From 946313af5905ac3679c1f496f000ba077ce038f0 Mon Sep 17 00:00:00 2001
From: dzwdz
Date: Fri, 15 Oct 2021 17:25:12 +0200
Subject: kernel: quit QEMU once there are no running processes left

---
 src/kernel/arch/generic.h   |  2 ++
 src/kernel/arch/i386/boot.s | 10 ++++++++++
 2 files changed, 12 insertions(+)

(limited to 'src/kernel/arch')

diff --git a/src/kernel/arch/generic.h b/src/kernel/arch/generic.h
index bbbb49f..fcc228e 100644
--- a/src/kernel/arch/generic.h
+++ b/src/kernel/arch/generic.h
@@ -15,6 +15,8 @@ extern char _bss_end;
 
 __attribute__((noreturn))
 void halt_cpu(void);
+__attribute__((noreturn))
+void cpu_shutdown(void);
 
 // src/arch/i386/sysenter.s
 _Noreturn void sysexit(struct registers);
diff --git a/src/kernel/arch/i386/boot.s b/src/kernel/arch/i386/boot.s
index 0101b40..9fd7d5d 100644
--- a/src/kernel/arch/i386/boot.s
+++ b/src/kernel/arch/i386/boot.s
@@ -7,6 +7,16 @@ _start:
 	push %ebx // address of the Multiboot struct
 	call kmain_early
 
+.global cpu_shutdown
+.type cpu_shutdown, @function
+cpu_shutdown:
+/* This quits QEMU. While I couldn't find this officially documented anywhere,
+ * it is used by QEMU in tests/tcg/i386/system/boot.S (as of commit 40d6ee), so
+ * I assume that this is safe-ish to use */
+	mov $0x604, %edx
+	mov $0x2000, %eax
+	outw %ax, %dx
+
 .global halt_cpu
 .type halt_cpu, @function
 halt_cpu:
-- 
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