The following commit has been merged into the x86/core branch of tip:
Commit-ID: a194acd316f93f3435a64de3b37dca2b5a77b338
Gitweb: https://git.kernel.org/tip/a194acd316f93f3435a64de3b37dca2b5a77b338
Author: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
AuthorDate: Wed, 03 Mar 2021 00:25:34 +09:00
Committer: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
CommitterDate: Tue, 23 Mar 2021 16:07:56 +01:00
x86/kprobes: Identify far indirect JMP correctly
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@xxxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Link: https://lkml.kernel.org/r/161469873475.49483.13257083019966335137.stgit@devnote2
---
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 9b31790..f6ec57f 100644
--- a/arch/x86/kernel/kprobes/core.c
+++ b/arch/x86/kernel/kprobes/core.c
@@ -467,8 +467,7 @@ 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.
|