diff options
| author | Menglong Dong <menglong8.dong@gmail.com> | 2026-01-24 14:19:57 +0800 |
|---|---|---|
| committer | Alexei Starovoitov <ast@kernel.org> | 2026-01-24 18:49:35 -0800 |
| commit | f1b56b3cbdb2d2a51d8ea91008eddf4d1d9f277b (patch) | |
| tree | 278c3302c1a897f73434ebc772ef57d7ec1472e4 /kernel/trace | |
| parent | 2d419c44658f75e7655794341a95c0687830f3df (diff) | |
bpf: use the least significant byte for the nr_args in trampoline
For now, ((u64 *)ctx)[-1] is used to store the nr_args in the trampoline.
However, 1 byte is enough to store such information. Therefore, we use
only the least significant byte of ((u64 *)ctx)[-1] to store the nr_args,
and reserve the rest for other usages.
Signed-off-by: Menglong Dong <dongml2@chinatelecom.cn>
Link: https://lore.kernel.org/r/20260124062008.8657-3-dongml2@chinatelecom.cn
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Diffstat (limited to 'kernel/trace')
| -rw-r--r-- | kernel/trace/bpf_trace.c | 6 |
1 files changed, 3 insertions, 3 deletions
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c index 0e9635bcd783..d466a1503da3 100644 --- a/kernel/trace/bpf_trace.c +++ b/kernel/trace/bpf_trace.c @@ -1194,7 +1194,7 @@ const struct bpf_func_proto bpf_get_branch_snapshot_proto = { BPF_CALL_3(get_func_arg, void *, ctx, u32, n, u64 *, value) { /* This helper call is inlined by verifier. */ - u64 nr_args = ((u64 *)ctx)[-1]; + u64 nr_args = ((u64 *)ctx)[-1] & 0xFF; if ((u64) n >= nr_args) return -EINVAL; @@ -1214,7 +1214,7 @@ static const struct bpf_func_proto bpf_get_func_arg_proto = { BPF_CALL_2(get_func_ret, void *, ctx, u64 *, value) { /* This helper call is inlined by verifier. */ - u64 nr_args = ((u64 *)ctx)[-1]; + u64 nr_args = ((u64 *)ctx)[-1] & 0xFF; *value = ((u64 *)ctx)[nr_args]; return 0; @@ -1231,7 +1231,7 @@ static const struct bpf_func_proto bpf_get_func_ret_proto = { BPF_CALL_1(get_func_arg_cnt, void *, ctx) { /* This helper call is inlined by verifier. */ - return ((u64 *)ctx)[-1]; + return ((u64 *)ctx)[-1] & 0xFF; } static const struct bpf_func_proto bpf_get_func_arg_cnt_proto = { |