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tracing: Fix user stack trace "??" output 

Commit c5c27a0a58 ("x86/stacktrace: Remove the pointless ULONG_MAX
marker") removes ULONG_MAX marker from user stack trace entries but
trace_user_stack_print() still uses the marker and it outputs unnecessary
"??".

For example:

            less-1911  [001] d..2    34.758944: <user stack trace>
   =>  <00007f16f2295910>
   => ??
   => ??
   => ??
   => ??
   => ??
   => ??
   => ??

The user stack trace code zeroes the storage before saving the stack, so if
the trace is shorter than the maximum number of entries it can terminate
the print loop if a zero entry is detected.

Link: http://lkml.kernel.org/r/20190630085438.25545-1-devel@etsukata.com

Cc: stable@vger.kernel.org
Fixes: 4285f2fcef ("tracing: Remove the ULONG_MAX stack trace hackery")
Signed-off-by: Eiichi Tsukata <devel@etsukata.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
This commit is contained in:
Eiichi Tsukata 2019-06-30 17:54:38 +09:00 committed by Steven Rostedt (VMware)
parent 0aeb1def44
commit 6d54ceb539
1 changed files with 1 additions and 8 deletions
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9
kernel/trace/trace_output.c
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@ -1109,17 +1109,10 @@ static enum print_line_t trace_user_stack_print(struct trace_iterator *iter,
for (i = 0; i < FTRACE_STACK_ENTRIES; i++) {
unsigned long ip = field->caller[i];
if (ip == ULONG_MAX || trace_seq_has_overflowed(s))
if (!ip || trace_seq_has_overflowed(s))
break;
trace_seq_puts(s, " => ");
if (!ip) {
trace_seq_puts(s, "??");
trace_seq_putc(s, '\n');
continue;
}
seq_print_user_ip(s, mm, ip, flags);
trace_seq_putc(s, '\n');
}