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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:

313029282726252423222120191817161514131211109876543210
RES0OSLK

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:

ComponentOffsetInstance
Debug0x300OSLAR_EL1

This interface is accessible as follows:

  • When IsCorePowered(), !DoubleLockStatus(), AllowExternalDebugAccess() and SoftwareLockStatus() accesses to this register are WI.
  • When IsCorePowered(), !DoubleLockStatus(), AllowExternalDebugAccess() and !SoftwareLockStatus() accesses to this register are WO.
  • When IsCorePowered(), !DoubleLockStatus(), !AllowExternalDebugAccess() and ARMv8.2-Debug is not implemented accesses to this register are IMPDEF.
  • Otherwise accesses to this register generate an error response.


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