From: Ingo Molnar <mingo@kernel.org>
To: Dmitry Safonov <dsafonov@virtuozzo.com>
Cc: linux-kernel@vger.kernel.org, mingo@redhat.com,
luto@amacapital.net, tglx@linutronix.de, hpa@zytor.com,
x86@kernel.org, akpm@linux-foundation.org, linux-mm@kvack.org,
0x7f454c46@gmail.com
Subject: Re: [PATCHv8 resend 1/2] x86/vdso: add mremap hook to vm_special_mapping
Date: Mon, 16 May 2016 12:54:29 +0200 [thread overview]
Message-ID: <20160516105429.GA20440@gmail.com> (raw)
In-Reply-To: <79f9fe67-a343-43b8-0933-a79461900c1b@virtuozzo.com>
* Dmitry Safonov <dsafonov@virtuozzo.com> wrote:
> On 05/10/2016 04:29 PM, Dmitry Safonov 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
> >
> >Signed-off-by: Dmitry Safonov <dsafonov@virtuozzo.com>
> >Acked-by: Andy Lutomirski <luto@kernel.org>
> >---
> >v8: add WARN_ON_ONCE on current->mm != new_vma->vm_mm
> >v7: build fix
> >v6: moved vdso_image_32 check and fixup code into vdso_fix_landing function
> > with ifdefs around
> >v5: as Andy suggested, add a check that new_vma->vm_mm and current->mm are
> > the same, also check not only in_ia32_syscall() but image == &vdso_image_32
> >v4: drop __maybe_unused & use image from mm->context instead vdso_image_32
> >v3: as Andy suggested, return EINVAL in case of splitting vdso blob on mremap;
> > used is_ia32_task instead of ifdefs
> >v2: added __maybe_unused for pt_regs in vdso_mremap
>
> Ping?
There's no 0/2 boilerplate explaining the background of the changes - why do you
want to mremap() the vDSO?
Thanks,
Ingo
next prev parent reply other threads:[~2016-05-16 10:54 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-05-10 13:29 [PATCHv8 resend 1/2] x86/vdso: add mremap hook to vm_special_mapping Dmitry Safonov
2016-05-10 13:29 ` [PATCHv8 resend 2/2] selftest/x86: add mremap vdso test Dmitry Safonov
2016-05-16 13:54 ` Ingo Molnar
2016-05-16 16:24 ` Dmitry Safonov
2016-05-16 18:25 ` Andy Lutomirski
2016-05-17 10:25 ` Dmitry Safonov
2016-05-16 9:38 ` [PATCHv8 resend 1/2] x86/vdso: add mremap hook to vm_special_mapping Dmitry Safonov
2016-05-16 10:54 ` Ingo Molnar [this message]
2016-05-16 11:14 ` Dmitry Safonov
2016-05-16 13:55 ` Ingo Molnar
2016-05-16 16:23 ` Dmitry Safonov
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20160516105429.GA20440@gmail.com \
--to=mingo@kernel.org \
--cc=0x7f454c46@gmail.com \
--cc=akpm@linux-foundation.org \
--cc=dsafonov@virtuozzo.com \
--cc=hpa@zytor.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=luto@amacapital.net \
--cc=mingo@redhat.com \
--cc=tglx@linutronix.de \
--cc=x86@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).