Messages in this thread | | | Date | Wed, 25 Mar 2015 19:33:16 +0100 | From | Ingo Molnar <> | Subject | Re: [PATCH v3 2/2] powerpc/mm: Tracking vDSO remap |
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* Laurent Dufour <ldufour@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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