From 7dfa64eb263a2dc3453a6667ca2f843202e11b31 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Alex=20R=C3=B8nne=20Petersen?= <alex@alexrp.com>
Date: Fri, 29 May 2026 08:20:36 +0200
Subject: [PATCH] std.os.linux.xtensa: add call0 support

---
 lib/std/os/linux/xtensa.zig | 26 ++++++++++++++++++++++++--
 1 file changed, 24 insertions(+), 2 deletions(-)

diff --git a/lib/std/os/linux/xtensa.zig b/lib/std/os/linux/xtensa.zig
index a54c8f13d2040cff3d31a3426f812258df1faece..95b81eb4d1ba7882dacc3b29f082eb3331695a81 100644
--- a/lib/std/os/linux/xtensa.zig
+++ b/lib/std/os/linux/xtensa.zig
@@ -115,9 +115,10 @@ pub fn clone() callconv(.naked) u32 {
     //
     // syscall(SYS_clone, flags, stack, ptid, tls, ctid)
     //         a2         a6,    a3,    a4,   a5,  a8
-    asm volatile (
+    if (builtin.abi != .call0) asm volatile (
         \\ entry sp, 16
-        \\
+    );
+    asm volatile (
         \\ movi a8, -16
         \\ and a3, a3, a8
         \\
@@ -128,10 +129,29 @@ pub fn clone() callconv(.naked) u32 {
         \\ mov a8, a6
         \\ mov a6, a4
         \\ mov a4, a8
+    );
+    if (builtin.abi == .call0) asm volatile (
+        \\ l32i a8, sp, 0
+    ) else asm volatile (
         \\ l32i a8, sp, 16
+    );
+    asm volatile (
         \\ movi a2, 116 // SYS_clone
         \\ syscall
+    );
+    if (builtin.abi == .call0) asm volatile (
+        \\ beqz a2, 1f
+        \\ // parent
+        \\ ret
         \\
+        \\ // child
+        \\1:
+        \\ movi a15, 0
+        \\ movi a0, 0
+        \\
+        \\ mov a2, a10
+        \\ callx0 a9
+    ) else asm volatile (
         \\ beqz a2, 1f
         \\ // parent
         \\ retw
@@ -143,6 +163,8 @@ pub fn clone() callconv(.naked) u32 {
         \\
         \\ mov a6, a10
         \\ callx4 a9
+    );
+    asm volatile (
         \\ movi a2, 118 // SYS_exit
         \\ syscall
     );
-- 
2.54.0