bpf: Re-define bpf_stream_vprintk as a magic kfunc

* void *aux__prog => struct bpf_prog_aux *aux__magic
* Set KF_MAGIC_ARGS flag
* Add relevant symbols to magic_kfuncs list
* Update selftests to use the new signature

bpf_stream_vprintk macro is changed to use bpf_stream_vprintk_impl,
and the extern definition of bpf_stream_vprintk is replaced with _impl
version in bpf_helpers.h

This should help with backwards compatibility, as the API of
bpf_stream_vprintk macro hasn't changed.

Signed-off-by: Ihor Solodrai <[email protected]>

Author: theihor

kernel/bpf/helpers.c

@@ -4528,7 +4528,7 @@ BTF_ID_FLAGS(func, bpf_strncasestr);
 #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, KF_MAGIC_ARGS | KF_TRUSTED_ARGS)
 BTF_ID_FLAGS(func, bpf_task_work_schedule_signal, KF_MAGIC_ARGS | KF_TRUSTED_ARGS)
 BTF_ID_FLAGS(func, bpf_task_work_schedule_resume, KF_MAGIC_ARGS | KF_TRUSTED_ARGS)
 BTF_ID_FLAGS(func, bpf_dynptr_from_file, KF_TRUSTED_ARGS)

kernel/bpf/stream.c

@@ -355,19 +355,22 @@ __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(int stream_id,
+				   const char *fmt__str,
+				   const void *args,
+				   u32 len__sz,
+				   struct bpf_prog_aux *aux__magic)
 {
 	struct bpf_bprintf_data data = {
 		.get_bin_args	= true,
 		.get_buf	= true,
 	};
-	struct bpf_prog_aux *aux = aux__prog;
 	u32 fmt_size = strlen(fmt__str) + 1;
 	struct bpf_stream *stream;
 	u32 data_len = len__sz;
 	int ret, num_args;
 
-	stream = bpf_stream_get(stream_id, aux);
+	stream = bpf_stream_get(stream_id, aux__magic);
 	if (!stream)
 		return -ENOENT;
 

kernel/bpf/verifier.c

@@ -3273,6 +3273,8 @@ BTF_ID(func, bpf_task_work_schedule_signal)
 BTF_ID(func, bpf_task_work_schedule_signal_impl)
 BTF_ID(func, bpf_task_work_schedule_resume)
 BTF_ID(func, bpf_task_work_schedule_resume_impl)
+BTF_ID(func, bpf_stream_vprintk)
+BTF_ID(func, bpf_stream_vprintk_impl)
 BTF_ID_LIST_END(magic_kfuncs)
 
 static s32 magic_kfunc_by_impl(s32 impl_func_id)

tools/lib/bpf/bpf_helpers.h

@@ -315,8 +315,9 @@ 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;
+struct bpf_prog_aux;
+extern int bpf_stream_vprintk_impl(int stream_id, const char *fmt__str, const void *args,
+				   __u32 len__sz, struct bpf_prog_aux *aux__magic) __weak __ksym;
 
 #define bpf_stream_printk(stream_id, fmt, args...)				\
 ({										\
@@ -328,7 +329,7 @@ extern int bpf_stream_vprintk(int stream_id, const char *fmt__str, const void *a
 	___bpf_fill(___param, args);						\
 	_Pragma("GCC diagnostic pop")						\
 										\
-	bpf_stream_vprintk(stream_id, ___fmt, ___param, sizeof(___param), NULL);\
+	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(BPF_STDOUT, "", NULL, 0);
 	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(BPF_STDOUT, "", (void *)46, 0);
 	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(BPF_STDOUT, ctx, NULL, 0);
 	return 0;
 }