endbr32

End Branch 32-bit

ENDBR32

Marker instruction for Indirect Branch Tracking (IBT).

Details

End Branch 32-bit marker for Control Flow Enforcement Technology (CET) Indirect Branch Tracking. Similar to ENDBR64, this marks valid indirect branch targets in 32-bit or compat mode; enforces CET-IBT policy when enabled. No flags are affected. Requires CET-IBT capability.

Pseudocode Operation

// Marker instruction for Indirect Branch Tracking (IBT)

Example

ENDBR32

Encoding

Binary Layout
F3
+0
0F
+1
1E
+2
FB
+3
 
Format Legacy
Opcode F3 0F 1E FB
Extension CET-IBT

Operands

Reference (Intel® SDM)

Instruction Forms

Opcode Instruction Op/En 64/32-bit Mode CPUID Description
F3 0F 1E FB ENDBR32 ZO V/V CET_IBT Terminate indirect branch in 32-bit and compatibility mode.

Description

Terminate an indirect branch in 32 bit and compatibility mode. This opcode is a NOP when CET indirect branch tracking is not enabled and on processors that do not support CET.

Operation

IF EndbranchEnabled(CPL) & (IA32_EFER.LMA = 0 | (IA32_EFER.LMA=1 & CS.L = 0)
IF CPL = 3
THEN
IA32_U_CET.TRACKER = IDLE
IA32_U_CET.SUPPRESS = 0
ELSE
IA32_S_CET.TRACKER = IDLE
IA32_S_CET.SUPPRESS = 0
FI;
FI;

Flags Affected

None. Exceptions #UD If the LOCK prefix is used. ENDBR32—Terminate an Indirect Branch in 32-bit and Compatibility Mode Vol. 2A 3-287