* Laurent Dufour <lduf...@linux.vnet.ibm.com> wrote:

> +static inline void arch_unmap(struct mm_struct *mm,
> +                     struct vm_area_struct *vma,
> +                     unsigned long start, unsigned long end)
> +{
> +     if (start <= mm->context.vdso_base && mm->context.vdso_base < end)
> +             mm->context.vdso_base = 0;
> +}

So AFAICS PowerPC can have multi-page vDSOs, right?

So what happens if I munmap() the middle or end of the vDSO? The above 
condition only seems to cover unmaps that affect the first page. I 
think 'affects any page' ought to be the right condition? (But I know 
nothing about PowerPC so I might be wrong.)


> +#define __HAVE_ARCH_REMAP
> +static inline void arch_remap(struct mm_struct *mm,
> +                           unsigned long old_start, unsigned long old_end,
> +                           unsigned long new_start, unsigned long new_end)
> +{
> +     /*
> +      * mremap() doesn't allow moving multiple vmas so we can limit the
> +      * check to old_start == vdso_base.
> +      */
> +     if (old_start == mm->context.vdso_base)
> +             mm->context.vdso_base = new_start;
> +}

mremap() doesn't allow moving multiple vmas, but it allows the 
movement of multi-page vmas and it also allows partial mremap()s, 
where it will split up a vma.

In particular, what happens if an mremap() is done with 
old_start == vdso_base, but a shorter end than the end of the vDSO? 
(i.e. a partial mremap() with fewer pages than the vDSO size)

Thanks,

        Ingo
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