From bd98b26786d21ffddb017ffe35ecaa4a9fd0aa4a Mon Sep 17 00:00:00 2001
From: Alejandro Sior <aho@sior.be>
Date: Sat, 18 Jun 2022 10:39:10 +0200
Subject: boot: arbitrary location of stage 1 and identity map more memory

---
 rt/+x86_64/stage0.s | 19 ++++++++++++++++++-
 rt/+x86_64/stage1.S | 24 +++++++++++++++++++-----
 rt/hare.sc          |  3 +++
 3 files changed, 40 insertions(+), 6 deletions(-)

(limited to 'rt')

diff --git a/rt/+x86_64/stage0.s b/rt/+x86_64/stage0.s
index 2961a10..e88c3b8 100644
--- a/rt/+x86_64/stage0.s
+++ b/rt/+x86_64/stage0.s
@@ -56,7 +56,7 @@ a20_ok:
 	# the rest :)
 load_stage1:
 	# :Start to read at the second sector
-	mov $0x1, %di
+	mov entry1_begin, %edi
 	# :Place the result just after us
 	mov $boot_stage1_start, %esi
 load_stage1_loop:
@@ -86,7 +86,24 @@ previous_sector:
 bios_idtr:
 	.quad 0
 
+.org 446
+
+entry1:
+.byte 0x80
+.byte 0x0
+.byte 0x0
+.byte 0x0
+.byte 0x0 # type
+.byte 0x0 # last
+.byte 0x0
+.byte 0x0
+entry1_begin:
+.int 0x0
+.int 512
+
 .org 510
 .word 0xaa55
 
+
+
 .include "rt/+x86_64/stage1.S"
diff --git a/rt/+x86_64/stage1.S b/rt/+x86_64/stage1.S
index 4f99d69..a3f35ab 100644
--- a/rt/+x86_64/stage1.S
+++ b/rt/+x86_64/stage1.S
@@ -74,25 +74,39 @@ pages_fill:
 	or $3, %edi
 	mov %edi, (_p4)
 
+	# Recursive map the page 4
+	mov $_p4, %edi
+	or $3, %edi
+	mov $_p4, %ebx
+	mov %edi, 4088(%ebx)
+
 	mov $_p2, %edi
 	or $3, %edi
 	mov %edi, (_p3)
 
 	mov $_p1, %edi
 	or $3, %edi
-	mov %edi, (_p2)
-
+	mov $_p3, %ebx
+	mov %edi, 8(%ebx)
 	
 	# :Now we are going to fill the first page
-	mov $0x3, %ebx
+	mov $(1 << 7| 0x3), %ebx
+	mov $512, %ecx
+	mov $_p2, %edi
+pages_fill_p2_loop:
+	mov %ebx, (%edi)
+	add $0x200000, %ebx
+	add $8, %edi
+	loop pages_fill_p2_loop
+
 	mov $512, %ecx
 	mov $_p1, %edi
 pages_fill_p1_loop:
 	mov %ebx, (%edi)
-	add $0x1000, %ebx
+	add $0x200000, %ebx
 	add $8, %edi
 	loop pages_fill_p1_loop
-	
+
 	# :Now that the pages are prepared, we must set the %cr3 to point to the level 4
 	# page table. This register contains the address of the level 4 page
 	mov $_p4, %edi
diff --git a/rt/hare.sc b/rt/hare.sc
index ac8c4c5..343f585 100644
--- a/rt/hare.sc
+++ b/rt/hare.sc
@@ -73,4 +73,7 @@ SECTIONS {
 
 
 	boot_end = .;
+
+	. = ALIGN(512);
+	buildup = .;
 }
-- 
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