linux-kernel - [PATCH] bpf-next: Avoid goto in regs_refine_cond

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Date: Wed, 20 Mar 2024 20:29:54 -0400
From: Harishankar Vishwanathan <harishankar.vishwanathan@...il.com>
To: alexei.starovoitov@...il.com
Cc: harishankar.vishwanathan@...gers.edu,
	andrii@...nel.org,
	sn624@...rutgers.edu,
	sn349@...rutgers.edu,
	m.shachnai@...gers.edu,
	paul@...valent.com,
	daniel@...earbox.net,
	Harishankar Vishwanathan <harishankar.vishwanathan@...il.com>,
	Alexei Starovoitov <ast@...nel.org>,
	John Fastabend <john.fastabend@...il.com>,
	Martin KaFai Lau <martin.lau@...ux.dev>,
	Eduard Zingerman <eddyz87@...il.com>,
	Song Liu <song@...nel.org>,
	Yonghong Song <yonghong.song@...ux.dev>,
	KP Singh <kpsingh@...nel.org>,
	Stanislav Fomichev <sdf@...gle.com>,
	Hao Luo <haoluo@...gle.com>,
	Jiri Olsa <jolsa@...nel.org>,
	bpf@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH] bpf-next: Avoid goto in regs_refine_cond_op()

In case of GE/GT/SGE/JST instructions, regs_refine_cond_op()
reuses the logic that does analysis of LE/LT/SLE/SLT instructions.
This commit avoids the use of a goto to perform the reuse.

Signed-off-by: Harishankar Vishwanathan <harishankar.vishwanathan@...il.com>
---
 kernel/bpf/verifier.c | 22 +++++++++++++---------
 1 file changed, 13 insertions(+), 9 deletions(-)

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index de7813947981..ca6cacf7b42f 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -14544,7 +14544,19 @@ static void regs_refine_cond_op(struct bpf_reg_state *reg1, struct bpf_reg_state
 	struct tnum t;
 	u64 val;
 
-again:
+	/* In case of GE/GT/SGE/JST, reuse LE/LT/SLE/SLT logic from below */
+	switch (opcode) {
+	case BPF_JGE:
+	case BPF_JGT:
+	case BPF_JSGE:
+	case BPF_JSGT:
+		opcode = flip_opcode(opcode);
+		swap(reg1, reg2);
+		break;
+	default:
+		break;
+	}
+
 	switch (opcode) {
 	case BPF_JEQ:
 		if (is_jmp32) {
@@ -14687,14 +14699,6 @@ static void regs_refine_cond_op(struct bpf_reg_state *reg1, struct bpf_reg_state
 			reg2->smin_value = max(reg1->smin_value + 1, reg2->smin_value);
 		}
 		break;
-	case BPF_JGE:
-	case BPF_JGT:
-	case BPF_JSGE:
-	case BPF_JSGT:
-		/* just reuse LE/LT logic above */
-		opcode = flip_opcode(opcode);
-		swap(reg1, reg2);
-		goto again;
 	default:
 		return;
 	}
-- 
2.40.1