ARM Architecture Reference Manual ARMv7-A and ARMv7-R edition

when MemArch_PMSA AlignmentFaultP(address, iswrite);
// TranslateAddress()
// ==================
Common Memory System Architecture Features
AddressDescriptor TranslateAddress(bits(32) VA, boolean ispriv, boolean iswrite)
case MemorySystemArchitecture() of
when MemArch_VMSA return TranslateAddressV(VA, ispriv, iswrite);
when MemArch_PMSA return TranslateAddressP(VA, ispriv, iswrite);
B2.4.4 Aligned memory accesses
The MemA[] function performs a memory access at the current privilege level, and the MemA_unpriv[] function
performs an access that is always unprivileged. In both cases the architecture requires the access to be
aligned, and in ARMv7 the function generates an Alignment fault if it is not.
Note
In versions of the architecture before ARMv7, if the SCTLR.A and SCTLR.U bits are both 0, an unaligned
access is forced to be aligned by replacing the low-order address bits with zeros.
// MemA[]
// ======
bits(8*size) MemA[bits(32) address, integer size]
return MemA_with_priv[address, size, CurrentModeIsPrivileged()];
MemA[bits(32) address, integer size] = bits(8*size) value
MemA_with_priv[address, size, CurrentModeIsPrivileged()] = value;
return;
// MemA_unpriv[]
// =============
bits(8*size) MemA_unpriv[bits(32) address, integer size]
return MemA_with_priv[address, size, FALSE];
MemA_unpriv[bits(32) address, integer size] = bits(8*size) value
MemA_with_priv[address, size, FALSE] = value;
return;
// MemA_with_priv[]
// ================
// Non-assignment form
bits(8*size) MemA_with_priv[bits(32) address, integer size, boolean privileged]
// Sort out alignment
if address == Align(address, size) then
VA = address;
elsif SCTLR.A == ‘1’ || SCTLR.U == ‘1’ then
ARM DDI 0406B Copyright © 1996-1998, 2000, 2004-2008 ARM Limited. All rights reserved. B2-31