From: Thomas Gleixner <tglx@linutronix.de>
To: Andy Lutomirski <luto@kernel.org>,
Lai Jiangshan <jiangshanlai@gmail.com>
Cc: LKML <linux-kernel@vger.kernel.org>,
Lai Jiangshan <laijs@linux.alibaba.com>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
X86 ML <x86@kernel.org>, "H. Peter Anvin" <hpa@zytor.com>,
Peter Zijlstra <peterz@infradead.org>,
Alexandre Chartre <alexandre.chartre@oracle.com>,
Andy Lutomirski <luto@kernel.org>,
"Gustavo A. R. Silva" <gustavoars@kernel.org>,
"Chang S. Bae" <chang.seok.bae@intel.com>,
Sasha Levin <sashal@kernel.org>
Subject: Re: [PATCH 1/2] x86/hw_breakpoint: Prevent data breakpoints on __per_cpu_offset
Date: Fri, 05 Feb 2021 12:45:54 +0100 [thread overview]
Message-ID: <877dnmagb1.fsf@nanos.tec.linutronix.de> (raw)
In-Reply-To: <CALCETrXk_xp5+tZiTOGzFLk76Pc3gGsnO80UzmHf=ZoqrUgr5w@mail.gmail.com>
On Thu, Feb 04 2021 at 16:11, Andy Lutomirski wrote:
> On Thu, Feb 4, 2021 at 6:26 AM Lai Jiangshan <jiangshanlai@gmail.com> wrote:
>> When FSGSBASE is enabled, paranoid_entry() fetches the per-CPU
>> GSBASE value via __per_cpu_offset or pcpu_unit_offsets.
>>
>> When data breakpoint is set on __per_cpu_offset[cpu] (read-write
>> operation), the specific cpu will be stuck in the infinite #DB loop.
>> RCU will try to send NMI to the specific cpu, but it is not working
>> either since NMI also relies on paranoid_entry().
>
> Should we consider having a .percpu..noinstr section and having
> objtool enforce this?
I think so.
Thanks,
tglx
next prev parent reply other threads:[~2021-02-05 11:50 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-04 15:27 [PATCH 1/2] x86/hw_breakpoint: Prevent data breakpoints on __per_cpu_offset Lai Jiangshan
2021-02-04 15:27 ` [PATCH 2/2] x86/hw_breakpoint: Prevent data breakpoints on cpu_dr7 Lai Jiangshan
2021-02-05 19:15 ` [tip: x86/urgent] x86/debug: " tip-bot2 for Lai Jiangshan
2021-02-05 0:11 ` [PATCH 1/2] x86/hw_breakpoint: Prevent data breakpoints on __per_cpu_offset Andy Lutomirski
2021-02-05 11:45 ` Thomas Gleixner [this message]
2021-02-05 12:46 ` Peter Zijlstra
2021-02-05 19:15 ` [tip: x86/urgent] x86/debug: " tip-bot2 for Lai Jiangshan
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