AcoSail/kernel_optimize_test
8
0
Fork 0
forked from luck/tmp_suning_uos_patched
Code Pull Requests Activity

kcsan: Add kcsan_set_access_mask() support

Browse Source 
When setting up an access mask with kcsan_set_access_mask(), KCSAN will
only report races if concurrent changes to bits set in access_mask are
observed. Conveying access_mask via a separate call avoids introducing
overhead in the common-case fast-path.

Acked-by: John Hubbard <jhubbard@nvidia.com>
Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Marco Elver 2020-02-11 17:04:22 +01:00 committed by Ingo Molnar
parent b738f6169f
commit 81af89e158
6 changed files with 73 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

11
include/linux/kcsan-checks.h
View File

@ -68,6 +68,16 @@ void kcsan_flat_atomic_end(void);
*/
void kcsan_atomic_next(int n);
/**
* kcsan_set_access_mask - set access mask
*
* Set the access mask for all accesses for the current context if non-zero.
* Only value changes to bits set in the mask will be reported.
*
* @mask bitmask
*/
void kcsan_set_access_mask(unsigned long mask);
#else /* CONFIG_KCSAN */
static inline void __kcsan_check_access(const volatile void *ptr, size_t size,
@ -78,6 +88,7 @@ static inline void kcsan_nestable_atomic_end(void) { }
static inline void kcsan_flat_atomic_begin(void) { }
static inline void kcsan_flat_atomic_end(void) { }
static inline void kcsan_atomic_next(int n) { }
static inline void kcsan_set_access_mask(unsigned long mask) { }
#endif /* CONFIG_KCSAN */

5
include/linux/kcsan.h
View File

@ -35,6 +35,11 @@ struct kcsan_ctx {
*/
int atomic_nest_count;
bool in_flat_atomic;
/*
* Access mask for all accesses if non-zero.
*/
unsigned long access_mask;
};
/**

1
init/init_task.c
View File

@ -167,6 +167,7 @@ struct task_struct init_task
.atomic_next = 0,
.atomic_nest_count = 0,
.in_flat_atomic = false,
.access_mask = 0,
},
#endif
#ifdef CONFIG_TRACE_IRQFLAGS

43
kernel/kcsan/core.c
View File

@ -39,6 +39,7 @@ static DEFINE_PER_CPU(struct kcsan_ctx, kcsan_cpu_ctx) = {
.atomic_next = 0,
.atomic_nest_count = 0,
.in_flat_atomic = false,
.access_mask = 0,
};
/*
@ -298,6 +299,15 @@ static noinline void kcsan_found_watchpoint(const volatile void *ptr,
if (!kcsan_is_enabled())
return;
/*
* The access_mask check relies on value-change comparison. To avoid
* reporting a race where e.g. the writer set up the watchpoint, but the
* reader has access_mask!=0, we have to ignore the found watchpoint.
*/
if (get_ctx()->access_mask != 0)
return;
/*
* Consume the watchpoint as soon as possible, to minimize the chances
* of !consumed. Consuming the watchpoint must always be guarded by
@ -341,6 +351,7 @@ kcsan_setup_watchpoint(const volatile void *ptr, size_t size, int type)
u32 _4;
u64 _8;
} expect_value;
unsigned long access_mask;
enum kcsan_value_change value_change = KCSAN_VALUE_CHANGE_MAYBE;
unsigned long ua_flags = user_access_save();
unsigned long irq_flags;
@ -435,18 +446,27 @@ kcsan_setup_watchpoint(const volatile void *ptr, size_t size, int type)
* Re-read value, and check if it is as expected; if not, we infer a
* racy access.
*/
access_mask = get_ctx()->access_mask;
switch (size) {
case 1:
expect_value._1 ^= READ_ONCE(*(const u8 *)ptr);
if (access_mask)
expect_value._1 &= (u8)access_mask;
break;
case 2:
expect_value._2 ^= READ_ONCE(*(const u16 *)ptr);
if (access_mask)
expect_value._2 &= (u16)access_mask;
break;
case 4:
expect_value._4 ^= READ_ONCE(*(const u32 *)ptr);
if (access_mask)
expect_value._4 &= (u32)access_mask;
break;
case 8:
expect_value._8 ^= READ_ONCE(*(const u64 *)ptr);
if (access_mask)
expect_value._8 &= (u64)access_mask;
break;
default:
break; /* ignore; we do not diff the values */
@ -460,11 +480,20 @@ kcsan_setup_watchpoint(const volatile void *ptr, size_t size, int type)
if (!remove_watchpoint(watchpoint)) {
/*
* Depending on the access type, map a value_change of MAYBE to
* TRUE (require reporting).
* TRUE (always report) or FALSE (never report).
*/
if (value_change == KCSAN_VALUE_CHANGE_MAYBE && (size > 8 || is_assert)) {
/* Always assume a value-change. */
value_change = KCSAN_VALUE_CHANGE_TRUE;
if (value_change == KCSAN_VALUE_CHANGE_MAYBE) {
if (access_mask != 0) {
/*
* For access with access_mask, we require a
* value-change, as it is likely that races on
* ~access_mask bits are expected.
*/
value_change = KCSAN_VALUE_CHANGE_FALSE;
} else if (size > 8 || is_assert) {
/* Always assume a value-change. */
value_change = KCSAN_VALUE_CHANGE_TRUE;
}
}
/*
@ -622,6 +651,12 @@ void kcsan_atomic_next(int n)
}
EXPORT_SYMBOL(kcsan_atomic_next);
void kcsan_set_access_mask(unsigned long mask)
{
get_ctx()->access_mask = mask;
}
EXPORT_SYMBOL(kcsan_set_access_mask);
void __kcsan_check_access(const volatile void *ptr, size_t size, int type)
{
check_access(ptr, size, type);

5
kernel/kcsan/kcsan.h
View File

@ -98,6 +98,11 @@ enum kcsan_value_change {
*/
KCSAN_VALUE_CHANGE_MAYBE,
/*
* Did not observe a value-change, and it is invalid to report the race.
*/
KCSAN_VALUE_CHANGE_FALSE,
/*
* The value was observed to change, and the race should be reported.
*/

13
kernel/kcsan/report.c
View File

@ -132,6 +132,9 @@ static bool rate_limit_report(unsigned long frame1, unsigned long frame2)
static bool
skip_report(enum kcsan_value_change value_change, unsigned long top_frame)
{
/* Should never get here if value_change==FALSE. */
WARN_ON_ONCE(value_change == KCSAN_VALUE_CHANGE_FALSE);
/*
* The first call to skip_report always has value_change==TRUE, since we
* cannot know the value written of an instrumented access. For the 2nd
@ -493,7 +496,15 @@ void kcsan_report(const volatile void *ptr, size_t size, int access_type,
kcsan_disable_current();
if (prepare_report(&flags, ptr, size, access_type, cpu_id, type)) {
if (print_report(ptr, size, access_type, value_change, cpu_id, type) && panic_on_warn)
/*
* Never report if value_change is FALSE, only if we it is
* either TRUE or MAYBE. In case of MAYBE, further filtering may
* be done once we know the full stack trace in print_report().
*/
bool reported = value_change != KCSAN_VALUE_CHANGE_FALSE &&
print_report(ptr, size, access_type, value_change, cpu_id, type);
if (reported && panic_on_warn)
panic("panic_on_warn set ...\n");
release_report(&flags, type);