From: will.deacon@arm.com (Will Deacon)
To: linux-arm-kernel@lists.infradead.org
Subject: A issue about ptrace/SINGLESTEP on arm64
Date: Mon, 16 Oct 2017 16:30:56 +0100 [thread overview]
Message-ID: <20171016153055.GD10500@arm.com> (raw)
In-Reply-To: <8ad32f6b-e04d-98f8-d944-7ec3582fbdf4@huawei.com>
On Mon, Oct 16, 2017 at 12:27:17PM +0800, chengjian (D) wrote:
> Hi
> I write demo use ptrace/SINGLESTEP to count the number of instructions
> executed by the process
> The parent process fork+exec a child process, and trace(SINGLESTEP) it,
>
> It works fine under the x86_64 architecture but has an exception under
> arm64.
My guess is that you are getting stuck in an LDXR/STXR loop, which cannot
be stepped. Can you jump the PC once the child appears to be "stuck"?
IIRC, GDB has special heuristics to step through LDXR/STXR critical
sections.
Will
WARNING: multiple messages have this Message-ID (diff)
From: Will Deacon <will.deacon@arm.com>
To: "chengjian (D)" <cj.chengjian@huawei.com>
Cc: catalin.marinas@arm.com, oleg@redhat.com, linux@armlinux.org.uk,
linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org,
"Xiexiuqi (Xie XiuQi)" <xiexiuqi@huawei.com>,
Li Bin <huawei.libin@huawei.com>
Subject: Re: A issue about ptrace/SINGLESTEP on arm64
Date: Mon, 16 Oct 2017 16:30:56 +0100 [thread overview]
Message-ID: <20171016153055.GD10500@arm.com> (raw)
In-Reply-To: <8ad32f6b-e04d-98f8-d944-7ec3582fbdf4@huawei.com>
On Mon, Oct 16, 2017 at 12:27:17PM +0800, chengjian (D) wrote:
> Hi
> I write demo use ptrace/SINGLESTEP to count the number of instructions
> executed by the process
> The parent process fork+exec a child process, and trace(SINGLESTEP) it,
>
> It works fine under the x86_64 architecture but has an exception under
> arm64.
My guess is that you are getting stuck in an LDXR/STXR loop, which cannot
be stepped. Can you jump the PC once the child appears to be "stuck"?
IIRC, GDB has special heuristics to step through LDXR/STXR critical
sections.
Will
next prev parent reply other threads:[~2017-10-16 15:30 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-10-16 4:27 A issue about ptrace/SINGLESTEP on arm64 chengjian (D)
2017-10-16 4:27 ` chengjian (D)
2017-10-16 15:30 ` Will Deacon [this message]
2017-10-16 15:30 ` Will Deacon
2017-10-17 2:04 ` chengjian (D)
2017-10-17 2:04 ` chengjian (D)
2017-10-17 9:23 ` Will Deacon
2017-10-17 9:23 ` Will Deacon
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