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SubjectRe: [PATCH] arm64: Support VDSO remapping
Hi Christopher,

On Wed, Nov 25, 2015 at 07:49:29AM -0500, Christopher Covington wrote:
> Some applications such as Checkpoint/Restore In Userspace (CRIU) remap and
> unmap the VDSO. Add support for this to the AArch64 kernel by copying in
> the PowerPC code with slight modifications.
>
> Signed-off-by: Christopher Covington <cov@codeaurora.org>
> ---
> arch/arm64/include/asm/Kbuild | 1 -
> arch/arm64/include/asm/mm-arch-hooks.h | 28 ++++++++++++++++++++++++++++
> arch/arm64/include/asm/mmu_context.h | 23 ++++++++++++++++++++++-
> 3 files changed, 50 insertions(+), 2 deletions(-)
> create mode 100644 arch/arm64/include/asm/mm-arch-hooks.h
>
> diff --git a/arch/arm64/include/asm/Kbuild b/arch/arm64/include/asm/Kbuild
> index 70fd9ff..b112a39 100644
> --- a/arch/arm64/include/asm/Kbuild
> +++ b/arch/arm64/include/asm/Kbuild
> @@ -25,7 +25,6 @@ generic-y += kvm_para.h
> generic-y += local.h
> generic-y += local64.h
> generic-y += mcs_spinlock.h
> -generic-y += mm-arch-hooks.h
> generic-y += mman.h
> generic-y += msgbuf.h
> generic-y += msi.h
> diff --git a/arch/arm64/include/asm/mm-arch-hooks.h b/arch/arm64/include/asm/mm-arch-hooks.h
> new file mode 100644
> index 0000000..e6923fb
> --- /dev/null
> +++ b/arch/arm64/include/asm/mm-arch-hooks.h
> @@ -0,0 +1,28 @@
> +/*
> + * Architecture specific mm hooks
> + *
> + * Copyright (C) 2015, IBM Corporation
> + * Author: Laurent Dufour <ldufour@linux.vnet.ibm.com>
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 as
> + * published by the Free Software Foundation.
> + */
> +
> +#ifndef __ASM_MM_ARCH_HOOKS_H
> +#define __ASM_MM_ARCH_HOOKS_H
> +
> +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 ((void *)old_start == mm->context.vdso)
> + mm->context.vdso = (void *)new_start;
> +}
> +#define arch_remap arch_remap
> +
> +#endif /* __ASM_MM_ARCH_HOOKS_H */
> diff --git a/arch/arm64/include/asm/mmu_context.h b/arch/arm64/include/asm/mmu_context.h
> index 2416578..9fe0773 100644
> --- a/arch/arm64/include/asm/mmu_context.h
> +++ b/arch/arm64/include/asm/mmu_context.h
> @@ -24,7 +24,6 @@
>
> #include <asm/cacheflush.h>
> #include <asm/proc-fns.h>
> -#include <asm-generic/mm_hooks.h>
> #include <asm/cputype.h>
> #include <asm/pgtable.h>
>
> @@ -147,4 +146,26 @@ switch_mm(struct mm_struct *prev, struct mm_struct *next,
> #define deactivate_mm(tsk,mm) do { } while (0)
> #define activate_mm(prev,next) switch_mm(prev, next, NULL)
>
> +static inline void arch_dup_mmap(struct mm_struct *oldmm,
> + struct mm_struct *mm)
> +{
> +}
> +
> +static inline void arch_exit_mmap(struct mm_struct *mm)
> +{
> +}
> +
> +static inline void arch_unmap(struct mm_struct *mm,
> + struct vm_area_struct *vma,
> + unsigned long start, unsigned long end)
> +{
> + if ((void *)start <= mm->context.vdso && mm->context.vdso < (void *)end)
> + mm->context.vdso = NULL;
> +}
> +
> +static inline void arch_bprm_mm_init(struct mm_struct *mm,
> + struct vm_area_struct *vma)
> +{
> +}

This is virtually identical to the PowerPC implementation, afaict. Any
chance we could move this to core code and define some generic vdso
accessors for the mm?

Will


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