bpf: Prepare btf_ctx_access for non raw_tp use case

This patch makes a few changes to btf_ctx_access() to prepare
it for non raw_tp use case where the attach_btf_id is not
necessary a BTF_KIND_TYPEDEF.

It moves the "btf_trace_" prefix check and typedef-follow logic to a new
function "check_attach_btf_id()" which is called only once during
bpf_check().  btf_ctx_access() only operates on a BTF_KIND_FUNC_PROTO
type now. That should also be more efficient since it is done only
one instead of every-time check_ctx_access() is called.

"check_attach_btf_id()" needs to find the func_proto type from
the attach_btf_id.  It needs to store the result into the
newly added prog->aux->attach_func_proto.  func_proto
btf type has no name, so a proper name should be stored into
"attach_func_name" also.

v2:
- Move the "btf_trace_" check to an earlier verifier phase (Alexei)

Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20191025001811.1718491-1-kafai@fb.com

1 files changed, 2 insertions, 0 deletions

diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index c3240898cc44..571c25d60710 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -1080,6 +1080,8 @@ static bool raw_tp_prog_is_valid_access(int off, int size,
 		return false;
 	if (off % size != 0)
 		return false;
+	if (!prog->aux->attach_btf_id)
+		return true;
 	return btf_ctx_access(off, size, type, prog, info);
 }