret = !!bsearch(&func_addr, report_filterlist.addrs,
report_filterlist.used, sizeof(unsigned long),
cmp_filterlist_addrs);
if (report_filterlist.whitelist)
ret = !ret;
out:
spin_unlock_irqrestore(&report_filterlist_lock, flags);
return ret;
}
static void set_report_filterlist_whitelist(bool whitelist)
{
unsigned long flags;
spin_lock_irqsave(&report_filterlist_lock, flags);
report_filterlist.whitelist = whitelist;
spin_unlock_irqrestore(&report_filterlist_lock, flags);
}
/* Returns 0 on success, error-code otherwise. */
static ssize_t insert_report_filterlist(const char *func)
{
unsigned long flags;
unsigned long addr = kallsyms_lookup_name(func);
ssize_t ret = 0;
if (!addr) {
pr_err("KCSAN: could not find function: '%s'\n", func);
return -ENOENT;
}
spin_lock_irqsave(&report_filterlist_lock, flags);
if (report_filterlist.addrs == NULL) {
/* initial allocation */
report_filterlist.addrs =
kmalloc_array(report_filterlist.size,
sizeof(unsigned long), GFP_KERNEL);
if (report_filterlist.addrs == NULL) {
ret = -ENOMEM;
goto out;
}
} else if (report_filterlist.used == report_filterlist.size) {
/* resize filterlist */
size_t new_size = report_filterlist.size * 2;
unsigned long *new_addrs =
krealloc(report_filterlist.addrs,
new_size * sizeof(unsigned long), GFP_KERNEL);
if (new_addrs == NULL) {
/* leave filterlist itself untouched */
ret = -ENOMEM;
goto out;
}
report_filterlist.size = new_size;
report_filterlist.addrs = new_addrs;
}
/* Note: deduplicating should be done in userspace. */
report_filterlist.addrs[report_filterlist.used++] =
kallsyms_lookup_name(func);
report_filterlist.sorted = false;
out:
spin_unlock_irqrestore(&report_filterlist_lock, flags);
return ret;
}
static int show_info(struct seq_file *file, void *v)
{
int i;
unsigned long flags;
/* show stats */
seq_printf(file, "enabled: %i\n", READ_ONCE(kcsan_enabled));
for (i = 0; i < KCSAN_COUNTER_COUNT; ++i)
seq_printf(file, "%s: %ld\n", counter_to_name(i),
atomic_long_read(&counters[i]));
/* show filter functions, and filter type */
spin_lock_irqsave(&report_filterlist_lock, flags);
seq_printf(file, "\n%s functions: %s\n",
report_filterlist.whitelist ? "whitelisted" : "blacklisted",
report_filterlist.used == 0 ? "none" : "");
for (i = 0; i < report_filterlist.used; ++i)
seq_printf(file, " %ps\n", (void *)report_filterlist.addrs[i]);
spin_unlock_irqrestore(&report_filterlist_lock, flags);
return 0;
}
static int debugfs_open(struct inode *inode, struct file *file)
{
return single_open(file, show_info, NULL);
}
static ssize_t debugfs_write(struct file *file, const char __user *buf,
size_t count, loff_t *off)
{
char kbuf[KSYM_NAME_LEN];
char *arg;
int read_len = count < (sizeof(kbuf) - 1) ? count : (sizeof(kbuf) - 1);
if (copy_from_user(kbuf, buf, read_len))
return -EFAULT;
kbuf[read_len] = '\0';
arg = strstrip(kbuf);
if (!strcmp(arg, "on")) {
WRITE_ONCE(kcsan_enabled, true);
} else if (!strcmp(arg, "off")) {
WRITE_ONCE(kcsan_enabled, false);
} else if (!strncmp(arg, "microbench=", sizeof("microbench=") - 1)) {
unsigned long iters;
if (kstrtoul(&arg[sizeof("microbench=") - 1], 0, &iters))
return -EINVAL;
microbenchmark(iters);
} else if (!strcmp(arg, "whitelist")) {
set_report_filterlist_whitelist(true);
} else if (!strcmp(arg, "blacklist")) {
set_report_filterlist_whitelist(false);
} else if (arg[0] == '!') {
ssize_t ret = insert_report_filterlist(&arg[1]);
if (ret < 0)
return ret;
} else {
return -EINVAL;
}
return count;
}
static const struct file_operations debugfs_ops = { .read = seq_read,
.open = debugfs_open,
.write = debugfs_write,
.release = single_release };
void __init kcsan_debugfs_init(void)
{
debugfs_create_file("kcsan", 0644, NULL, NULL, &debugfs_ops);
}
