From: Masami Hiramatsu <mhiramat@kernel.org>
To: Jisheng Zhang <Jisheng.Zhang@synaptics.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will@kernel.org>,
linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org, Liao Chang <liaochang1@huawei.com>
Subject: Re: [PATCH] arm64: kprobes: Restore local irqflag if kprobes is cancelled
Date: Mon, 12 Apr 2021 22:11:44 +0900 [thread overview]
Message-ID: <20210412221144.2da50e902df14cda0d86eeaa@kernel.org> (raw)
In-Reply-To: <20210412174101.6bfb0594@xhacker.debian>
Hi Jisheng,
On Mon, 12 Apr 2021 17:41:01 +0800
Jisheng Zhang <Jisheng.Zhang@synaptics.com> wrote:
> If instruction being single stepped caused a page fault, the kprobes
> is cancelled to let the page fault handler continue as a normal page
> fault. But the local irqflags are disabled so cpu will restore pstate
> with DAIF masked. After pagefault is serviced, the kprobes is
> triggerred again, we overwrite the saved_irqflag by calling
> kprobes_save_local_irqflag(). NOTE, DAIF is masked in this new saved
> irqflag. After kprobes is serviced, the cpu pstate is retored with
> DAIF masked.
>
> This patch is inspired by one patch for riscv from Liao Chang.
Thanks for pointing it out. But I think kprobes_restore_local_irqflag()
is also needed for kcb->kprobe_status == KPROBE_REENTER case...no.
This is more complicated. In the reenter case, I think we have to retry
the kpreprobe_fault_handler() with recovered previous kprobes so that
it can handle page fault in its handler.
Hmm, RISC-V and other code also needs same fix.
Thank you,
>
> Signed-off-by: Jisheng Zhang <Jisheng.Zhang@synaptics.com>
> ---
> arch/arm64/kernel/probes/kprobes.c | 6 ++++--
> 1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/arch/arm64/kernel/probes/kprobes.c b/arch/arm64/kernel/probes/kprobes.c
> index 66aac2881ba8..85645b2b0c7a 100644
> --- a/arch/arm64/kernel/probes/kprobes.c
> +++ b/arch/arm64/kernel/probes/kprobes.c
> @@ -267,10 +267,12 @@ int __kprobes kprobe_fault_handler(struct pt_regs *regs, unsigned int fsr)
> if (!instruction_pointer(regs))
> BUG();
>
> - if (kcb->kprobe_status == KPROBE_REENTER)
> + if (kcb->kprobe_status == KPROBE_REENTER) {
> restore_previous_kprobe(kcb);
> - else
> + } else {
> + kprobes_restore_local_irqflag(kcb, regs);
> reset_current_kprobe();
> + }
>
> break;
> case KPROBE_HIT_ACTIVE:
> --
> 2.31.0
>
--
Masami Hiramatsu <mhiramat@kernel.org>
next prev parent reply other threads:[~2021-04-12 13:11 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-12 9:41 [PATCH] arm64: kprobes: Restore local irqflag if kprobes is cancelled Jisheng Zhang
2021-04-12 13:11 ` Masami Hiramatsu [this message]
2021-04-12 14:46 ` Masami Hiramatsu
2021-04-13 17:49 ` Will Deacon
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=20210412221144.2da50e902df14cda0d86eeaa@kernel.org \
--to=mhiramat@kernel.org \
--cc=Jisheng.Zhang@synaptics.com \
--cc=catalin.marinas@arm.com \
--cc=liaochang1@huawei.com \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-kernel@vger.kernel.org \
--cc=will@kernel.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).