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/gdt64.S | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)
 create mode 100644 rt/+x86_64/gdt64.S

(limited to 'rt/+x86_64/gdt64.S')

diff --git a/rt/+x86_64/gdt64.S b/rt/+x86_64/gdt64.S
new file mode 100644
index 0000000..c6166bf
--- /dev/null
+++ b/rt/+x86_64/gdt64.S
@@ -0,0 +1,19 @@
+gdt64:
+	.quad 0
+gdt64_code:
+	.short 0xFFFF
+	.short 0x0000
+	.byte 0x0
+	.byte 0b10011010
+	.byte 0b10101111
+	.byte 0x0
+gdt64_data:
+	.short 0xFFFF
+	.short 0x0000
+	.byte 0x0
+	.byte 0b10010010
+	.byte 0b11001111
+	.byte 0x0
+gdtr64:
+	.short gdtr64 - gdt64 - 1
+	.int gdt64
-- 
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