From: Brian Gerst <bgerst@didntduck.org>
To: Alexander Nyberg <alexn@telia.com>
Cc: ak@suse.de, linux-kernel@vger.kernel.org, akpm@osdl.org,
nicolas@boichat.ch
Subject: Re: x86_64: Bug in new out of line put_user()
Date: Thu, 21 Apr 2005 20:32:03 -0400 [thread overview]
Message-ID: <42684603.5050500@didntduck.org> (raw)
In-Reply-To: <1114038609.500.2.camel@localhost.localdomain>
Alexander Nyberg wrote:
> The new out of line put_user() assembly on x86_64 changes %rcx without
> telling GCC about it causing things like:
>
> http://bugme.osdl.org/show_bug.cgi?id=4515
>
> See to it that %rcx is not changed (made it consistent with get_user()).
>
>
> Signed-off-by: Alexander Nyberg <alexn@telia.com>
>
> Index: test/arch/x86_64/lib/getuser.S
> ===================================================================
> --- test.orig/arch/x86_64/lib/getuser.S 2005-04-20 23:55:35.000000000 +0200
> +++ test/arch/x86_64/lib/getuser.S 2005-04-21 00:54:16.000000000 +0200
> @@ -78,9 +78,9 @@
> __get_user_8:
> GET_THREAD_INFO(%r8)
> addq $7,%rcx
> - jc bad_get_user
> + jc 40f
> cmpq threadinfo_addr_limit(%r8),%rcx
> - jae bad_get_user
> + jae 40f
> subq $7,%rcx
> 4: movq (%rcx),%rdx
> xorl %eax,%eax
> Index: test/arch/x86_64/lib/putuser.S
> ===================================================================
> --- test.orig/arch/x86_64/lib/putuser.S 2005-04-21 00:50:24.000000000 +0200
> +++ test/arch/x86_64/lib/putuser.S 2005-04-21 01:02:15.000000000 +0200
> @@ -46,36 +46,45 @@
> __put_user_2:
> GET_THREAD_INFO(%r8)
> addq $1,%rcx
> - jc bad_put_user
> + jc 20f
> cmpq threadinfo_addr_limit(%r8),%rcx
> - jae bad_put_user
> -2: movw %dx,-1(%rcx)
> + jae 20f
> +2: decq %rcx
> + movw %dx,(%rcx)
> xorl %eax,%eax
> ret
> +20: decq %rcx
> + jmp bad_put_user
>
> .p2align 4
> .globl __put_user_4
> __put_user_4:
> GET_THREAD_INFO(%r8)
> addq $3,%rcx
> - jc bad_put_user
> + jc 30f
> cmpq threadinfo_addr_limit(%r8),%rcx
> - jae bad_put_user
> -3: movl %edx,-3(%rcx)
> + jae 30f
> +3: subq $3,%rcx
> + movl %edx,(%rcx)
> xorl %eax,%eax
> ret
> +30: subq $3,%rcx
> + jmp bad_put_user
>
> .p2align 4
> .globl __put_user_8
> __put_user_8:
> GET_THREAD_INFO(%r8)
> addq $7,%rcx
> - jc bad_put_user
> + jc 40f
> cmpq threadinfo_addr_limit(%r8),%rcx
> - jae bad_put_user
> -4: movq %rdx,-7(%rcx)
> + jae 40f
> +4: subq $7,%rcx
> + movq %rdx,(%rcx)
> xorl %eax,%eax
> ret
> +40: subq $7,%rcx
> + jmp bad_put_user
>
> bad_put_user:
> movq $(-EFAULT),%rax
>
>
> -
This patch has a serious bug. The 2, 3 and 4 labels must be on the mov
instructions in order to catch faults.
--
Brian Gerst
next prev parent reply other threads:[~2005-04-22 0:31 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-04-20 23:10 x86_64: Bug in new out of line put_user() Alexander Nyberg
2005-04-21 11:10 ` Andi Kleen
2005-04-21 13:05 ` Nicolas Boichat
2005-04-21 23:55 ` Nicolas Boichat
2005-04-22 0:32 ` Brian Gerst [this message]
2005-04-22 8:22 ` Alexander Nyberg
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