From c4a165640f8cbf4844426c8cea87246db3953467 Mon Sep 17 00:00:00 2001
From: Joshua Wise <joshua@rebirth.joshuawise.com>
Date: Wed, 10 Sep 2008 18:23:05 -0400
Subject: [PATCH] Also add realmode warm booter

---
 grubload/Makefile      |  8 +++++++-
 grubload/multiboot_c.c | 11 +++++++++--
 2 files changed, 16 insertions(+), 3 deletions(-)

diff --git a/grubload/Makefile b/grubload/Makefile
index 971fb5c..c850bb3 100644
--- a/grubload/Makefile
+++ b/grubload/Makefile
@@ -1,4 +1,4 @@
-OBJS=multiboot_c.o multiboot_asm.o console.o minilib.o
+OBJS=multiboot_c.o multiboot_asm.o console.o minilib.o realmode.o
 CC=gcc
 CFLAGS=-nostdlib -I../include -I. -fno-builtin -nostdinc
 
@@ -6,3 +6,9 @@ all: multiboot
 
 multiboot: $(OBJS)
 	ld -o multiboot $(OBJS) -Ttext=0x100000
+
+realmode.bin: realmode.asm
+	nasm -o realmode.bin realmode.asm
+
+realmode.o: realmode.bin
+	objcopy -I binary -B i386 -O elf32-i386 realmode.bin realmode.o
diff --git a/grubload/multiboot_c.c b/grubload/multiboot_c.c
index c87b675..25522e2 100644
--- a/grubload/multiboot_c.c
+++ b/grubload/multiboot_c.c
@@ -1,5 +1,8 @@
 #include "console.h"
 
+extern char _binary_realmode_bin_start[];
+extern int _binary_realmode_bin_size;
+
 struct mb_info
 {
 	unsigned long flags;
@@ -23,6 +26,8 @@ void c_start(unsigned int magic, struct mb_info *wee)
 	unsigned short *grubptr = 0x7CFE;
 	int i;
 	
+	void (*realmode)() = 0x4000;
+	
 	puts("Magic is: ");
 	puthex(magic);
 	puts("\nMultiboot header is: ");
@@ -41,6 +46,8 @@ void c_start(unsigned int magic, struct mb_info *wee)
 		puts("  Size: "); puthex(wee->mods[i].mod_end - wee->mods[i].mod_start); puts("\n");
 		puts("  Name: "); puts(wee->mods[i].mod_string); puts("\n");
 	}
-	while (1)
-		;
+
+	puts("Now returning to real mode.\n");	
+	memcpy(0x4000, _binary_realmode_bin_start, (int)&_binary_realmode_bin_size);
+	realmode();
 }
-- 
2.43.0