Merge branch 'bpf: Add helpers to access traced function arguments'

Jiri Olsa says:

====================
Add new helpers to access traced function arguments that
came out of the trampoline batch changes [1].

  Get n-th argument of the traced function:
    long bpf_get_func_arg(void *ctx, u32 n, u64 *value)

  Get return value of the traced function:
    long bpf_get_func_ret(void *ctx, u64 *value)

  Get arguments count of the traced funtion:
    long bpf_get_func_arg_cnt(void *ctx)

v2 changes:
  - added acks
  - updated stack diagram
  - return -EOPNOTSUPP instead of -EINVAL in bpf_get_func_ret
  - removed gpl_only for all helpers
  - added verifier fix to allow proper arguments checks,
    Andrii asked for checking also 'int *b' argument in
    bpf_modify_return_test programs and it turned out that it's currently
    not supported by verifier - we can't read argument that is int pointer,
    so I had to add verifier change to allow that + adding verifier selftest
  - checking all arguments in bpf_modify_return_test test programs
  - moved helpers proto gets in tracing_prog_func_proto with attach type check

thanks,
jirka

[1] https://lore.kernel.org/bpf/20211118112455.475349-1-jolsa@kernel.org/
====================

Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 5 insertions, 0 deletions

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 7a40022e3d00..965fffaf0308 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -777,6 +777,7 @@ void bpf_ksym_add(struct bpf_ksym *ksym);
 void bpf_ksym_del(struct bpf_ksym *ksym);
 int bpf_jit_charge_modmem(u32 pages);
 void bpf_jit_uncharge_modmem(u32 pages);
+bool bpf_prog_has_trampoline(const struct bpf_prog *prog);
 #else
 static inline int bpf_trampoline_link_prog(struct bpf_prog *prog,
 					   struct bpf_trampoline *tr)
@@ -805,6 +806,10 @@ static inline bool is_bpf_image_address(unsigned long address)
 {
 	return false;
 }
+static inline bool bpf_prog_has_trampoline(const struct bpf_prog *prog)
+{
+	return false;
+}
 #endif
 
 struct bpf_func_info_aux {