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

Protected Memory System Architecture (PMSA)
base_address = DRBAR[r];
access_control = DRACR[r];
if size_enable == ‘1’ then // Region is enabled
lsbit = UInt(size_enable) + 1;
if lsbit < 2 then UNPREDICTABLE;
if lsbit == 32 || va == base_address then
if lsbit >= 8 then // can have subregions
subregion = UInt(va);
hit = (size_enable == ‘0’);
else
hit = TRUE;
if hit then
texcb = access_control;
S = access_control;
perms.ap = access_control;
perms.xn = access_control;
region_found = TRUE;
// Generate the memory attributes, and also the permissions if no region found.
if region_found then
result.memattrs = DefaultTEXDecode(texcb, S);
else
if SCTLR.BR == ‘0’ || NOT(ispriv) then
DataAbort(address, bits(4) UNKNOWN, boolean UNKNOWN, iswrite, DAbort_Background);
else
result.memattrs = DefaultMemoryAttributes(va);
perms.ap = ‘011’;
perms.xn = if va == ‘1111’ then NOT(SCTLR.V) else va;
// Check the permissions.
CheckPermission(perms, VA, boolean UNKNOWN, bits(4) UNKNOWN, iswrite, ispriv);
return result;
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