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

On Wed, Feb 21, 2024 at 1:18 AM Jiri Olsa olsajiri@gmail.com wrote:

On Tue, Feb 20, 2024 at 11:51:01AM +0800, Menglong Dong wrote:

SNIP

...

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

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

could we reuse btf_check_func_type_match instead? perhaps just adding extra argument with arguments bitmap to it?

This is a little difficult, as the way we check the consistency of t1 and t2 is a little different.

in btf_check_func_type_match(), we check the args of t1 and t2 by index. But in btf_check_func_part_match(), we check the args of t1 and t2 by offset. Reusing can make btf_check_func_type_match become complex and hard to understand.

Anyway, let me have a try to see if it works to reuse btf_check_func_type_match().

Thanks! Menglong Dong

jirka

...

+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; -- 2.39.2