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

[Andy Shevchenko]

On Mon, Feb 02, 2026 at 10:58:27AM +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.
> 
> Remove the __printf(2,3) annotation on this function, as this is can
> only be validated for literals. 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.

Yeah, it was discussed in the past that binary printf() should not be annotated
as we have BPF code that doesn't compile (with the default WERROR=y).

-- 
With Best Regards,
Andy Shevchenko