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linux-sg2042/kernel/kcsan/kcsan_test.c

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// SPDX-License-Identifier: GPL-2.0
/*
* KCSAN test with various race scenarious to test runtime behaviour. Since the
* interface with which KCSAN's reports are obtained is via the console, this is
* the output we should verify. For each test case checks the presence (or
* absence) of generated reports. Relies on 'console' tracepoint to capture
* reports as they appear in the kernel log.
*
* Makes use of KUnit for test organization, and the Torture framework for test
* thread control.
*
* Copyright (C) 2020, Google LLC.
* Author: Marco Elver <elver@google.com>
*/
#define pr_fmt(fmt) "kcsan_test: " fmt
#include <kunit/test.h>
#include <linux/jiffies.h>
#include <linux/kcsan-checks.h>
#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/seqlock.h>
#include <linux/spinlock.h>
#include <linux/string.h>
#include <linux/timer.h>
#include <linux/torture.h>
#include <linux/tracepoint.h>
#include <linux/types.h>
#include <trace/events/printk.h>
#ifdef CONFIG_CC_HAS_TSAN_COMPOUND_READ_BEFORE_WRITE
#define __KCSAN_ACCESS_RW(alt) (KCSAN_ACCESS_COMPOUND | KCSAN_ACCESS_WRITE)
#else
#define __KCSAN_ACCESS_RW(alt) (alt)
#endif
/* Points to current test-case memory access "kernels". */
static void (*access_kernels[2])(void);
static struct task_struct **threads; /* Lists of threads. */
static unsigned long end_time; /* End time of test. */
/* Report as observed from console. */
static struct {
spinlock_t lock;
int nlines;
char lines[3][512];
} observed = {
.lock = __SPIN_LOCK_UNLOCKED(observed.lock),
};
/* Setup test checking loop. */
static __no_kcsan inline void
begin_test_checks(void (*func1)(void), void (*func2)(void))
{
kcsan_disable_current();
/*
* Require at least as long as KCSAN_REPORT_ONCE_IN_MS, to ensure at
* least one race is reported.
*/
end_time = jiffies + msecs_to_jiffies(CONFIG_KCSAN_REPORT_ONCE_IN_MS + 500);
/* Signal start; release potential initialization of shared data. */
smp_store_release(&access_kernels[0], func1);
smp_store_release(&access_kernels[1], func2);
}
/* End test checking loop. */
static __no_kcsan inline bool
end_test_checks(bool stop)
{
if (!stop && time_before(jiffies, end_time)) {
/* Continue checking */
might_sleep();
return false;
}
kcsan_enable_current();
return true;
}
/*
* Probe for console output: checks if a race was reported, and obtains observed
* lines of interest.
*/
__no_kcsan
static void probe_console(void *ignore, const char *buf, size_t len)
{
unsigned long flags;
int nlines;
/*
* Note that KCSAN reports under a global lock, so we do not risk the
* possibility of having multiple reports interleaved. If that were the
* case, we'd expect tests to fail.
*/
spin_lock_irqsave(&observed.lock, flags);
nlines = observed.nlines;
if (strnstr(buf, "BUG: KCSAN: ", len) && strnstr(buf, "test_", len)) {
/*
* KCSAN report and related to the test.
*
* The provided @buf is not NUL-terminated; copy no more than
* @len bytes and let strscpy() add the missing NUL-terminator.
*/
strscpy(observed.lines[0], buf, min(len + 1, sizeof(observed.lines[0])));
nlines = 1;
} else if ((nlines == 1 || nlines == 2) && strnstr(buf, "bytes by", len)) {
strscpy(observed.lines[nlines++], buf, min(len + 1, sizeof(observed.lines[0])));
if (strnstr(buf, "race at unknown origin", len)) {
if (WARN_ON(nlines != 2))
goto out;
/* No second line of interest. */
strcpy(observed.lines[nlines++], "<none>");
}
}
out:
WRITE_ONCE(observed.nlines, nlines); /* Publish new nlines. */
spin_unlock_irqrestore(&observed.lock, flags);
}
/* Check if a report related to the test exists. */
__no_kcsan
static bool report_available(void)
{
return READ_ONCE(observed.nlines) == ARRAY_SIZE(observed.lines);
}
/* Report information we expect in a report. */
struct expect_report {
/* Access information of both accesses. */
struct {
void *fn; /* Function pointer to expected function of top frame. */
void *addr; /* Address of access; unchecked if NULL. */
size_t size; /* Size of access; unchecked if @addr is NULL. */
int type; /* Access type, see KCSAN_ACCESS definitions. */
} access[2];
};
/* Check observed report matches information in @r. */
__no_kcsan
static bool report_matches(const struct expect_report *r)
{
const bool is_assert = (r->access[0].type | r->access[1].type) & KCSAN_ACCESS_ASSERT;
bool ret = false;
unsigned long flags;
typeof(observed.lines) expect;
const char *end;
char *cur;
int i;
/* Doubled-checked locking. */
if (!report_available())
return false;
/* Generate expected report contents. */
/* Title */
cur = expect[0];
end = &expect[0][sizeof(expect[0]) - 1];
cur += scnprintf(cur, end - cur, "BUG: KCSAN: %s in ",
is_assert ? "assert: race" : "data-race");
if (r->access[1].fn) {
char tmp[2][64];
int cmp;
/* Expect lexographically sorted function names in title. */
scnprintf(tmp[0], sizeof(tmp[0]), "%pS", r->access[0].fn);
scnprintf(tmp[1], sizeof(tmp[1]), "%pS", r->access[1].fn);
cmp = strcmp(tmp[0], tmp[1]);
cur += scnprintf(cur, end - cur, "%ps / %ps",
cmp < 0 ? r->access[0].fn : r->access[1].fn,
cmp < 0 ? r->access[1].fn : r->access[0].fn);
} else {
scnprintf(cur, end - cur, "%pS", r->access[0].fn);
/* The exact offset won't match, remove it. */
cur = strchr(expect[0], '+');
if (cur)
*cur = '\0';
}
/* Access 1 */
cur = expect[1];
end = &expect[1][sizeof(expect[1]) - 1];
if (!r->access[1].fn)
cur += scnprintf(cur, end - cur, "race at unknown origin, with ");
/* Access 1 & 2 */
for (i = 0; i < 2; ++i) {
const int ty = r->access[i].type;
const char *const access_type =
(ty & KCSAN_ACCESS_ASSERT) ?
((ty & KCSAN_ACCESS_WRITE) ?
"assert no accesses" :
"assert no writes") :
((ty & KCSAN_ACCESS_WRITE) ?
((ty & KCSAN_ACCESS_COMPOUND) ?
"read-write" :
"write") :
"read");
const char *const access_type_aux =
(ty & KCSAN_ACCESS_ATOMIC) ?
" (marked)" :
((ty & KCSAN_ACCESS_SCOPED) ? " (scoped)" : "");
if (i == 1) {
/* Access 2 */
cur = expect[2];
end = &expect[2][sizeof(expect[2]) - 1];
if (!r->access[1].fn) {
/* Dummy string if no second access is available. */
strcpy(cur, "<none>");
break;
}
}
cur += scnprintf(cur, end - cur, "%s%s to ", access_type,
access_type_aux);
if (r->access[i].addr) /* Address is optional. */
cur += scnprintf(cur, end - cur, "0x%px of %zu bytes",
r->access[i].addr, r->access[i].size);
}
spin_lock_irqsave(&observed.lock, flags);
if (!report_available())
goto out; /* A new report is being captured. */
/* Finally match expected output to what we actually observed. */
ret = strstr(observed.lines[0], expect[0]) &&
/* Access info may appear in any order. */
((strstr(observed.lines[1], expect[1]) &&
strstr(observed.lines[2], expect[2])) ||
(strstr(observed.lines[1], expect[2]) &&
strstr(observed.lines[2], expect[1])));
out:
spin_unlock_irqrestore(&observed.lock, flags);
return ret;
}
/* ===== Test kernels ===== */
static long test_sink;
static long test_var;
/* @test_array should be large enough to fall into multiple watchpoint slots. */
static long test_array[3 * PAGE_SIZE / sizeof(long)];
static struct {
long val[8];
} test_struct;
static DEFINE_SEQLOCK(test_seqlock);
/*
* Helper to avoid compiler optimizing out reads, and to generate source values
* for writes.
*/
__no_kcsan
static noinline void sink_value(long v) { WRITE_ONCE(test_sink, v); }
static noinline void test_kernel_read(void) { sink_value(test_var); }
static noinline void test_kernel_write(void)
{
test_var = READ_ONCE_NOCHECK(test_sink) + 1;
}
static noinline void test_kernel_write_nochange(void) { test_var = 42; }
/* Suffixed by value-change exception filter. */
static noinline void test_kernel_write_nochange_rcu(void) { test_var = 42; }
static noinline void test_kernel_read_atomic(void)
{
sink_value(READ_ONCE(test_var));
}
static noinline void test_kernel_write_atomic(void)
{
WRITE_ONCE(test_var, READ_ONCE_NOCHECK(test_sink) + 1);
}
static noinline void test_kernel_atomic_rmw(void)
{
/* Use builtin, so we can set up the "bad" atomic/non-atomic scenario. */
__atomic_fetch_add(&test_var, 1, __ATOMIC_RELAXED);
}
__no_kcsan
static noinline void test_kernel_write_uninstrumented(void) { test_var++; }
static noinline void test_kernel_data_race(void) { data_race(test_var++); }
static noinline void test_kernel_assert_writer(void)
{
ASSERT_EXCLUSIVE_WRITER(test_var);
}
static noinline void test_kernel_assert_access(void)
{
ASSERT_EXCLUSIVE_ACCESS(test_var);
}
#define TEST_CHANGE_BITS 0xff00ff00
static noinline void test_kernel_change_bits(void)
{
if (IS_ENABLED(CONFIG_KCSAN_IGNORE_ATOMICS)) {
/*
* Avoid race of unknown origin for this test, just pretend they
* are atomic.
*/
kcsan_nestable_atomic_begin();
test_var ^= TEST_CHANGE_BITS;
kcsan_nestable_atomic_end();
} else
WRITE_ONCE(test_var, READ_ONCE(test_var) ^ TEST_CHANGE_BITS);
}
static noinline void test_kernel_assert_bits_change(void)
{
ASSERT_EXCLUSIVE_BITS(test_var, TEST_CHANGE_BITS);
}
static noinline void test_kernel_assert_bits_nochange(void)
{
ASSERT_EXCLUSIVE_BITS(test_var, ~TEST_CHANGE_BITS);
}
/* To check that scoped assertions do trigger anywhere in scope. */
static noinline void test_enter_scope(void)
{
int x = 0;
/* Unrelated accesses to scoped assert. */
READ_ONCE(test_sink);
kcsan_check_read(&x, sizeof(x));
}
static noinline void test_kernel_assert_writer_scoped(void)
{
ASSERT_EXCLUSIVE_WRITER_SCOPED(test_var);
test_enter_scope();
}
static noinline void test_kernel_assert_access_scoped(void)
{
ASSERT_EXCLUSIVE_ACCESS_SCOPED(test_var);
test_enter_scope();
}
static noinline void test_kernel_rmw_array(void)
{
int i;
for (i = 0; i < ARRAY_SIZE(test_array); ++i)
test_array[i]++;
}
static noinline void test_kernel_write_struct(void)
{
kcsan_check_write(&test_struct, sizeof(test_struct));
kcsan_disable_current();
test_struct.val[3]++; /* induce value change */
kcsan_enable_current();
}
static noinline void test_kernel_write_struct_part(void)
{
test_struct.val[3] = 42;
}
static noinline void test_kernel_read_struct_zero_size(void)
{
kcsan_check_read(&test_struct.val[3], 0);
}
static noinline void test_kernel_jiffies_reader(void)
{
sink_value((long)jiffies);
}
static noinline void test_kernel_seqlock_reader(void)
{
unsigned int seq;
do {
seq = read_seqbegin(&test_seqlock);
sink_value(test_var);
} while (read_seqretry(&test_seqlock, seq));
}
static noinline void test_kernel_seqlock_writer(void)
{
unsigned long flags;
write_seqlock_irqsave(&test_seqlock, flags);
test_var++;
write_sequnlock_irqrestore(&test_seqlock, flags);
}
static noinline void test_kernel_atomic_builtins(void)
{
/*
* Generate concurrent accesses, expecting no reports, ensuring KCSAN
* treats builtin atomics as actually atomic.
*/
__atomic_load_n(&test_var, __ATOMIC_RELAXED);
}
/* ===== Test cases ===== */
/* Simple test with normal data race. */
__no_kcsan
static void test_basic(struct kunit *test)
{
const struct expect_report expect = {
.access = {
{ test_kernel_write, &test_var, sizeof(test_var), KCSAN_ACCESS_WRITE },
{ test_kernel_read, &test_var, sizeof(test_var), 0 },
},
};
static const struct expect_report never = {
.access = {
{ test_kernel_read, &test_var, sizeof(test_var), 0 },
{ test_kernel_read, &test_var, sizeof(test_var), 0 },
},
};
bool match_expect = false;
bool match_never = false;
begin_test_checks(test_kernel_write, test_kernel_read);
do {
match_expect |= report_matches(&expect);
match_never = report_matches(&never);
} while (!end_test_checks(match_never));
KUNIT_EXPECT_TRUE(test, match_expect);
KUNIT_EXPECT_FALSE(test, match_never);
}
/*
* Stress KCSAN with lots of concurrent races on different addresses until
* timeout.
*/
__no_kcsan
static void test_concurrent_races(struct kunit *test)
{
const struct expect_report expect = {
.access = {
/* NULL will match any address. */
{ test_kernel_rmw_array, NULL, 0, __KCSAN_ACCESS_RW(KCSAN_ACCESS_WRITE) },
{ test_kernel_rmw_array, NULL, 0, __KCSAN_ACCESS_RW(0) },
},
};
static const struct expect_report never = {
.access = {
{ test_kernel_rmw_array, NULL, 0, 0 },
{ test_kernel_rmw_array, NULL, 0, 0 },
},
};
bool match_expect = false;
bool match_never = false;
begin_test_checks(test_kernel_rmw_array, test_kernel_rmw_array);
do {
match_expect |= report_matches(&expect);
match_never |= report_matches(&never);
} while (!end_test_checks(false));
KUNIT_EXPECT_TRUE(test, match_expect); /* Sanity check matches exist. */
KUNIT_EXPECT_FALSE(test, match_never);
}
/* Test the KCSAN_REPORT_VALUE_CHANGE_ONLY option. */
__no_kcsan
static void test_novalue_change(struct kunit *test)
{
const struct expect_report expect = {
.access = {
{ test_kernel_write_nochange, &test_var, sizeof(test_var), KCSAN_ACCESS_WRITE },
{ test_kernel_read, &test_var, sizeof(test_var), 0 },
},
};
bool match_expect = false;
begin_test_checks(test_kernel_write_nochange, test_kernel_read);
do {
match_expect = report_matches(&expect);
} while (!end_test_checks(match_expect));
if (IS_ENABLED(CONFIG_KCSAN_REPORT_VALUE_CHANGE_ONLY))
KUNIT_EXPECT_FALSE(test, match_expect);
else
KUNIT_EXPECT_TRUE(test, match_expect);
}
/*
* Test that the rules where the KCSAN_REPORT_VALUE_CHANGE_ONLY option should
* never apply work.
*/
__no_kcsan
static void test_novalue_change_exception(struct kunit *test)
{
const struct expect_report expect = {
.access = {
{ test_kernel_write_nochange_rcu, &test_var, sizeof(test_var), KCSAN_ACCESS_WRITE },
{ test_kernel_read, &test_var, sizeof(test_var), 0 },
},
};
bool match_expect = false;
begin_test_checks(test_kernel_write_nochange_rcu, test_kernel_read);
do {
match_expect = report_matches(&expect);
} while (!end_test_checks(match_expect));
KUNIT_EXPECT_TRUE(test, match_expect);
}
/* Test that data races of unknown origin are reported. */
__no_kcsan
static void test_unknown_origin(struct kunit *test)
{
const struct expect_report expect = {
.access = {
{ test_kernel_read, &test_var, sizeof(test_var), 0 },
{ NULL },
},
};
bool match_expect = false;
begin_test_checks(test_kernel_write_uninstrumented, test_kernel_read);
do {
match_expect = report_matches(&expect);
} while (!end_test_checks(match_expect));
if (IS_ENABLED(CONFIG_KCSAN_REPORT_RACE_UNKNOWN_ORIGIN))
KUNIT_EXPECT_TRUE(test, match_expect);
else
KUNIT_EXPECT_FALSE(test, match_expect);
}
/* Test KCSAN_ASSUME_PLAIN_WRITES_ATOMIC if it is selected. */
__no_kcsan
static void test_write_write_assume_atomic(struct kunit *test)
{
const struct expect_report expect = {
.access = {
{ test_kernel_write, &test_var, sizeof(test_var), KCSAN_ACCESS_WRITE },
{ test_kernel_write, &test_var, sizeof(test_var), KCSAN_ACCESS_WRITE },
},
};
bool match_expect = false;
begin_test_checks(test_kernel_write, test_kernel_write);
do {
sink_value(READ_ONCE(test_var)); /* induce value-change */
match_expect = report_matches(&expect);
} while (!end_test_checks(match_expect));
if (IS_ENABLED(CONFIG_KCSAN_ASSUME_PLAIN_WRITES_ATOMIC))
KUNIT_EXPECT_FALSE(test, match_expect);
else
KUNIT_EXPECT_TRUE(test, match_expect);
}
/*
* Test that data races with writes larger than word-size are always reported,
* even if KCSAN_ASSUME_PLAIN_WRITES_ATOMIC is selected.
*/
__no_kcsan
static void test_write_write_struct(struct kunit *test)
{
const struct expect_report expect = {
.access = {
{ test_kernel_write_struct, &test_struct, sizeof(test_struct), KCSAN_ACCESS_WRITE },
{ test_kernel_write_struct, &test_struct, sizeof(test_struct), KCSAN_ACCESS_WRITE },
},
};
bool match_expect = false;
begin_test_checks(test_kernel_write_struct, test_kernel_write_struct);
do {
match_expect = report_matches(&expect);
} while (!end_test_checks(match_expect));
KUNIT_EXPECT_TRUE(test, match_expect);
}
/*
* Test that data races where only one write is larger than word-size are always
* reported, even if KCSAN_ASSUME_PLAIN_WRITES_ATOMIC is selected.
*/
__no_kcsan
static void test_write_write_struct_part(struct kunit *test)
{
const struct expect_report expect = {
.access = {
{ test_kernel_write_struct, &test_struct, sizeof(test_struct), KCSAN_ACCESS_WRITE },
{ test_kernel_write_struct_part, &test_struct.val[3], sizeof(test_struct.val[3]), KCSAN_ACCESS_WRITE },
},
};
bool match_expect = false;
begin_test_checks(test_kernel_write_struct, test_kernel_write_struct_part);
do {
match_expect = report_matches(&expect);
} while (!end_test_checks(match_expect));
KUNIT_EXPECT_TRUE(test, match_expect);
}
/* Test that races with atomic accesses never result in reports. */
__no_kcsan
static void test_read_atomic_write_atomic(struct kunit *test)
{
bool match_never = false;
begin_test_checks(test_kernel_read_atomic, test_kernel_write_atomic);
do {
match_never = report_available();
} while (!end_test_checks(match_never));
KUNIT_EXPECT_FALSE(test, match_never);
}
/* Test that a race with an atomic and plain access result in reports. */
__no_kcsan
static void test_read_plain_atomic_write(struct kunit *test)
{
const struct expect_report expect = {
.access = {
{ test_kernel_read, &test_var, sizeof(test_var), 0 },
{ test_kernel_write_atomic, &test_var, sizeof(test_var), KCSAN_ACCESS_WRITE | KCSAN_ACCESS_ATOMIC },
},
};
bool match_expect = false;
if (IS_ENABLED(CONFIG_KCSAN_IGNORE_ATOMICS))
return;
begin_test_checks(test_kernel_read, test_kernel_write_atomic);
do {
match_expect = report_matches(&expect);
} while (!end_test_checks(match_expect));
KUNIT_EXPECT_TRUE(test, match_expect);
}
/* Test that atomic RMWs generate correct report. */
__no_kcsan
static void test_read_plain_atomic_rmw(struct kunit *test)
{
const struct expect_report expect = {
.access = {
{ test_kernel_read, &test_var, sizeof(test_var), 0 },
{ test_kernel_atomic_rmw, &test_var, sizeof(test_var),
KCSAN_ACCESS_COMPOUND | KCSAN_ACCESS_WRITE | KCSAN_ACCESS_ATOMIC },
},
};
bool match_expect = false;
if (IS_ENABLED(CONFIG_KCSAN_IGNORE_ATOMICS))
return;
begin_test_checks(test_kernel_read, test_kernel_atomic_rmw);
do {
match_expect = report_matches(&expect);
} while (!end_test_checks(match_expect));
KUNIT_EXPECT_TRUE(test, match_expect);
}
/* Zero-sized accesses should never cause data race reports. */
__no_kcsan
static void test_zero_size_access(struct kunit *test)
{
const struct expect_report expect = {
.access = {
{ test_kernel_write_struct, &test_struct, sizeof(test_struct), KCSAN_ACCESS_WRITE },
{ test_kernel_write_struct, &test_struct, sizeof(test_struct), KCSAN_ACCESS_WRITE },
},
};
const struct expect_report never = {
.access = {
{ test_kernel_write_struct, &test_struct, sizeof(test_struct), KCSAN_ACCESS_WRITE },
{ test_kernel_read_struct_zero_size, &test_struct.val[3], 0, 0 },
},
};
bool match_expect = false;
bool match_never = false;
begin_test_checks(test_kernel_write_struct, test_kernel_read_struct_zero_size);
do {
match_expect |= report_matches(&expect);
match_never = report_matches(&never);
} while (!end_test_checks(match_never));
KUNIT_EXPECT_TRUE(test, match_expect); /* Sanity check. */
KUNIT_EXPECT_FALSE(test, match_never);
}
/* Test the data_race() macro. */
__no_kcsan
static void test_data_race(struct kunit *test)
{
bool match_never = false;
begin_test_checks(test_kernel_data_race, test_kernel_data_race);
do {
match_never = report_available();
} while (!end_test_checks(match_never));
KUNIT_EXPECT_FALSE(test, match_never);
}
__no_kcsan
static void test_assert_exclusive_writer(struct kunit *test)
{
const struct expect_report expect = {
.access = {
{ test_kernel_assert_writer, &test_var, sizeof(test_var), KCSAN_ACCESS_ASSERT },
{ test_kernel_write_nochange, &test_var, sizeof(test_var), KCSAN_ACCESS_WRITE },
},
};
bool match_expect = false;
begin_test_checks(test_kernel_assert_writer, test_kernel_write_nochange);
do {
match_expect = report_matches(&expect);
} while (!end_test_checks(match_expect));
KUNIT_EXPECT_TRUE(test, match_expect);
}
__no_kcsan
static void test_assert_exclusive_access(struct kunit *test)
{
const struct expect_report expect = {
.access = {
{ test_kernel_assert_access, &test_var, sizeof(test_var), KCSAN_ACCESS_ASSERT | KCSAN_ACCESS_WRITE },
{ test_kernel_read, &test_var, sizeof(test_var), 0 },
},
};
bool match_expect = false;
begin_test_checks(test_kernel_assert_access, test_kernel_read);
do {
match_expect = report_matches(&expect);
} while (!end_test_checks(match_expect));
KUNIT_EXPECT_TRUE(test, match_expect);
}
__no_kcsan
static void test_assert_exclusive_access_writer(struct kunit *test)
{
const struct expect_report expect_access_writer = {
.access = {
{ test_kernel_assert_access, &test_var, sizeof(test_var), KCSAN_ACCESS_ASSERT | KCSAN_ACCESS_WRITE },
{ test_kernel_assert_writer, &test_var, sizeof(test_var), KCSAN_ACCESS_ASSERT },
},
};
const struct expect_report expect_access_access = {
.access = {
{ test_kernel_assert_access, &test_var, sizeof(test_var), KCSAN_ACCESS_ASSERT | KCSAN_ACCESS_WRITE },
{ test_kernel_assert_access, &test_var, sizeof(test_var), KCSAN_ACCESS_ASSERT | KCSAN_ACCESS_WRITE },
},
};
const struct expect_report never = {
.access = {
{ test_kernel_assert_writer, &test_var, sizeof(test_var), KCSAN_ACCESS_ASSERT },
{ test_kernel_assert_writer, &test_var, sizeof(test_var), KCSAN_ACCESS_ASSERT },
},
};
bool match_expect_access_writer = false;
bool match_expect_access_access = false;
bool match_never = false;
begin_test_checks(test_kernel_assert_access, test_kernel_assert_writer);
do {
match_expect_access_writer |= report_matches(&expect_access_writer);
match_expect_access_access |= report_matches(&expect_access_access);
match_never |= report_matches(&never);
} while (!end_test_checks(match_never));
KUNIT_EXPECT_TRUE(test, match_expect_access_writer);
KUNIT_EXPECT_TRUE(test, match_expect_access_access);
KUNIT_EXPECT_FALSE(test, match_never);
}
__no_kcsan
static void test_assert_exclusive_bits_change(struct kunit *test)
{
const struct expect_report expect = {
.access = {
{ test_kernel_assert_bits_change, &test_var, sizeof(test_var), KCSAN_ACCESS_ASSERT },
{ test_kernel_change_bits, &test_var, sizeof(test_var),
KCSAN_ACCESS_WRITE | (IS_ENABLED(CONFIG_KCSAN_IGNORE_ATOMICS) ? 0 : KCSAN_ACCESS_ATOMIC) },
},
};
bool match_expect = false;
begin_test_checks(test_kernel_assert_bits_change, test_kernel_change_bits);
do {
match_expect = report_matches(&expect);
} while (!end_test_checks(match_expect));
KUNIT_EXPECT_TRUE(test, match_expect);
}
__no_kcsan
static void test_assert_exclusive_bits_nochange(struct kunit *test)
{
bool match_never = false;
begin_test_checks(test_kernel_assert_bits_nochange, test_kernel_change_bits);
do {
match_never = report_available();
} while (!end_test_checks(match_never));
KUNIT_EXPECT_FALSE(test, match_never);
}
__no_kcsan
static void test_assert_exclusive_writer_scoped(struct kunit *test)
{
const struct expect_report expect_start = {
.access = {
{ test_kernel_assert_writer_scoped, &test_var, sizeof(test_var), KCSAN_ACCESS_ASSERT | KCSAN_ACCESS_SCOPED },
{ test_kernel_write_nochange, &test_var, sizeof(test_var), KCSAN_ACCESS_WRITE },
},
};
const struct expect_report expect_anywhere = {
.access = {
{ test_enter_scope, &test_var, sizeof(test_var), KCSAN_ACCESS_ASSERT | KCSAN_ACCESS_SCOPED },
{ test_kernel_write_nochange, &test_var, sizeof(test_var), KCSAN_ACCESS_WRITE },
},
};
bool match_expect_start = false;
bool match_expect_anywhere = false;
begin_test_checks(test_kernel_assert_writer_scoped, test_kernel_write_nochange);
do {
match_expect_start |= report_matches(&expect_start);
match_expect_anywhere |= report_matches(&expect_anywhere);
} while (!end_test_checks(match_expect_start && match_expect_anywhere));
KUNIT_EXPECT_TRUE(test, match_expect_start);
KUNIT_EXPECT_TRUE(test, match_expect_anywhere);
}
__no_kcsan
static void test_assert_exclusive_access_scoped(struct kunit *test)
{
const struct expect_report expect_start1 = {
.access = {
{ test_kernel_assert_access_scoped, &test_var, sizeof(test_var), KCSAN_ACCESS_ASSERT | KCSAN_ACCESS_WRITE | KCSAN_ACCESS_SCOPED },
{ test_kernel_read, &test_var, sizeof(test_var), 0 },
},
};
const struct expect_report expect_start2 = {
.access = { expect_start1.access[0], expect_start1.access[0] },
};
const struct expect_report expect_inscope = {
.access = {
{ test_enter_scope, &test_var, sizeof(test_var), KCSAN_ACCESS_ASSERT | KCSAN_ACCESS_WRITE | KCSAN_ACCESS_SCOPED },
{ test_kernel_read, &test_var, sizeof(test_var), 0 },
},
};
bool match_expect_start = false;
bool match_expect_inscope = false;
begin_test_checks(test_kernel_assert_access_scoped, test_kernel_read);
end_time += msecs_to_jiffies(1000); /* This test requires a bit more time. */
do {
match_expect_start |= report_matches(&expect_start1) || report_matches(&expect_start2);
match_expect_inscope |= report_matches(&expect_inscope);
} while (!end_test_checks(match_expect_start && match_expect_inscope));
KUNIT_EXPECT_TRUE(test, match_expect_start);
KUNIT_EXPECT_TRUE(test, match_expect_inscope);
}
/*
* jiffies is special (declared to be volatile) and its accesses are typically
* not marked; this test ensures that the compiler nor KCSAN gets confused about
* jiffies's declaration on different architectures.
*/
__no_kcsan
static void test_jiffies_noreport(struct kunit *test)
{
bool match_never = false;
begin_test_checks(test_kernel_jiffies_reader, test_kernel_jiffies_reader);
do {
match_never = report_available();
} while (!end_test_checks(match_never));
KUNIT_EXPECT_FALSE(test, match_never);
}
/* Test that racing accesses in seqlock critical sections are not reported. */
__no_kcsan
static void test_seqlock_noreport(struct kunit *test)
{
bool match_never = false;
begin_test_checks(test_kernel_seqlock_reader, test_kernel_seqlock_writer);
do {
match_never = report_available();
} while (!end_test_checks(match_never));
KUNIT_EXPECT_FALSE(test, match_never);
}
/*
* Test atomic builtins work and required instrumentation functions exist. We
* also test that KCSAN understands they're atomic by racing with them via
* test_kernel_atomic_builtins(), and expect no reports.
*
* The atomic builtins _SHOULD NOT_ be used in normal kernel code!
*/
static void test_atomic_builtins(struct kunit *test)
{
bool match_never = false;
begin_test_checks(test_kernel_atomic_builtins, test_kernel_atomic_builtins);
do {
long tmp;
kcsan_enable_current();
__atomic_store_n(&test_var, 42L, __ATOMIC_RELAXED);
KUNIT_EXPECT_EQ(test, 42L, __atomic_load_n(&test_var, __ATOMIC_RELAXED));
KUNIT_EXPECT_EQ(test, 42L, __atomic_exchange_n(&test_var, 20, __ATOMIC_RELAXED));
KUNIT_EXPECT_EQ(test, 20L, test_var);
tmp = 20L;
KUNIT_EXPECT_TRUE(test, __atomic_compare_exchange_n(&test_var, &tmp, 30L,
0, __ATOMIC_RELAXED,
__ATOMIC_RELAXED));
KUNIT_EXPECT_EQ(test, tmp, 20L);
KUNIT_EXPECT_EQ(test, test_var, 30L);
KUNIT_EXPECT_FALSE(test, __atomic_compare_exchange_n(&test_var, &tmp, 40L,
1, __ATOMIC_RELAXED,
__ATOMIC_RELAXED));
KUNIT_EXPECT_EQ(test, tmp, 30L);
KUNIT_EXPECT_EQ(test, test_var, 30L);
KUNIT_EXPECT_EQ(test, 30L, __atomic_fetch_add(&test_var, 1, __ATOMIC_RELAXED));
KUNIT_EXPECT_EQ(test, 31L, __atomic_fetch_sub(&test_var, 1, __ATOMIC_RELAXED));
KUNIT_EXPECT_EQ(test, 30L, __atomic_fetch_and(&test_var, 0xf, __ATOMIC_RELAXED));
KUNIT_EXPECT_EQ(test, 14L, __atomic_fetch_xor(&test_var, 0xf, __ATOMIC_RELAXED));
KUNIT_EXPECT_EQ(test, 1L, __atomic_fetch_or(&test_var, 0xf0, __ATOMIC_RELAXED));
KUNIT_EXPECT_EQ(test, 241L, __atomic_fetch_nand(&test_var, 0xf, __ATOMIC_RELAXED));
KUNIT_EXPECT_EQ(test, -2L, test_var);
__atomic_thread_fence(__ATOMIC_SEQ_CST);
__atomic_signal_fence(__ATOMIC_SEQ_CST);
kcsan_disable_current();
match_never = report_available();
} while (!end_test_checks(match_never));
KUNIT_EXPECT_FALSE(test, match_never);
}
/*
* Generate thread counts for all test cases. Values generated are in interval
* [2, 5] followed by exponentially increasing thread counts from 8 to 32.
*
* The thread counts are chosen to cover potentially interesting boundaries and
* corner cases (2 to 5), and then stress the system with larger counts.
*/
static const void *nthreads_gen_params(const void *prev, char *desc)
{
long nthreads = (long)prev;
if (nthreads < 0 || nthreads >= 32)
nthreads = 0; /* stop */
else if (!nthreads)
nthreads = 2; /* initial value */
else if (nthreads < 5)
nthreads++;
else if (nthreads == 5)
nthreads = 8;
else
nthreads *= 2;
if (!IS_ENABLED(CONFIG_PREEMPT) || !IS_ENABLED(CONFIG_KCSAN_INTERRUPT_WATCHER)) {
/*
* Without any preemption, keep 2 CPUs free for other tasks, one
* of which is the main test case function checking for
* completion or failure.
*/
const long min_unused_cpus = IS_ENABLED(CONFIG_PREEMPT_NONE) ? 2 : 0;
const long min_required_cpus = 2 + min_unused_cpus;
if (num_online_cpus() < min_required_cpus) {
pr_err_once("Too few online CPUs (%u < %ld) for test\n",
num_online_cpus(), min_required_cpus);
nthreads = 0;
} else if (nthreads >= num_online_cpus() - min_unused_cpus) {
/* Use negative value to indicate last param. */
nthreads = -(num_online_cpus() - min_unused_cpus);
pr_warn_once("Limiting number of threads to %ld (only %d online CPUs)\n",
-nthreads, num_online_cpus());
}
}
snprintf(desc, KUNIT_PARAM_DESC_SIZE, "threads=%ld", abs(nthreads));
return (void *)nthreads;
}
#define KCSAN_KUNIT_CASE(test_name) KUNIT_CASE_PARAM(test_name, nthreads_gen_params)
static struct kunit_case kcsan_test_cases[] = {
KCSAN_KUNIT_CASE(test_basic),
KCSAN_KUNIT_CASE(test_concurrent_races),
KCSAN_KUNIT_CASE(test_novalue_change),
KCSAN_KUNIT_CASE(test_novalue_change_exception),
KCSAN_KUNIT_CASE(test_unknown_origin),
KCSAN_KUNIT_CASE(test_write_write_assume_atomic),
KCSAN_KUNIT_CASE(test_write_write_struct),
KCSAN_KUNIT_CASE(test_write_write_struct_part),
KCSAN_KUNIT_CASE(test_read_atomic_write_atomic),
KCSAN_KUNIT_CASE(test_read_plain_atomic_write),
KCSAN_KUNIT_CASE(test_read_plain_atomic_rmw),
KCSAN_KUNIT_CASE(test_zero_size_access),
KCSAN_KUNIT_CASE(test_data_race),
KCSAN_KUNIT_CASE(test_assert_exclusive_writer),
KCSAN_KUNIT_CASE(test_assert_exclusive_access),
KCSAN_KUNIT_CASE(test_assert_exclusive_access_writer),
KCSAN_KUNIT_CASE(test_assert_exclusive_bits_change),
KCSAN_KUNIT_CASE(test_assert_exclusive_bits_nochange),
KCSAN_KUNIT_CASE(test_assert_exclusive_writer_scoped),
KCSAN_KUNIT_CASE(test_assert_exclusive_access_scoped),
KCSAN_KUNIT_CASE(test_jiffies_noreport),
KCSAN_KUNIT_CASE(test_seqlock_noreport),
KCSAN_KUNIT_CASE(test_atomic_builtins),
{},
};
/* ===== End test cases ===== */
/* Concurrent accesses from interrupts. */
__no_kcsan
static void access_thread_timer(struct timer_list *timer)
{
static atomic_t cnt = ATOMIC_INIT(0);
unsigned int idx;
void (*func)(void);
idx = (unsigned int)atomic_inc_return(&cnt) % ARRAY_SIZE(access_kernels);
/* Acquire potential initialization. */
func = smp_load_acquire(&access_kernels[idx]);
if (func)
func();
}
/* The main loop for each thread. */
__no_kcsan
static int access_thread(void *arg)
{
struct timer_list timer;
unsigned int cnt = 0;
unsigned int idx;
void (*func)(void);
timer_setup_on_stack(&timer, access_thread_timer, 0);
do {
might_sleep();
if (!timer_pending(&timer))
mod_timer(&timer, jiffies + 1);
else {
/* Iterate through all kernels. */
idx = cnt++ % ARRAY_SIZE(access_kernels);
/* Acquire potential initialization. */
func = smp_load_acquire(&access_kernels[idx]);
if (func)
func();
}
} while (!torture_must_stop());
del_timer_sync(&timer);
destroy_timer_on_stack(&timer);
torture_kthread_stopping("access_thread");
return 0;
}
__no_kcsan
static int test_init(struct kunit *test)
{
unsigned long flags;
int nthreads;
int i;
spin_lock_irqsave(&observed.lock, flags);
for (i = 0; i < ARRAY_SIZE(observed.lines); ++i)
observed.lines[i][0] = '\0';
observed.nlines = 0;
spin_unlock_irqrestore(&observed.lock, flags);
if (!torture_init_begin((char *)test->name, 1))
return -EBUSY;
if (WARN_ON(threads))
goto err;
for (i = 0; i < ARRAY_SIZE(access_kernels); ++i) {
if (WARN_ON(access_kernels[i]))
goto err;
}
nthreads = abs((long)test->param_value);
if (WARN_ON(!nthreads))
goto err;
threads = kcalloc(nthreads + 1, sizeof(struct task_struct *), GFP_KERNEL);
if (WARN_ON(!threads))
goto err;
threads[nthreads] = NULL;
for (i = 0; i < nthreads; ++i) {
if (torture_create_kthread(access_thread, NULL, threads[i]))
goto err;
}
torture_init_end();
return 0;
err:
kfree(threads);
threads = NULL;
torture_init_end();
return -EINVAL;
}
__no_kcsan
static void test_exit(struct kunit *test)
{
struct task_struct **stop_thread;
int i;
if (torture_cleanup_begin())
return;
for (i = 0; i < ARRAY_SIZE(access_kernels); ++i)
WRITE_ONCE(access_kernels[i], NULL);
if (threads) {
for (stop_thread = threads; *stop_thread; stop_thread++)
torture_stop_kthread(reader_thread, *stop_thread);
kfree(threads);
threads = NULL;
}
torture_cleanup_end();
}
static struct kunit_suite kcsan_test_suite = {
.name = "kcsan",
.test_cases = kcsan_test_cases,
.init = test_init,
.exit = test_exit,
};
static struct kunit_suite *kcsan_test_suites[] = { &kcsan_test_suite, NULL };
__no_kcsan
static void register_tracepoints(struct tracepoint *tp, void *ignore)
{
check_trace_callback_type_console(probe_console);
if (!strcmp(tp->name, "console"))
WARN_ON(tracepoint_probe_register(tp, probe_console, NULL));
}
__no_kcsan
static void unregister_tracepoints(struct tracepoint *tp, void *ignore)
{
if (!strcmp(tp->name, "console"))
tracepoint_probe_unregister(tp, probe_console, NULL);
}
/*
* We only want to do tracepoints setup and teardown once, therefore we have to
* customize the init and exit functions and cannot rely on kunit_test_suite().
*/
static int __init kcsan_test_init(void)
{
/*
* Because we want to be able to build the test as a module, we need to
* iterate through all known tracepoints, since the static registration
* won't work here.
*/
for_each_kernel_tracepoint(register_tracepoints, NULL);
return __kunit_test_suites_init(kcsan_test_suites);
}
static void kcsan_test_exit(void)
{
__kunit_test_suites_exit(kcsan_test_suites);
for_each_kernel_tracepoint(unregister_tracepoints, NULL);
tracepoint_synchronize_unregister();
}
late_initcall(kcsan_test_init);
module_exit(kcsan_test_exit);
MODULE_LICENSE("GPL v2");
MODULE_AUTHOR("Marco Elver <elver@google.com>");
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