linux-kernel - [PATCH] x86/kprobes: Remove dead code

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Date:   Wed, 24 Mar 2021 22:36:41 +0500
From:   Muhammad Usama Anjum <musamaanjum@...il.com>
To:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        x86@...nel.org, "H. Peter Anvin" <hpa@...or.com>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org,
        colin.king@...onical.com, dan.carpenter@...cle.com
Cc:     musamaanjum@...il.com, linux-kernel@...r.kernel.org
Subject: [PATCH] x86/kprobes: Remove dead code

The condition in switch statement `opcode & 0xf0` cannot evaluate to
0xff. So this case statement will never execute. Remove it.

Fixes: 6256e668b7 ("x86/kprobes: Use int3 instead of debug trap for single-step")
Signed-off-by: Muhammad Usama Anjum <musamaanjum@...il.com>
---
 arch/x86/kernel/kprobes/core.c | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/arch/x86/kernel/kprobes/core.c b/arch/x86/kernel/kprobes/core.c
index 89d9f26785c7..3b7bcc077020 100644
--- a/arch/x86/kernel/kprobes/core.c
+++ b/arch/x86/kernel/kprobes/core.c
@@ -177,9 +177,6 @@ int can_boost(struct insn *insn, void *addr)
 	case 0xf0:
 		/* clear and set flags are boostable */
 		return (opcode == 0xf5 || (0xf7 < opcode && opcode < 0xfe));
-	case 0xff:
-		/* indirect jmp is boostable */
-		return X86_MODRM_REG(insn->modrm.bytes[0]) == 4;
 	default:
 		/* CS override prefix and call are not boostable */
 		return (opcode != 0x2e && opcode != 0x9a);
-- 
2.25.1