[<prev] [next>] [<thread-prev] [day] [month] [year] [list]
Message-ID: <55c32279-1a96-0a31-ca2b-ae4e34365625@huawei.com>
Date: Fri, 23 Sep 2022 09:24:55 +0800
From: "liaochang (A)" <liaochang1@...wei.com>
To: Will Deacon <will@...nel.org>
CC: <catalin.marinas@....com>, <guoren@...nel.org>,
<paul.walmsley@...ive.com>, <palmer@...belt.com>,
<aou@...s.berkeley.edu>, <rostedt@...dmis.org>,
<mhiramat@...nel.org>, <maz@...nel.org>,
<alexandru.elisei@....com>, <linux-arm-kernel@...ts.infradead.org>,
<linux-kernel@...r.kernel.org>, <linux-csky@...r.kernel.org>,
<linux-riscv@...ts.infradead.org>
Subject: Re: [PATCH V2 3/3] arm64/kprobe: Optimize the performance of patching
single-step slot
在 2022/9/22 21:38, Will Deacon 写道:
> On Tue, Sep 13, 2022 at 11:34:54AM +0800, Liao Chang wrote:
>> Single-step slot would not be used until kprobe is enabled, that means
>> no race condition occurs on it under SMP, hence it is safe to pacth ss
>> slot without stopping machine.
>>
>> Signed-off-by: Liao Chang <liaochang1@...wei.com>
>> ---
>> arch/arm64/kernel/probes/kprobes.c | 5 ++---
>> 1 file changed, 2 insertions(+), 3 deletions(-)
>>
>> diff --git a/arch/arm64/kernel/probes/kprobes.c b/arch/arm64/kernel/probes/kprobes.c
>> index d1d182320245..5902e33fd3b6 100644
>> --- a/arch/arm64/kernel/probes/kprobes.c
>> +++ b/arch/arm64/kernel/probes/kprobes.c
>> @@ -44,11 +44,10 @@ post_kprobe_handler(struct kprobe *, struct kprobe_ctlblk *, struct pt_regs *);
>> static void __kprobes arch_prepare_ss_slot(struct kprobe *p)
>> {
>> kprobe_opcode_t *addr = p->ainsn.api.insn;
>> - void *addrs[] = {addr, addr + 1};
>> - u32 insns[] = {p->opcode, BRK64_OPCODE_KPROBES_SS};
>>
>> /* prepare insn slot */
>> - aarch64_insn_patch_text(addrs, insns, 2);
>> + aarch64_insn_write(addr, p->opcode);
>> + aarch64_insn_write(addr + 1, BRK64_OPCODE_KPROBES_SS);
>>
>> flush_icache_range((uintptr_t)addr, (uintptr_t)(addr + MAX_INSN_SIZE));
>
> Hmm, so it looks like prior to your change we were doing the cache
> maintebnance twice: once in aarch64_insn_patch_text() from stop machine
> context and then again in the flush_icache_range() call above.
>
> I suppose the cleanest thing would be to drop the flush_icache_range()
> call and then use aarch64_insn_patch_text_nosync() instead of
> aarch64_insn_write() in your change.
OK,I will improve it in next version, thanks.
>
> Will
> .
--
BR,
Liao, Chang
Powered by blists - more mailing lists