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ArmPkg/CpuDxe: translate invalid memory types in EfiAttributeToArmAttribute 

The single user of EfiAttributeToArmAttribute () is the protocol
method EFI_CPU_ARCH_PROTOCOL.SetMemoryAttributes(), which uses the
return value to compare against the ARM attributes of an existing mapping,
to infer whether it is actually necessary to change anything, or whether
the requested update is redundant. This saves some cache and TLB
maintenance on 32-bit ARM systems that use uncached translation tables.

However, EFI_CPU_ARCH_PROTOCOL.SetMemoryAttributes() may be invoked with
only permission bits set, in which case the implied requested action is to
update the permissions of the region without modifying the cacheability
attributes. This is currently not possible, because
EfiAttributeToArmAttribute () ASSERT()s [on AArch64] on Attributes arguments
that lack a cacheability bit.

So let's simply return TT_ATTR_INDX_MASK (AArch64) or
TT_DESCRIPTOR_SECTION_TYPE_FAULT (ARM) in these cases (or'ed with the
appropriate permission bits). This way, the return value is equally
suitable for checking whether the attributes need to be modified, but
in a way that accommodates the use without a cacheability bit set.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: Leif Lindholm <leif.lindholm@linaro.org>
This commit is contained in:
Ard Biesheuvel 2017-02-15 17:11:54 +00:00
parent b7a09b71b6
commit ce82984fe7
2 changed files with 1 additions and 6 deletions
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4
ArmPkg/Drivers/CpuDxe/AArch64/Mmu.c
View File

@ -216,9 +216,7 @@ EfiAttributeToArmAttribute (
ArmAttributes = TT_ATTR_INDX_MEMORY_WRITE_BACK;
break;
default:
DEBUG ((EFI_D_ERROR, "EfiAttributeToArmAttribute: 0x%lX attributes is not supported.\n", EfiAttributes));
ASSERT (0);
ArmAttributes = TT_ATTR_INDX_DEVICE_MEMORY;
ArmAttributes = TT_ATTR_INDX_MASK;
}
// Set the access flag to match the block attributes

3
ArmPkg/Drivers/CpuDxe/Arm/Mmu.c
View File

@ -733,10 +733,7 @@ EfiAttributeToArmAttribute (
case EFI_MEMORY_UCE:
default:
// Cannot be implemented UEFI definition unclear for ARM
// Cause a page fault if these ranges are accessed.
ArmAttributes = TT_DESCRIPTOR_SECTION_TYPE_FAULT;
DEBUG ((EFI_D_PAGE, "SetMemoryAttributes(): Unsupported attribute %x will page fault on access\n", EfiAttributes));
break;
}