Commit 9fcad995 authored by Chuang Wang's avatar Chuang Wang Committed by Ingo Molnar
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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: default avatarChuang Wang <nashuiliang@gmail.com>
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
Acked-by: default avatarMasami Hiramatsu (Google) <mhiramat@kernel.org>
Link: https://lore.kernel.org/r/20221129084022.718355-1-nashuiliang@gmail.com
parent 7bdb1767

arch/x86/kernel/kprobes/core.c

+11 −9
Original line number Diff line number Diff line
@@ -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))