linux-kernel - Re: [PATCHv8 1/2] x86/vdso: add mremap hook to vm_special

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Date:	Thu, 5 May 2016 14:55:12 +0300
From:	Dmitry Safonov <dsafonov@...tuozzo.com>
To:	Ingo Molnar <mingo@...nel.org>
CC:	Andy Lutomirski <luto@...capital.net>,
	Ingo Molnar <mingo@...hat.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>, X86 ML <x86@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	Dmitry Safonov <0x7f454c46@...il.com>
Subject: Re: [PATCHv8 1/2] x86/vdso: add mremap hook to vm_special_mapping

On 05/05/2016 02:52 PM, Ingo Molnar wrote:
>
> * Dmitry Safonov <dsafonov@...tuozzo.com> wrote:
>
>> On 04/26/2016 12:38 AM, Andy Lutomirski wrote:
>>> On Mon, Apr 25, 2016 at 4:37 AM, Dmitry Safonov <dsafonov@...tuozzo.com> wrote:
>>>> Add possibility for userspace 32-bit applications to move
>>>> vdso mapping. Previously, when userspace app called
>>>> mremap for vdso, in return path it would land on previous
>>>> address of vdso page, resulting in segmentation violation.
>>>> Now it lands fine and returns to userspace with remapped vdso.
>>>> This will also fix context.vdso pointer for 64-bit, which does not
>>>> affect the user of vdso after mremap by now, but this may change.
>>>>
>>>> As suggested by Andy, return EINVAL for mremap that splits vdso image.
>>>>
>>>> Renamed and moved text_mapping structure declaration inside
>>>> map_vdso, as it used only there and now it complement
>>>> vvar_mapping variable.
>>>>
>>>> There is still problem for remapping vdso in glibc applications:
>>>> linker relocates addresses for syscalls on vdso page, so
>>>> you need to relink with the new addresses. Or the next syscall
>>>> through glibc may fail:
>>>>   Program received signal SIGSEGV, Segmentation fault.
>>>>   #0  0xf7fd9b80 in __kernel_vsyscall ()
>>>>   #1  0xf7ec8238 in _exit () from /usr/lib32/libc.so.6
>>> Acked-by: Andy Lutomirski <luto@...nel.org>
>>>
>>> Ingo, can you apply this?
>>
>> Hm, so I'm not sure - should I resend those two?
>> Or just ping?
>
> Please send a clean series with updated Acked-by's, etc.


Thanks, Ingo, will do.
Sorry for html in the last email - mail agent got an
update and I overlooked html composing become turned on.

-- 
Regards,
Dmitry Safonov