From: Michael Ellerman <mpe@ellerman.id.au>
To: Andreas Schwab <schwab@linux-m68k.org>
Cc: Paul Mackerras <paulus@samba.org>,
linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/3] powerpc/uaccess: Switch __put_user_size_allowed() to __put_user_asm_goto()
Date: Wed, 04 Nov 2020 00:21:44 +1100 [thread overview]
Message-ID: <875z6mvamv.fsf@mpe.ellerman.id.au> (raw)
In-Reply-To: <871rhgwzcg.fsf@igel.home>
Andreas Schwab <schwab@linux-m68k.org> writes:
> #
> # Automatically generated file; DO NOT EDIT.
> # Linux/powerpc 5.10.0-rc1 Kernel Configuration
> #
> CONFIG_CC_VERSION_TEXT="gcc-4.9 (SUSE Linux) 4.9.3"
So it seems to be a combination of GCC 4.9 and ...
> # CONFIG_PPC_RADIX_MMU is not set
That ^, which specifically causes PPC_KUAP=n.
When PPC_KUAP=y allow_user_access() inlines an isync and mtspr, both of
which contain a memory clobber, and that seems to hide the bug.
I think for now we just have to stop using asm goto for put_user() on
GCC 4.9.
I'll send a patch for that.
cheers
next prev parent reply other threads:[~2020-11-03 13:48 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <94ba5a5138f99522e1562dbcdb38d31aa790dc89.1599216721.git.christophe.leroy__44535.5968013004$1599217383$gmane$org@csgroup.eu>
2020-10-27 23:26 ` [PATCH 1/3] powerpc/uaccess: Switch __put_user_size_allowed() to __put_user_asm_goto() Andreas Schwab
2020-10-27 23:37 ` Andreas Schwab
2020-10-28 5:19 ` Michael Ellerman
2020-10-28 7:59 ` Andreas Schwab
2020-10-29 20:29 ` Andreas Schwab
2020-11-03 13:21 ` Michael Ellerman [this message]
2020-09-04 11:01 Christophe Leroy
2020-09-17 11:27 ` Michael Ellerman
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