In the x86_64 JIT, tailcall info is propagated through the trampoline when
the target program is tail_call_reachable. However, this propagation is
unnecessary if the target is a main prog, or a subprog that is not
tail_call_reachable.
Since the verifier can determine if a subprog is tail_call_reachable, it
should only propagate tailcall info when the target is subprog and the
subprog is actually tail_call_reachable.
Acked-by: Yonghong Song <yonghong.song@xxxxxxxxx>
Signed-off-by: Leon Hwang <leon.hwang@xxxxxxxxx>
---
include/linux/bpf.h | 1 +
kernel/bpf/verifier.c | 4 +++-
2 files changed, 4 insertions(+), 1 deletion(-)
diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index c3ba4d4751747..0c3b147c84af9 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -1253,6 +1253,7 @@ struct bpf_attach_target_info {
struct module *tgt_mod;
const char *tgt_name;
const struct btf_type *tgt_type;
+ bool tgt_tail_call_reachable;
};
#define BPF_DISPATCHER_MAX 48 /* Fits in 2048B */
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 797cf3ed32e0f..2e2f027b86375 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -21946,6 +21946,8 @@ int bpf_check_attach_target(struct bpf_verifier_log *log,
bpf_log(log, "Subprog %s doesn't exist\n", tname);
return -EINVAL;
}
+ tgt_info->tgt_tail_call_reachable = subprog &&
+ aux->func[subprog]->aux->tail_call_reachable;
if (aux->func && aux->func[subprog]->aux->exception_cb) {
bpf_log(log,
"%s programs cannot attach to exception callback\n",
@@ -22315,7 +22317,7 @@ static int check_attach_btf_id(struct bpf_verifier_env *env)
if (!tr)
return -ENOMEM;
- if (tgt_prog && tgt_prog->aux->tail_call_reachable)
+ if (tgt_prog && tgt_info.tgt_tail_call_reachable)
tr->flags = BPF_TRAMP_F_TAIL_CALL_CTX;
prog->aux->dst_trampoline = tr;
--
2.44.0
