Re: [PATCH] arm64/kernel/probes: Use BUG_ON instead of if condition followed by BUG.
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
Re: [PATCH] arm64/kernel/probes: Use BUG_ON instead of if condition followed by BUG.
On Tue, 30 Mar 2021 04:57:50 -0700 zhouchuangao wrote: > It can be optimized at compile time. > Anyway, this seems to make the code simpler. Reviewed-by: Masami Hiramatsu Thanks! > Signed-off-by: zhouchuangao > --- > 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
Re:Re: [PATCH] arm64/kernel/probes: Use BUG_ON instead of if condition followed by BUG.
>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:
..
ff8008660bec: d65f03c0ret
ff8008660bf0: d421brk #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
Re: [PATCH] arm64/kernel/probes: Use BUG_ON instead of if condition followed by BUG.
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
[PATCH] arm64/kernel/probes: Use BUG_ON instead of if condition followed by BUG.
It can be optimized at compile time. Signed-off-by: zhouchuangao --- 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
