* Re: [PATCH] tracing: remove __printf() attribute on __ftrace_vbprintk() [not found] <20260202095834.1328352-1-arnd@kernel.org> @ 2026-02-03 12:12 ` kernel test robot 2026-02-03 14:58 ` Andy Shevchenko 0 siblings, 1 reply; 4+ messages in thread From: kernel test robot @ 2026-02-03 12:12 UTC (permalink / raw) To: Arnd Bergmann, Steven Rostedt, Masami Hiramatsu, Simon Horman, Jeff Layton, Anna Schumaker, Chuck Lever Cc: llvm, oe-kbuild-all, Arnd Bergmann, Mathieu Desnoyers, Andrew Morton, Linux Memory Management List, Andy Shevchenko, Randy Dunlap, Yury Norov, Joel Fernandes, linux-kernel, linux-trace-kernel Hi Arnd, kernel test robot noticed the following build warnings: [auto build test WARNING on next-20260130] [cannot apply to trace/for-next linus/master v6.19-rc8 v6.19-rc7 v6.19-rc6 v6.19-rc8] [If your patch is applied to the wrong git tree, kindly drop us a note. And when submitting patch, we suggest to use '--base' as documented in https://git-scm.com/docs/git-format-patch#_base_tree_information] url: https://github.com/intel-lab-lkp/linux/commits/Arnd-Bergmann/tracing-remove-__printf-attribute-on-__ftrace_vbprintk/20260202-180958 base: next-20260130 patch link: https://lore.kernel.org/r/20260202095834.1328352-1-arnd%40kernel.org patch subject: [PATCH] tracing: remove __printf() attribute on __ftrace_vbprintk() config: riscv-allmodconfig (https://download.01.org/0day-ci/archive/20260203/202602032036.FQK7gJvV-lkp@intel.com/config) compiler: clang version 22.0.0git (https://github.com/llvm/llvm-project 9b8addffa70cee5b2acc5454712d9cf78ce45710) reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260203/202602032036.FQK7gJvV-lkp@intel.com/reproduce) If you fix the issue in a separate patch/commit (i.e. not just a new version of the same patch/commit), kindly add following tags | Reported-by: kernel test robot <lkp@intel.com> | Closes: https://lore.kernel.org/oe-kbuild-all/202602032036.FQK7gJvV-lkp@intel.com/ All warnings (new ones prefixed by >>): >> kernel/trace/trace_printk.c:212:34: warning: diagnostic behavior may be improved by adding the 'format(printf, 2, 3)' attribute to the declaration of '__trace_bprintk' [-Wmissing-format-attribute] 212 | ret = trace_vbprintk(ip, fmt, ap); | ^ include/linux/trace_printk.h:110:5: note: '__trace_bprintk' declared here 110 | int __trace_bprintk(unsigned long ip, const char *fmt, ...); | ^ 1 warning generated. vim +212 kernel/trace/trace_printk.c 1ba28e02a18cbd kernel/trace/trace_bprintk.c Lai Jiangshan 2009-03-06 199 48ead02030f849 kernel/trace/trace_printk.c Frederic Weisbecker 2009-03-12 200 int __trace_bprintk(unsigned long ip, const char *fmt, ...) 1427cdf0592368 kernel/trace/trace_bprintk.c Lai Jiangshan 2009-03-06 201 { 769b0441f438c4 kernel/trace/trace_printk.c Frederic Weisbecker 2009-03-06 202 int ret; 769b0441f438c4 kernel/trace/trace_printk.c Frederic Weisbecker 2009-03-06 203 va_list ap; 1427cdf0592368 kernel/trace/trace_bprintk.c Lai Jiangshan 2009-03-06 204 769b0441f438c4 kernel/trace/trace_printk.c Frederic Weisbecker 2009-03-06 205 if (unlikely(!fmt)) 769b0441f438c4 kernel/trace/trace_printk.c Frederic Weisbecker 2009-03-06 206 return 0; 769b0441f438c4 kernel/trace/trace_printk.c Frederic Weisbecker 2009-03-06 207 b9f9108cad3998 kernel/trace/trace_printk.c Steven Rostedt (Red Hat 2015-09-29 208) if (!trace_printk_enabled) 769b0441f438c4 kernel/trace/trace_printk.c Frederic Weisbecker 2009-03-06 209 return 0; 769b0441f438c4 kernel/trace/trace_printk.c Frederic Weisbecker 2009-03-06 210 769b0441f438c4 kernel/trace/trace_printk.c Frederic Weisbecker 2009-03-06 211 va_start(ap, fmt); 40ce74f19c2807 kernel/trace/trace_printk.c Steven Rostedt 2009-03-19 @212 ret = trace_vbprintk(ip, fmt, ap); 769b0441f438c4 kernel/trace/trace_printk.c Frederic Weisbecker 2009-03-06 213 va_end(ap); 769b0441f438c4 kernel/trace/trace_printk.c Frederic Weisbecker 2009-03-06 214 return ret; 1427cdf0592368 kernel/trace/trace_bprintk.c Lai Jiangshan 2009-03-06 215 } 48ead02030f849 kernel/trace/trace_printk.c Frederic Weisbecker 2009-03-12 216 EXPORT_SYMBOL_GPL(__trace_bprintk); 1427cdf0592368 kernel/trace/trace_bprintk.c Lai Jiangshan 2009-03-06 217 -- 0-DAY CI Kernel Test Service https://github.com/intel/lkp-tests/wiki ^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] tracing: remove __printf() attribute on __ftrace_vbprintk() 2026-02-03 12:12 ` [PATCH] tracing: remove __printf() attribute on __ftrace_vbprintk() kernel test robot @ 2026-02-03 14:58 ` Andy Shevchenko 2026-02-03 15:56 ` Arnd Bergmann 0 siblings, 1 reply; 4+ messages in thread From: Andy Shevchenko @ 2026-02-03 14:58 UTC (permalink / raw) To: kernel test robot Cc: Arnd Bergmann, Steven Rostedt, Masami Hiramatsu, Simon Horman, Jeff Layton, Anna Schumaker, Chuck Lever, llvm, oe-kbuild-all, Arnd Bergmann, Mathieu Desnoyers, Andrew Morton, Linux Memory Management List, Randy Dunlap, Yury Norov, Joel Fernandes, linux-kernel, linux-trace-kernel On Tue, Feb 03, 2026 at 08:12:57PM +0800, kernel test robot wrote: > kernel test robot noticed the following build warnings: Yeah, you need to go for the full stack of these calls and mark the bottom one with __diag() to avoid these warnings. That's my understanding and what BPF people required. Chasing this one-by-one would produce unneeded churn. -- With Best Regards, Andy Shevchenko ^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] tracing: remove __printf() attribute on __ftrace_vbprintk() 2026-02-03 14:58 ` Andy Shevchenko @ 2026-02-03 15:56 ` Arnd Bergmann 2026-02-03 17:17 ` Andy Shevchenko 0 siblings, 1 reply; 4+ messages in thread From: Arnd Bergmann @ 2026-02-03 15:56 UTC (permalink / raw) To: Andy Shevchenko, kernel test robot Cc: Arnd Bergmann, Steven Rostedt, Masami Hiramatsu, Simon Horman, Jeff Layton, Anna Schumaker, Chuck Lever, llvm, oe-kbuild-all, Mathieu Desnoyers, Andrew Morton, Linux Memory Management List, Randy Dunlap, Yury Norov, Joel Fernandes, linux-kernel, linux-trace-kernel On Tue, Feb 3, 2026, at 15:58, Andy Shevchenko wrote: > On Tue, Feb 03, 2026 at 08:12:57PM +0800, kernel test robot wrote: > >> kernel test robot noticed the following build warnings: > > Yeah, you need to go for the full stack of these calls and mark the > bottom one with __diag() to avoid these warnings. That's my understanding > and what BPF people required. Chasing this one-by-one would produce > unneeded churn. From what I can tell, I can just move the printf attribute to the __ftrace_vbprintk() definition to make this bit work. I'll send an updated patch: --- a/kernel/trace/trace_printk.c +++ b/kernel/trace/trace_printk.c @@ -197,6 +197,7 @@ struct notifier_block module_trace_bprintk_format_nb = { .notifier_call = module_trace_bprintk_format_notify, }; +__printf(2, 3) int __trace_bprintk(unsigned long ip, const char *fmt, ...) { int ret; There are unrelated warnings for BPF that I managed to shut up the same way, doing diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c index b54ec0e945aa..45d026fc4e8a 100644 --- a/kernel/bpf/helpers.c +++ b/kernel/bpf/helpers.c @@ -1046,6 +1046,7 @@ int bpf_bprintf_prepare(const char *fmt, u32 fmt_size, const u64 *raw_args, return err; } +__printf(3, 0) BPF_CALL_5(bpf_snprintf, char *, str, u32, str_size, char *, fmt, const void *, args, u32, data_len) { diff --git a/kernel/bpf/stream.c b/kernel/bpf/stream.c index 24730df55e69..816fd7fba3d2 100644 --- a/kernel/bpf/stream.c +++ b/kernel/bpf/stream.c @@ -212,6 +212,7 @@ __bpf_kfunc_start_defs(); * Avoid using enum bpf_stream_id so that kfunc users don't have to pull in the * enum in headers. */ +__printf(2, 0) __bpf_kfunc int bpf_stream_vprintk(int stream_id, const char *fmt__str, const void *args, u32 len__sz, struct bpf_prog_aux *aux) { diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c index eadaef8592a3..2d3de71ab86a 100644 --- a/kernel/trace/bpf_trace.c +++ b/kernel/trace/bpf_trace.c @@ -359,6 +359,7 @@ static const struct bpf_func_proto bpf_probe_write_user_proto = { #define MAX_TRACE_PRINTK_VARARGS 3 #define BPF_TRACE_PRINTK_SIZE 1024 +__printf(1, 0) BPF_CALL_5(bpf_trace_printk, char *, fmt, u32, fmt_size, u64, arg1, u64, arg2, u64, arg3) { @@ -412,6 +413,7 @@ const struct bpf_func_proto *bpf_get_trace_printk_proto(void) return &bpf_trace_printk_proto; } +__printf(1, 0) BPF_CALL_4(bpf_trace_vprintk, char *, fmt, u32, fmt_size, const void *, args, u32, data_len) { @@ -455,6 +457,7 @@ const struct bpf_func_proto *bpf_get_trace_vprintk_proto(void) return &bpf_trace_vprintk_proto; } +__printf(2, 0) BPF_CALL_5(bpf_seq_printf, struct seq_file *, m, char *, fmt, u32, fmt_size, const void *, args, u32, data_len) { Since those functions have no callers, the annotation on the print functions does nothing. With those added, and a couple of drivers fixed to use the correct printf attributes, the only remaining one I see is in samples/trace_events/trace-events-sample.h: In file included from /home/arnd/arm-soc/include/trace/define_trace.h:132, from /home/arnd/arm-soc/samples/trace_events/trace-events-sample.h:640, from /home/arnd/arm-soc/samples/trace_events/trace-events-sample.c:12: /home/arnd/arm-soc/samples/trace_events/./trace-events-sample.h: In function 'trace_event_get_offsets_foo_bar': /home/arnd/arm-soc/include/trace/stages/stage5_get_offsets.h:33:31: error: function 'trace_event_get_offsets_foo_bar' might be a candidate for 'gnu_printf' format attribute [-Werror=suggest-attribute=format] 33 | { (void)sizeof(struct _test_no_array_##item *); } | ^~~~~~~~~~~~~~~ /home/arnd/arm-soc/include/trace/trace_events.h:285:9: note: in definition of macro 'DECLARE_EVENT_CLASS' 285 | tstruct; \ | ^~~~~~~ /home/arnd/arm-soc/include/trace/trace_events.h:43:30: note: in expansion of macro 'PARAMS' 43 | PARAMS(tstruct), \ | ^~~~~~ /home/arnd/arm-soc/samples/trace_events/./trace-events-sample.h:291:1: note: in expansion of macro 'TRACE_EVENT' 291 | TRACE_EVENT(foo_bar, | ^~~~~~~~~~~ /home/arnd/arm-soc/samples/trace_events/./trace-events-sample.h:299:9: note: in expansion of macro 'TP_STRUCT__entry' 299 | TP_STRUCT__entry( | ^~~~~~~~~~~~~~~~ /home/arnd/arm-soc/samples/trace_events/./trace-events-sample.h:301:17: note: in expansion of macro '__field' 301 | __field( int, bar ) | ^~~~~~~ /home/arnd/arm-soc/samples/trace_events/./trace-events-sample.h: In function 'do_trace_event_raw_event_foo_bar': I don't think this is related, but I also don't see an obvious workaround other than forcing the warning off around that definition. Arnd ^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] tracing: remove __printf() attribute on __ftrace_vbprintk() 2026-02-03 15:56 ` Arnd Bergmann @ 2026-02-03 17:17 ` Andy Shevchenko 0 siblings, 0 replies; 4+ messages in thread From: Andy Shevchenko @ 2026-02-03 17:17 UTC (permalink / raw) To: Arnd Bergmann Cc: kernel test robot, Arnd Bergmann, Steven Rostedt, Masami Hiramatsu, Simon Horman, Jeff Layton, Anna Schumaker, Chuck Lever, llvm, oe-kbuild-all, Mathieu Desnoyers, Andrew Morton, Linux Memory Management List, Randy Dunlap, Yury Norov, Joel Fernandes, linux-kernel, linux-trace-kernel On Tue, Feb 03, 2026 at 04:56:03PM +0100, Arnd Bergmann wrote: > On Tue, Feb 3, 2026, at 15:58, Andy Shevchenko wrote: > > On Tue, Feb 03, 2026 at 08:12:57PM +0800, kernel test robot wrote: > > > >> kernel test robot noticed the following build warnings: > > > > Yeah, you need to go for the full stack of these calls and mark the > > bottom one with __diag() to avoid these warnings. That's my understanding > > and what BPF people required. Chasing this one-by-one would produce > > unneeded churn. > > From what I can tell, I can just move the printf attribute > to the __ftrace_vbprintk() definition to make this bit work. Ah, that's cool! ... > There are unrelated warnings for BPF that I managed to > shut up the same way, doing BPF rejected such an approach, see lore discussions in the past (patches from me). Here some pointers (but not all of them): 20251208141618.2805983-1-andriy.shevchenko@linux.intel.com 202512090407.VxRO6xAS-lkp@intel.com 20251210131234.3185985-1-andriy.shevchenko@linux.intel.com 20251216122514.7ee70d5f@canb.auug.org.au 20251215202430.c35c2d29c4f9ff614d2ab534@linux-foundation.org -- With Best Regards, Andy Shevchenko ^ permalink raw reply [flat|nested] 4+ messages in thread
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[not found] <20260202095834.1328352-1-arnd@kernel.org>
2026-02-03 12:12 ` [PATCH] tracing: remove __printf() attribute on __ftrace_vbprintk() kernel test robot
2026-02-03 14:58 ` Andy Shevchenko
2026-02-03 15:56 ` Arnd Bergmann
2026-02-03 17:17 ` Andy Shevchenko
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