@@ -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);
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 | ================================================================== Signed-off-by: Marco Elver <elver@google.com> --- kernel/kcsan/report.c | 35 +++++++++++++++++++++++------------ 1 file changed, 23 insertions(+), 12 deletions(-)