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# OSLAR_EL1, OS Lock Access Register

The OSLAR_EL1 characteristics are:

## Purpose

Used to lock or unlock the OS lock.

## Configuration

External register OSLAR_EL1 bits [31:0] are architecturally mapped to AArch64 System register OSLAR_EL1[31:0] .

External register OSLAR_EL1 bits [31:0] are architecturally mapped to AArch32 System register DBGOSLAR[31:0] .

OSLAR_EL1 is in the Core power domain.

If ARMv8.2-Debug is not implemented, it is IMPLEMENTATION DEFINED whether external debug accesses to OSLAR_EL1 are ignored and return an error when AllowExternalDebugAccess() returns FALSE for the access.

If ARMv8.2-Debug is implemented, external debug accesses to OSLAR_EL1 are ignored and return an error when AllowExternalDebugAccess() returns FALSE for the access.

## Attributes

OSLAR_EL1 is a 32-bit register.

## Field descriptions

The OSLAR_EL1 bit assignments are:

31 | 30 | 29 | 28 | 27 | 26 | 25 | 24 | 23 | 22 | 21 | 20 | 19 | 18 | 17 | 16 | 15 | 14 | 13 | 12 | 11 | 10 | 9 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0
RES0 | OSLK

#### Bits [31:1]

Reserved, RES0.

#### OSLK, bit [0]

On writes to OSLAR_EL1, bit[0] is copied to the OS lock.

Use EDPRSR.OSLK to check the current status of the lock.

## Accessing the OSLAR_EL1

Note

SoftwareLockStatus() depends on the type of access attempted and AllowExternalDebugAccess() has a new definition from Armv8.4. Refer to the Pseudocode definitions for more information.

#### OSLAR_EL1 can be accessed through the external debug interface:

Component | Offset | Instance
--- | --- | ---
Debug | 0x300 | OSLAR_EL1

This interface is accessible as follows:

- When IsCorePowered(), !DoubleLockStatus(), AllowExternalDebugAccess() and SoftwareLockStatus() access to this register is WI.
- When IsCorePowered(), !DoubleLockStatus(), AllowExternalDebugAccess() and !SoftwareLockStatus() access to this register is WO.
- When IsCorePowered(), !DoubleLockStatus(), !AllowExternalDebugAccess() and ARMv8.2-Debug is not implemented access to this register is IMPDEF.
- Otherwise access to this register returns an Error.

AArch32 Registers | AArch64 Registers | AArch32 Instructions | AArch64 Instructions | Index by Encoding | External Registers | External Registers by Offset | Registers by Functional Group | Proprietary Notice

27/03/2019 21:59; e5e4db499bf9867a4b93324c4dbac985d3da9376

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