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kcsan: Test support for compound instrumentation 

Changes kcsan-test module to support checking reports that include
compound instrumentation. Since we should not fail the test if this
support is unavailable, we have to add a config variable that the test
can use to decide what to check for.

Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit is contained in:
Marco Elver 2020-07-24 09:00:05 +02:00 committed by Paul E. McKenney
parent 9d1335cc1e
commit bec4a24748
2 changed files with 56 additions and 14 deletions
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65
kernel/kcsan/kcsan-test.c
View File

@ -27,6 +27,12 @@
#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);
@ -186,20 +192,21 @@ static bool report_matches(const struct expect_report *r)
/* Access 1 & 2 */
for (i = 0; i < 2; ++i) {
const int ty = r->access[i].type;
const char *const access_type =
(r->access[i].type & KCSAN_ACCESS_ASSERT) ?
((r->access[i].type & KCSAN_ACCESS_WRITE) ?
"assert no accesses" :
"assert no writes") :
((r->access[i].type & KCSAN_ACCESS_WRITE) ?
"write" :
"read");
(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 =
(r->access[i].type & KCSAN_ACCESS_ATOMIC) ?
" (marked)" :
((r->access[i].type & KCSAN_ACCESS_SCOPED) ?
" (scoped)" :
"");
(ty & KCSAN_ACCESS_ATOMIC) ?
" (marked)" :
((ty & KCSAN_ACCESS_SCOPED) ? " (scoped)" : "");
if (i == 1) {
/* Access 2 */
@ -277,6 +284,12 @@ 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++; }
@ -439,8 +452,8 @@ 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_WRITE },
{ test_kernel_rmw_array, NULL, 0, 0 },
{ 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 = {
@ -629,6 +642,29 @@ static void test_read_plain_atomic_write(struct kunit *test)
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)
@ -942,6 +978,7 @@ static struct kunit_case kcsan_test_cases[] = {
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),

5
lib/Kconfig.kcsan
View File

@ -40,6 +40,11 @@ menuconfig KCSAN
if KCSAN
# Compiler capabilities that should not fail the test if they are unavailable.
config CC_HAS_TSAN_COMPOUND_READ_BEFORE_WRITE
def_bool (CC_IS_CLANG && $(cc-option,-fsanitize=thread -mllvm -tsan-compound-read-before-write=1)) || \
(CC_IS_GCC && $(cc-option,-fsanitize=thread --param tsan-compound-read-before-write=1))
config KCSAN_VERBOSE
bool "Show verbose reports with more information about system state"
depends on PROVE_LOCKING