github-mirror/linux
1
0
Fork 0
mirror of https://github.com/torvalds/linux.git synced 2026-07-28 10:09:10 +02:00
Code Issues Actions Packages Projects Releases Wiki Activity Graph

bpf: clean up btf_scan_decl_tags()

Browse Source 
Refactor the newly introduced btf_scan_decl_tags() to improve
readability and maintainability. The current implementation uses a
manual if-else chain and a magic number offset to strip the "arg:"
prefix from declaration tags.

Replace the if-else logic with a table-driven approach using a static
const array. This separates the tag data from the scanning logic, making
the helper more extensible for future tags. Additionally, replace the
magic number '4' with a sizeof-based calculation on the prefix string to
ensure the offset remains synchronized with the search key.

Finally, optimize the loop by moving the is_global check to the top of
the block. This allows the verifier to fail-fast on static subprograms
without performing unnecessary BTF string and type lookups.

Signed-off-by: Matt Bobrowski <mattbobrowski@google.com>
Reviewed-by: Emil Tsalapatis <emil@etsalapatis.com>
Link: https://lore.kernel.org/r/20260603201822.770596-1-mattbobrowski@google.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Matt Bobrowski 2026-06-03 20:18:22 +00:00 committed by Alexei Starovoitov
parent 5b88319e47
commit fbd6dc50d9
1 changed files with 30 additions and 16 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

46
kernel/bpf/btf.c
View File

@ -7808,14 +7808,28 @@ static int btf_scan_decl_tags(struct bpf_verifier_env *env,
u32 arg_idx, bool is_global, u32 *tags)
{
int id = btf_named_start_id(btf, false) - 1;
const char tag_key[] = "arg:";
static const struct {
const char *tag_value;
enum btf_arg_tag arg_tag;
} tag_values[] = {
{ "ctx", ARG_TAG_CTX },
{ "trusted", ARG_TAG_TRUSTED },
{ "untrusted", ARG_TAG_UNTRUSTED },
{ "nonnull", ARG_TAG_NONNULL },
{ "nullable", ARG_TAG_NULLABLE },
{ "arena", ARG_TAG_ARENA },
};
/*
* The 'arg:<tag>' decl_tag takes precedence over the derivation
* of the register type from the BTF type itself.
*/
while ((id = btf_find_next_decl_tag(btf, fn_t, arg_idx, "arg:", id)) > 0) {
const struct btf_type *tag_t = btf_type_by_id(btf, id);
const char *tag = __btf_name_by_offset(btf, tag_t->name_off) + 4;
while ((id = btf_find_next_decl_tag(btf, fn_t, arg_idx, tag_key, id)) > 0) {
const struct btf_type *tag_t;
const char *tag;
int i;
bool found;
/* disallow arg tags in static subprogs */
if (!is_global) {
@ -7825,19 +7839,19 @@ static int btf_scan_decl_tags(struct bpf_verifier_env *env,
return -EOPNOTSUPP;
}
if (strcmp(tag, "ctx") == 0) {
*tags |= ARG_TAG_CTX;
} else if (strcmp(tag, "trusted") == 0) {
*tags |= ARG_TAG_TRUSTED;
} else if (strcmp(tag, "untrusted") == 0) {
*tags |= ARG_TAG_UNTRUSTED;
} else if (strcmp(tag, "nonnull") == 0) {
*tags |= ARG_TAG_NONNULL;
} else if (strcmp(tag, "nullable") == 0) {
*tags |= ARG_TAG_NULLABLE;
} else if (strcmp(tag, "arena") == 0) {
*tags |= ARG_TAG_ARENA;
} else {
tag_t = btf_type_by_id(btf, id);
tag = __btf_name_by_offset(btf, tag_t->name_off) + (sizeof(tag_key) - 1);
found = false;
for (i = 0; i < ARRAY_SIZE(tag_values); ++i) {
if (!strcmp(tag, tag_values[i].tag_value)) {
*tags |= tag_values[i].arg_tag;
found = true;
break;
}
}
if (!found) {
bpf_log(&env->log, "arg#%d has unsupported set of tags\n", arg_idx);
return -EOPNOTSUPP;
}