On 30 June 2015 at 16:50, Mark Salter <msalter@xxxxxxxxxx> wrote:
> On Tue, 2015-06-30 at 12:17 +0200, Ard Biesheuvel wrote:
>
>> Currently, we infer the UEFI memory region mapping permissions
>> from the memory region type (i.e., runtime services code are
>> mapped RWX and runtime services data mapped RW-). This appears to
>> work fine but is not entirely UEFI spec compliant. So instead, use
>> the designated permission attributes to decide how these regions
>> should be mapped.
>>
>> Since UEFIv2.5 introduces a new EFI_MEMORY_RO permission attribute,
>> and redefines EFI_MEMORY_WP as a cacheability attribute, use only
>> the former as a read-only attribute. For setting the PXN bit, the
>> corresponding EFI_MEMORY_XP attribute is used.
>>
>> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>
>> ---
>> arch/arm64/kernel/efi.c | 32 +++++++++++++-------
>> 1 file changed, 21 insertions(+), 11 deletions(-)
>>
>> diff --git a/arch/arm64/kernel/efi.c b/arch/arm64/kernel/efi.c
>> index ab21e0d58278..5dcab58d5d30 100644
>> --- a/arch/arm64/kernel/efi.c
>> +++ b/arch/arm64/kernel/efi.c
>> @@ -247,20 +247,30 @@ static bool __init efi_virtmap_init(void)
>> memrange_efi_to_native(&paddr, &npages);
>> size = npages << PAGE_SHIFT;
>>
>> - pr_info(" EFI remap 0x%016llx => %p\n",
>> - md->phys_addr, (void *)md->virt_addr);
>> -
>> - /*
>> - * Only regions of type EFI_RUNTIME_SERVICES_CODE need to be
>> - * executable, everything else can be mapped with the XN bits
>> - * set.
>> - */
>> if (!is_normal_ram(md))
>> prot = __pgprot(PROT_DEVICE_nGnRE);
>> - else if (md->type == EFI_RUNTIME_SERVICES_CODE)
>> - prot = PAGE_KERNEL_EXEC;
>> else
>> - prot = PAGE_KERNEL;
>> + prot = PAGE_KERNEL_EXEC;
>> +
>> + /*
>> + * On 64 KB granule kernels, only use strict permissions when
>> + * the region does not share a 64 KB page frame with another
>> + * region at either end.
>> + */
>> + if (!IS_ENABLED(CONFIG_ARM64_64K_PAGES) ||
>> + !(md->virt_addr % PAGE_SIZE ||
>> + (md->phys_addr + md->num_pages * EFI_PAGE_SIZE) % PAGE_SIZE)) {
>
> I think this would read easier with:
>
> (PAGE_ALIGNED(md->virt_addr) &&
> PAGE_ALIGNED(md->phys_addr + md->num_pages * EFI_PAGE_SIZE))) {
>
Yes, good point, I will change that.
>> +
>> + if (md->attribute & EFI_MEMORY_RO)
>> + prot |= __pgprot(PTE_RDONLY);
>> + if (md->attribute & EFI_MEMORY_XP)
>> + prot |= __pgprot(PTE_PXN);
>> + }
>> +
>> + pr_info(" EFI remap 0x%016llx => %p (R%c%c)\n",
>> + md->phys_addr, (void *)md->virt_addr,
>> + prot & __pgprot(PTE_RDONLY) ? '-' : 'W',
>> + prot & __pgprot(PTE_PXN) ? '-' : 'X');
>
> You can't maninulate pgprot_t directly like that. It will
> break STRICT_MM_TYPECHECKS. You need to use __pgprot_modify()
> and/or pgprot_val().
>
> arch/arm64/kernel/efi.c: In function ‘efi_virtmap_init’:
> arch/arm64/kernel/efi.c:266:10: error: invalid operands to binary | (have ‘pgprot_t’ and ‘pgprot_t’)
> prot |= __pgprot(PTE_RDONLY);
> ^
> ...
>
> (In trying that, I see there are a number of other places which
> need some STRICT_MM_TYPECHECKS fixing)
>
Actually, I had 'prot |= PTE_RDONLY' but then changed it to the above
thinking that it would pass the strict type checks, but apparently not
:-)
I will fix that up as well.
Thanks,
Ard.
>>
>> create_pgd_mapping(&efi_mm, paddr, md->virt_addr, size, prot);
>> }
>
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