* [PATCH] x86/kprobes: Use switch-case for 0xFF opcodes in prepare_emulation
@ 2022-11-29 8:39 Chuang Wang
2022-11-30 13:38 ` Masami Hiramatsu
2023-01-10 12:03 ` [tip: perf/core] " tip-bot2 for Chuang Wang
0 siblings, 2 replies; 3+ messages in thread
From: Chuang Wang @ 2022-11-29 8:39 UTC (permalink / raw)
Cc: Chuang Wang, Thomas Gleixner, Ingo Molnar, Borislav Petkov,
Dave Hansen, x86, H. Peter Anvin, Mark Brown, Rob Herring,
Greg Kroah-Hartman, Alex Deucher, Masami Hiramatsu (Google),
Peter Zijlstra, linux-kernel
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>
---
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
^ permalink raw reply [flat|nested] 3+ messages in thread* Re: [PATCH] x86/kprobes: Use switch-case for 0xFF opcodes in prepare_emulation
2022-11-29 8:39 [PATCH] x86/kprobes: Use switch-case for 0xFF opcodes in prepare_emulation Chuang Wang
@ 2022-11-30 13:38 ` Masami Hiramatsu
2023-01-10 12:03 ` [tip: perf/core] " tip-bot2 for Chuang Wang
1 sibling, 0 replies; 3+ messages in thread
From: Masami Hiramatsu @ 2022-11-30 13:38 UTC (permalink / raw)
To: Chuang Wang
Cc: Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen, x86,
H. Peter Anvin, Mark Brown, Rob Herring, Greg Kroah-Hartman,
Alex Deucher, Masami Hiramatsu (Google),
Peter Zijlstra, linux-kernel
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>
^ permalink raw reply [flat|nested] 3+ messages in thread* [tip: perf/core] x86/kprobes: Use switch-case for 0xFF opcodes in prepare_emulation
2022-11-29 8:39 [PATCH] x86/kprobes: Use switch-case for 0xFF opcodes in prepare_emulation Chuang Wang
2022-11-30 13:38 ` Masami Hiramatsu
@ 2023-01-10 12:03 ` tip-bot2 for Chuang Wang
1 sibling, 0 replies; 3+ messages in thread
From: tip-bot2 for Chuang Wang @ 2023-01-10 12:03 UTC (permalink / raw)
To: linux-tip-commits
Cc: Chuang Wang, Ingo Molnar, Masami Hiramatsu (Google), x86, linux-kernel
The following commit has been merged into the perf/core branch of tip:
Commit-ID: 9fcad995c6c52cc9791f7ee9f1386a5684055f9c
Gitweb: https://git.kernel.org/tip/9fcad995c6c52cc9791f7ee9f1386a5684055f9c
Author: Chuang Wang <nashuiliang@gmail.com>
AuthorDate: Tue, 29 Nov 2022 16:39:51 +08:00
Committer: Ingo Molnar <mingo@kernel.org>
CommitterDate: Tue, 10 Jan 2023 12:37:14 +01:00
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
---
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 33390ed..fd0420a 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))
^ permalink raw reply [flat|nested] 3+ messages in thread
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2022-11-29 8:39 [PATCH] x86/kprobes: Use switch-case for 0xFF opcodes in prepare_emulation Chuang Wang
2022-11-30 13:38 ` Masami Hiramatsu
2023-01-10 12:03 ` [tip: perf/core] " tip-bot2 for Chuang Wang
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