autdb

Authenticate Data Address (Key B)

AUTDB <Xd>, <Xn>

Authenticates a data address signed with Key B.

Details

Authenticates a 64-bit data address in Xd using Key B and a modifier in Xn. Similar to AUTDA, this instruction cryptographically verifies the pointer authentication code embedded in Xd for data pointers using the alternate (Key B) authentication key. If authentication fails, the result is corrupted. This instruction is AArch64-only and requires ARMv8.3-A or later with PAC extension enabled; it does not affect condition flags.

Pseudocode Operation

Xd ← AuthDB(Xd, Xn)

Example

AUTDB x0, x1

Encoding

Binary Layout
1
1
0
11010110
00001
00
0
111
Rn
Rd
 
Format Data Processing
Opcode 0xDAC11C00
Extension PAC (Security)

Operands

  • Xd
    Destination 64-bit integer register
  • Xn
    Modifier

Reference (Arm A64 ISA)

Instruction Forms

Encoding Instruction ISA Bit pattern
0xDAC11C00 AUTDB <Xd>, <Xn|SP> A64 1 | 1 | 0 | 11010110 | 00001 | 00 | 0 | 111 | Rn | Rd

Description

Authenticate Data address, using key B. This instruction authenticates a data address, using a modifier and key B. The address is in the general-purpose register that is specified by <Xd>. The modifier is: 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.

Operation

if IsFeatureImplemented(FEAT_PAuth) then
    if source_is_sp then
        X[d, 64] = AuthDB(X[d, 64], SP[], FALSE);
    else
        X[d, 64] = AuthDB(X[d, 64], X[n, 64], FALSE);