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Date: Wed, 25 Mar 2015 19:33:16 +0100 From: Ingo Molnar <mingo@...nel.org> To: Laurent Dufour <ldufour@...ux.vnet.ibm.com> Cc: Benjamin Herrenschmidt <benh@...nel.crashing.org>, Paul Mackerras <paulus@...ba.org>, Michael Ellerman <mpe@...erman.id.au>, Jeff Dike <jdike@...toit.com>, Richard Weinberger <richard@....at>, Guan Xuetao <gxt@...c.pku.edu.cn>, Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, "H. Peter Anvin" <hpa@...or.com>, x86@...nel.org, Arnd Bergmann <arnd@...db.de>, linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org, linux-s390@...r.kernel.org, user-mode-linux-devel@...ts.sourceforge.net, user-mode-linux-user@...ts.sourceforge.net, linux-arch@...r.kernel.org, linux-mm@...ck.org, cov@...eaurora.org, criu@...nvz.org Subject: Re: [PATCH v3 2/2] powerpc/mm: Tracking vDSO remap * Laurent Dufour <ldufour@...ux.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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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