On Mon, Mar 11, 2024 at 7:01 PM 梦龙董 dongmenglong.8@bytedance.com wrote:
On Tue, Mar 12, 2024 at 9:46 AM Alexei Starovoitov alexei.starovoitov@gmail.com wrote:
On Mon, Mar 11, 2024 at 2:34 AM Menglong Dong dongmenglong.8@bytedance.com wrote:
In this commit, we add the 'accessed_args' field to struct bpf_prog_aux, which is used to record the accessed index of the function args in btf_ctx_access().
Meanwhile, we add the function btf_check_func_part_match() to compare the accessed function args of two function prototype. This function will be used in the following commit.
Signed-off-by: Menglong Dong dongmenglong.8@bytedance.com
include/linux/bpf.h | 4 ++ kernel/bpf/btf.c | 108 +++++++++++++++++++++++++++++++++++++++++++- 2 files changed, 110 insertions(+), 2 deletions(-)
diff --git a/include/linux/bpf.h b/include/linux/bpf.h index 95e07673cdc1..0f677fdcfcc7 100644 --- a/include/linux/bpf.h +++ b/include/linux/bpf.h @@ -1461,6 +1461,7 @@ struct bpf_prog_aux { const struct btf_type *attach_func_proto; /* function name for valid attach_btf_id */ const char *attach_func_name;
u64 accessed_args; struct bpf_prog **func; void *jit_data; /* JIT specific data. arch dependent */ struct bpf_jit_poke_descriptor *poke_tab;@@ -2565,6 +2566,9 @@ struct bpf_reg_state; int btf_prepare_func_args(struct bpf_verifier_env *env, int subprog); int btf_check_type_match(struct bpf_verifier_log *log, const struct bpf_prog *prog, struct btf *btf, const struct btf_type *t); +int btf_check_func_part_match(struct btf *btf1, const struct btf_type *t1,
struct btf *btf2, const struct btf_type *t2,u64 func_args);const char *btf_find_decl_tag_value(const struct btf *btf, const struct btf_type *pt, int comp_idx, const char *tag_key); int btf_find_next_decl_tag(const struct btf *btf, const struct btf_type *pt, diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c index 170d017e8e4a..c2a0299d4358 100644 --- a/kernel/bpf/btf.c +++ b/kernel/bpf/btf.c @@ -6125,19 +6125,24 @@ static bool is_int_ptr(struct btf *btf, const struct btf_type *t) }
static u32 get_ctx_arg_idx(struct btf *btf, const struct btf_type *func_proto,
int off)
int off, int *aligned_idx){ const struct btf_param *args; const struct btf_type *t; u32 offset = 0, nr_args; int i;
if (aligned_idx)*aligned_idx = -ENOENT;if (!func_proto) return off / 8; nr_args = btf_type_vlen(func_proto); args = (const struct btf_param *)(func_proto + 1); for (i = 0; i < nr_args; i++) {if (aligned_idx && offset == off)*aligned_idx = i; t = btf_type_skip_modifiers(btf, args[i].type, NULL); offset += btf_type_is_ptr(t) ? 8 : roundup(t->size, 8); if (off < offset)@@ -6207,7 +6212,7 @@ bool btf_ctx_access(int off, int size, enum bpf_access_type type, tname, off); return false; }
arg = get_ctx_arg_idx(btf, t, off);
arg = get_ctx_arg_idx(btf, t, off, NULL); args = (const struct btf_param *)(t + 1); /* if (t == NULL) Fall back to default BPF prog with * MAX_BPF_FUNC_REG_ARGS u64 arguments.@@ -6217,6 +6222,9 @@ bool btf_ctx_access(int off, int size, enum bpf_access_type type, /* skip first 'void *__data' argument in btf_trace_##name typedef */ args++; nr_args--;
prog->aux->accessed_args |= (1 << (arg + 1));} else {prog->aux->accessed_args |= (1 << arg);What do you need this aligned_idx for ? I'd expect that above "accessed_args |= (1 << arg);" is enough.
Which aligned_idx? No aligned_idx in the btf_ctx_access(), and aligned_idx is only used in the btf_check_func_part_match().
In the btf_check_func_part_match(), I need to compare the t1->args[i] and t2->args[j], which have the same offset. And the aligned_idx is to find the "j" according to the offset of t1->args[i].
And that's my question. Why you don't do the max of accessed_args across all attach points and do btf_check_func_type_match() to that argno instead of nargs1. This 'offset += btf_type_is_ptr(t1) ? 8 : roundup... is odd.