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Message-Id: <20221129084022.718355-1-nashuiliang@gmail.com>
Date: Tue, 29 Nov 2022 16:39:51 +0800
From: Chuang Wang <nashuiliang@...il.com>
To: unlisted-recipients:; (no To-header on input)
Cc: Chuang Wang <nashuiliang@...il.com>,
Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
"H. Peter Anvin" <hpa@...or.com>, Mark Brown <broonie@...nel.org>,
Rob Herring <robh@...nel.org>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Alex Deucher <alexander.deucher@....com>,
"Masami Hiramatsu (Google)" <mhiramat@...nel.org>,
Peter Zijlstra <peterz@...radead.org>,
linux-kernel@...r.kernel.org
Subject: [PATCH] x86/kprobes: Use switch-case for 0xFF opcodes in prepare_emulation
For the `FF /digit` opcodes in prepare_emulation, use switch-case
instead of hand-written code to make the logic easier to understand.
Signed-off-by: Chuang Wang <nashuiliang@...il.com>
---
arch/x86/kernel/kprobes/core.c | 20 +++++++++++---------
1 file changed, 11 insertions(+), 9 deletions(-)
diff --git a/arch/x86/kernel/kprobes/core.c b/arch/x86/kernel/kprobes/core.c
index 66299682b6b7..66ec32b6cd0e 100644
--- a/arch/x86/kernel/kprobes/core.c
+++ b/arch/x86/kernel/kprobes/core.c
@@ -655,17 +655,19 @@ static int prepare_emulation(struct kprobe *p, struct insn *insn)
* is determined by the MOD/RM byte.
*/
opcode = insn->modrm.bytes[0];
- if ((opcode & 0x30) == 0x10) {
- if ((opcode & 0x8) == 0x8)
- return -EOPNOTSUPP; /* far call */
- /* call absolute, indirect */
+ switch (X86_MODRM_REG(opcode)) {
+ case 0b010: /* FF /2, call near, absolute indirect */
p->ainsn.emulate_op = kprobe_emulate_call_indirect;
- } else if ((opcode & 0x30) == 0x20) {
- if ((opcode & 0x8) == 0x8)
- return -EOPNOTSUPP; /* far jmp */
- /* jmp near absolute indirect */
+ break;
+ case 0b100: /* FF /4, jmp near, absolute indirect */
p->ainsn.emulate_op = kprobe_emulate_jmp_indirect;
- } else
+ break;
+ case 0b011: /* FF /3, call far, absolute indirect */
+ case 0b101: /* FF /5, jmp far, absolute indirect */
+ return -EOPNOTSUPP;
+ }
+
+ if (!p->ainsn.emulate_op)
break;
if (insn->addr_bytes != sizeof(unsigned long))
--
2.37.2
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