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Re: [PATCH 2/6] x86/vdso: introduce do_map_vdso() and vdso_type enum

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On 06/03/2016 12:50 PM, Cyrill Gorcunov wrote:
> On Wed, Jun 01, 2016 at 04:11:33PM +0300, Dmitry Safonov wrote:
>> Make in-kernel API to map vDSO blobs on x86.
>>
>> Cc: Andy Lutomirski <luto@kernel.org>
>> Cc: Ingo Molnar <mingo@redhat.com>
>> Cc: Thomas Gleixner <tglx@linutronix.de>
>> Cc: "H. Peter Anvin" <hpa@zytor.com>
>> Signed-off-by: Dmitry Safonov <dsafonov@virtuozzo.com>
>
> Hi! Sorry for delay in reply. Dima, here is a moment I somehow missing:
> when do_map_vdso is called it is implied that old vdso is unmapped already,
> or both can be present in the system?
>

Both can be present. There are some limitations: if first vDSO was
32-bit, syscalls through it wouldn't work, only on the last mapped.
It's because of mm->context.vdso pointer, which for 32-bit vDSO
should point on it. (and this code make it point to a new mapped vDSO)

On RFC I did patch that unmaps previous vDSO, but I have though
it's better to simplify this code and drop unmapping.

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[PATCH 2/6] x86/vdso: introduce do_map_vdso() and vdso_type enum Dmitry Safonov <dsafonov@virtuozzo.com> - 2016-06-01 15:20 +0200
  Re: [PATCH 2/6] x86/vdso: introduce do_map_vdso() and vdso_type enum Cyrill Gorcunov <gorcunov@gmail.com> - 2016-06-03 12:00 +0200
    Re: [PATCH 2/6] x86/vdso: introduce do_map_vdso() and vdso_type enum Dmitry Safonov <dsafonov@virtuozzo.com> - 2016-06-03 12:40 +0200

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