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ERETAA, ERETAB

Exception Return, with pointer authentication. This instruction authenticates the address in ELR, using SP as the modifier and the specified key, the PE restores PSTATE from the SPSR for the current Exception level, and branches to the authenticated address.

Key A is used for ERETAA, and key B is used for ERETAB.

If the authentication passes, the PE continues execution at the target of the branch. If the authentication fails, a Translation fault is generated.

The authenticated address is not written back to ELR.

The PE checks the SPSR for the current Exception level for an illegal return event. See Illegal return events from AArch64 state.

ERETAA and ERETAB are undefined at EL0.

Integer
(Armv8.3)

313029282726252423222120191817161514131211109876543210
110101101001111100001M1111111111
ARnop4

ERETAA (M == 0)

ERETAA

ERETAB (M == 1)

ERETAB

if PSTATE.EL == EL0 then UNDEFINED;
boolean use_key_a = (M == '0');

if !HavePACExt() then
    UNDEFINED;

Operation

AArch64.CheckForERetTrap(TRUE, use_key_a);
bits(64) target;

if use_key_a then
    target = AuthIA(ELR[], SP[], TRUE);
else
    target = AuthIB(ELR[], SP[], TRUE);

AArch64.ExceptionReturn(target, SPSR[]);
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