Re: [PATCH bpf-next 1/5] bpf: tracing: add support to record and check the accessed args

On 2/19/24 19:51, Menglong Dong 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 | 121 ++++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 125 insertions(+)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h index c7aa99b44dbd..0225b8dbdd9d 100644 --- a/include/linux/bpf.h +++ b/include/linux/bpf.h @@ -1464,6 +1464,7 @@ 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;

@@ -2566,6 +2567,9 @@ 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 6ff0bd1a91d5..3a6931402fe4 100644 --- a/kernel/bpf/btf.c +++ b/kernel/bpf/btf.c @@ -6203,6 +6203,9 @@ 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);
  

  }

if (arg > nr_args) { @@ -7010,6 +7013,124 @@ int btf_check_type_match(struct bpf_verifier_log *log, const struct bpf_prog *pr return btf_check_func_type_match(log, btf1, t1, btf2, t2); } +static u32 get_ctx_arg_total_size(struct btf *btf, const struct btf_type *t) +{

• const struct btf_param *args;
• u32 size = 0, nr_args;
• int i;
• nr_args = btf_type_vlen(t);
• args = (const struct btf_param *)(t + 1);
• for (i = 0; i < nr_args; i++) {

• t = btf_type_skip_modifiers(btf, args[i].type, NULL);
  

• size += btf_type_is_ptr(t) ? 8 : roundup(t->size, 8);
  

• }
• return size;

+}

+static int get_ctx_arg_idx_aligned(struct btf *btf, const struct btf_type *t,

• 		   int off)
  

+{

• const struct btf_param *args;
• u32 offset = 0, nr_args;
• int i;
• nr_args = btf_type_vlen(t);
• args = (const struct btf_param *)(t + 1);
• for (i = 0; i < nr_args; i++) {

• if (offset == off)
  

• 	return i;
  

• t = btf_type_skip_modifiers(btf, args[i].type, NULL);
  

• offset += btf_type_is_ptr(t) ? 8 : roundup(t->size, 8);
  

• if (offset > off)
  

• 	return -1;
  

• }
• return -1;

+}

This one is very similar to get_ctx_arg_idx(). How about to refactor get_ctx_arg_idx() and share the code between get_ctx_arg_idx() and get_ctx_arg_idx_aligned().

For example,

-static u32 get_ctx_arg_idx(struct btf *btf, const struct btf_type *func_proto, - int off) +static u32 _get_ctx_arg_idx(struct btf *btf, const struct btf_type *func_proto, + int off, u32 *arg_off) { const struct btf_param *args; const struct btf_type *t; u32 offset = 0, nr_args; int i;

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 (arg_off) + *arg_off = offset; t = btf_type_skip_modifiers(btf, args[i].type, NULL); offset += btf_type_is_ptr(t) ? 8 : roundup(t->size, 8); if (off < offset) return i; }

+ if (arg_off) + *arg_off = offset; t = btf_type_skip_modifiers(btf, func_proto->type, NULL); offset += btf_type_is_ptr(t) ? 8 : roundup(t->size, 8); if (off < offset) return nr_args;

return nr_args + 1; }

+static u32 get_ctx_arg_idx(struct btf *btf, const struct btf_type *func_proto, + int off) +{ + return _get_ctx_arg_idx(btf, func_proto, off, NULL); +} + +static u32 get_ctx_arg_idx_aligned(struct btf *btf, + const struct btf_type *func_proto, + int off) +{ + u32 arg_off; + u32 arg_idx = _get_ctx_arg_idx(btf, func_proto, off, &arg_off); + return arg_off == off ? arg_idx : -1; +} +

+/* This function is similar to btf_check_func_type_match(), except that it

• • only compare some function args of the function prototype t1 and t2.
• */

+int btf_check_func_part_match(struct btf *btf1, const struct btf_type *func1,

• 	      struct btf *btf2, const struct btf_type *func2,
  

• 	      u64 func_args)
  

+{

• const struct btf_param *args1, *args2;
• u32 nargs1, i, offset = 0;
• const char *s1, *s2;
• if (!btf_type_is_func_proto(func1) || !btf_type_is_func_proto(func2))

• return -EINVAL;
  

• args1 = (const struct btf_param *)(func1 + 1);
• args2 = (const struct btf_param *)(func2 + 1);
• nargs1 = btf_type_vlen(func1);
• for (i = 0; i <= nargs1; i++) {

• const struct btf_type *t1, *t2;
  

• if (!(func_args & (1 << i)))
  

• 	goto next;
  

• if (i < nargs1) {
  

• 	int t2_index;
  

• 	/* get the index of the arg corresponding to args1[i]
  

• 	 * by the offset.
  

• 	 */
  

• 	t2_index = get_ctx_arg_idx_aligned(btf2, func2,
  

• 					   offset);
  

• 	if (t2_index < 0)
  

• 		return -EINVAL;
  

• 	t1 = btf_type_skip_modifiers(btf1, args1[i].type, NULL);
  

• 	t2 = btf_type_skip_modifiers(btf2, args2[t2_index].type,
  

• 				     NULL);
  

• } else {
  

• 	/* i == nargs1, this is the index of return value of t1 */
  

• 	if (get_ctx_arg_total_size(btf1, func1) !=
  

• 	    get_ctx_arg_total_size(btf2, func2))
  

• 		return -EINVAL;
  

• 	/* check the return type of t1 and t2 */
  

• 	t1 = btf_type_skip_modifiers(btf1, func1->type, NULL);
  

• 	t2 = btf_type_skip_modifiers(btf2, func2->type, NULL);
  

• }
  

• if (t1->info != t2->info ||
  

•     (btf_type_has_size(t1) && t1->size != t2->size))
  

• 	return -EINVAL;
  

• if (btf_type_is_int(t1) || btf_is_any_enum(t1))
  

• 	goto next;
  

• if (btf_type_is_struct(t1))
  

• 	goto on_struct;
  

• if (!btf_type_is_ptr(t1))
  

• 	return -EINVAL;
  

• t1 = btf_type_skip_modifiers(btf1, t1->type, NULL);
  

• t2 = btf_type_skip_modifiers(btf2, t2->type, NULL);
  

• if (!btf_type_is_struct(t1) || !btf_type_is_struct(t2))
  

• 	return -EINVAL;
  

+on_struct:

• s1 = btf_name_by_offset(btf1, t1->name_off);
  

• s2 = btf_name_by_offset(btf2, t2->name_off);
  

• if (strcmp(s1, s2))
  

• 	return -EINVAL;
  

+next:

• if (i < nargs1) {
  

• 	t1 = btf_type_skip_modifiers(btf1, args1[i].type, NULL);
  

• 	offset += btf_type_is_ptr(t1) ? 8 : roundup(t1->size, 8);
  

• }
  

• }
• return 0;

+}

• static bool btf_is_dynptr_ptr(const struct btf *btf, const struct btf_type *t) { const char *name;