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authorAndrii Nakryiko <andrii@kernel.org>2023-12-14 17:13:25 -0800
committerAlexei Starovoitov <ast@kernel.org>2023-12-19 18:06:46 -0800
commit4ba1d0f23414135e4f426dae4cb5cdc2ce246f89 (patch)
treeafd2128f045eed09c7d826b44ea423136c1f7369 /include
parentc337f237291b41b308c80124236876cf66c77906 (diff)
bpf: abstract away global subprog arg preparation logic from reg state setup
btf_prepare_func_args() is used to understand expectations and restrictions on global subprog arguments. But current implementation is hard to extend, as it intermixes BTF-based func prototype parsing and interpretation logic with setting up register state at subprog entry. Worse still, those registers are not completely set up inside btf_prepare_func_args(), requiring some more logic later in do_check_common(). Like calling mark_reg_unknown() and similar initialization operations. This intermixing of BTF interpretation and register state setup is problematic. First, it causes duplication of BTF parsing logic for global subprog verification (to set up initial state of global subprog) and global subprog call sites analysis (when we need to check that whatever is being passed into global subprog matches expectations), performed in btf_check_subprog_call(). Given we want to extend global func argument with tags later, this duplication is problematic. So refactor btf_prepare_func_args() to do only BTF-based func proto and args parsing, returning high-level argument "expectations" only, with no regard to specifics of register state. I.e., if it's a context argument, instead of setting register state to PTR_TO_CTX, we return ARG_PTR_TO_CTX enum for that argument as "an argument specification" for further processing inside do_check_common(). Similarly for SCALAR arguments, PTR_TO_MEM, etc. This allows to reuse btf_prepare_func_args() in following patches at global subprog call site analysis time. It also keeps register setup code consistently in one place, do_check_common(). Besides all this, we cache this argument specs information inside env->subprog_info, eliminating the need to redo these potentially expensive BTF traversals, especially if BPF program's BTF is big and/or there are lots of global subprog calls. Acked-by: Eduard Zingerman <eddyz87@gmail.com> Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Link: https://lore.kernel.org/r/20231215011334.2307144-2-andrii@kernel.org Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Diffstat (limited to 'include')
-rw-r--r--include/linux/bpf.h3
-rw-r--r--include/linux/bpf_verifier.h16
2 files changed, 17 insertions, 2 deletions
diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 7a8d4c81a39a..c050c82cc9a5 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -2470,8 +2470,7 @@ int btf_check_subprog_arg_match(struct bpf_verifier_env *env, int subprog,
struct bpf_reg_state *regs);
int btf_check_subprog_call(struct bpf_verifier_env *env, int subprog,
struct bpf_reg_state *regs);
-int btf_prepare_func_args(struct bpf_verifier_env *env, int subprog,
- struct bpf_reg_state *reg, u32 *nargs);
+int btf_prepare_func_args(struct bpf_verifier_env *env, int subprog);
int btf_check_type_match(struct bpf_verifier_log *log, const struct bpf_prog *prog,
struct btf *btf, const struct btf_type *t);
const char *btf_find_decl_tag_value(const struct btf *btf, const struct btf_type *pt,
diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h
index c2819a6579a5..5742e9c0a7b8 100644
--- a/include/linux/bpf_verifier.h
+++ b/include/linux/bpf_verifier.h
@@ -606,6 +606,13 @@ static inline bool bpf_verifier_log_needed(const struct bpf_verifier_log *log)
#define BPF_MAX_SUBPROGS 256
+struct bpf_subprog_arg_info {
+ enum bpf_arg_type arg_type;
+ union {
+ u32 mem_size;
+ };
+};
+
struct bpf_subprog_info {
/* 'start' has to be the first field otherwise find_subprog() won't work */
u32 start; /* insn idx of function entry point */
@@ -617,6 +624,10 @@ struct bpf_subprog_info {
bool is_cb: 1;
bool is_async_cb: 1;
bool is_exception_cb: 1;
+ bool args_cached: 1;
+
+ u8 arg_cnt;
+ struct bpf_subprog_arg_info args[MAX_BPF_FUNC_REG_ARGS];
};
struct bpf_verifier_env;
@@ -727,6 +738,11 @@ struct bpf_verifier_env {
char tmp_str_buf[TMP_STR_BUF_LEN];
};
+static inline struct bpf_subprog_info *subprog_info(struct bpf_verifier_env *env, int subprog)
+{
+ return &env->subprog_info[subprog];
+}
+
__printf(2, 0) void bpf_verifier_vlog(struct bpf_verifier_log *log,
const char *fmt, va_list args);
__printf(2, 3) void bpf_verifier_log_write(struct bpf_verifier_env *env,