From 1bf5e324005ce7122a195af106cec656960648dc Mon Sep 17 00:00:00 2001
From: dzwdz
Date: Sat, 10 Jul 2021 17:41:32 +0200
Subject: a sensible source structure

The idea is that src/kernel/ is only allowed to interface with the
hardware using whatever's defined in src/arch/generic.h. I'll probably
write a small script for checking this later on.

This is a giant commit so I've probably fucked something up. It boots
fine on Bochs and QEMU, so at least there's that.
---
 src/arch/i386/sysenter.s | 31 +++++++++++++++++++++++++++++++
 1 file changed, 31 insertions(+)
 create mode 100644 src/arch/i386/sysenter.s

(limited to 'src/arch/i386/sysenter.s')

diff --git a/src/arch/i386/sysenter.s b/src/arch/i386/sysenter.s
new file mode 100644
index 0000000..666c0f0
--- /dev/null
+++ b/src/arch/i386/sysenter.s
@@ -0,0 +1,31 @@
+/* arch/i386/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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