[PATCH v1 1/1] bpf: Disable -Wsuggest-attribute=format

[PATCH v1 1/1] bpf: Disable -Wsuggest-attribute=format

[Andy Shevchenko]

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/bpf/stream.c:241:9: error: function ‘bpf_stream_vprintk_impl’ might be a candidate for ‘gnu_printf’ format attribute [-Werror=suggest-attribute=format]
  241 |         ret = bstr_printf(data.buf, MAX_BPRINTF_BUF, fmt__str, 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 disabling that warning since the code is
generated and warning is not so useful in this case — it can't check
the parameters for now.

Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202512061425.x0qTt9ww-lkp@intel.com/
Closes: https://lore.kernel.org/oe-kbuild-all/202512061640.9hKTnB8p-lkp@intel.com/
Closes: https://lore.kernel.org/oe-kbuild-all/202512081321.2h9ThWTg-lkp@intel.com/
Fixes: 5ab154f1463a ("bpf: Introduce BPF standard streams")
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")
Suggested-by: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
---
 kernel/bpf/Makefile   | 11 +++++++++--
 kernel/trace/Makefile |  6 ++++++
 2 files changed, 15 insertions(+), 2 deletions(-)

diff --git a/kernel/bpf/Makefile b/kernel/bpf/Makefile
index 232cbc97434d..cf7e8a972f98 100644
--- a/kernel/bpf/Makefile
+++ b/kernel/bpf/Makefile
@@ -6,7 +6,14 @@ cflags-nogcse-$(CONFIG_X86)$(CONFIG_CC_IS_GCC) := -fno-gcse
 endif
 CFLAGS_core.o += -Wno-override-init $(cflags-nogcse-yy)
 
-obj-$(CONFIG_BPF_SYSCALL) += syscall.o verifier.o inode.o helpers.o tnum.o log.o token.o liveness.o
+obj-$(CONFIG_BPF_SYSCALL) += syscall.o verifier.o inode.o tnum.o log.o token.o liveness.o
+
+obj-$(CONFIG_BPF_SYSCALL) += helpers.o stream.o
+# The ____bpf_snprintf() uses the format string that triggers a compiler warning.
+CFLAGS_helpers.o += -Wno-suggest-attribute=format
+# The bpf_stream_vprintk_impl() uses the format string that triggers a compiler warning.
+CFLAGS_stream.o += -Wno-suggest-attribute=format
+
 obj-$(CONFIG_BPF_SYSCALL) += bpf_iter.o map_iter.o task_iter.o prog_iter.o link_iter.o
 obj-$(CONFIG_BPF_SYSCALL) += hashtab.o arraymap.o percpu_freelist.o bpf_lru_list.o lpm_trie.o map_in_map.o bloom_filter.o
 obj-$(CONFIG_BPF_SYSCALL) += local_storage.o queue_stack_maps.o ringbuf.o bpf_insn_array.o
@@ -14,7 +21,7 @@ obj-$(CONFIG_BPF_SYSCALL) += bpf_local_storage.o bpf_task_storage.o
 obj-${CONFIG_BPF_LSM}	  += bpf_inode_storage.o
 obj-$(CONFIG_BPF_SYSCALL) += disasm.o mprog.o
 obj-$(CONFIG_BPF_JIT) += trampoline.o
-obj-$(CONFIG_BPF_SYSCALL) += btf.o memalloc.o rqspinlock.o stream.o
+obj-$(CONFIG_BPF_SYSCALL) += btf.o memalloc.o rqspinlock.o
 ifeq ($(CONFIG_MMU)$(CONFIG_64BIT),yy)
 obj-$(CONFIG_BPF_SYSCALL) += arena.o range_tree.o
 endif
diff --git a/kernel/trace/Makefile b/kernel/trace/Makefile
index fc5dcc888e13..1673b395c14c 100644
--- a/kernel/trace/Makefile
+++ b/kernel/trace/Makefile
@@ -104,7 +104,13 @@ obj-$(CONFIG_TRACE_EVENT_INJECT) += trace_events_inject.o
 obj-$(CONFIG_SYNTH_EVENTS) += trace_events_synth.o
 obj-$(CONFIG_HIST_TRIGGERS) += trace_events_hist.o
 obj-$(CONFIG_USER_EVENTS) += trace_events_user.o
+
 obj-$(CONFIG_BPF_EVENTS) += bpf_trace.o
+# The BPF printing functions use the format string that triggers a compiler warning.
+# Since the code is generated and warning is not so useful in this case (it can't
+# check the parameters for now) disable the warning.
+CFLAGS_bpf_trace.o += -Wno-suggest-attribute=format
+
 obj-$(CONFIG_KPROBE_EVENTS) += trace_kprobe.o
 obj-$(CONFIG_TRACEPOINTS) += error_report-traces.o
 obj-$(CONFIG_TRACEPOINTS) += power-traces.o
-- 
2.50.1