with GCC 13.2.1 and W=1, there's compiling warning like this:
kernel/panic.c: In function ‘__warn’:
kernel/panic.c:676:17: warning: function ‘__warn’ might be a candidate for ‘gnu_printf’ format attribute [-Wsuggest-attribute=format]
676 | vprintk(args->fmt, args->args);
| ^~~~~~~
The normal __printf(x,y) adding can't fix it. So add workaround which
disables -Wsuggest-attribute=format to mute it.
Signed-off-by: Baoquan He <[email protected]>
---
kernel/panic.c | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/kernel/panic.c b/kernel/panic.c
index 2807639aab51..d49b68184c56 100644
--- a/kernel/panic.c
+++ b/kernel/panic.c
@@ -666,8 +666,13 @@ void __warn(const char *file, int line, void *caller, unsigned taint,
pr_warn("WARNING: CPU: %d PID: %d at %pS\n",
raw_smp_processor_id(), current->pid, caller);
+#pragma GCC diagnostic push
+#ifndef __clang__
+#pragma GCC diagnostic ignored "-Wsuggest-attribute=format"
+#endif
if (args)
vprintk(args->fmt, args->args);
+#pragma GCC diagnostic pop
print_modules();
--
2.41.0
On Sun, 7 Jan 2024 17:16:41 +0800 Baoquan He <[email protected]> wrote:
> with GCC 13.2.1 and W=1, there's compiling warning like this:
>
> kernel/panic.c: In function ‘__warn’:
> kernel/panic.c:676:17: warning: function ‘__warn’ might be a candidate for ‘gnu_printf’ format attribute [-Wsuggest-attribute=format]
> 676 | vprintk(args->fmt, args->args);
> | ^~~~~~~
>
> The normal __printf(x,y) adding can't fix it. So add workaround which
> disables -Wsuggest-attribute=format to mute it.
>
> ...
>
> --- a/kernel/panic.c
> +++ b/kernel/panic.c
> @@ -666,8 +666,13 @@ void __warn(const char *file, int line, void *caller, unsigned taint,
> pr_warn("WARNING: CPU: %d PID: %d at %pS\n",
> raw_smp_processor_id(), current->pid, caller);
>
> +#pragma GCC diagnostic push
> +#ifndef __clang__
> +#pragma GCC diagnostic ignored "-Wsuggest-attribute=format"
> +#endif
> if (args)
> vprintk(args->fmt, args->args);
> +#pragma GCC diagnostic pop
>
> print_modules();
__warn() clearly isn't such a candidate. I'm suspecting that gcc's
implementation of this warning is pretty crude. Is it a new thing in
gcc-13.2?
A bit of context for [email protected]:
struct warn_args {
const char *fmt;
va_list args;
};
...
void __warn(const char *file, int line, void *caller, unsigned taint,
struct pt_regs *regs, struct warn_args *args)
{
disable_trace_on_warning();
if (file)
pr_warn("WARNING: CPU: %d PID: %d at %s:%d %pS\n",
raw_smp_processor_id(), current->pid, file, line,
caller);
else
pr_warn("WARNING: CPU: %d PID: %d at %pS\n",
raw_smp_processor_id(), current->pid, caller);
if (args)
vprintk(args->fmt, args->args);
print_modules();
if (regs)
show_regs(regs);
check_panic_on_warn("kernel");
if (!regs)
dump_stack();
print_irqtrace_events(current);
print_oops_end_marker();
trace_error_report_end(ERROR_DETECTOR_WARN, (unsigned long)caller);
/* Just a warning, don't kill lockdep. */
add_taint(taint, LOCKDEP_STILL_OK);
}
On 01/07/24 at 10:21am, Andrew Morton wrote:
> On Sun, 7 Jan 2024 17:16:41 +0800 Baoquan He <[email protected]> wrote:
>
> > with GCC 13.2.1 and W=1, there's compiling warning like this:
> >
> > kernel/panic.c: In function ‘__warn’:
> > kernel/panic.c:676:17: warning: function ‘__warn’ might be a candidate for ‘gnu_printf’ format attribute [-Wsuggest-attribute=format]
> > 676 | vprintk(args->fmt, args->args);
> > | ^~~~~~~
> >
> > The normal __printf(x,y) adding can't fix it. So add workaround which
> > disables -Wsuggest-attribute=format to mute it.
> >
> > ...
> >
> > --- a/kernel/panic.c
> > +++ b/kernel/panic.c
> > @@ -666,8 +666,13 @@ void __warn(const char *file, int line, void *caller, unsigned taint,
> > pr_warn("WARNING: CPU: %d PID: %d at %pS\n",
> > raw_smp_processor_id(), current->pid, caller);
> >
> > +#pragma GCC diagnostic push
> > +#ifndef __clang__
> > +#pragma GCC diagnostic ignored "-Wsuggest-attribute=format"
> > +#endif
> > if (args)
> > vprintk(args->fmt, args->args);
> > +#pragma GCC diagnostic pop
> >
> > print_modules();
>
> __warn() clearly isn't such a candidate. I'm suspecting that gcc's
> implementation of this warning is pretty crude. Is it a new thing in
> gcc-13.2?
Yeah, this isn't like other warnings in kernel. The compiler seems too
smart by look into the parameter 'args' of 'struct warn_args*'.
>
> A bit of context for [email protected]:
>
> struct warn_args {
> const char *fmt;
> va_list args;
> };
>
> ...
>
> void __warn(const char *file, int line, void *caller, unsigned taint,
> struct pt_regs *regs, struct warn_args *args)
> {
> disable_trace_on_warning();
>
> if (file)
> pr_warn("WARNING: CPU: %d PID: %d at %s:%d %pS\n",
> raw_smp_processor_id(), current->pid, file, line,
> caller);
> else
> pr_warn("WARNING: CPU: %d PID: %d at %pS\n",
> raw_smp_processor_id(), current->pid, caller);
>
> if (args)
> vprintk(args->fmt, args->args);
>
> print_modules();
>
> if (regs)
> show_regs(regs);
>
> check_panic_on_warn("kernel");
>
> if (!regs)
> dump_stack();
>
> print_irqtrace_events(current);
>
> print_oops_end_marker();
> trace_error_report_end(ERROR_DETECTOR_WARN, (unsigned long)caller);
>
> /* Just a warning, don't kill lockdep. */
> add_taint(taint, LOCKDEP_STILL_OK);
> }
>