From: Joshua Wise <joshua@rebirth.joshuawise.com>
Date: Wed, 10 Sep 2008 22:24:10 +0000 (-0400)
Subject: Merge ELF loader.
X-Git-Url: http://git.joshuawise.com/netwatch.git/commitdiff_plain/86c89e89a88d25e85956b258005b52e0f2686b89?hp=d56898ee77b960cfe7f1d75bca2725d9d5337553

Merge ELF loader.
---

diff --git a/grubload/Makefile b/grubload/Makefile
index 041f09c..f0f9742 100644
--- a/grubload/Makefile
+++ b/grubload/Makefile
@@ -1,4 +1,4 @@
-OBJS=multiboot_c.o multiboot_asm.o console.o minilib.o loader.o
+OBJS=multiboot_c.o multiboot_asm.o console.o minilib.o realmode.o loader.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 f871687..03e2143 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: ");
@@ -51,7 +56,7 @@ void c_start(unsigned int magic, struct mb_info *wee)
 
 	load_elf(wee->mods[0].mod_start, wee->mods[0].mod_end - wee->mods[0].mod_start);
 
-
-	while (1)
-		;
+	puts("Now returning to real mode.\n");	
+	memcpy(0x4000, _binary_realmode_bin_start, (int)&_binary_realmode_bin_size);
+	realmode();	// goodbye!
 }
diff --git a/grubload/realmode.asm b/grubload/realmode.asm
new file mode 100644
index 0000000..b504b00
--- /dev/null
+++ b/grubload/realmode.asm
@@ -0,0 +1,106 @@
+	[bits 32]	; Starts in 32 bit mode, then will drop back later.
+	org 0x4000
+entry:
+	cli
+	; clean up 32 bit regs
+	mov eax, 0x0
+	mov ebx, 0x0
+	mov ecx, 0x0
+	mov edx, 0x0
+	mov esi, 0x0
+	mov edi, 0x0
+	mov ebp, 0x0
+	mov esp, 0x0
+	
+	lgdt [gdtp]
+	
+	mov ax, 0x10
+	mov ds, ax
+	mov es, ax
+	mov fs, ax
+	mov gs, ax
+	mov ss, ax
+	
+	jmp 0x8:nextp	; Clear CS bits now too
+
+nextp:
+	
+	mov eax, cr0
+	xor eax, 0x1	; Clear PE
+	mov cr0, eax
+	
+	jmp 0x0:nowreal	; and jmp away
+
+
+	[bits 16]
+nowreal:
+	mov long eax, 0x0000
+	mov ds, ax
+	mov es, ax
+	mov fs, ax
+	mov gs, ax
+	mov ss, ax
+	
+	mov sp, 0xFFFF	; set up the stack
+
+	mov al, 0xAB
+	out 0x80, al
+
+	cli
+	lidt [idtp]
+
+	mov si, RETMSG
+	call disp
+
+	int 0x19		; warm boot without clearing RAM.
+	call handload_drive	; hopefully shouldn't happen
+	; ok, we give up
+	cli
+halt:	hlt
+	jmp halt
+
+disp:
+	lodsb
+	or al, al
+	jz .done
+	mov ah, 0x0E
+	mov bx, 0x0007
+	int 0x10
+	jmp disp
+.done:
+	ret
+
+; handload_drive should be unnecessary; int 19 should take care of it for
+; us...
+handload_drive:
+	mov ax, 0x07C0
+	mov es, ax
+	mov ax, 0x0201	; read one sector
+	mov bx, 0x0000	; to the normal location
+	mov cx, 0x0001	; disk sector 1
+	mov dx, 0x0080	; drive 0
+	int 0x13
+	jc readerr
+	
+	mov si, READSUCC
+	call disp
+	
+	jmp 0x7C0:0x0	; and return control to grub!
+readerr:
+	mov si, READFAIL
+	call disp
+	ret
+
+RETMSG	db "SMM installer finished, booting your system of choice.",10,13,0
+READSUCC db "Read successful; rebooting into boot sector.",10,13,0
+READFAIL db "Boot disk read failure; system halted.",10,13,0
+
+
+idtp	db 0xFF, 0x03, 0x00, 0x00, 0x00, 0x00
+
+gdtp	dw 0x1F
+	dd gdt
+
+gdt	dd 0, 0
+	dd 0x0000FFFF, 0x00009e00	; CS
+	dd 0x0000FFFF, 0x00009300	; DS