* [PATCH] arm64/kernel/probes: Use BUG_ON instead of if condition followed by BUG.
@ 2021-03-30 11:57 zhouchuangao
2021-03-30 12:08 ` Will Deacon
` (2 more replies)
0 siblings, 3 replies; 5+ messages in thread
From: zhouchuangao @ 2021-03-30 11:57 UTC (permalink / raw)
To: Catalin Marinas, Will Deacon, Masami Hiramatsu,
Jean-Philippe Brucker, Andrew Morton, Qais Yousef, zhouchuangao,
linux-arm-kernel, linux-kernel
It can be optimized at compile time.
Signed-off-by: zhouchuangao <zhouchuangao@vivo.com>
---
arch/arm64/kernel/probes/kprobes.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)
diff --git a/arch/arm64/kernel/probes/kprobes.c b/arch/arm64/kernel/probes/kprobes.c
index 66aac28..ecf0f61 100644
--- a/arch/arm64/kernel/probes/kprobes.c
+++ b/arch/arm64/kernel/probes/kprobes.c
@@ -264,8 +264,7 @@ int __kprobes kprobe_fault_handler(struct pt_regs *regs, unsigned int fsr)
* normal page fault.
*/
instruction_pointer_set(regs, (unsigned long) cur->addr);
- if (!instruction_pointer(regs))
- BUG();
+ BUG_ON(!instruction_pointer(regs));
if (kcb->kprobe_status == KPROBE_REENTER)
restore_previous_kprobe(kcb);
--
2.7.4
^ permalink raw reply related [flat|nested] 5+ messages in thread
* Re: [PATCH] arm64/kernel/probes: Use BUG_ON instead of if condition followed by BUG.
2021-03-30 11:57 [PATCH] arm64/kernel/probes: Use BUG_ON instead of if condition followed by BUG zhouchuangao
@ 2021-03-30 12:08 ` Will Deacon
2021-04-01 10:49 ` 周传高
2021-04-01 21:21 ` Masami Hiramatsu
2021-04-14 10:07 ` Catalin Marinas
2 siblings, 1 reply; 5+ messages in thread
From: Will Deacon @ 2021-03-30 12:08 UTC (permalink / raw)
To: zhouchuangao
Cc: Catalin Marinas, Masami Hiramatsu, Jean-Philippe Brucker,
Andrew Morton, Qais Yousef, linux-arm-kernel, linux-kernel
On Tue, Mar 30, 2021 at 04:57:50AM -0700, zhouchuangao wrote:
> It can be optimized at compile time.
Hmm, I don't see it (and I also don't understand why we care). Do you have
numbers showing that this is worthwhile?
Will
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re:Re: [PATCH] arm64/kernel/probes: Use BUG_ON instead of if condition followed by BUG.
2021-03-30 12:08 ` Will Deacon
@ 2021-04-01 10:49 ` 周传高
0 siblings, 0 replies; 5+ messages in thread
From: 周传高 @ 2021-04-01 10:49 UTC (permalink / raw)
To: Will Deacon
Cc: Catalin Marinas, Masami Hiramatsu, Jean-Philippe Brucker,
Andrew Morton, Qais Yousef, linux-arm-kernel, linux-kernel
>On Tue, Mar 30, 2021 at 04:57:50AM -0700, zhouchuangao wrote:>> It can be optimized at compile time.
>
>Hmm, I don't see it (and I also don't understand why we care). Do you have
>numbers showing that this is worthwhile?
>
#define BUG_ON(condition) do { if (unlikely(condition)) BUG(); } while (0)
BUG_ON uses unlikely in if(). Through disassembly, we can see that
brk #0x800 is compiled to the end of the function.
As you can see below:
......
ffffff8008660bec: d65f03c0 ret
ffffff8008660bf0: d4210000 brk #0x800
Usually, the condition in if () is not satisfied. For the multi-stage pipeline,
we do not need to perform fetch decode and excute operation on brk
instruction.
In my opinion, this can improve the efficiency of the multi-stage pipeline.
zhouchuangao
>Will
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] arm64/kernel/probes: Use BUG_ON instead of if condition followed by BUG.
2021-03-30 11:57 [PATCH] arm64/kernel/probes: Use BUG_ON instead of if condition followed by BUG zhouchuangao
2021-03-30 12:08 ` Will Deacon
@ 2021-04-01 21:21 ` Masami Hiramatsu
2021-04-14 10:07 ` Catalin Marinas
2 siblings, 0 replies; 5+ messages in thread
From: Masami Hiramatsu @ 2021-04-01 21:21 UTC (permalink / raw)
To: zhouchuangao
Cc: Catalin Marinas, Will Deacon, Jean-Philippe Brucker,
Andrew Morton, Qais Yousef, linux-arm-kernel, linux-kernel
On Tue, 30 Mar 2021 04:57:50 -0700
zhouchuangao <zhouchuangao@vivo.com> wrote:
> It can be optimized at compile time.
>
Anyway, this seems to make the code simpler.
Reviewed-by: Masami Hiramatsu <mhiramat@kernel.org>
Thanks!
> Signed-off-by: zhouchuangao <zhouchuangao@vivo.com>
> ---
> arch/arm64/kernel/probes/kprobes.c | 3 +--
> 1 file changed, 1 insertion(+), 2 deletions(-)
>
> diff --git a/arch/arm64/kernel/probes/kprobes.c b/arch/arm64/kernel/probes/kprobes.c
> index 66aac28..ecf0f61 100644
> --- a/arch/arm64/kernel/probes/kprobes.c
> +++ b/arch/arm64/kernel/probes/kprobes.c
> @@ -264,8 +264,7 @@ int __kprobes kprobe_fault_handler(struct pt_regs *regs, unsigned int fsr)
> * normal page fault.
> */
> instruction_pointer_set(regs, (unsigned long) cur->addr);
> - if (!instruction_pointer(regs))
> - BUG();
> + BUG_ON(!instruction_pointer(regs));
>
> if (kcb->kprobe_status == KPROBE_REENTER)
> restore_previous_kprobe(kcb);
> --
> 2.7.4
>
--
Masami Hiramatsu <mhiramat@kernel.org>
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] arm64/kernel/probes: Use BUG_ON instead of if condition followed by BUG.
2021-03-30 11:57 [PATCH] arm64/kernel/probes: Use BUG_ON instead of if condition followed by BUG zhouchuangao
2021-03-30 12:08 ` Will Deacon
2021-04-01 21:21 ` Masami Hiramatsu
@ 2021-04-14 10:07 ` Catalin Marinas
2 siblings, 0 replies; 5+ messages in thread
From: Catalin Marinas @ 2021-04-14 10:07 UTC (permalink / raw)
To: Masami Hiramatsu, Jean-Philippe Brucker, Qais Yousef,
Andrew Morton, Will Deacon, linux-kernel, zhouchuangao,
linux-arm-kernel
Cc: Catalin Marinas
On Tue, 30 Mar 2021 04:57:50 -0700, zhouchuangao wrote:
> It can be optimized at compile time.
Applied to arm64 (for-next/misc), it saves one line ;). Thanks!
[1/1] arm64/kernel/probes: Use BUG_ON instead of if condition followed by BUG.
https://git.kernel.org/arm64/c/839157876f97
--
Catalin
^ permalink raw reply [flat|nested] 5+ messages in thread
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2021-03-30 11:57 [PATCH] arm64/kernel/probes: Use BUG_ON instead of if condition followed by BUG zhouchuangao
2021-03-30 12:08 ` Will Deacon
2021-04-01 10:49 ` 周传高
2021-04-01 21:21 ` Masami Hiramatsu
2021-04-14 10:07 ` Catalin Marinas
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