Re: [PATCH] [v2] tracing: move __printf() attribute on __ftrace_vbprintk()

[Andy Shevchenko <andriy.shevchenko@linux.intel.com>]

On Tue, Feb 03, 2026 at 05:45:29PM +0100, Arnd Bergmann wrote:

> The sunrpc change to use trace_printk() for debugging caused
> a new warning for every instance of dprintk() in some configurations,
> when -Wformat-security is enabled:
> 
> fs/nfs/getroot.c: In function 'nfs_get_root':
> fs/nfs/getroot.c:90:17: error: format not a string literal and no format arguments [-Werror=format-security]
>    90 |                 nfs_errorf(fc, "NFS: Couldn't getattr on root");
> 
> I've been slowly chipping away at those warnings over time with the
> intention of enabling them by default in the future. While I could not
> figure out why this only happens for this one instance, I see that the
> __trace_bprintk() function is always called with a local variable as
> the format string, rather than a literal.
> 
> Move the __printf(2,3) annotation on this function from the declaration
> to the caller. As this is can only be validated for literals, the
> attribute on the declaration causes the warnings every time, but
> removing it entirely introduces a new warning on the __ftrace_vbprintk()
> definition.
> 
> The format strings still get checked because the underlying literal keeps
> getting passed into __trace_printk() in the "else" branch, which is not
> taken but still evaluated for compile-time warnings.

Acked-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>

-- 
With Best Regards,
Andy Shevchenko