From e50cbe8eb763cf63fb44b047d5164f6fbf07eb39 Mon Sep 17 00:00:00 2001
From: Alejandro Sior <aho@sior.be>
Date: Fri, 13 May 2022 20:50:39 +0200
Subject: boot: longmode to realmode stub

This is the initial commit to the repo. It adds all the code.
The last proper thing that I got working before committing is
calling real mode functions from long mode using a stub.
Next up, I would like to implement a disk reader abstraction over
the BIOS in order to read form partitions (most notably FAT32).
---
 rt/+x86_64/gdt32.S | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)
 create mode 100644 rt/+x86_64/gdt32.S

(limited to 'rt/+x86_64/gdt32.S')

diff --git a/rt/+x86_64/gdt32.S b/rt/+x86_64/gdt32.S
new file mode 100644
index 0000000..21ab796
--- /dev/null
+++ b/rt/+x86_64/gdt32.S
@@ -0,0 +1,20 @@
+gdt32:
+	.quad 0
+gdt32_code:
+	.short 0xFFFF
+	.short 0x0000
+	.byte 0x00
+	.byte 0b10011010
+	.byte 0b11001111
+	.byte 0x00
+gdt32_data:
+	.short 0xFFFF
+	.short 0x0000
+	.byte 0x00
+	.byte 0b10010010
+	.byte 0b11001111
+	.byte 0x00
+.globl gdtr32
+gdtr32:
+	.short gdtr32 - gdt32 - 1
+	.int gdt32
-- 
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