From 746c5aaf4b2d325d7f0bfb457ec0b3e1789d175c Mon Sep 17 00:00:00 2001
From: Aiden Gall <aiden@aidengall.xyz>
Date: Tue, 14 Oct 2025 20:06:30 +0100
Subject: add support for indirect branch tracking

---
 config.inc |  3 +++
 tco.asm    | 19 ++++++++++++-------
 2 files changed, 15 insertions(+), 7 deletions(-)

diff --git a/config.inc b/config.inc
index ae7ee48..b499536 100644
--- a/config.inc
+++ b/config.inc
@@ -7,3 +7,6 @@ STACK_CAPACITY = 64*4096
 ; - aligned_alloc (C11)
 ; - mmap (linux)
 MALLOC equ aligned_alloc
+
+; enable indirect branch tracking support
+IBT_ENABLE = 1
diff --git a/tco.asm b/tco.asm
index a26de62..4b3f268 100644
--- a/tco.asm
+++ b/tco.asm
@@ -15,15 +15,20 @@
 
 format ELF64
 
-public tco_go
-public tco_args
-public tco_yield
-
 ; assembly-time configuration options
 include 'config.inc'
 assert (STACK_CAPACITY mod 16) = 0
 assert MALLOC in <posix_memalign,aligned_alloc,mmap>
 
+macro fn lbl {
+	label lbl
+	public lbl
+
+	if IBT_ENABLE
+		endbr64
+	end if
+}
+
 ; circular singly-linked list containing callee-saved registers and instruction
 ; pointer to resume execution of coroutine when yielded to
 struc ctx_node next {
@@ -60,7 +65,7 @@ end if
 section '.text' executable
 ; int tco_go(void (*f)(...))
 ; spawns a coroutine
-tco_go:
+fn tco_go
 	call stash
 
 	; pushing rdi also aligns stack to 16 byte boundary for function call
@@ -154,7 +159,7 @@ end if
 
 ; void tco_args(...)
 ; sets the arguments of the next coroutine
-tco_args:
+fn tco_args
 	irps reg, rax rdi rsi rdx r10 r8 r9 {
 		mov [coroutine_args.#reg], reg
 	}
@@ -170,7 +175,7 @@ tco_args:
 
 ; void tco_yield(void)
 ; yield to next coroutine
-tco_yield:
+fn tco_yield
 	call stash
 	xor eax, eax
 	jmp switch
-- 
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