From: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
To: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Cc: Alexei Starovoitov <ast@kernel.org>, bpf <bpf@vger.kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
linux-trace-kernel <linux-trace-kernel@vger.kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
John Fastabend <john.fastabend@gmail.com>,
Andrii Nakryiko <andrii@kernel.org>,
Martin KaFai Lau <martin.lau@linux.dev>,
Eduard Zingerman <eddyz87@gmail.com>, Song Liu <song@kernel.org>,
Yonghong Song <yonghong.song@linux.dev>,
KP Singh <kpsingh@kernel.org>,
Stanislav Fomichev <sdf@fomichev.me>, Hao Luo <haoluo@google.com>,
Jiri Olsa <jolsa@kernel.org>,
Matt Bobrowski <mattbobrowski@google.com>,
Steven Rostedt <rostedt@goodmis.org>,
Masami Hiramatsu <mhiramat@kernel.org>,
Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
Alan Maguire <alan.maguire@oracle.com>,
kernel test robot <lkp@intel.com>
Subject: Re: [PATCH v1 1/1] bpf: Mark BPF printing functions with __printf() attribute
Date: Wed, 10 Dec 2025 15:13:46 +0200 [thread overview]
Message-ID: <aTlyCimsBUsU5QgZ@smile.fi.intel.com> (raw)
In-Reply-To: <CAADnVQLkSoOL8+kELdmX5nzNcXm-s4VbA5+Q-MPcNySsSiu+RQ@mail.gmail.com>
On Wed, Dec 10, 2025 at 04:09:19PM +0900, Alexei Starovoitov wrote:
> On Tue, Dec 9, 2025 at 10:37 PM Andy Shevchenko
> <andriy.shevchenko@linux.intel.com> wrote:
> >
> > On Tue, Dec 09, 2025 at 06:12:46PM +0900, Alexei Starovoitov wrote:
> > > On Tue, Dec 9, 2025 at 1:21 AM Andy Shevchenko
> > > <andriy.shevchenko@linux.intel.com> wrote:
> > > >
> > > > The printing functions in BPF code are using printf() type of format,
> > > > and compiler is not happy about them as is:
> > > >
> > > > kernel/bpf/helpers.c:1069:9: error: function ‘____bpf_snprintf’ might be a candidate for ‘gnu_printf’ format attribute [-Werror=suggest-attribute=format]
> > > > 1069 | err = bstr_printf(str, str_size, fmt, data.bin_args);
> > > > | ^~~
> > > >
> > > > kernel/trace/bpf_trace.c:377:9: error: function ‘____bpf_trace_printk’ might be a candidate for ‘gnu_printf’ format attribute [-Werror=suggest-attribute=format]
> > > > 377 | ret = bstr_printf(data.buf, MAX_BPRINTF_BUF, fmt, data.bin_args);
> > > > | ^~~
> > > >
> > > > kernel/trace/bpf_trace.c:433:9: error: function ‘____bpf_trace_vprintk’ might be a candidate for ‘gnu_printf’ format attribute [-Werror=suggest-attribute=format]
> > > > 433 | ret = bstr_printf(data.buf, MAX_BPRINTF_BUF, fmt, data.bin_args);
> > > > | ^~~
> > > >
> > > > kernel/trace/bpf_trace.c:475:9: error: function ‘____bpf_seq_printf’ might be a candidate for ‘gnu_printf’ format attribute [-Werror=suggest-attribute=format]
> > > > 475 | seq_bprintf(m, fmt, data.bin_args);
> > > > | ^~~~~~~~~~~
> > > >
> > > > Fix the compilation errors by adding __printf() attribute. For that
> > > > we need to pass it down to the BPF_CALL_x() and wrap into PRINTF_BPF_CALL_*()
> > > > to make code neater.
> >
> > > This is pointless churn to shut up a warning.
> >
> > In some cases, like mine, it's an error.
> >
> > > Teach syzbot to stop this spam instead.
> >
> > It prevents to perform `make W=1` builds with the default CONFIG_WERROR,
> > which is 'y'.
> >
> > > At the end this patch doesn't make any visible difference,
> > > since user declarations of these helpers are auto generated
> > > from uapi/bpf.h file and __printf attribute is not there.
> >
> > I see, thanks for the review.
> > Any recommendations on how to fix this properly?
>
> Add -Wno-suggest-attribute=format
> to corresponding files in Makefile.
Thanks, I just sent a new patch.
> I think it's cleaner than __diag_ignore() in the .c
--
With Best Regards,
Andy Shevchenko
prev parent reply other threads:[~2025-12-10 13:13 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-12-08 16:18 [PATCH v1 1/1] bpf: Mark BPF printing functions with __printf() attribute Andy Shevchenko
2025-12-09 9:12 ` Alexei Starovoitov
2025-12-09 13:37 ` Andy Shevchenko
2025-12-10 7:09 ` Alexei Starovoitov
2025-12-10 13:13 ` Andy Shevchenko [this message]
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