autia

Authenticate Code (Inst A)

AUTIA <Xd>, <Xn|SP>

Authenticates a pointer signed with Key A. Corrupts pointer if failed.

Pseudocode Operation

authenticated_pointer ← AuthenticatePointer(Xd, Xn, KeyA)
if authentication_fails then
  Xd ← corrupted_value
else
  Xd ← authenticated_pointer
end if

Example

AUTIA x0, x1

Encoding

Binary Layout

1

31

1

30

0

29

11010110

28:21

00001

20:16

00

15:14

0

13

100

12:10

Rn

9:5

Rd

4:0

 

Format Data Processing

Opcode 0xDAC11000

Extension PAC (Security)

Operands

• Xd
  Ptr
• Xn
  Modifier

Related

Other forms of autia

• autia Authenticate Instruction Address (Key A)

More in PAC (Security)

Reference

View in Arm A64 ISA Reference ↗ Arm A64 ISA

Instruction Forms

Encoding	Instruction		ISA		Bit pattern
0xDAC11000	AUTIA <Xd>, <Xn|SP>		A64		1 | 1 | 0 | 11010110 | 00001 | 00 | 0 | 100 | Rn | Rd

Description

Authenticate Instruction address, using key A. This instruction authenticates an instruction address, using a modifier and key A. If the authentication passes, the upper bits of the address are restored to enable subsequent use of the address. For information on behavior if the authentication fails, see Faulting on pointer authentication. The address is: The modifier is: If FEAT_PAuth_LR is implemented and PSTATE.PACM is 1, then AUTIA1716 and AUTIASP include a second modifier that is:

Operation

if IsFeatureImplemented(FEAT_PAuth) then
    if source_is_sp then
        if IsFeatureImplemented(FEAT_PAuth_LR) && PSTATE.PACM == '1' then
            X[d, 64] = AuthIA2(X[d, 64], SP[], X[16, 64], FALSE);
        else
            X[d, 64] = AuthIA(X[d, 64], SP[], FALSE);
    else
        if IsFeatureImplemented(FEAT_PAuth_LR) && PSTATE.PACM == '1' && autia1716 then
            X[d, 64] = AuthIA2(X[d, 64], X[n, 64], X[15, 64], FALSE);
        else
            X[d, 64] = AuthIA(X[d, 64], X[n, 64], FALSE);