From: Masami Hiramatsu mhiramat@kernel.org
[ Upstream commit a194acd316f93f3435a64de3b37dca2b5a77b338 ]
Since Grp5 far indirect JMP is FF "mod 101 r/m", it should be (modrm & 0x38) == 0x28, and near indirect JMP is also 0x38 == 0x20. So we can mask modrm with 0x30 and check 0x20. This is actually what the original code does, it also doesn't care the last bit. So the result code is same.
Thus, I think this is just a cosmetic cleanup.
Signed-off-by: Masami Hiramatsu mhiramat@kernel.org Signed-off-by: Peter Zijlstra (Intel) peterz@infradead.org Link: https://lkml.kernel.org/r/161469873475.49483.13257083019966335137.stgit@devn... Signed-off-by: Li Huafei lihuafei1@huawei.com --- arch/x86/kernel/kprobes/core.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-)
diff --git a/arch/x86/kernel/kprobes/core.c b/arch/x86/kernel/kprobes/core.c index 40d5c603ce8e..d03baf1f4024 100644 --- a/arch/x86/kernel/kprobes/core.c +++ b/arch/x86/kernel/kprobes/core.c @@ -478,8 +478,7 @@ static void set_resume_flags(struct kprobe *p, struct insn *insn) p->ainsn.is_call = 1; p->ainsn.is_abs_ip = 1; break; - } else if (((opcode & 0x31) == 0x20) || - ((opcode & 0x31) == 0x21)) { + } else if ((opcode & 0x30) == 0x20) { /* * jmp near and far, absolute indirect * ip is correct.