Merge branch 'enhance-bpf-global-subprogs-with-argument-tags'

Andrii Nakryiko says:

====================
Enhance BPF global subprogs with argument tags

This patch set adds verifier support for annotating user's global BPF subprog
arguments with few commonly requested annotations, to improve global subprog
verification experience.

These tags are:
  - ability to annotate a special PTR_TO_CTX argument;
  - ability to annotate a generic PTR_TO_MEM as non-null.

We utilize btf_decl_tag attribute for this and provide two helper macros as
part of bpf_helpers.h in libbpf (patch #8).

Besides this we also add abilit to pass a pointer to dynptr into global
subprog. This is done based on type name match (struct bpf_dynptr *). This
allows to pass dynptrs into global subprogs, for use cases that deal with
variable-sized generic memory pointers.

Big chunk of the patch set (patches #1 through #5) are various refactorings to
make verifier internals around global subprog validation logic easier to
extend and support long term, eliminating BTF parsing logic duplication,
factoring out argument expectation definitions from BTF parsing, etc.

New functionality is added in patch #6 (ctx and non-null) and patch #7
(dynptr), extending global subprog checks with awareness for arg tags.

Patch #9 adds simple tests validating each of the added tags and dynptr
argument passing.

Patch #10 adds a simple negative case for freplace programs to make sure that
target BPF programs with "unreliable" BTF func proto cannot be freplaced.

v2->v3:
  - patch #10 improved by checking expected verifier error (Eduard);
v1->v2:
  - dropped packet args for now (Eduard);
  - added back unreliable=true detection for entry BPF programs (Eduard);
  - improved subprog arg validation (Eduard);
  - switched dynptr arg from tag to just type name based check (Eduard).
====================

Link: https://lore.kernel.org/r/20231215011334.2307144-1-andrii@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

2 files changed, 22 insertions, 14 deletions

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 7a8d4c81a39a..7671530d6e4e 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -2466,12 +2466,7 @@ int btf_distill_func_proto(struct bpf_verifier_log *log,
 			   struct btf_func_model *m);
 
 struct bpf_reg_state;
-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..d07d857ca67f 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 +738,16 @@ struct bpf_verifier_env {
 	char tmp_str_buf[TMP_STR_BUF_LEN];
 };
 
+static inline struct bpf_func_info_aux *subprog_aux(struct bpf_verifier_env *env, int subprog)
+{
+	return &env->prog->aux->func_info_aux[subprog];
+}
+
+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,
@@ -764,14 +785,6 @@ bpf_prog_offload_replace_insn(struct bpf_verifier_env *env, u32 off,
 void
 bpf_prog_offload_remove_insns(struct bpf_verifier_env *env, u32 off, u32 cnt);
 
-int check_ptr_off_reg(struct bpf_verifier_env *env,
-		      const struct bpf_reg_state *reg, int regno);
-int check_func_arg_reg_off(struct bpf_verifier_env *env,
-			   const struct bpf_reg_state *reg, int regno,
-			   enum bpf_arg_type arg_type);
-int check_mem_reg(struct bpf_verifier_env *env, struct bpf_reg_state *reg,
-		   u32 regno, u32 mem_size);
-
 /* this lives here instead of in bpf.h because it needs to dereference tgt_prog */
 static inline u64 bpf_trampoline_compute_key(const struct bpf_prog *tgt_prog,
 					     struct btf *btf, u32 btf_id)