From d093a8eea6bfb0ff7e621e9ba3307dae698322aa Mon Sep 17 00:00:00 2001
From: dzwdz
Date: Sat, 10 Jul 2021 16:37:45 +0200
Subject: separate the source code from object files; more modular Makefile

---
 src/platform/sysenter.s | 31 +++++++++++++++++++++++++++++++
 1 file changed, 31 insertions(+)
 create mode 100644 src/platform/sysenter.s

(limited to 'src/platform/sysenter.s')

diff --git a/src/platform/sysenter.s b/src/platform/sysenter.s
new file mode 100644
index 0000000..270dc08
--- /dev/null
+++ b/src/platform/sysenter.s
@@ -0,0 +1,31 @@
+/* kernel/gdt.c */
+.set SEG_r0code, 1
+.set SEG_r3code, 3
+.set SEG_r3data, 4
+
+.set IA32_SYSENTER_CS, 0x174
+
+.section .text
+.global sysexit
+.type sysexit, @function
+sysexit:
+	pop %ecx
+	pop %edx
+
+	mov $(SEG_r3data << 3 | 3), %ax
+	mov %ax, %ds
+	mov %ax, %es
+	mov %ax, %fs
+	mov %ax, %gs
+
+	sysexit
+
+
+.global sysenter_setup
+.type sysenter_setup, @function
+sysenter_setup:
+	xor %edx, %edx
+	mov $(SEG_r0code << 3), %eax
+	mov $IA32_SYSENTER_CS, %ecx
+	wrmsr
+	ret
-- 
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