autib

Authenticate Code (Inst B)

AUTIB <Xd>, <Xn|SP>

Authenticates a pointer signed with Key B.

Pseudocode Operation

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

Example

AUTIB x0, x1

Encoding

Binary Layout

1

31

1

30

0

29

11010110

28:21

00001

20:16

00

15:14

0

13

101

12:10

Rn

9:5

Rd

4:0

 

Format Data Processing

Opcode 0xDAC11400

Extension PAC (Security)

Operands

• Xd
  Ptr
• Xn
  Modifier

Related

Other forms of autib

• autib Authenticate Instruction Address (Key B)

More in PAC (Security)

Reference

View in Arm A64 ISA Reference ↗ Arm A64 ISA

Instruction Forms

Encoding	Instruction		ISA		Bit pattern
0xDAC11400	AUTIB <Xd>, <Xn|SP>		A64		1 | 1 | 0 | 11010110 | 00001 | 00 | 0 | 101 | Rn | Rd

Description

Authenticate Instruction address, using key B. This instruction authenticates an instruction address, using a modifier and key B. 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 AUTIB1716 and AUTIBSP 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] = AuthIB2(X[d, 64], SP[], X[16, 64], FALSE);
        else
            X[d, 64] = AuthIB(X[d, 64], SP[], FALSE);
    else
        if IsFeatureImplemented(FEAT_PAuth_LR) && PSTATE.PACM == '1' && autib1716 then
            X[d, 64] = AuthIB2(X[d, 64], X[n, 64], X[15, 64], FALSE);
        else
            X[d, 64] = AuthIB(X[d, 64], X[n, 64], FALSE);