Re: [PATCH bpf-next] libbpf: add basic BTF sanity validation

[Martin KaFai Lau <martin.lau@linux.dev>]

On 8/23/23 4:44 PM, Andrii Nakryiko wrote:
> +/* Validate basic sanity of BTF. It's intentionally less thorough than
> + * kernel's validation and validates only properties of BTF that libbpf relies
> + * on to be correct (e.g., valid type IDs, valid string offsets, etc)
> + */
> +int btf_sanity_check(const struct btf *btf)
> +{
> +	const struct btf_type *t;
> +	__u32 i, n = btf__type_cnt(btf);
> +	int err;
> +
> +	for (i = 1; i < n; i++) {
> +		t = btf_type_by_id(btf, i);
> +		err = btf_validate_type(btf, t, i);
> +		if (err)
> +			return err;
> +	}
> +	return 0;
> +}
> +
>   static void *btf_get_raw_data(const struct btf *btf, __u32 *size, bool swap_endian);
>   
>   int btf_load_into_kernel(struct btf *btf, char *log_buf, size_t log_sz, __u32 log_level)
> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> index 4c3967d94b6d..71a3c768d9af 100644
> --- a/tools/lib/bpf/libbpf.c
> +++ b/tools/lib/bpf/libbpf.c
> @@ -2833,6 +2833,13 @@ static int bpf_object__init_btf(struct bpf_object *obj,
>   			pr_warn("Error loading ELF section %s: %d.\n", BTF_ELF_SEC, err);
>   			goto out;
>   		}
> +		err = btf_sanity_check(obj->btf);

Should btf_sanity_check() be called in btf_parse_type_sec() instead such that 
btf__parse_elf() can also have sanity check?