From 62bc238ac3b2482033358deac0c728d351c16f57 Mon Sep 17 00:00:00 2001
From: Nico Weber <thakis@chromium.org>
Date: Mon, 6 Sep 2021 13:11:16 -0400
Subject: Kernel: Let aarch64 port call into C++

Put all but the first core into a loop, make room for some stack,
and call init().
---
 Kernel/Prekernel/Arch/aarch64/boot.S   | 13 ++++++++++++-
 Kernel/Prekernel/Arch/aarch64/init.cpp | 11 +++++++++++
 Kernel/Prekernel/CMakeLists.txt        |  1 +
 3 files changed, 24 insertions(+), 1 deletion(-)
 create mode 100644 Kernel/Prekernel/Arch/aarch64/init.cpp

diff --git a/Kernel/Prekernel/Arch/aarch64/boot.S b/Kernel/Prekernel/Arch/aarch64/boot.S
index 25c0fcb7ea..acb60dc455 100644
--- a/Kernel/Prekernel/Arch/aarch64/boot.S
+++ b/Kernel/Prekernel/Arch/aarch64/boot.S
@@ -9,7 +9,18 @@
 .global start
 .type start, @function
 start:
-  b Lhalt
+  // Let only core 0 continue, put other cores to sleep.
+  mrs x13, MPIDR_EL1
+  and x13, x13, 0xff
+  cbnz x13, Lhalt
+
+  // Let stack start before .text for now.
+  // 512 kiB (0x8000) of stack are probably not sufficient, especially once we give the other cores some stack too,
+  // but for now it's ok.
+  ldr x14, =start
+  mov sp, x14
+
+  b init
 
 Lhalt:
   wfi
diff --git a/Kernel/Prekernel/Arch/aarch64/init.cpp b/Kernel/Prekernel/Arch/aarch64/init.cpp
new file mode 100644
index 0000000000..86af24a419
--- /dev/null
+++ b/Kernel/Prekernel/Arch/aarch64/init.cpp
@@ -0,0 +1,11 @@
+/*
+ * Copyright (c) 2021, Nico Weber <thakis@chromium.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+extern "C" [[noreturn]] void init();
+extern "C" [[noreturn]] void init()
+{
+    for (;;) { }
+}
diff --git a/Kernel/Prekernel/CMakeLists.txt b/Kernel/Prekernel/CMakeLists.txt
index 9c71f6bd70..d3bd1a7538 100644
--- a/Kernel/Prekernel/CMakeLists.txt
+++ b/Kernel/Prekernel/CMakeLists.txt
@@ -3,6 +3,7 @@ set(SOURCES
 if ("${SERENITY_ARCH}" STREQUAL "aarch64")
     set(SOURCES
         ${SOURCES}
+        Arch/aarch64/init.cpp
         Arch/aarch64/boot.S
     )
 else()
-- 
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