[PATCH v33 05/14] arm64: mm: allow for unmapping part of kernel mapping

[Ard Biesheuvel]

On 15 March 2017 at 09:59, AKASHI Takahiro <takahiro.akashi at linaro.org> wrote:
> create_pgd_mapping() is enhanced here so that it will accept
> PAGE_KERNEL_INVALID protection attribute and unmap a given range of memory.
>
> The feature will be used in a later kdump patch to implement the protection
> against possible corruption of crash dump kernel memory which is to be set
> aside from ther other memory on primary kernel.
>
> Note that, in this implementation, it assumes that all the range of memory
> to be processed is mapped in page-level since the only current user is
> kdump where page mappings are also required.
>
> Signed-off-by: AKASHI Takahiro <takahiro.akashi at linaro.org>

Couldn't we use unmap_kernel_range() for this?

> ---
>  arch/arm64/include/asm/pgtable-prot.h |  1 +
>  arch/arm64/mm/mmu.c                   | 17 +++++++++++------
>  2 files changed, 12 insertions(+), 6 deletions(-)
>
> diff --git a/arch/arm64/include/asm/pgtable-prot.h b/arch/arm64/include/asm/pgtable-prot.h
> index 2142c7726e76..945d84cd5df7 100644
> --- a/arch/arm64/include/asm/pgtable-prot.h
> +++ b/arch/arm64/include/asm/pgtable-prot.h
> @@ -54,6 +54,7 @@
>  #define PAGE_KERNEL_ROX                __pgprot(_PAGE_DEFAULT | PTE_UXN | PTE_DIRTY | PTE_RDONLY)
>  #define PAGE_KERNEL_EXEC       __pgprot(_PAGE_DEFAULT | PTE_UXN | PTE_DIRTY | PTE_WRITE)
>  #define PAGE_KERNEL_EXEC_CONT  __pgprot(_PAGE_DEFAULT | PTE_UXN | PTE_DIRTY | PTE_WRITE | PTE_CONT)
> +#define PAGE_KERNEL_INVALID    __pgprot(0)
>
>  #define PAGE_HYP               __pgprot(_PAGE_DEFAULT | PTE_HYP | PTE_HYP_XN)
>  #define PAGE_HYP_EXEC          __pgprot(_PAGE_DEFAULT | PTE_HYP | PTE_RDONLY)
> diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
> index d28dbcf596b6..cb359a3927ef 100644
> --- a/arch/arm64/mm/mmu.c
> +++ b/arch/arm64/mm/mmu.c
> @@ -128,7 +128,10 @@ static void alloc_init_pte(pmd_t *pmd, unsigned long addr,
>         do {
>                 pte_t old_pte = *pte;
>
> -               set_pte(pte, pfn_pte(pfn, prot));
> +               if (pgprot_val(prot))
> +                       set_pte(pte, pfn_pte(pfn, prot));
> +               else
> +                       pte_clear(null, null, pte);
>                 pfn++;
>
>                 /*
> @@ -309,12 +312,14 @@ static void __init create_mapping_noalloc(phys_addr_t phys, unsigned long virt,
>         __create_pgd_mapping(init_mm.pgd, phys, virt, size, prot, NULL, false);
>  }
>
> -void __init create_pgd_mapping(struct mm_struct *mm, phys_addr_t phys,
> -                              unsigned long virt, phys_addr_t size,
> -                              pgprot_t prot, bool page_mappings_only)
> +/*
> + * Note that PAGE_KERNEL_INVALID should be used with page_mappings_only
> + * true for now.
> + */
> +void create_pgd_mapping(struct mm_struct *mm, phys_addr_t phys,
> +                       unsigned long virt, phys_addr_t size,
> +                       pgprot_t prot, bool page_mappings_only)
>  {
> -       BUG_ON(mm == &init_mm);
> -
>         __create_pgd_mapping(mm->pgd, phys, virt, size, prot,
>                              pgd_pgtable_alloc, page_mappings_only);
>  }
> --
> 2.11.1
>
>
> _______________________________________________
> linux-arm-kernel mailing list
> linux-arm-kernel at lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel