Branch to Register, with pointer authentication. This instruction authenticates the address in the general-purpose register that is specified by <Xn>, using a modifier and the specified key, and branches to the authenticated address.
The modifier is:
Key A is used for BRAA and BRAAZ, and key B is used for BRAB and BRABZ.
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 the general-purpose register.
| 31 | 30 | 29 | 28 | 27 | 26 | 25 | 24 | 23 | 22 | 21 | 20 | 19 | 18 | 17 | 16 | 15 | 14 | 13 | 12 | 11 | 10 | 9 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 |
| 1 | 1 | 0 | 1 | 0 | 1 | 1 | Z | 0 | 0 | 0 | 1 | 1 | 1 | 1 | 1 | 0 | 0 | 0 | 0 | 1 | M | Rn | Rm | ||||||||
| op | A | ||||||||||||||||||||||||||||||
integer n = UInt(Rn); BranchType branch_type; integer m = UInt(Rm); boolean pac = (A == '1'); boolean use_key_a = (M == '0'); boolean source_is_sp = ((Z == '1') && (m == 31)); if !pac && m != 0 then UNDEFINED; elsif pac && !HavePACExt() then UNDEFINED; case op of when '00' branch_type = BranchType_INDIR; when '01' branch_type = BranchType_INDCALL; when '10' branch_type = BranchType_RET; otherwise UNDEFINED; if pac then if Z == '0' && m != 31 then UNDEFINED; if branch_type == BranchType_RET then if n != 31 then UNDEFINED; n = 30; source_is_sp = TRUE;
| <Xn> |
Is the 64-bit name of the general-purpose register holding the address to be branched to, encoded in the "Rn" field. |
| <Xm|SP> |
Is the 64-bit name of the general-purpose source register or stack pointer holding the modifier, encoded in the "Rm" field. |
bits(64) target = X[n]; boolean auth_then_branch = TRUE; if pac then bits(64) modifier = if source_is_sp then SP[] else X[m]; if use_key_a then target = AuthIA(target, modifier, auth_then_branch); else target = AuthIB(target, modifier, auth_then_branch); if branch_type == BranchType_INDCALL then X[30] = PC[] + 4; // Value in BTypeNext will be used to set PSTATE.BTYPE case branch_type of when BranchType_INDIR // BR, BRAA, BRAB, BRAAZ, BRABZ if InGuardedPage then if n == 16 || n == 17 then BTypeNext = '01'; else BTypeNext = '11'; else BTypeNext = '01'; when BranchType_INDCALL // BLR, BLRAA, BLRAB, BLRAAZ, BLRABZ BTypeNext = '10'; when BranchType_RET // RET, RETAA, RETAB BTypeNext = '00'; boolean branch_conditional = FALSE; BranchTo(target, branch_type, branch_conditional);
Internal version only: isa v33.11seprel, AdvSIMD v29.05, pseudocode v2021-09_rel, sve v2021-09_rc3d ; Build timestamp: 2021-10-06T11:41
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