Subject: [PATCHv6 7/8] arm64: efi: Use ioremap_exec for code sections

From: [email-masked] (Laura Abbott)
Date: Tue, 25 Nov 2014 10:57:31 -0800

On 11/25/2014 9:26 AM, Mark Rutland wrote:
> Hi Laura,
>
> On Fri, Nov 21, 2014 at 09:50:44PM +0000, Laura Abbott wrote:
>> ioremap is not guaranteed to return memory with proper
>> execution permissions. Introduce ioremap_exec which will
>> ensure that permission bits are set as expected for EFI
>> code sections.
>>
>> Tested-by: Kees Cook <[email-masked]>
>> Signed-off-by: Laura Abbott <[email-masked]>
>> ---
>>   arch/arm64/include/asm/io.h      |  1 +
>>   arch/arm64/include/asm/pgtable.h |  1 +
>>   arch/arm64/kernel/efi.c          | 12 +++++++++++-
>>   arch/arm64/mm/ioremap.c          | 11 +++++++++++
>>   4 files changed, 24 insertions(+), 1 deletion(-)
>>
>> diff --git a/arch/arm64/include/asm/io.h b/arch/arm64/include/asm/io.h
>> index 79f1d519..7dd8465 100644
>> --- a/arch/arm64/include/asm/io.h
>> +++ b/arch/arm64/include/asm/io.h
>> @@ -230,6 +230,7 @@ extern void __memset_io(volatile void __iomem *, int, size_t);
>>   extern void __iomem *__ioremap(phys_addr_t phys_addr, size_t size, pgprot_t prot);
>>   extern void __iounmap(volatile void __iomem *addr);
>>   extern void __iomem *ioremap_cache(phys_addr_t phys_addr, size_t size);
>> +extern void __iomem *ioremap_exec(phys_addr_t phys_addr, size_t size);
>>
>>   #define ioremap(addr, size)		__ioremap((addr), (size), __pgprot(PROT_DEVICE_nGnRE))
>>   #define ioremap_nocache(addr, size)	__ioremap((addr), (size), __pgprot(PROT_DEVICE_nGnRE))
>> diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
>> index 41a43bf..9b1d9d0 100644
>> --- a/arch/arm64/include/asm/pgtable.h
>> +++ b/arch/arm64/include/asm/pgtable.h
>> @@ -65,6 +65,7 @@ extern void __pgd_error(const char *file, int line, unsigned long val);
>>   #define PROT_DEVICE_nGnRE	(PROT_DEFAULT | PTE_PXN | PTE_UXN | PTE_ATTRINDX(MT_DEVICE_nGnRE))
>>   #define PROT_NORMAL_NC		(PROT_DEFAULT | PTE_PXN | PTE_UXN | PTE_ATTRINDX(MT_NORMAL_NC))
>>   #define PROT_NORMAL		(PROT_DEFAULT | PTE_PXN | PTE_UXN | PTE_ATTRINDX(MT_NORMAL))
>> +#define PROT_NORMAL_EXEC	(PROT_DEFAULT | PTE_UXN | PTE_ATTRINDX(MT_NORMAL))
>>
>>   #define PROT_SECT_DEVICE_nGnRE	(PROT_SECT_DEFAULT | PMD_SECT_PXN | PMD_SECT_UXN | PMD_ATTRINDX(MT_DEVICE_nGnRE))
>>   #define PROT_SECT_NORMAL	(PROT_SECT_DEFAULT | PMD_SECT_PXN | PMD_SECT_UXN | PMD_ATTRINDX(MT_NORMAL))
>> diff --git a/arch/arm64/kernel/efi.c b/arch/arm64/kernel/efi.c
>> index 95c49eb..9e41f95 100644
>> --- a/arch/arm64/kernel/efi.c
>> +++ b/arch/arm64/kernel/efi.c
>> @@ -47,6 +47,14 @@ static int __init is_normal_ram(efi_memory_desc_t *md)
>>   	return 0;
>>   }
>>
>> +static int __init is_code(efi_memory_desc_t *md)
>> +{
>> +	if (md->attribute & EFI_RUNTIME_SERVICES_CODE)
>> +		return 1;
>> +	return 0;
>> +}
>> +
>> +
>>   static void __init efi_setup_idmap(void)
>>   {
>>   	struct memblock_region *r;
>> @@ -338,7 +346,9 @@ static int __init remap_region(efi_memory_desc_t *md, void **new)
>>   	memrange_efi_to_native(&paddr, &npages);
>>   	size = npages << PAGE_SHIFT;
>>
>> -	if (is_normal_ram(md))
>> +	if (is_code(md))
>> +		vaddr = (__force u64)ioremap_exec(paddr, size);
>> +	else if (is_normal_ram(md))
>>   		vaddr = (__force u64)ioremap_cache(paddr, size);
>>   	else
>>   		vaddr = (__force u64)ioremap(paddr, size);
>
> All of the above looks fine to me.
>
>> diff --git a/arch/arm64/mm/ioremap.c b/arch/arm64/mm/ioremap.c
>> index cbb99c8..b998441 100644
>> --- a/arch/arm64/mm/ioremap.c
>> +++ b/arch/arm64/mm/ioremap.c
>> @@ -103,6 +103,17 @@ void __iomem *ioremap_cache(phys_addr_t phys_addr, size_t size)
>>   }
>>   EXPORT_SYMBOL(ioremap_cache);
>>
>> +void __iomem *ioremap_exec(phys_addr_t phys_addr, size_t size)
>> +{
>> +	/* For normal memory we already have a cacheable mapping. */
>> +	if (pfn_valid(__phys_to_pfn(phys_addr)))
>> +		return (void __iomem *)__phys_to_virt(phys_addr);
>
> Is this guaranteed to be executable in all cases once the stricter page
> permissions are in force?
>

No but the updated version of the patch which adds the stricter page
permission adds a call to update the page permissions to be executable.
  
> Thanks,
> Mark.

Thanks,
Laura

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