[PATCH bpf 0/2] bpf: btf: allow typedef func_proto

[PATCH bpf 0/2] bpf: btf: allow typedef func_proto

[Yonghong Song]

The current btf implementation disallows the typedef of
a func_proto type. This actually is allowed per C standard.
This patch fixed btf verification to permit such types.
Patch #1 fixed the kernel side and Patch #2 fixed
the tools test_btf test.

Yonghong Song (2):
  bpf: btf: allow typedef func_proto
  tools/bpf: fix test_btf for typedef func_proto case

 kernel/bpf/btf.c                       | 3 ++-
 tools/testing/selftests/bpf/test_btf.c | 9 +++------
 2 files changed, 5 insertions(+), 7 deletions(-)

-- 
2.17.1

[PATCH bpf 1/2] bpf: btf: allow typedef func_proto

[Yonghong Song]

Current implementation does not allow typedef func_proto.
But it is actually allowed.
  -bash-4.4$ cat t.c
  typedef int (f) (int);
  f *g;
  -bash-4.4$ clang -O2 -g -c -target bpf t.c -Xclang -target-feature -Xclang +dwarfris
  -bash-4.4$ pahole -JV t.o
  File t.o:
  [1] PTR (anon) type_id=2
  [2] TYPEDEF f type_id=3
  [3] FUNC_PROTO (anon) return=4 args=(4 (anon))
  [4] INT int size=4 bit_offset=0 nr_bits=32 encoding=SIGNED
  -bash-4.4$

This patch related btf verifier to allow such (typedef func_proto)
patterns.

Fixes: 2667a2626f4d ("bpf: btf: Add BTF_KIND_FUNC and BTF_KIND_FUNC_PROTO")
Acked-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Yonghong Song <yhs@fb.com>
---
 kernel/bpf/btf.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index befe570be5ba..c57bd10340ed 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -1459,7 +1459,8 @@ static int btf_modifier_resolve(struct btf_verifier_env *env,
 
 		/* "typedef void new_void", "const void"...etc */
 		if (!btf_type_is_void(next_type) &&
-		    !btf_type_is_fwd(next_type)) {
+		    !btf_type_is_fwd(next_type) &&
+		    !btf_type_is_func_proto(next_type)) {
 			btf_verifier_log_type(env, v->t, "Invalid type_id");
 			return -EINVAL;
 		}
-- 
2.17.1

[PATCH bpf 2/2] tools/bpf: fix test_btf for typedef func_proto case

[Yonghong Song]

Fixed one test_btf raw test such that typedef func_proto
is permitted now.

Fixes: 78a2540e8945 ("tools/bpf: Add tests for BTF_KIND_FUNC_PROTO and BTF_KIND_FUNC")
Acked-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Yonghong Song <yhs@fb.com>
---
 tools/testing/selftests/bpf/test_btf.c | 9 +++------
 1 file changed, 3 insertions(+), 6 deletions(-)

diff --git a/tools/testing/selftests/bpf/test_btf.c b/tools/testing/selftests/bpf/test_btf.c
index a0bd04befe87..91420fa83b08 100644
--- a/tools/testing/selftests/bpf/test_btf.c
+++ b/tools/testing/selftests/bpf/test_btf.c
@@ -1881,13 +1881,12 @@ static struct btf_raw_test raw_tests[] = {
 },
 
 {
-	.descr = "func proto (CONST=>TYPEDEF=>FUNC_PROTO)",
+	.descr = "func proto (TYPEDEF=>FUNC_PROTO)",
 	.raw_types = {
 		BTF_TYPE_INT_ENC(0, BTF_INT_SIGNED, 0, 32, 4),	/* [1] */
 		BTF_TYPE_INT_ENC(0, 0, 0, 32, 4),		/* [2] */
-		BTF_CONST_ENC(4),				/* [3] */
-		BTF_TYPEDEF_ENC(NAME_TBD, 5),			/* [4] */
-		BTF_FUNC_PROTO_ENC(0, 2),			/* [5] */
+		BTF_TYPEDEF_ENC(NAME_TBD, 4),			/* [3] */
+		BTF_FUNC_PROTO_ENC(0, 2),			/* [4] */
 			BTF_FUNC_PROTO_ARG_ENC(0, 1),
 			BTF_FUNC_PROTO_ARG_ENC(0, 2),
 		BTF_END_RAW,
@@ -1901,8 +1900,6 @@ static struct btf_raw_test raw_tests[] = {
 	.key_type_id = 1,
 	.value_type_id = 1,
 	.max_entries = 4,
-	.btf_load_err = true,
-	.err_str = "Invalid type_id",
 },
 
 {
-- 
2.17.1

Re: [PATCH bpf 0/2] bpf: btf: allow typedef func_proto

[Alexei Starovoitov]

On Tue, Jan 29, 2019 at 04:38:16PM -0800, Yonghong Song wrote:
> The current btf implementation disallows the typedef of
> a func_proto type. This actually is allowed per C standard.
> This patch fixed btf verification to permit such types.
> Patch #1 fixed the kernel side and Patch #2 fixed
> the tools test_btf test.

Applied, Thanks