linux-arm-kernel.lists.infradead.org archive mirror
 help / color / mirror / Atom feed
From: Will Deacon <will@kernel.org>
To: Liao Chang <liaochang1@huawei.com>
Cc: catalin.marinas@arm.com, guoren@kernel.org,
	paul.walmsley@sifive.com, palmer@dabbelt.com,
	aou@eecs.berkeley.edu, rostedt@goodmis.org, mhiramat@kernel.org,
	maz@kernel.org, alexandru.elisei@arm.com,
	linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org, linux-csky@vger.kernel.org,
	linux-riscv@lists.infradead.org
Subject: Re: [PATCH V2 3/3] arm64/kprobe: Optimize the performance of patching single-step slot
Date: Thu, 22 Sep 2022 14:38:51 +0100	[thread overview]
Message-ID: <20220922133850.GC12095@willie-the-truck> (raw)
In-Reply-To: <20220913033454.104519-4-liaochang1@huawei.com>

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@huawei.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.

Will

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

  reply	other threads:[~2022-09-22 13:40 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-09-13  3:34 [PATCH V2 0/3] kprobe: Optimize the performance of patching ss Liao Chang
2022-09-13  3:34 ` [PATCH V2 1/3] riscv/kprobe: Optimize the performance of patching single-step slot Liao Chang
2022-09-13  3:34 ` [PATCH V2 2/3] csky/kprobe: " Liao Chang
2022-09-13  3:34 ` [PATCH V2 3/3] arm64/kprobe: " Liao Chang
2022-09-22 13:38   ` Will Deacon [this message]
2022-09-23  1:24     ` liaochang (A)
2022-09-13 11:19 ` [PATCH V2 0/3] kprobe: Optimize the performance of patching ss Masami Hiramatsu

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20220922133850.GC12095@willie-the-truck \
    --to=will@kernel.org \
    --cc=alexandru.elisei@arm.com \
    --cc=aou@eecs.berkeley.edu \
    --cc=catalin.marinas@arm.com \
    --cc=guoren@kernel.org \
    --cc=liaochang1@huawei.com \
    --cc=linux-arm-kernel@lists.infradead.org \
    --cc=linux-csky@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-riscv@lists.infradead.org \
    --cc=maz@kernel.org \
    --cc=mhiramat@kernel.org \
    --cc=palmer@dabbelt.com \
    --cc=paul.walmsley@sifive.com \
    --cc=rostedt@goodmis.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).