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System Control Coprocessor

ID012310 Non-Confidential, Unrestricted Access

Attempts to write to this register in Secure Privileged mode when CP15SDISABLE is HIGH

result in an Undefined exception, see TrustZone write access disable on page 2-9.

Table 3-153 lists the results of attempted access for each mode.

To read or write a TLB Lockdown entry, you must use this procedure:

1. Write TLB Lockdown Index Register to select the required TLB Lockdown entry.

2. Read or write TLB Lockdown VA Register.

3. Read or write TLB Lockdown Attributes Register.

4. Read or write TLB Lockdown PA Register. For writes, this sets the valid bit, enabling the

complete new entry to be used.

This procedure must not be interruptible, so your code must disable interrupts before it accesses

the TLB lockdown access registers.

Note

Software must avoid the creation of inconsistencies between the main TLB entries and the

entries already loaded in the micro-TLBs.

[25] SPV Indicates that this page table entry supports sub-pages. Page table entries that support

sub-pages must be marked as Global, see c15, TLB lockdown access registers on page 3-149:

0 = Sub-pages are not valid

1 = Sub-pages are valid.

[24:11] SBZ UNP/SBZ.

[10:7] Domain Specifies the Domain number for the page table entry.

[6] XN Specifies Execute Never attribute: when set, the contents of the memory region that this page

table entry describes cannot be executed as code. An attempt to execute an instruction in this

region results in a permission fault:

0 = Can execute

1 = Cannot execute.

[5:3] TEX TEX[2:0] bits. Describes the memory region attributes. See Memory region attributes on

page 6-14.

[2] C C bit. Describes the memory region attributes. See Memory region attributes on page 6-14.

[1] B B bit. Describes the memory region attributes. See Memory region attributes on page 6-14.

[0] S Indicates if the memory region that this page table entry describes is shareable:

0 = Region is not shared

1 = Region is shared.

Table 3-152 TLB Lockdown Attributes Register bit functions (continued)

Bits Field name Function

Table 3-153 Results of access to the TLB lockdown access registers

Secure Privileged Non-secure Privileged

User

Read Write Read Write

Data Data Undefined exception Undefined exception Undefined exception

ARM ARM1176JZF-S User Manual

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