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ArmPkg/ArmMmuLib: Implement EFI_MEMORY_RP using access flag 

Implement support for read-protected memory by wiring it up to the
access flag in the page table descriptor. The resulting mapping is
implicitly non-writable and non-executable as well, but this is good
enough for implementing this attribute, as we never rely on write or
execute permissions without read permissions.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Reviewed-by: Leif Lindholm <quic_llindhol@quicinc.com>
This commit is contained in:
Ard Biesheuvel 2023-02-07 16:09:56 +01:00 committed by mergify[bot]
parent 041c7a31c2
commit 6b821be140
4 changed files with 144 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

8
ArmPkg/Drivers/CpuDxe/AArch64/Mmu.c
View File

@ -64,6 +64,10 @@ PageAttributeToGcdAttribute (
}
// Determine protection attributes
if ((PageAttributes & TT_AF) == 0) {
GcdAttributes |= EFI_MEMORY_RP;
}
if (((PageAttributes & TT_AP_MASK) == TT_AP_NO_RO) ||
((PageAttributes & TT_AP_MASK) == TT_AP_RO_RO))
{
@ -301,7 +305,9 @@ EfiAttributeToArmAttribute (
}
// Set the access flag to match the block attributes
ArmAttributes |= TT_AF;
if ((EfiAttributes & EFI_MEMORY_RP) == 0) {
ArmAttributes |= TT_AF;
}
// Determine protection attributes
if ((EfiAttributes & EFI_MEMORY_RO) != 0) {

34
ArmPkg/Include/Library/ArmMmuLib.h
View File

@ -21,6 +21,40 @@ ArmConfigureMmu (
OUT UINTN *TranslationTableSize OPTIONAL
);
/**
Convert a region of memory to read-protected, by clearing the access flag.
@param BaseAddress The start of the region.
@param Length The size of the region.
@retval EFI_SUCCESS The attributes were set successfully.
@retval EFI_OUT_OF_RESOURCES The operation failed due to insufficient memory.
**/
EFI_STATUS
EFIAPI
ArmSetMemoryRegionNoAccess (
IN EFI_PHYSICAL_ADDRESS BaseAddress,
IN UINT64 Length
);
/**
Convert a region of memory to read-enabled, by setting the access flag.
@param BaseAddress The start of the region.
@param Length The size of the region.
@retval EFI_SUCCESS The attributes were set successfully.
@retval EFI_OUT_OF_RESOURCES The operation failed due to insufficient memory.
**/
EFI_STATUS
EFIAPI
ArmClearMemoryRegionNoAccess (
IN EFI_PHYSICAL_ADDRESS BaseAddress,
IN UINT64 Length
);
EFI_STATUS
EFIAPI
ArmSetMemoryRegionNoExec (

58
ArmPkg/Library/ArmMmuLib/AArch64/ArmMmuLibCore.c
View File

@ -438,7 +438,11 @@ GcdAttributeToPageAttribute (
PageAttributes |= TT_AP_NO_RO;
}
return PageAttributes | TT_AF;
if ((GcdAttributes & EFI_MEMORY_RP) == 0) {
PageAttributes |= TT_AF;
}
return PageAttributes;
}
EFI_STATUS
@ -459,9 +463,9 @@ ArmSetMemoryAttributes (
// No memory type was set in Attributes, so we are going to update the
// permissions only.
//
PageAttributes &= TT_AP_MASK | TT_UXN_MASK | TT_PXN_MASK;
PageAttributes &= TT_AP_MASK | TT_UXN_MASK | TT_PXN_MASK | TT_AF;
PageAttributeMask = ~(TT_ADDRESS_MASK_BLOCK_ENTRY | TT_AP_MASK |
TT_PXN_MASK | TT_XN_MASK);
TT_PXN_MASK | TT_XN_MASK | TT_AF);
}
return UpdateRegionMapping (
@ -534,6 +538,54 @@ ArmClearMemoryRegionNoExec (
);
}
/**
Convert a region of memory to read-protected, by clearing the access flag.
@param BaseAddress The start of the region.
@param Length The size of the region.
@retval EFI_SUCCESS The attributes were set successfully.
@retval EFI_OUT_OF_RESOURCES The operation failed due to insufficient memory.
**/
EFI_STATUS
ArmSetMemoryRegionNoAccess (
IN EFI_PHYSICAL_ADDRESS BaseAddress,
IN UINT64 Length
)
{
return SetMemoryRegionAttribute (
BaseAddress,
Length,
0,
~(TT_ADDRESS_MASK_BLOCK_ENTRY | TT_AF)
);
}
/**
Convert a region of memory to read-enabled, by setting the access flag.
@param BaseAddress The start of the region.
@param Length The size of the region.
@retval EFI_SUCCESS The attributes were set successfully.
@retval EFI_OUT_OF_RESOURCES The operation failed due to insufficient memory.
**/
EFI_STATUS
ArmClearMemoryRegionNoAccess (
IN EFI_PHYSICAL_ADDRESS BaseAddress,
IN UINT64 Length
)
{
return SetMemoryRegionAttribute (
BaseAddress,
Length,
TT_AF,
~TT_ADDRESS_MASK_BLOCK_ENTRY
);
}
EFI_STATUS
ArmSetMemoryRegionReadOnly (
IN EFI_PHYSICAL_ADDRESS BaseAddress,

48
ArmPkg/Library/ArmMmuLib/Arm/ArmMmuLibUpdate.c
View File

@ -523,3 +523,51 @@ ArmClearMemoryRegionReadOnly (
TT_DESCRIPTOR_SECTION_AP_MASK
);
}
/**
Convert a region of memory to read-protected, by clearing the access flag.
@param BaseAddress The start of the region.
@param Length The size of the region.
@retval EFI_SUCCESS The attributes were set successfully.
@retval EFI_OUT_OF_RESOURCES The operation failed due to insufficient memory.
**/
EFI_STATUS
ArmSetMemoryRegionNoAccess (
IN EFI_PHYSICAL_ADDRESS BaseAddress,
IN UINT64 Length
)
{
return SetMemoryAttributes (
BaseAddress,
Length,
EFI_MEMORY_RP,
TT_DESCRIPTOR_SECTION_AF
);
}
/**
Convert a region of memory to read-enabled, by setting the access flag.
@param BaseAddress The start of the region.
@param Length The size of the region.
@retval EFI_SUCCESS The attributes were set successfully.
@retval EFI_OUT_OF_RESOURCES The operation failed due to insufficient memory.
**/
EFI_STATUS
ArmClearMemoryRegionNoAccess (
IN EFI_PHYSICAL_ADDRESS BaseAddress,
IN UINT64 Length
)
{
return SetMemoryAttributes (
BaseAddress,
Length,
0,
TT_DESCRIPTOR_SECTION_AF
);
}