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From: Michael Ellerman <mpe@ellerman.id.au>
To: Nicholas Piggin <npiggin@gmail.com>, linuxppc-dev@lists.ozlabs.org
Cc: Ganesh Goudar <ganeshgr@linux.ibm.com>,
	Nicholas Piggin <npiggin@gmail.com>
Subject: Re: [PATCH 2/2] powerpc/64: poison __per_cpu_offset to catch use-before-init
Date: Mon, 01 Aug 2022 22:02:03 +1000	[thread overview]
Message-ID: <87bkt4b29w.fsf@mpe.ellerman.id.au> (raw)
In-Reply-To: <20220711030653.150950-2-npiggin@gmail.com>

Nicholas Piggin <npiggin@gmail.com> writes:
> If the boot CPU tries to access per-cpu data of other CPUs before
> per cpu areas are set up, it will unexpectedly use offset 0.
>
> Try to catch such accesses by poisoning the __per_cpu_offset array.

I wasn't sure about this.

On bare metal it's just an instant checkstop which is very user hostile.

I worry it's just going to cause unusual configurations/options to crash
for folks, like eg. booting with page_poison=1 did a while back.

Can we put it behind a debug option? Maybe CONFIG_DEBUG_VM ?

cheers

  reply	other threads:[~2022-08-01 12:02 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-07-11  3:06 [PATCH 1/2] powerpc/mce: mce_init use early_cpu_to_node Nicholas Piggin
2022-07-11  3:06 ` [PATCH 2/2] powerpc/64: poison __per_cpu_offset to catch use-before-init Nicholas Piggin
2022-08-01 12:02   ` Michael Ellerman [this message]
2022-07-29 13:02 ` [PATCH 1/2] powerpc/mce: mce_init use early_cpu_to_node Michael Ellerman

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