* Laurent Dufour <ldufour@xxxxxxxxxxxxxxxxxx> 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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