Messages in this thread | | | Subject | Re: [PATCH] powerpc/vdso: Separate vvar vma from vdso | From | Christophe Leroy <> | Date | Tue, 30 Mar 2021 12:17:59 +0200 |
| |
Le 26/03/2021 à 20:17, Dmitry Safonov a écrit : > Since commit 511157ab641e ("powerpc/vdso: Move vdso datapage up front") > VVAR page is in front of the VDSO area. In result it breaks CRIU > (Checkpoint Restore In Userspace) [1], where CRIU expects that "[vdso]" > from /proc/../maps points at ELF/vdso image, rather than at VVAR data page. > Laurent made a patch to keep CRIU working (by reading aux vector). > But I think it still makes sence to separate two mappings into different > VMAs. It will also make ppc64 less "special" for userspace and as > a side-bonus will make VVAR page un-writable by debugger (which previously > would COW page and can be unexpected). > > I opportunistically Cc stable on it: I understand that usually such > stuff isn't a stable material, but that will allow us in CRIU have > one workaround less that is needed just for one release (v5.11) on > one platform (ppc64), which we otherwise have to maintain. > I wouldn't go as far as to say that the commit 511157ab641e is ABI > regression as no other userspace got broken, but I'd really appreciate > if it gets backported to v5.11 after v5.12 is released, so as not > to complicate already non-simple CRIU-vdso code. Thanks! > > Cc: Andrei Vagin <avagin@gmail.com> > Cc: Andy Lutomirski <luto@kernel.org> > Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> > Cc: Christophe Leroy <christophe.leroy@csgroup.eu> > Cc: Laurent Dufour <ldufour@linux.ibm.com> > Cc: Michael Ellerman <mpe@ellerman.id.au> > Cc: Paul Mackerras <paulus@samba.org> > Cc: linuxppc-dev@lists.ozlabs.org > Cc: stable@vger.kernel.org # v5.11 > [1]: https://github.com/checkpoint-restore/criu/issues/1417 > Signed-off-by: Dmitry Safonov <dima@arista.com> > Tested-by: Christophe Leroy <christophe.leroy@csgroup.eu> > --- > arch/powerpc/include/asm/mmu_context.h | 2 +- > arch/powerpc/kernel/vdso.c | 54 +++++++++++++++++++------- > 2 files changed, 40 insertions(+), 16 deletions(-) > > diff --git a/arch/powerpc/include/asm/mmu_context.h b/arch/powerpc/include/asm/mmu_context.h > index 652ce85f9410..4bc45d3ed8b0 100644 > --- a/arch/powerpc/include/asm/mmu_context.h > +++ b/arch/powerpc/include/asm/mmu_context.h > @@ -263,7 +263,7 @@ extern void arch_exit_mmap(struct mm_struct *mm); > static inline void arch_unmap(struct mm_struct *mm, > unsigned long start, unsigned long end) > { > - unsigned long vdso_base = (unsigned long)mm->context.vdso - PAGE_SIZE; > + unsigned long vdso_base = (unsigned long)mm->context.vdso; > > if (start <= vdso_base && vdso_base < end) > mm->context.vdso = NULL; > diff --git a/arch/powerpc/kernel/vdso.c b/arch/powerpc/kernel/vdso.c > index e839a906fdf2..b14907209822 100644 > --- a/arch/powerpc/kernel/vdso.c > +++ b/arch/powerpc/kernel/vdso.c > @@ -55,10 +55,10 @@ static int vdso_mremap(const struct vm_special_mapping *sm, struct vm_area_struc > { > unsigned long new_size = new_vma->vm_end - new_vma->vm_start; > > - if (new_size != text_size + PAGE_SIZE) > + if (new_size != text_size) > return -EINVAL;
In ARM64 you have removed the above test in commit 871402e05b24cb56 ("mm: forbid splitting special mappings"). Do we need to keep it here ?
> > - current->mm->context.vdso = (void __user *)new_vma->vm_start + PAGE_SIZE; > + current->mm->context.vdso = (void __user *)new_vma->vm_start; > > return 0; > }
| |