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bpf: support multiple tags per argument

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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@kernel.org>
Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20240105000909.2818934-5-andrii@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Andrii Nakryiko 2024-01-04 16:09:05 -08:00 committed by Alexei Starovoitov
parent 54c11ec493
commit 522bb2c1f8
2 changed files with 47 additions and 27 deletions
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2
include/linux/bpf.h
View file

@ -2472,6 +2472,8 @@ 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);

72
kernel/bpf/btf.c
View file

@ -3310,30 +3310,48 @@ static int btf_find_kptr(const struct btf *btf, const struct btf_type *t,
return BTF_FIELD_FOUND;
}
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)
{
int len = strlen(tag_key);
int i, n;
for (i = last_id + 1, n = btf_nr_types(btf); i < n; i++) {
const struct btf_type *t = btf_type_by_id(btf, i);
if (!btf_type_is_decl_tag(t))
continue;
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;
return i;
}
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;
int i;
const struct btf_type *t;
int len, id;
for (i = 1; i < btf_nr_types(btf); i++) {
const struct btf_type *t = btf_type_by_id(btf, i);
int len = strlen(tag_key);
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);
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)
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;
}
if (!value)
return ERR_PTR(-ENOENT);
return value;
}
@ -7032,20 +7050,16 @@ 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);
@ -7061,6 +7075,10 @@ 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))