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DBGOSLAR
AArch32 Registers
AArch64 Registers
AArch32 Instructions
AArch64 Instructions
Index by Encoding
External Registers
External Registers by Offset
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Proprietary Notice

DBGOSLAR, Debug OS Lock Access Register

The DBGOSLAR characteristics are:

Purpose

Provides a lock for the debug registers. The OS Lock also disables some debug exceptions and debug events.

Configuration

This register is present only when FEAT_AA32EL1 is implemented. Otherwise, direct accesses to DBGOSLAR are UNDEFINED.

The OS Lock can also be locked or unlocked using the AArch64 System register OSLAR_EL1 and External register OSLAR_EL1.

Attributes

DBGOSLAR is a 32-bit register.

Field descriptions

313029282726252423222120191817161514131211109876543210
OSLA

OSLA, bits [31:0]

OS Lock Access. Writing the value 0xC5ACCE55 to the DBGOSLAR sets the OS Lock to 1. Writing any other value sets the OS Lock to 0.

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

Accessing DBGOSLAR

Accesses to this register use the following encodings in the System register encoding space:

MCR{<c>}{<q>} <coproc>, {#}<opc1>, <Rt>, <CRn>, <CRm>{, {#}<opc2>}

coprocopc1CRnCRmopc2
0b11100b0000b00010b00000b100

if !IsFeatureImplemented(FEAT_AA32EL1) then Undefined(); elsif PSTATE.EL == EL0 then Undefined(); elsif PSTATE.EL == EL1 then if HaveEL(EL3) && EL3SDDUndefPriority() && IsFeatureImplemented(FEAT_AA64EL3) && !ELUsingAArch32(EL3) && MDCR_EL3().TDOSA == '1' then Undefined(); elsif EL2Enabled() && IsFeatureImplemented(FEAT_AA64EL2) && !ELUsingAArch32(EL2) && MDCR_EL2().[TDE,TDOSA] != '00' then AArch64_AArch32SystemAccessTrap(EL2, 0x05); elsif EL2Enabled() && IsFeatureImplemented(FEAT_AA32EL2) && ELUsingAArch32(EL2) && HDCR().[TDE,TDOSA] != '00' then AArch32_TakeHypTrapException(0x05); elsif HaveEL(EL3) && IsFeatureImplemented(FEAT_AA64EL3) && !ELUsingAArch32(EL3) && MDCR_EL3().TDOSA == '1' then if EL3SDDUndef() then Undefined(); else AArch64_AArch32SystemAccessTrap(EL3, 0x05); end; else DBGOSLAR() = R(t); end; elsif PSTATE.EL == EL2 then if HaveEL(EL3) && EL3SDDUndefPriority() && IsFeatureImplemented(FEAT_AA64EL3) && !ELUsingAArch32(EL3) && MDCR_EL3().TDOSA == '1' then Undefined(); elsif HaveEL(EL3) && IsFeatureImplemented(FEAT_AA64EL3) && !ELUsingAArch32(EL3) && MDCR_EL3().TDOSA == '1' then if EL3SDDUndef() then Undefined(); else AArch64_AArch32SystemAccessTrap(EL3, 0x05); end; else DBGOSLAR() = R(t); end; elsif PSTATE.EL == EL3 then DBGOSLAR() = R(t); end;

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

2026-03-26 20:27:25, 2026-03_rel

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