Ard,
On Tue, Mar 21, 2017 at 11:16:34AM +0000, Ard Biesheuvel wrote:
> 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?
I've almost forgotten this function, but my understanding is that
this function (and map counterpart) is mainly for "VM area" (< PAGE_OFFSET).
While it seems to (actually does) work instead of create_pgd_mapping() for now,
I'm not sure whether it is an expected usage (now and future).
So I think that it would be safe to keep using create_pgd_mapping().
Thanks,
-Takahiro AKASHI
> > ---
> > 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
