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kcsan: Show full access type in report
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This commit adds access-type information to KCSAN's reports as follows:
"read", "read (marked)", "write", and "write (marked)".

Suggested-by: Paul E. McKenney <[email protected]>
Signed-off-by: Marco Elver <[email protected]>
Signed-off-by: Paul E. McKenney <[email protected]>
Signed-off-by: Ingo Molnar <[email protected]>
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@melver
melver authored and Ingo Molnar committed Mar 21, 2020
1 parent 5c36142 commit 47144ec
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Showing 3 changed files with 37 additions and 23 deletions.
15 changes: 8 additions & 7 deletions kernel/kcsan/core.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -255,7 +255,7 @@ static inline unsigned int get_delay(void)

static noinline void kcsan_found_watchpoint(const volatile void *ptr,
size_t size,
bool is_write,
int type,
atomic_long_t *watchpoint,
long encoded_watchpoint)
{
Expand All @@ -276,7 +276,7 @@ static noinline void kcsan_found_watchpoint(const volatile void *ptr,
flags = user_access_save();

if (consumed) {
kcsan_report(ptr, size, is_write, true, raw_smp_processor_id(),
kcsan_report(ptr, size, type, true, raw_smp_processor_id(),
KCSAN_REPORT_CONSUMED_WATCHPOINT);
} else {
/*
Expand All @@ -292,8 +292,9 @@ static noinline void kcsan_found_watchpoint(const volatile void *ptr,
}

static noinline void
kcsan_setup_watchpoint(const volatile void *ptr, size_t size, bool is_write)
kcsan_setup_watchpoint(const volatile void *ptr, size_t size, int type)
{
const bool is_write = (type & KCSAN_ACCESS_WRITE) != 0;
atomic_long_t *watchpoint;
union {
u8 _1;
Expand Down Expand Up @@ -415,13 +416,13 @@ kcsan_setup_watchpoint(const volatile void *ptr, size_t size, bool is_write)
* No need to increment 'data_races' counter, as the racing
* thread already did.
*/
kcsan_report(ptr, size, is_write, size > 8 || value_change,
kcsan_report(ptr, size, type, size > 8 || value_change,
smp_processor_id(), KCSAN_REPORT_RACE_SIGNAL);
} else if (value_change) {
/* Inferring a race, since the value should not have changed. */
kcsan_counter_inc(KCSAN_COUNTER_RACES_UNKNOWN_ORIGIN);
if (IS_ENABLED(CONFIG_KCSAN_REPORT_RACE_UNKNOWN_ORIGIN))
kcsan_report(ptr, size, is_write, true,
kcsan_report(ptr, size, type, true,
smp_processor_id(),
KCSAN_REPORT_RACE_UNKNOWN_ORIGIN);
}
Expand Down Expand Up @@ -455,10 +456,10 @@ static __always_inline void check_access(const volatile void *ptr, size_t size,
*/

if (unlikely(watchpoint != NULL))
kcsan_found_watchpoint(ptr, size, is_write, watchpoint,
kcsan_found_watchpoint(ptr, size, type, watchpoint,
encoded_watchpoint);
else if (unlikely(should_watch(ptr, type)))
kcsan_setup_watchpoint(ptr, size, is_write);
kcsan_setup_watchpoint(ptr, size, type);
}

/* === Public interface ===================================================== */
Expand Down
2 changes: 1 addition & 1 deletion kernel/kcsan/kcsan.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -103,7 +103,7 @@ enum kcsan_report_type {
/*
* Print a race report from thread that encountered the race.
*/
extern void kcsan_report(const volatile void *ptr, size_t size, bool is_write,
extern void kcsan_report(const volatile void *ptr, size_t size, int access_type,
bool value_change, int cpu_id, enum kcsan_report_type type);

#endif /* _KERNEL_KCSAN_KCSAN_H */
43 changes: 28 additions & 15 deletions kernel/kcsan/report.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -24,7 +24,7 @@
static struct {
const volatile void *ptr;
size_t size;
bool is_write;
int access_type;
int task_pid;
int cpu_id;
unsigned long stack_entries[NUM_STACK_ENTRIES];
Expand All @@ -41,8 +41,10 @@ static DEFINE_SPINLOCK(report_lock);
* Special rules to skip reporting.
*/
static bool
skip_report(bool is_write, bool value_change, unsigned long top_frame)
skip_report(int access_type, bool value_change, unsigned long top_frame)
{
const bool is_write = (access_type & KCSAN_ACCESS_WRITE) != 0;

if (IS_ENABLED(CONFIG_KCSAN_REPORT_VALUE_CHANGE_ONLY) && is_write &&
!value_change) {
/*
Expand All @@ -63,9 +65,20 @@ skip_report(bool is_write, bool value_change, unsigned long top_frame)
return kcsan_skip_report_debugfs(top_frame);
}

static inline const char *get_access_type(bool is_write)
static const char *get_access_type(int type)
{
return is_write ? "write" : "read";
switch (type) {
case 0:
return "read";
case KCSAN_ACCESS_ATOMIC:
return "read (marked)";
case KCSAN_ACCESS_WRITE:
return "write";
case KCSAN_ACCESS_WRITE | KCSAN_ACCESS_ATOMIC:
return "write (marked)";
default:
BUG();
}
}

/* Return thread description: in task or interrupt. */
Expand Down Expand Up @@ -112,7 +125,7 @@ static int sym_strcmp(void *addr1, void *addr2)
/*
* Returns true if a report was generated, false otherwise.
*/
static bool print_report(const volatile void *ptr, size_t size, bool is_write,
static bool print_report(const volatile void *ptr, size_t size, int access_type,
bool value_change, int cpu_id,
enum kcsan_report_type type)
{
Expand All @@ -124,15 +137,15 @@ static bool print_report(const volatile void *ptr, size_t size, bool is_write,
/*
* Must check report filter rules before starting to print.
*/
if (skip_report(is_write, true, stack_entries[skipnr]))
if (skip_report(access_type, true, stack_entries[skipnr]))
return false;

if (type == KCSAN_REPORT_RACE_SIGNAL) {
other_skipnr = get_stack_skipnr(other_info.stack_entries,
other_info.num_stack_entries);

/* @value_change is only known for the other thread */
if (skip_report(other_info.is_write, value_change,
if (skip_report(other_info.access_type, value_change,
other_info.stack_entries[other_skipnr]))
return false;
}
Expand Down Expand Up @@ -170,7 +183,7 @@ static bool print_report(const volatile void *ptr, size_t size, bool is_write,
switch (type) {
case KCSAN_REPORT_RACE_SIGNAL:
pr_err("%s to 0x%px of %zu bytes by %s on cpu %i:\n",
get_access_type(other_info.is_write), other_info.ptr,
get_access_type(other_info.access_type), other_info.ptr,
other_info.size, get_thread_desc(other_info.task_pid),
other_info.cpu_id);

Expand All @@ -181,14 +194,14 @@ static bool print_report(const volatile void *ptr, size_t size, bool is_write,

pr_err("\n");
pr_err("%s to 0x%px of %zu bytes by %s on cpu %i:\n",
get_access_type(is_write), ptr, size,
get_access_type(access_type), ptr, size,
get_thread_desc(in_task() ? task_pid_nr(current) : -1),
cpu_id);
break;

case KCSAN_REPORT_RACE_UNKNOWN_ORIGIN:
pr_err("race at unknown origin, with %s to 0x%px of %zu bytes by %s on cpu %i:\n",
get_access_type(is_write), ptr, size,
get_access_type(access_type), ptr, size,
get_thread_desc(in_task() ? task_pid_nr(current) : -1),
cpu_id);
break;
Expand Down Expand Up @@ -223,7 +236,7 @@ static void release_report(unsigned long *flags, enum kcsan_report_type type)
* required for the report type, simply acquires report_lock and returns true.
*/
static bool prepare_report(unsigned long *flags, const volatile void *ptr,
size_t size, bool is_write, int cpu_id,
size_t size, int access_type, int cpu_id,
enum kcsan_report_type type)
{
if (type != KCSAN_REPORT_CONSUMED_WATCHPOINT &&
Expand All @@ -243,7 +256,7 @@ static bool prepare_report(unsigned long *flags, const volatile void *ptr,

other_info.ptr = ptr;
other_info.size = size;
other_info.is_write = is_write;
other_info.access_type = access_type;
other_info.task_pid = in_task() ? task_pid_nr(current) : -1;
other_info.cpu_id = cpu_id;
other_info.num_stack_entries = stack_trace_save(other_info.stack_entries, NUM_STACK_ENTRIES, 1);
Expand Down Expand Up @@ -302,14 +315,14 @@ static bool prepare_report(unsigned long *flags, const volatile void *ptr,
goto retry;
}

void kcsan_report(const volatile void *ptr, size_t size, bool is_write,
void kcsan_report(const volatile void *ptr, size_t size, int access_type,
bool value_change, int cpu_id, enum kcsan_report_type type)
{
unsigned long flags = 0;

kcsan_disable_current();
if (prepare_report(&flags, ptr, size, is_write, cpu_id, type)) {
if (print_report(ptr, size, is_write, value_change, cpu_id, type) && panic_on_warn)
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)
panic("panic_on_warn set ...\n");

release_report(&flags, type);
Expand Down

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