On Wed, 2015-03-25 at 19:36 +0100, Ingo Molnar wrote: > * Ingo Molnar <mingo@xxxxxxxxxx> wrote: > > > > +#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. > > I.e. mremap() supports the shrinking (and growing) of vmas. In that > case mremap() will unmap the end of the vma and will shrink the > remaining vDSO vma. > > Doesn't that result in a non-working vDSO that should zero out > vdso_base? Right. Now we can't completely prevent the user from shooting itself in the foot I suppose, though there is a legit usage scenario which is to move the vDSO around which it would be nice to support. I think it's reasonable to put the onus on the user here to do the right thing. Cheers, Ben. > Thanks, > > Ingo > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx"> email@xxxxxxxxx </a>