On Tue, Dec 9, 2025 at 1:21 AM Andy Shevchenko <[email protected]> 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. > > Reported-by: kernel test robot <[email protected]> > Closes: > https://lore.kernel.org/oe-kbuild-all/[email protected]/ > Closes: > https://lore.kernel.org/oe-kbuild-all/[email protected]/ > Closes: > https://lore.kernel.org/oe-kbuild-all/[email protected]/ > Fixes: 10aceb629e19 ("bpf: Add bpf_trace_vprintk helper") > Fixes: 7b15523a989b ("bpf: Add a bpf_snprintf helper") > Fixes: 492e639f0c22 ("bpf: Add bpf_seq_printf and bpf_seq_write helpers") > Fixes: f3694e001238 ("bpf: add BPF_CALL_x macros for declaring helpers") > Signed-off-by: Andy Shevchenko <[email protected]> > --- > > This is combined change and I think there is no need to split it, but if > required > I can do it in a four changes. Note, the culprits are older than 4 years and > stable > kernels anyway don't go that deep nowadays.
This is pointless churn to shut up a warning. Teach syzbot to stop this spam instead. 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. pw-bot: cr
