bpf: add _impl suffix for bpf_stream_vprintk() kfunc

Rename bpf_stream_vprintk() to bpf_stream_vprintk_impl().

This makes bpf_stream_vprintk() follow the already established "_impl"
suffix-based naming convention for kfuncs with the bpf_prog_aux
argument provided by the verifier implicitly. This convention will be
taken advantage of with the upcoming KF_IMPLICIT_ARGS feature to
preserve backwards compatibility to BPF programs.

Acked-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Mykyta Yatsenko <yatsenko@meta.com>
Link: https://lore.kernel.org/r/20251104-implv2-v3-2-4772b9ae0e06@meta.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Ihor Solodrai <ihor.solodrai@linux.dev>

Author: mykyta5

kernel/bpf/helpers.c

@@ -4380,7 +4380,7 @@ BTF_ID_FLAGS(func, bpf_strnstr);
 #if defined(CONFIG_BPF_LSM) && defined(CONFIG_CGROUPS)
 BTF_ID_FLAGS(func, bpf_cgroup_read_xattr, KF_RCU)
 #endif
-BTF_ID_FLAGS(func, bpf_stream_vprintk, KF_TRUSTED_ARGS)
+BTF_ID_FLAGS(func, bpf_stream_vprintk_impl, KF_TRUSTED_ARGS)
 BTF_ID_FLAGS(func, bpf_task_work_schedule_signal_impl, KF_TRUSTED_ARGS)
 BTF_ID_FLAGS(func, bpf_task_work_schedule_resume_impl, KF_TRUSTED_ARGS)
 BTF_KFUNCS_END(common_btf_ids)

kernel/bpf/stream.c

@@ -355,7 +355,8 @@ __bpf_kfunc_start_defs();
  * Avoid using enum bpf_stream_id so that kfunc users don't have to pull in the
  * enum in headers.
  */
-__bpf_kfunc int bpf_stream_vprintk(int stream_id, const char *fmt__str, const void *args, u32 len__sz, void *aux__prog)
+__bpf_kfunc int bpf_stream_vprintk_impl(int stream_id, const char *fmt__str, const void *args,
+					u32 len__sz, void *aux__prog)
 {
 	struct bpf_bprintf_data data = {
 		.get_bin_args	= true,

tools/bpf/bpftool/Documentation/bpftool-prog.rst

@@ -182,7 +182,7 @@ bpftool prog tracelog
 
 bpftool prog tracelog { stdout | stderr } *PROG*
     Dump the BPF stream of the program. BPF programs can write to these streams
-    at runtime with the **bpf_stream_vprintk**\ () kfunc. The kernel may write
+    at runtime with the **bpf_stream_vprintk_impl**\ () kfunc. The kernel may write
     error messages to the standard error stream. This facility should be used
     only for debugging purposes.
 

tools/lib/bpf/bpf_helpers.h

@@ -315,20 +315,20 @@ enum libbpf_tristate {
 			  ___param, sizeof(___param));		\
 })
 
-extern int bpf_stream_vprintk(int stream_id, const char *fmt__str, const void *args,
-			      __u32 len__sz, void *aux__prog) __weak __ksym;
-
-#define bpf_stream_printk(stream_id, fmt, args...)				\
-({										\
-	static const char ___fmt[] = fmt;					\
-	unsigned long long ___param[___bpf_narg(args)];				\
-										\
-	_Pragma("GCC diagnostic push")						\
-	_Pragma("GCC diagnostic ignored \"-Wint-conversion\"")			\
-	___bpf_fill(___param, args);						\
-	_Pragma("GCC diagnostic pop")						\
-										\
-	bpf_stream_vprintk(stream_id, ___fmt, ___param, sizeof(___param), NULL);\
+extern int bpf_stream_vprintk_impl(int stream_id, const char *fmt__str, const void *args,
+				   __u32 len__sz, void *aux__prog) __weak __ksym;
+
+#define bpf_stream_printk(stream_id, fmt, args...)					\
+({											\
+	static const char ___fmt[] = fmt;						\
+	unsigned long long ___param[___bpf_narg(args)];					\
+											\
+	_Pragma("GCC diagnostic push")							\
+	_Pragma("GCC diagnostic ignored \"-Wint-conversion\"")				\
+	___bpf_fill(___param, args);							\
+	_Pragma("GCC diagnostic pop")							\
+											\
+	bpf_stream_vprintk_impl(stream_id, ___fmt, ___param, sizeof(___param), NULL);	\
 })
 
 /* Use __bpf_printk when bpf_printk call has 3 or fewer fmt args

tools/testing/selftests/bpf/progs/stream_fail.c

@@ -10,23 +10,23 @@ SEC("syscall")
 __failure __msg("Possibly NULL pointer passed")
 int stream_vprintk_null_arg(void *ctx)
 {
-	bpf_stream_vprintk(BPF_STDOUT, "", NULL, 0, NULL);
+	bpf_stream_vprintk_impl(BPF_STDOUT, "", NULL, 0, NULL);
 	return 0;
 }
 
 SEC("syscall")
 __failure __msg("R3 type=scalar expected=")
 int stream_vprintk_scalar_arg(void *ctx)
 {
-	bpf_stream_vprintk(BPF_STDOUT, "", (void *)46, 0, NULL);
+	bpf_stream_vprintk_impl(BPF_STDOUT, "", (void *)46, 0, NULL);
 	return 0;
 }
 
 SEC("syscall")
 __failure __msg("arg#1 doesn't point to a const string")
 int stream_vprintk_string_arg(void *ctx)
 {
-	bpf_stream_vprintk(BPF_STDOUT, ctx, NULL, 0, NULL);
+	bpf_stream_vprintk_impl(BPF_STDOUT, ctx, NULL, 0, NULL);
 	return 0;
 }