From: Masami Hiramatsu <mhiramat@kernel.org>
To: Doug Anderson <dianders@chromium.org>
Cc: "liwei (GF)" <liwei391@huawei.com>,
Daniel Thompson <daniel.thompson@linaro.org>,
Jason Wessel <jason.wessel@windriver.com>,
Marc Zyngier <maz@kernel.org>,
Mark Rutland <mark.rutland@arm.com>,
Masami Hiramatsu <mhiramat@kernel.org>,
David Miller <davem@davemloft.net>, Will Deacon <will@kernel.org>,
Catalin Marinas <catalin.marinas@arm.com>,
Linux ARM <linux-arm-kernel@lists.infradead.org>,
LKML <linux-kernel@vger.kernel.org>,
liwei1412@163.com
Subject: Re: [PATCH 2/4] arm64: Extract kprobes_save_local_irqflag() and kprobes_restore_local_irqflag()
Date: Tue, 19 May 2020 00:14:43 +0900 [thread overview]
Message-ID: <20200519001443.a1d1843e7809a7a68530fda5@kernel.org> (raw)
In-Reply-To: <CAD=FV=XMSsMFpPzBckkWhP6iDR4WM+qdV7J=aQCBbbBit_rDwg@mail.gmail.com>
On Sat, 16 May 2020 09:17:21 -0700
Doug Anderson <dianders@chromium.org> wrote:
> Hi,
>
> On Sat, May 16, 2020 at 1:47 AM liwei (GF) <liwei391@huawei.com> wrote:
> >
> > >> - kprobes_save_local_irqflag(kcb, regs);
> > >> + kernel_prepare_single_step(&kcb->saved_irqflag, regs);
> > >
> > > Is there some reason to have two functions? It seems like every time
> > > you call kernel_enable_single_step() you'd want to call
> > > kernel_prepare_single_step(). ...and every time you call
> > > kernel_disable_single_step() you'd want to call
> > > kernel_cleanup_single_step().
> > >
> > > Maybe you can just add the flags parameter to
> > > kernel_enable_single_step() / kernel_disable_single_step() and put the
> > > code in there?
> > >
> >
> > As kernel_enable_single_step() / kernel_disable_single_step() are also called in
> > breakpoint_handler() and watchpoint_handler(), i am not sure it's a right thing
> > to put the daif flag prepare/cleanup into them, especially we don't have a context
> > to save the flags.
>
> I think you misunderstood what I was suggesting. Maybe better with
> examples? I was suggesting doing this:
>
> kcb->saved_irqflag = kernel_enable_single_step(regs);
> ...
> kernel_disable_single_step(kcb->saved_irqflag, regs);
>
> To me that seems better than what you have now:
>
> kcb->saved_irqflag = kernel_prepare_single_step(regs);
> kernel_enable_single_step(regs);
> ...
> kernel_cleanup_single_step(kcb->saved_irqflag, regs);
> kernel_disable_single_step();
>
> ...or am I confused?
+1, this sounds good to me. Currently arch/arm64/kernel/probes/kprobes.c
has a code which sololy use kernel_disable_single_step() without regs
restoring, but it looks like a bug there. So maybe you need following patch.
Thank you,
-----
From: Masami Hiramatsu <mhiramat@kernel.org>
Date: Mon, 18 May 2020 23:08:28 +0900
Subject: [PATCH] arm64: kprobes: Restore saved interrupt flag before disabling
single step
Restore the saved interrupt flag in kprobe_ctlblk to regs->pstate
when a page fault happens on single-stepping instruction.
Without this fix, we will lose the flag if it happens because
kcb->saved_irqflag only knows the previous flag.
Fixes: 2dd0e8d2d2a1 ("arm64: Kprobes with single stepping support")
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Cc: stable@vger.kernel.org
---
arch/arm64/kernel/probes/kprobes.c | 1 +
1 file changed, 1 insertion(+)
diff --git a/arch/arm64/kernel/probes/kprobes.c b/arch/arm64/kernel/probes/kprobes.c
index d1c95dcf1d78..73fb99770f69 100644
--- a/arch/arm64/kernel/probes/kprobes.c
+++ b/arch/arm64/kernel/probes/kprobes.c
@@ -308,6 +308,7 @@ int __kprobes kprobe_fault_handler(struct pt_regs *regs, unsigned int fsr)
if (!instruction_pointer(regs))
BUG();
+ kprobes_restore_local_irqflag(kcb, regs);
kernel_disable_single_step();
if (kcb->kprobe_status == KPROBE_REENTER)
--
2.25.1
--
Masami Hiramatsu <mhiramat@kernel.org>
next prev parent reply other threads:[~2020-05-18 15:14 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-09 21:41 [PATCH 0/4] arm64: kgdb/kdb: Fix single-step debugging issues Wei Li
2020-05-09 21:41 ` [PATCH 1/4] arm64: kgdb: Fix single-step exception handling oops Wei Li
2020-05-14 0:21 ` Doug Anderson
2020-05-09 21:41 ` [PATCH 2/4] arm64: Extract kprobes_save_local_irqflag() and kprobes_restore_local_irqflag() Wei Li
2020-05-10 8:59 ` Masami Hiramatsu
2020-05-14 0:21 ` Doug Anderson
2020-05-16 8:47 ` liwei (GF)
2020-05-16 16:17 ` Doug Anderson
2020-05-18 15:14 ` Masami Hiramatsu [this message]
2020-05-09 21:41 ` [PATCH 3/4] arm64: kgdb: Fix single-stepping into the irq handler wrongly Wei Li
2020-05-14 0:21 ` Doug Anderson
2020-05-09 21:41 ` [PATCH 4/4] arm64: kgdb: Set PSTATE.SS to 1 to reenable single-step Wei Li
2020-05-14 0:23 ` Doug Anderson
2020-05-16 8:20 ` liwei (GF)
2020-05-14 0:34 ` [PATCH 0/4] arm64: kgdb/kdb: Fix single-step debugging issues Doug Anderson
2020-05-16 8:20 ` liwei (GF)
2020-06-29 21:20 ` Doug Anderson
2020-06-30 7:22 ` Will Deacon
2020-07-06 21:37 ` Doug Anderson
2020-07-08 22:06 ` Will Deacon
2020-07-08 22:22 ` Doug Anderson
2020-07-07 1:37 ` liwei (GF)
2020-07-08 22:02 ` Will Deacon
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