Add ability to iterate multiple decl_tag types pointed to the same
function argument. Use this to support multiple __arg_xxx tags per
global subprog argument.
We leave btf_find_decl_tag_value() intact, but change its implementation
to use a new btf_find_next_decl_tag() which can be straightforwardly
used to find next BTF type ID of a matching btf_decl_tag type.
btf_prepare_func_args() is switched from btf_find_decl_tag_value() to
btf_find_next_decl_tag() to gain multiple tags per argument support.
Signed-off-by: Andrii Nakryiko <andrii@xxxxxxxxxx>
---
include/linux/bpf.h | 2 ++
kernel/bpf/btf.c | 64 +++++++++++++++++++++++++++++----------------
2 files changed, 43 insertions(+), 23 deletions(-)
diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 7671530d6e4e..7ab4a290418a 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -2471,6 +2471,8 @@ int btf_check_type_match(struct bpf_verifier_log *log, const struct bpf_prog *pr
struct btf *btf, const struct btf_type *t);
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,
+ int comp_idx, const char *tag_key, int last_id);
struct bpf_prog *bpf_prog_by_id(u32 id);
struct bpf_link *bpf_link_by_id(u32 id);
diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index ccaf57e755fc..368d8fe19d35 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -3310,30 +3310,48 @@ static int btf_find_kptr(const struct btf *btf, const struct btf_type *t,
return BTF_FIELD_FOUND;
}
-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,
+ int comp_idx, const char *tag_key, int last_id)
{
- const char *value = NULL;
- int i;
+ int len = strlen(tag_key);
+ int i, n;
- for (i = 1; i < btf_nr_types(btf); i++) {
+ for (i = last_id + 1, n = btf_nr_types(btf); i < n; i++) {
const struct btf_type *t = btf_type_by_id(btf, i);
- int len = strlen(tag_key);
if (!btf_type_is_decl_tag(t))
continue;
- if (pt != btf_type_by_id(btf, t->type) ||
- btf_type_decl_tag(t)->component_idx != comp_idx)
+ if (pt != btf_type_by_id(btf, t->type))
+ continue;
+ if (btf_type_decl_tag(t)->component_idx != comp_idx)
continue;
if (strncmp(__btf_name_by_offset(btf, t->name_off), tag_key, len))
continue;
- /* Prevent duplicate entries for same type */
- if (value)
- return ERR_PTR(-EEXIST);
- value = __btf_name_by_offset(btf, t->name_off) + len;
+ return i;
}
- if (!value)
- return ERR_PTR(-ENOENT);
+ return -ENOENT;
+}
+
+const char *btf_find_decl_tag_value(const struct btf *btf, const struct btf_type *pt,
+ int comp_idx, const char *tag_key)
+{
+ const char *value = NULL;
+ const struct btf_type *t;
+ int len, id;
+
+ id = btf_find_next_decl_tag(btf, pt, comp_idx, tag_key, 0);
+ if (id < 0)
+ return ERR_PTR(id);
+
+ t = btf_type_by_id(btf, id);
+ len = strlen(tag_key);
+ value = __btf_name_by_offset(btf, t->name_off) + len;
+
+ /* Prevent duplicate entries for same type */
+ id = btf_find_next_decl_tag(btf, pt, comp_idx, tag_key, id);
+ if (id >= 0)
+ return ERR_PTR(-EEXIST);
+
return value;
}
@@ -6870,20 +6888,16 @@ int btf_prepare_func_args(struct bpf_verifier_env *env, int subprog)
* Only PTR_TO_CTX and SCALAR are supported atm.
*/
for (i = 0; i < nargs; i++) {
- const char *tag;
u32 tags = 0;
+ int id = 0;
- tag = btf_find_decl_tag_value(btf, fn_t, i, "arg:");
- if (IS_ERR(tag) && PTR_ERR(tag) == -ENOENT) {
- tag = NULL;
- } else if (IS_ERR(tag)) {
- bpf_log(log, "arg#%d type's tag fetching failure: %ld\n", i, PTR_ERR(tag));
- return PTR_ERR(tag);
- }
/* 'arg:<tag>' decl_tag takes precedence over derivation of
* register type from BTF type itself
*/
- if (tag) {
+ while ((id = btf_find_next_decl_tag(btf, fn_t, i, "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;
+
/* disallow arg tags in static subprogs */
if (!is_global) {
bpf_log(log, "arg#%d type tag is not supported in static functions\n", i);
@@ -6899,6 +6913,10 @@ int btf_prepare_func_args(struct bpf_verifier_env *env, int subprog)
return -EOPNOTSUPP;
}
}
+ if (id != -ENOENT) {
+ bpf_log(log, "arg#%d type tag fetching failure: %d\n", i, id);
+ return id;
+ }
t = btf_type_by_id(btf, args[i].type);
while (btf_type_is_modifier(t))
--
2.34.1
