Commit 47144eca authored by Marco Elver's avatar Marco Elver Committed by Ingo Molnar
Browse files

kcsan: Show full access type in report 



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

Suggested-by: default avatarPaul E. McKenney <paulmck@kernel.org>
Signed-off-by: default avatarMarco Elver <elver@google.com>
Signed-off-by: default avatarPaul E. McKenney <paulmck@kernel.org>
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 5c361425

kernel/kcsan/core.c

+8 −7
Original line number Diff line number Diff line
@@ -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)

{
@@ -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 {

		/*
@@ -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;
@@ -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);

	}
@@ -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 ===================================================== */

kernel/kcsan/kcsan.h

+1 −1
Original line number Diff line number Diff line
@@ -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 */

kernel/kcsan/report.c

+28 −15
Original line number Diff line number Diff line
@@ -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];
@@ -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) {

		/*
@@ -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. */
@@ -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)

{
@@ -124,7 +137,7 @@ 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) {
@@ -132,7 +145,7 @@ static bool print_report(const volatile void *ptr, size_t size, bool is_write, 
						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;

	}
@@ -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);
@@ -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;
@@ -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 &&
@@ -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);
@@ -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);