From 09df5c0ef24c1b50c8700401d2dcf3487df8a85d Mon Sep 17 00:00:00 2001 From: Eiichi Tsukata Date: Sun, 30 Jun 2019 17:54:38 +0900 Subject: [PATCH] tracing: Fix user stack trace "??" output commit 6d54ceb539aacc3df65c89500e8b045924f3ef81 upstream. Commit c5c27a0a5838 ("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: => <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: 4285f2fcef80 ("tracing: Remove the ULONG_MAX stack trace hackery") Signed-off-by: Eiichi Tsukata Signed-off-by: Steven Rostedt (VMware) Signed-off-by: Greg Kroah-Hartman --- kernel/trace/trace_output.c | 9 +-------- 1 file changed, 1 insertion(+), 8 deletions(-) diff --git a/kernel/trace/trace_output.c b/kernel/trace/trace_output.c index ba751f993c3b6..cab4a5398f1d4 100644 --- a/kernel/trace/trace_output.c +++ b/kernel/trace/trace_output.c @@ -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'); } -- 2.51.0