From 36089d20ca1f7c57f36c4172759a5084bdf87a3a Mon Sep 17 00:00:00 2001
From: dzwdz
Date: Wed, 21 Jul 2021 21:31:52 +0200
Subject: barebones syscall

---
 src/kernel/arch/i386/sysenter.s | 28 ++++++++++++++++++++++++++++
 1 file changed, 28 insertions(+)

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

diff --git a/src/kernel/arch/i386/sysenter.s b/src/kernel/arch/i386/sysenter.s
index 0cfeb10..3fcd4c3 100644
--- a/src/kernel/arch/i386/sysenter.s
+++ b/src/kernel/arch/i386/sysenter.s
@@ -4,6 +4,8 @@
 .set SEG_r3data, 4
 
 .set IA32_SYSENTER_CS, 0x174
+.set IA32_SYSENTER_ESP, 0x175
+.set IA32_SYSENTER_EIP, 0x176
 
 .section .text
 .global sysexit
@@ -30,7 +32,33 @@ sysexit:
 .type sysenter_setup, @function
 sysenter_setup:
 	xor %edx, %edx
+
 	mov $(SEG_r0code << 3), %eax
 	mov $IA32_SYSENTER_CS, %ecx
 	wrmsr
+
+	mov $IA32_SYSENTER_ESP, %ecx
+	mov $_bss_end, %eax
+	wrmsr
+
+	mov $IA32_SYSENTER_EIP, %ecx
+	mov $sysenter_handler, %eax
+	wrmsr
+
 	ret
+
+sysenter_handler:
+	pushal
+
+	mov %cr0, %eax
+	and $0x7FFFFFFF, %eax  // disable paging
+	mov %eax, %cr0
+
+	call syscall_handler
+
+	mov %cr0, %eax
+	or  $0x80000000, %eax  // enable paging
+	mov %eax, %cr0
+
+	popal
+	sysexit
-- 
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