Commit be3f6967 authored by Marco Elver's avatar Marco Elver Committed by Paul E. McKenney
Browse files

kcsan: Show location access was reordered to 



Also show the location the access was reordered to. An example report:

| ==================================================================
| BUG: KCSAN: data-race in test_kernel_wrong_memorder / test_kernel_wrong_memorder
|
| read-write to 0xffffffffc01e61a8 of 8 bytes by task 2311 on cpu 5:
|  test_kernel_wrong_memorder+0x57/0x90
|  access_thread+0x99/0xe0
|  kthread+0x2ba/0x2f0
|  ret_from_fork+0x22/0x30
|
| read-write (reordered) to 0xffffffffc01e61a8 of 8 bytes by task 2310 on cpu 7:
|  test_kernel_wrong_memorder+0x57/0x90
|  access_thread+0x99/0xe0
|  kthread+0x2ba/0x2f0
|  ret_from_fork+0x22/0x30
|   |
|   +-> reordered to: test_kernel_wrong_memorder+0x80/0x90
|
| Reported by Kernel Concurrency Sanitizer on:
| CPU: 7 PID: 2310 Comm: access_thread Not tainted 5.14.0-rc1+ #18
| Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.14.0-2 04/01/2014
| ==================================================================

Reviewed-by: default avatarBoqun Feng <boqun.feng@gmail.com>
Signed-off-by: default avatarMarco Elver <elver@google.com>
Signed-off-by: default avatarPaul E. McKenney <paulmck@kernel.org>
parent 3cc21a53

kernel/kcsan/report.c

+23 −12
Original line number Diff line number Diff line
@@ -308,10 +308,12 @@ static int get_stack_skipnr(const unsigned long stack_entries[], int num_entries 


/*

 * Skips to the first entry that matches the function of @ip, and then replaces

 * that entry with @ip, returning the entries to skip.

 * that entry with @ip, returning the entries to skip with @replaced containing

 * the replaced entry.

 */

static int

replace_stack_entry(unsigned long stack_entries[], int num_entries, unsigned long ip)

replace_stack_entry(unsigned long stack_entries[], int num_entries, unsigned long ip,

		    unsigned long *replaced)

{

	unsigned long symbolsize, offset;

	unsigned long target_func;
@@ -330,6 +332,7 @@ replace_stack_entry(unsigned long stack_entries[], int num_entries, unsigned lon 
		func -= offset;



		if (func == target_func) {

			*replaced = stack_entries[skip];

			stack_entries[skip] = ip;

			return skip;

		}
@@ -342,9 +345,10 @@ replace_stack_entry(unsigned long stack_entries[], int num_entries, unsigned lon 
}



static int

sanitize_stack_entries(unsigned long stack_entries[], int num_entries, unsigned long ip)

sanitize_stack_entries(unsigned long stack_entries[], int num_entries, unsigned long ip,

		       unsigned long *replaced)

{

	return ip ? replace_stack_entry(stack_entries, num_entries, ip) :

	return ip ? replace_stack_entry(stack_entries, num_entries, ip, replaced) :

			  get_stack_skipnr(stack_entries, num_entries);

}
@@ -360,6 +364,14 @@ static int sym_strcmp(void *addr1, void *addr2) 
	return strncmp(buf1, buf2, sizeof(buf1));

}



static void

print_stack_trace(unsigned long stack_entries[], int num_entries, unsigned long reordered_to)

{

	stack_trace_print(stack_entries, num_entries, 0);

	if (reordered_to)

		pr_err("  |\n  +-> reordered to: %pS\n", (void *)reordered_to);

}



static void print_verbose_info(struct task_struct *task)

{

	if (!task)
@@ -378,10 +390,12 @@ static void print_report(enum kcsan_value_change value_change, 
			 struct other_info *other_info,

			 u64 old, u64 new, u64 mask)

{

	unsigned long reordered_to = 0;

	unsigned long stack_entries[NUM_STACK_ENTRIES] = { 0 };

	int num_stack_entries = stack_trace_save(stack_entries, NUM_STACK_ENTRIES, 1);

	int skipnr = sanitize_stack_entries(stack_entries, num_stack_entries, ai->ip);

	int skipnr = sanitize_stack_entries(stack_entries, num_stack_entries, ai->ip, &reordered_to);

	unsigned long this_frame = stack_entries[skipnr];

	unsigned long other_reordered_to = 0;

	unsigned long other_frame = 0;

	int other_skipnr = 0; /* silence uninit warnings */
@@ -394,7 +408,7 @@ static void print_report(enum kcsan_value_change value_change, 
	if (other_info) {

		other_skipnr = sanitize_stack_entries(other_info->stack_entries,

						      other_info->num_stack_entries,

						      other_info->ai.ip);

						      other_info->ai.ip, &other_reordered_to);

		other_frame = other_info->stack_entries[other_skipnr];



		/* @value_change is only known for the other thread */
@@ -434,10 +448,9 @@ static void print_report(enum kcsan_value_change value_change, 
		       other_info->ai.cpu_id);



		/* Print the other thread's stack trace. */

		stack_trace_print(other_info->stack_entries + other_skipnr,

		print_stack_trace(other_info->stack_entries + other_skipnr,

				  other_info->num_stack_entries - other_skipnr,

				  0);



				  other_reordered_to);

		if (IS_ENABLED(CONFIG_KCSAN_VERBOSE))

			print_verbose_info(other_info->task);
@@ -451,9 +464,7 @@ static void print_report(enum kcsan_value_change value_change, 
		       get_thread_desc(ai->task_pid), ai->cpu_id);

	}

	/* Print stack trace of this thread. */

	stack_trace_print(stack_entries + skipnr, num_stack_entries - skipnr,

			  0);



	print_stack_trace(stack_entries + skipnr, num_stack_entries - skipnr, reordered_to);

	if (IS_ENABLED(CONFIG_KCSAN_VERBOSE))

		print_verbose_info(current);