On Mon, Dec 22, 2014 at 07:08:41PM +0000, Ard Biesheuvel wrote:
> The 'physmem' memblock table allows us to classify memory as RAM even
> if it is not covered by the ordinary 'memory' memblock table.
>
> Under CONFIG_STRICT_DEVMEM, we can use this to:
> - allow read-only access to parts of RAM that are not considered memory
> by the kernel, this is mainly intended for exposing UEFI configuration
> tables such as SMBIOS to userland;
> - avoid using non-cached mappings for those parts of RAM, as it may
> result in mismatched attributes.
Looks fine to me assuming that the rest of the series is ok:
Acked-by: Will Deacon <will.deacon@xxxxxxx>
Will
> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>
> ---
> arch/arm64/Kconfig | 1 +
> arch/arm64/mm/mmap.c | 2 +-
> arch/arm64/mm/mmu.c | 15 ++++++++++++++-
> 3 files changed, 16 insertions(+), 2 deletions(-)
>
> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> index b1f9a20a3677..86902f8d8e36 100644
> --- a/arch/arm64/Kconfig
> +++ b/arch/arm64/Kconfig
> @@ -60,6 +60,7 @@ config ARM64
> select HAVE_GENERIC_DMA_COHERENT
> select HAVE_HW_BREAKPOINT if PERF_EVENTS
> select HAVE_MEMBLOCK
> + select HAVE_MEMBLOCK_PHYS_MAP
> select HAVE_PATA_PLATFORM
> select HAVE_PERF_EVENTS
> select HAVE_PERF_REGS
> diff --git a/arch/arm64/mm/mmap.c b/arch/arm64/mm/mmap.c
> index 54922d1275b8..9f558ab41f39 100644
> --- a/arch/arm64/mm/mmap.c
> +++ b/arch/arm64/mm/mmap.c
> @@ -126,7 +126,7 @@ int devmem_is_allowed(unsigned long pfn)
> {
> if (iomem_is_exclusive(pfn << PAGE_SHIFT))
> return 0;
> - if (!page_is_ram(pfn))
> + if (!pfn_valid(pfn))
> return 1;
> return 0;
> }
> diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
> index 328638548871..083be3de1a87 100644
> --- a/arch/arm64/mm/mmu.c
> +++ b/arch/arm64/mm/mmu.c
> @@ -122,7 +122,7 @@ early_param("cachepolicy", early_cachepolicy);
> pgprot_t phys_mem_access_prot(struct file *file, unsigned long pfn,
> unsigned long size, pgprot_t vma_prot)
> {
> - if (!pfn_valid(pfn))
> + if (!memblock_is_physmem(PFN_PHYS(pfn)))
> return pgprot_noncached(vma_prot);
> else if (file->f_flags & O_SYNC)
> return pgprot_writecombine(vma_prot);
> @@ -130,6 +130,19 @@ pgprot_t phys_mem_access_prot(struct file *file, unsigned long pfn,
> }
> EXPORT_SYMBOL(phys_mem_access_prot);
>
> +/*
> + * This definition of phys_mem_access_prot_allowed() overrides
> + * the __weak definition in drivers/char/mem.c
> + */
> +int phys_mem_access_prot_allowed(struct file *file, unsigned long pfn,
> + unsigned long size, pgprot_t *prot)
> +{
> + /* Disallow read-write access to system RAM */
> + if (memblock_is_physmem(PFN_PHYS(pfn)) && pgprot_val(*prot) & PTE_WRITE)
> + return 0;
> + return 1;
> +}
> +
> static void __init *early_alloc(unsigned long sz)
> {
> void *ptr = __va(memblock_alloc(sz, sz));
> --
> 1.8.3.2
>
>
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