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    SubjectRe: [RFC PATCH] proc: clear_refs: do not clear reserved pages
    On Mon, Jan 16, 2012 at 04:19:43AM +0000, Nicolas Pitre wrote:
    > On Sun, 15 Jan 2012, Will Deacon wrote:
    > > Something like what I've got below seems to do the trick, and clear_refs
    > > also seems to behave when it's presented with the gate_vma. If Russell is
    > > happy with the approach, we can move to the gate_vma in the future.
    >
    > I like it much better, although I haven't tested it fully yet.
    >
    > However your patch is missing the worst of the current ARM hack I would
    > be glad to see go as follows:
    >
    > diff --git a/arch/arm/include/asm/mmu_context.h b/arch/arm/include/asm/mmu_context.h
    > index 71605d9f8e..876e545297 100644
    > --- a/arch/arm/include/asm/mmu_context.h
    > +++ b/arch/arm/include/asm/mmu_context.h
    > @@ -18,6 +18,7 @@
    > #include <asm/cacheflush.h>
    > #include <asm/cachetype.h>
    > #include <asm/proc-fns.h>
    > +#include <asm-generic/mm_hooks.h>
    >
    > void __check_kvm_seq(struct mm_struct *mm);
    >
    > @@ -133,32 +135,4 @@ 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)
    >
    > -/*
    > - * We are inserting a "fake" vma for the user-accessible vector page so
    > - * gdb and friends can get to it through ptrace and /proc/<pid>/mem.
    > - * But we also want to remove it before the generic code gets to see it
    > - * during process exit or the unmapping of it would cause total havoc.
    > - * (the macro is used as remove_vma() is static to mm/mmap.c)
    > - */
    > -#define arch_exit_mmap(mm) \
    > -do { \
    > - struct vm_area_struct *high_vma = find_vma(mm, 0xffff0000); \
    > - if (high_vma) { \
    > - BUG_ON(high_vma->vm_next); /* it should be last */ \
    > - if (high_vma->vm_prev) \
    > - high_vma->vm_prev->vm_next = NULL; \
    > - else \
    > - mm->mmap = NULL; \
    > - rb_erase(&high_vma->vm_rb, &mm->mm_rb); \
    > - mm->mmap_cache = NULL; \
    > - mm->map_count--; \
    > - remove_vma(high_vma); \
    > - } \
    > -} while (0)
    > -
    > -static inline void arch_dup_mmap(struct mm_struct *oldmm,
    > - struct mm_struct *mm)
    > -{
    > -}
    > -
    > #endif

    Nice, I missed those hunks! I'm more than happy to include this for v2
    (which I'll just post to the ARM list). I'll also give this some testing on
    the boards that I have.

    Thanks,

    Will


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