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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@gmail.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Link: https://lore.kernel.org/r/20221129084022.718355-1-nashuiliang@gmail.com
This commit is contained in:
Chuang Wang 2022-11-29 16:39:51 +08:00 committed by Ingo Molnar
parent 7bdb1767bf
commit 9fcad995c6
1 changed files with 11 additions and 9 deletions
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20
arch/x86/kernel/kprobes/core.c
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@ -655,17 +655,19 @@ static int prepare_emulation(struct kprobe *p, struct insn *insn)
* is determined by the MOD/RM byte. * is determined by the MOD/RM byte.
*/ */
opcode = insn->modrm.bytes[0]; opcode = insn->modrm.bytes[0];
if ((opcode & 0x30) == 0x10) { switch (X86_MODRM_REG(opcode)) {
if ((opcode & 0x8) == 0x8) case 0b010: /* FF /2, call near, absolute indirect */
return -EOPNOTSUPP; /* far call */
/* call absolute, indirect */
p->ainsn.emulate_op = kprobe_emulate_call_indirect; p->ainsn.emulate_op = kprobe_emulate_call_indirect;
} else if ((opcode & 0x30) == 0x20) { break;
if ((opcode & 0x8) == 0x8) case 0b100: /* FF /4, jmp near, absolute indirect */
return -EOPNOTSUPP; /* far jmp */
/* jmp near absolute indirect */
p->ainsn.emulate_op = kprobe_emulate_jmp_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; break;
if (insn->addr_bytes != sizeof(unsigned long)) if (insn->addr_bytes != sizeof(unsigned long))