On Tue, Mar 12, 2024 at 9:51 AM Alexei Starovoitov alexei.starovoitov@gmail.com wrote:
On Mon, Mar 11, 2024 at 2:35 AM Menglong Dong dongmenglong.8@bytedance.com wrote:
Add target btf to the function args of bpf_check_attach_target(), then the caller can specify the btf to check.
Signed-off-by: Menglong Dong dongmenglong.8@bytedance.com
include/linux/bpf_verifier.h | 1 + kernel/bpf/syscall.c | 6 ++++-- kernel/bpf/trampoline.c | 1 + kernel/bpf/verifier.c | 8 +++++--- 4 files changed, 11 insertions(+), 5 deletions(-)
diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h index 4b0f6600e499..6cb20efcfac3 100644 --- a/include/linux/bpf_verifier.h +++ b/include/linux/bpf_verifier.h @@ -811,6 +811,7 @@ static inline void bpf_trampoline_unpack_key(u64 key, u32 *obj_id, u32 *btf_id) int bpf_check_attach_target(struct bpf_verifier_log *log, const struct bpf_prog *prog, const struct bpf_prog *tgt_prog,
struct btf *btf, u32 btf_id, struct bpf_attach_target_info *tgt_info);void bpf_free_kfunc_btf_tab(struct bpf_kfunc_btf_tab *tab); diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c index d1cd645ef9ac..6128c3131141 100644 --- a/kernel/bpf/syscall.c +++ b/kernel/bpf/syscall.c @@ -3401,9 +3401,11 @@ static int bpf_tracing_prog_attach(struct bpf_prog *prog, * need a new trampoline and a check for compatibility */ struct bpf_attach_target_info tgt_info = {};
struct btf *btf;
err = bpf_check_attach_target(NULL, prog, tgt_prog, btf_id,&tgt_info);
btf = tgt_prog ? tgt_prog->aux->btf : prog->aux->attach_btf;I think it's better to keep this bit inside bpf_check_attach_target(), since a lot of other code in there is working with if (tgt_prog) ... so if the caller messes up passing tgt_prog->aux->btf with tgt_prog the bug will be difficult to debug.
In the previous version, I pass the attach_btf with the following way:
+ origin_btf = prog->aux->attach_btf; + /* use the new attach_btf to check the target */ + prog->aux->attach_btf = attach_btf; err = bpf_check_attach_target(NULL, prog, tgt_prog, btf_id, &tgt_info); + prog->aux->attach_btf = origin_btf;
And Jiri suggested to add the attach_btf to the function args of bpf_check_attach_target().
Ennn....Should I convert to the old way?
Thanks! Menglong Dong
err = bpf_check_attach_target(NULL, prog, tgt_prog, btf,btf_id, &tgt_info);