On 10/5/20 9:21 PM, Andrii Nakryiko wrote:
On Mon, Oct 5, 2020 at 9:40 AM Luigi Rizzo <lrizzo@xxxxxxxxxx> wrote:
bpf_program__set_attach_target() will always fail with fd=0 (attach to a
kernel symbol) because obj->btf_vmlinux is NULL and there is no way to
set it.
Fix this by using libbpf_find_vmlinux_btf_id()
(on a side note: it is unclear whether btf_vmlinux is meant to be
just temporary storage for use in bpf_object__load_xattr(), or
a property of bpf_object, in which case it could be initialuzed
opportunistically, and properly released in bpf_object__close() ).
It's more of a former. vmlinux BTF shouldn't be needed past
bpf_object's load phase, so there is no need to keep a few megabytes
of memory laying around needlessly.
Could you send a v3 with updated commit message wrt side note and prepend
e.g. 'bpf, libbpf: ' into subject prefix?
Please also carry Andrii's ACK forward.
Signed-off-by: Luigi Rizzo <lrizzo@xxxxxxxxxx>
---
tools/lib/bpf/libbpf.c | 5 ++---
1 file changed, 2 insertions(+), 3 deletions(-)
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index a4f55f8a460d..33bf102259dd 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -10353,9 +10353,8 @@ int bpf_program__set_attach_target(struct bpf_program *prog,
btf_id = libbpf_find_prog_btf_id(attach_func_name,
attach_prog_fd);
else
- btf_id = __find_vmlinux_btf_id(prog->obj->btf_vmlinux,
- attach_func_name,
- prog->expected_attach_type);
+ btf_id = libbpf_find_vmlinux_btf_id(attach_func_name,
+ prog->expected_attach_type);
It's a bit inefficient, if you need to do this for a few programs, but
it's ok as a fix. We'll need to unify this internal vmlinux BTF
caching at some point.
Acked-by: Andrii Nakryiko <andriin@xxxxxx>
if (btf_id < 0)
return btf_id;
--
2.28.0.806.g8561365e88-goog
