From b1afefa62ca9d77c8b1d386c3512fb4f21cb7db1 Mon Sep 17 00:00:00 2001 From: "Steven Rostedt (Google)" Date: Tue, 12 Mar 2024 11:30:02 -0400 Subject: [PATCH] tracing: Use strcmp() in __assign_str() WARN_ON() check The WARN_ON() check in __assign_str() to catch where the source variable to the macro doesn't match the source variable to __string() gives an error in clang: >> include/trace/events/sunrpc.h:703:4: warning: result of comparison against a string literal is unspecified (use an explicit string comparison function instead) [-Wstring-compare] 670 | __assign_str(progname, "unknown"); That's because the __assign_str() macro has: WARN_ON_ONCE((src) != __data_offsets.dst##_ptr_); Where "src" is a string literal. Clang warns when comparing a string literal directly as it is undefined to what the value of the literal is. Since this is still to make sure the same string that goes to __string() is the same as __assign_str(), for string literals do a test for that and then use strcmp() in those cases Note that this depends on commit 51270d573a8d ("tracing/net_sched: Fix tracepoints that save qdisc_dev() as a string") being applied, as this was what found that bug. Link: https://lore.kernel.org/linux-trace-kernel/20240312113002.00031668@gandalf.local.home Cc: Masami Hiramatsu Cc: Mathieu Desnoyers Cc: Nathan Chancellor Reported-by: kernel test robot Closes: https://lore.kernel.org/oe-kbuild-all/202402292111.KIdExylU-lkp@intel.com/ Fixes: 433e1d88a3be ("tracing: Add warning if string in __assign_str() does not match __string()") Signed-off-by: Steven Rostedt (Google) --- include/trace/stages/stage6_event_callback.h | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/include/trace/stages/stage6_event_callback.h b/include/trace/stages/stage6_event_callback.h index a0c15f67eabe..83da83a0c14f 100644 --- a/include/trace/stages/stage6_event_callback.h +++ b/include/trace/stages/stage6_event_callback.h @@ -35,7 +35,9 @@ do { \ char *__str__ = __get_str(dst); \ int __len__ = __get_dynamic_array_len(dst) - 1; \ - WARN_ON_ONCE((src) != __data_offsets.dst##_ptr_); \ + WARN_ON_ONCE(__builtin_constant_p(src) ? \ + strcmp((src), __data_offsets.dst##_ptr_) : \ + (src) != __data_offsets.dst##_ptr_); \ memcpy(__str__, __data_offsets.dst##_ptr_ ? : \ EVENT_NULL_STR, __len__); \ __str__[__len__] = '\0'; \ -- 2.20.1