The UEFI spec stipulates that unaligned accesses should be enabled on CPUs that support them, which means all of them, given that we no longer support pre-v7 ARM cores, and the AARCH64 bindings mandate support for unaligned accesses unconditionally.
This means that one should not assume that CopyMem () is safe to call on regions that may be mapped using device attributes, which is the case for the NOR flash. Since we have no control over the mappings when running under the OS, and given that write accesses require device mappings, we should not call CopyMem () in the read path either, but use our own implementation that is guaranteed to take alignment into account. Contributed-under: TianoCore Contribution Agreement 1.0 Signed-off-by: Ard Biesheuvel <[email protected]> --- v2: - simplify the AlignedCopyMem () implementation, given that we do not require memmove() semantics for copying between NOR flash and memory - document the above - add macro to perform alignment check - drop redundant/unnecessary casts and parentheses ArmPlatformPkg/Drivers/NorFlashDxe/NorFlashDxe.c | 63 +++++++++++++++++++- 1 file changed, 61 insertions(+), 2 deletions(-) diff --git a/ArmPlatformPkg/Drivers/NorFlashDxe/NorFlashDxe.c b/ArmPlatformPkg/Drivers/NorFlashDxe/NorFlashDxe.c index 3abbe5cb32bc..ca61ac5e1983 100644 --- a/ArmPlatformPkg/Drivers/NorFlashDxe/NorFlashDxe.c +++ b/ArmPlatformPkg/Drivers/NorFlashDxe/NorFlashDxe.c @@ -744,6 +744,65 @@ NorFlashWriteBlocks ( return Status; } +#define BOTH_ALIGNED(a, b, align) ((((UINTN)(a) | (UINTN)(b)) & ((align) - 1)) == 0) + +/** + Copy Length bytes from Source to Destination, using aligned accesses only. + Note that this implementation uses memcpy() semantics rather then memmove() + semantics, i.e., SourceBuffer and DestinationBuffer should not overlap. + + @param DestinationBuffer The target of the copy request. + @param SourceBuffer The place to copy from. + @param Length The number of bytes to copy. + + @return Destination + +**/ +STATIC +VOID * +AlignedCopyMem ( + OUT VOID *DestinationBuffer, + IN CONST VOID *SourceBuffer, + IN UINTN Length + ) +{ + UINT8 *Destination8; + CONST UINT8 *Source8; + UINT32 *Destination32; + CONST UINT32 *Source32; + UINT64 *Destination64; + CONST UINT64 *Source64; + + if (BOTH_ALIGNED(DestinationBuffer, SourceBuffer, 8) && Length >= 8) { + Destination64 = DestinationBuffer; + Source64 = SourceBuffer; + while (Length >= 8) { + *Destination64++ = *Source64++; + Length -= 8; + } + + Destination8 = (UINT8 *)Destination64; + Source8 = (CONST UINT8 *)Source64; + } else if (BOTH_ALIGNED(DestinationBuffer, SourceBuffer, 4) && Length >= 4) { + Destination32 = DestinationBuffer; + Source32 = SourceBuffer; + while (Length >= 4) { + *Destination32++ = *Source32++; + Length -= 4; + } + + Destination8 = (UINT8 *)Destination32; + Source8 = (CONST UINT8 *)Source32; + } else { + Destination8 = DestinationBuffer; + Source8 = SourceBuffer; + } + while (Length-- != 0) { + *Destination8++ = *Source8++; + } + return DestinationBuffer; +} + EFI_STATUS NorFlashReadBlocks ( IN NOR_FLASH_INSTANCE *Instance, @@ -791,7 +850,7 @@ NorFlashReadBlocks ( SEND_NOR_COMMAND (Instance->DeviceBaseAddress, 0, P30_CMD_READ_ARRAY); // Readout the data - CopyMem(Buffer, (UINTN *)StartAddress, BufferSizeInBytes); + AlignedCopyMem (Buffer, (VOID *)StartAddress, BufferSizeInBytes); return EFI_SUCCESS; } @@ -832,7 +891,7 @@ NorFlashRead ( SEND_NOR_COMMAND (Instance->DeviceBaseAddress, 0, P30_CMD_READ_ARRAY); // Readout the data - CopyMem (Buffer, (UINTN *)(StartAddress + Offset), BufferSizeInBytes); + AlignedCopyMem (Buffer, (VOID *)StartAddress + Offset, BufferSizeInBytes); return EFI_SUCCESS; } -- 2.7.4 _______________________________________________ edk2-devel mailing list [email protected] https://lists.01.org/mailman/listinfo/edk2-devel
