[bpf-next,v3,2/9] bpf/verifier: Factor out check_atomic_rmw()

Commit Message

Peilin Ye Feb. 20, 2025, 1:20 a.m. UTC

Currently, check_atomic() only handles atomic read-modify-write (RMW)
instructions.  Since we are planning to introduce other types of atomic
instructions (i.e., atomic load/store), extract the existing RMW
handling logic into its own function named check_atomic_rmw().

Remove the @insn_idx parameter as it is not really necessary.  Use
'env->insn_idx' instead, as in other places in verifier.c.

Signed-off-by: Peilin Ye <[e-mail]>
---
 kernel/bpf/verifier.c | 53 +++++++++++++++++++++++--------------------
 1 file changed, 29 insertions(+), 24 deletions(-)

Patch

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 21658bd5e6d8..63d810bbc26e 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -7615,28 +7615,12 @@  static int check_mem_access(struct bpf_verifier_env *env, int insn_idx, u32 regn
 static int save_aux_ptr_type(struct bpf_verifier_env *env, enum bpf_reg_type type,
 			     bool allow_trust_mismatch);
 
-static int check_atomic(struct bpf_verifier_env *env, int insn_idx, struct bpf_insn *insn)
+static int check_atomic_rmw(struct bpf_verifier_env *env,
+			    struct bpf_insn *insn)
 {
 	int load_reg;
 	int err;
 
-	switch (insn->imm) {
-	case BPF_ADD:
-	case BPF_ADD | BPF_FETCH:
-	case BPF_AND:
-	case BPF_AND | BPF_FETCH:
-	case BPF_OR:
-	case BPF_OR | BPF_FETCH:
-	case BPF_XOR:
-	case BPF_XOR | BPF_FETCH:
-	case BPF_XCHG:
-	case BPF_CMPXCHG:
-		break;
-	default:
-		verbose(env, "BPF_ATOMIC uses invalid atomic opcode %02x\n", insn->imm);
-		return -EINVAL;
-	}
-
 	if (BPF_SIZE(insn->code) != BPF_W && BPF_SIZE(insn->code) != BPF_DW) {
 		verbose(env, "invalid atomic operand size\n");
 		return -EINVAL;
@@ -7698,12 +7682,12 @@  static int check_atomic(struct bpf_verifier_env *env, int insn_idx, struct bpf_i
 	/* Check whether we can read the memory, with second call for fetch
 	 * case to simulate the register fill.
 	 */
-	err = check_mem_access(env, insn_idx, insn->dst_reg, insn->off,
+	err = check_mem_access(env, env->insn_idx, insn->dst_reg, insn->off,
 			       BPF_SIZE(insn->code), BPF_READ, -1, true, false);
 	if (!err && load_reg >= 0)
-		err = check_mem_access(env, insn_idx, insn->dst_reg, insn->off,
-				       BPF_SIZE(insn->code), BPF_READ, load_reg,
-				       true, false);
+		err = check_mem_access(env, env->insn_idx, insn->dst_reg,
+				       insn->off, BPF_SIZE(insn->code),
+				       BPF_READ, load_reg, true, false);
 	if (err)
 		return err;
 
@@ -7713,13 +7697,34 @@  static int check_atomic(struct bpf_verifier_env *env, int insn_idx, struct bpf_i
 			return err;
 	}
 	/* Check whether we can write into the same memory. */
-	err = check_mem_access(env, insn_idx, insn->dst_reg, insn->off,
+	err = check_mem_access(env, env->insn_idx, insn->dst_reg, insn->off,
 			       BPF_SIZE(insn->code), BPF_WRITE, -1, true, false);
 	if (err)
 		return err;
 	return 0;
 }
 
+static int check_atomic(struct bpf_verifier_env *env, struct bpf_insn *insn)
+{
+	switch (insn->imm) {
+	case BPF_ADD:
+	case BPF_ADD | BPF_FETCH:
+	case BPF_AND:
+	case BPF_AND | BPF_FETCH:
+	case BPF_OR:
+	case BPF_OR | BPF_FETCH:
+	case BPF_XOR:
+	case BPF_XOR | BPF_FETCH:
+	case BPF_XCHG:
+	case BPF_CMPXCHG:
+		return check_atomic_rmw(env, insn);
+	default:
+		verbose(env, "BPF_ATOMIC uses invalid atomic opcode %02x\n",
+			insn->imm);
+		return -EINVAL;
+	}
+}
+
 /* When register 'regno' is used to read the stack (either directly or through
  * a helper function) make sure that it's within stack boundary and, depending
  * on the access type and privileges, that all elements of the stack are
@@ -19187,7 +19192,7 @@  static int do_check(struct bpf_verifier_env *env)
 			enum bpf_reg_type dst_reg_type;
 
 			if (BPF_MODE(insn->code) == BPF_ATOMIC) {
-				err = check_atomic(env, env->insn_idx, insn);
+				err = check_atomic(env, insn);
 				if (err)
 					return err;
 				env->insn_idx++;