Messages in this thread | | | Date | Wed, 30 Nov 2022 22:38:14 +0900 | From | Masami Hiramatsu (Google) <> | Subject | Re: [PATCH] x86/kprobes: Use switch-case for 0xFF opcodes in prepare_emulation |
| |
On Tue, 29 Nov 2022 16:39:51 +0800 Chuang Wang <nashuiliang@gmail.com> wrote:
> 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>
This looks good to me.
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Thank you!
> --- > 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 >
-- Masami Hiramatsu (Google) <mhiramat@kernel.org>
| |