Messages in this thread | | | Subject | Re: [PATCHv8 resend 1/2] x86/vdso: add mremap hook to vm_special_mapping | From | Dmitry Safonov <> | Date | Mon, 16 May 2016 12:38:37 +0300 |
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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
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