When attaching a freplace hook, failures can occur, but currently, no output is provided to help developers diagnose the root cause. This commit adds a new method, bpf_check_attach_target_with_kernel_log, which outputs the verifier log to the kernel. Developers can then use dmesg to obtain more detailed information about the failure. For an example of eBPF code, Link: https://github.com/Asphaltt/learn-by-example/blob/main/ebpf/freplace/main.go Co-developed-by: Leon Hwang <hffilwlqm@xxxxxxxxx> Signed-off-by: Leon Hwang <hffilwlqm@xxxxxxxxx> Signed-off-by: Manjusaka <me@xxxxxxxxxxxx> --- include/linux/bpf_verifier.h | 7 +++++++ kernel/bpf/syscall.c | 3 ++- kernel/bpf/trampoline.c | 3 ++- kernel/bpf/verifier.c | 19 +++++++++++++++++++ 4 files changed, 30 insertions(+), 2 deletions(-) diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h index 6503c85b10a3..0ba119665410 100644 --- a/include/linux/bpf_verifier.h +++ b/include/linux/bpf_verifier.h @@ -830,11 +830,18 @@ static inline void bpf_trampoline_unpack_key(u64 key, u32 *obj_id, u32 *btf_id) *btf_id = key & 0x7FFFFFFF; } +int bpf_check_attach_target_with_kernel_log(const struct bpf_prog *prog, + const struct bpf_prog *tgt_prog, + u32 btf_id, + struct bpf_attach_target_info *tgt_info); + int bpf_check_attach_target(struct bpf_verifier_log *log, const struct bpf_prog *prog, const struct bpf_prog *tgt_prog, u32 btf_id, struct bpf_attach_target_info *tgt_info); + + void bpf_free_kfunc_btf_tab(struct bpf_kfunc_btf_tab *tab); int mark_chain_precision(struct bpf_verifier_env *env, int regno); diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c index 0719192a3482..d6ae9e8c40b2 100644 --- a/kernel/bpf/syscall.c +++ b/kernel/bpf/syscall.c @@ -3464,8 +3464,9 @@ static int bpf_tracing_prog_attach(struct bpf_prog *prog, */ struct bpf_attach_target_info tgt_info = {}; - err = bpf_check_attach_target(NULL, prog, tgt_prog, btf_id, + err = bpf_check_attach_target_with_kernel_log(prog, tgt_prog, btf_id, &tgt_info); + if (err) goto out_unlock; diff --git a/kernel/bpf/trampoline.c b/kernel/bpf/trampoline.c index f8302a5ca400..22dcc058e0d6 100644 --- a/kernel/bpf/trampoline.c +++ b/kernel/bpf/trampoline.c @@ -699,9 +699,10 @@ int bpf_trampoline_link_cgroup_shim(struct bpf_prog *prog, u64 key; int err; - err = bpf_check_attach_target(NULL, prog, NULL, + err = bpf_check_attach_target_with_kernel_log(prog, NULL, prog->aux->attach_btf_id, &tgt_info); + if (err) return err; diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 4cb5441ad75f..1d5dbbcac1bd 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -21145,6 +21145,25 @@ static int check_non_sleepable_error_inject(u32 btf_id) return btf_id_set_contains(&btf_non_sleepable_error_inject, btf_id); } +int bpf_check_attach_target_with_kernel_log(const struct bpf_prog *prog, + const struct bpf_prog *tgt_prog, + u32 btf_id, + struct bpf_attach_target_info *tgt_info) +{ + struct bpf_verifier_log *log; + int err; + + log = kzalloc(sizeof(*log), GFP_KERNEL | __GFP_NOWARN); + if (!log) { + err = -ENOMEM; + return err; + } + log->level = BPF_LOG_KERNEL; + err = bpf_check_attach_target(log, prog, tgt_prog, btf_id, tgt_info); + kfree(log); + return err; +} + int bpf_check_attach_target(struct bpf_verifier_log *log, const struct bpf_prog *prog, const struct bpf_prog *tgt_prog, -- 2.34.1
