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Message-ID: <20251208161800.2902699-2-andriy.shevchenko@linux.intel.com>
Date: Mon, 8 Dec 2025 17:18:01 +0100
From: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To: Alexei Starovoitov <ast@...nel.org>,
bpf@...r.kernel.org,
linux-kernel@...r.kernel.org,
linux-trace-kernel@...r.kernel.org
Cc: Daniel Borkmann <daniel@...earbox.net>,
John Fastabend <john.fastabend@...il.com>,
Andrii Nakryiko <andrii@...nel.org>,
Martin KaFai Lau <martin.lau@...ux.dev>,
Eduard Zingerman <eddyz87@...il.com>,
Song Liu <song@...nel.org>,
Yonghong Song <yonghong.song@...ux.dev>,
KP Singh <kpsingh@...nel.org>,
Stanislav Fomichev <sdf@...ichev.me>,
Hao Luo <haoluo@...gle.com>,
Jiri Olsa <jolsa@...nel.org>,
Matt Bobrowski <mattbobrowski@...gle.com>,
Steven Rostedt <rostedt@...dmis.org>,
Masami Hiramatsu <mhiramat@...nel.org>,
Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
Alan Maguire <alan.maguire@...cle.com>,
Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
kernel test robot <lkp@...el.com>
Subject: [PATCH v1 1/1] bpf: Mark BPF printing functions with __printf() attribute
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 <lkp@...el.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: 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 <andriy.shevchenko@...ux.intel.com>
---
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.
include/linux/filter.h | 24 +++++++++++++++---------
kernel/bpf/helpers.c | 2 +-
kernel/trace/bpf_trace.c | 6 +++---
3 files changed, 19 insertions(+), 13 deletions(-)
diff --git a/include/linux/filter.h b/include/linux/filter.h
index fd54fed8f95f..31034a74af22 100644
--- a/include/linux/filter.h
+++ b/include/linux/filter.h
@@ -607,9 +607,9 @@ static inline bool insn_is_cast_user(const struct bpf_insn *insn)
__BPF_MAP(n, __BPF_DECL_ARGS, __BPF_N, u64, __ur_1, u64, __ur_2, \
u64, __ur_3, u64, __ur_4, u64, __ur_5)
-#define BPF_CALL_x(x, attr, name, ...) \
+#define BPF_CALL_x(x, __attr, attr, name, ...) \
static __always_inline \
- u64 ____##name(__BPF_MAP(x, __BPF_DECL_ARGS, __BPF_V, __VA_ARGS__)); \
+ __attr u64 ____##name(__BPF_MAP(x, __BPF_DECL_ARGS, __BPF_V, __VA_ARGS__)); \
typedef u64 (*btf_##name)(__BPF_MAP(x, __BPF_DECL_ARGS, __BPF_V, __VA_ARGS__)); \
attr u64 name(__BPF_REG(x, __BPF_DECL_REGS, __BPF_N, __VA_ARGS__)); \
attr u64 name(__BPF_REG(x, __BPF_DECL_REGS, __BPF_N, __VA_ARGS__)) \
@@ -620,14 +620,20 @@ static inline bool insn_is_cast_user(const struct bpf_insn *insn)
u64 ____##name(__BPF_MAP(x, __BPF_DECL_ARGS, __BPF_V, __VA_ARGS__))
#define __NOATTR
-#define BPF_CALL_0(name, ...) BPF_CALL_x(0, __NOATTR, name, __VA_ARGS__)
-#define BPF_CALL_1(name, ...) BPF_CALL_x(1, __NOATTR, name, __VA_ARGS__)
-#define BPF_CALL_2(name, ...) BPF_CALL_x(2, __NOATTR, name, __VA_ARGS__)
-#define BPF_CALL_3(name, ...) BPF_CALL_x(3, __NOATTR, name, __VA_ARGS__)
-#define BPF_CALL_4(name, ...) BPF_CALL_x(4, __NOATTR, name, __VA_ARGS__)
-#define BPF_CALL_5(name, ...) BPF_CALL_x(5, __NOATTR, name, __VA_ARGS__)
+#define BPF_CALL_0(name, ...) BPF_CALL_x(0, __NOATTR, __NOATTR, name, __VA_ARGS__)
+#define BPF_CALL_1(name, ...) BPF_CALL_x(1, __NOATTR, __NOATTR, name, __VA_ARGS__)
+#define BPF_CALL_2(name, ...) BPF_CALL_x(2, __NOATTR, __NOATTR, name, __VA_ARGS__)
+#define BPF_CALL_3(name, ...) BPF_CALL_x(3, __NOATTR, __NOATTR, name, __VA_ARGS__)
+#define BPF_CALL_4(name, ...) BPF_CALL_x(4, __NOATTR, __NOATTR, name, __VA_ARGS__)
+#define BPF_CALL_5(name, ...) BPF_CALL_x(5, __NOATTR, __NOATTR, name, __VA_ARGS__)
-#define NOTRACE_BPF_CALL_1(name, ...) BPF_CALL_x(1, notrace, name, __VA_ARGS__)
+#define PRINTF_BPF_CALL_x(p, name, x, ...) \
+ BPF_CALL_x(x, __printf(p, 0), __NOATTR, name, __VA_ARGS__)
+
+#define PRINTF_BPF_CALL_4(p, name, ...) PRINTF_BPF_CALL_x(p, name, 4, __VA_ARGS__)
+#define PRINTF_BPF_CALL_5(p, name, ...) PRINTF_BPF_CALL_x(p, name, 5, __VA_ARGS__)
+
+#define NOTRACE_BPF_CALL_1(name, ...) BPF_CALL_x(1, __NOATTR, notrace, name, __VA_ARGS__)
#define bpf_ctx_range(TYPE, MEMBER) \
offsetof(TYPE, MEMBER) ... offsetofend(TYPE, MEMBER) - 1
diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index db72b96f9c8c..cbc66865e3dc 100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -1046,7 +1046,7 @@ int bpf_bprintf_prepare(const char *fmt, u32 fmt_size, const u64 *raw_args,
return err;
}
-BPF_CALL_5(bpf_snprintf, char *, str, u32, str_size, char *, fmt,
+PRINTF_BPF_CALL_5(3, bpf_snprintf, char *, str, u32, str_size, char *, fmt,
const void *, args, u32, data_len)
{
struct bpf_bprintf_data data = {
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index d57727abaade..5fd46b4bcf48 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -359,7 +359,7 @@ static const struct bpf_func_proto bpf_probe_write_user_proto = {
#define MAX_TRACE_PRINTK_VARARGS 3
#define BPF_TRACE_PRINTK_SIZE 1024
-BPF_CALL_5(bpf_trace_printk, char *, fmt, u32, fmt_size, u64, arg1,
+PRINTF_BPF_CALL_5(1, bpf_trace_printk, char *, fmt, u32, fmt_size, u64, arg1,
u64, arg2, u64, arg3)
{
u64 args[MAX_TRACE_PRINTK_VARARGS] = { arg1, arg2, arg3 };
@@ -412,7 +412,7 @@ const struct bpf_func_proto *bpf_get_trace_printk_proto(void)
return &bpf_trace_printk_proto;
}
-BPF_CALL_4(bpf_trace_vprintk, char *, fmt, u32, fmt_size, const void *, args,
+PRINTF_BPF_CALL_4(1, bpf_trace_vprintk, char *, fmt, u32, fmt_size, const void *, args,
u32, data_len)
{
struct bpf_bprintf_data data = {
@@ -455,7 +455,7 @@ const struct bpf_func_proto *bpf_get_trace_vprintk_proto(void)
return &bpf_trace_vprintk_proto;
}
-BPF_CALL_5(bpf_seq_printf, struct seq_file *, m, char *, fmt, u32, fmt_size,
+PRINTF_BPF_CALL_5(2, bpf_seq_printf, struct seq_file *, m, char *, fmt, u32, fmt_size,
const void *, args, u32, data_len)
{
struct bpf_bprintf_data data = {
--
2.50.1
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