From: Dmitry Safonov <dsafonov@virtuozzo.com>
To: <linux-kernel@vger.kernel.org>, <mingo@redhat.com>
Cc: <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 12:38:37 +0300 [thread overview]
Message-ID: <79f9fe67-a343-43b8-0933-a79461900c1b@virtuozzo.com> (raw)
In-Reply-To: <1462886951-23376-1-git-send-email-dsafonov@virtuozzo.com>
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?
next prev parent reply other threads:[~2016-05-16 9:59 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 ` Dmitry Safonov [this message]
2016-05-16 10:54 ` [PATCHv8 resend 1/2] x86/vdso: add mremap hook to vm_special_mapping Ingo Molnar
2016-05-16 11:14 ` Dmitry Safonov
2016-05-16 13:55 ` Ingo Molnar
2016-05-16 16:23 ` Dmitry Safonov
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