From 4bea7daf0e70a1540b8533c8253c197bb282416e Mon Sep 17 00:00:00 2001
From: Joshua Wise <joshua@rebirth.joshuawise.com>
Date: Fri, 5 Sep 2008 17:42:02 -0400
Subject: [PATCH] aseg with a working C execution environment

---
 aseg/Makefile  |  4 ++--
 aseg/aseg.asm  | 44 ++++++++++++++++++++------------------------
 aseg/aseg.lds  | 22 ++++++++++++++++++++--
 aseg/counter.c | 10 ++++++++++
 4 files changed, 52 insertions(+), 28 deletions(-)
 create mode 100644 aseg/counter.c

diff --git a/aseg/Makefile b/aseg/Makefile
index f86bc2a..5bef71f 100644
--- a/aseg/Makefile
+++ b/aseg/Makefile
@@ -6,5 +6,5 @@ aseg.bin: aseg.asm
 aseg.o: aseg.bin
 	objcopy -I binary -B i386 -O elf32-i386 aseg.bin aseg.o
 
-aseg.elf: aseg.bin aseg.lds
-	ld -o aseg.elf -T aseg.lds
\ No newline at end of file
+aseg.elf: aseg.bin aseg.lds counter.o
+	ld -o aseg.elf -T aseg.lds counter.o
diff --git a/aseg/aseg.asm b/aseg/aseg.asm
index f10955a..ee83272 100644
--- a/aseg/aseg.asm
+++ b/aseg/aseg.asm
@@ -1,8 +1,6 @@
 	org 0xA8000
 [bits 16]
 entry:
-;	mov al, 0x01		; Say where we are.
-;	out 0x80, al
 	mov ax, 0xA800
 	mov ds, ax		; Take us out of flat unreal mode, and
 	mov es, ax		; put us in true real mode.
@@ -11,38 +9,25 @@ entry:
 	mov ss, ax
 	jmp 0xA800:(entry2-0xA8000)	; Long jump to a correct cs.
 entry2:
-;	mov al, 0x02
-;	out 0x80, al
 	lgdt [(gdtr-0xA8000)]		; Set up a new GDT.
 	mov eax, 0x1
 	mov cr0, eax			; ... and enter pmode!
-	mov al, 0x03			; Say we got here.
-	out 0x80, al
 	jmp long 0x10:continue		; Now longjmp into the new code.
 [bits 32]
 continue:
-;	mov al, 0x04			; Now we're in protected mode.
-;	out 0x80, al
-	
 	mov ax, 0x08			; Set up segment selectors.
 	mov ds, ax
 	mov es, ax
 	mov fs, ax
 	mov gs, ax
 	mov ss, ax
-	mov esp, 0x1fffffff
+	mov esp, [dataptr]
 
-;	mov al, 0x05
+;	mov al, [cstat]
+;	add al, 1
 ;	out 0x80, al
-
-	mov al, [cstat]
-	add al, 1
-	out 0x80, al
-	mov [cstat], al
+;	mov [cstat], al
 	
-	mov eax, 0x11223344
-	mov dword [status], eax
-
 	mov dx, 0xCF8			; save off the old config value
 	in dword eax, dx
 	mov [esp-4], eax
@@ -85,14 +70,21 @@ continue:
 	mov byte [eax+10], '2'
 	mov byte [eax+11], 0x1F
 	
-	mov dx, 0x3D4
+	mov dx, 0x3D4			; restore the old stuff
 	mov al, [esp-6]
 	out dx, al
-	
+
+	mov al, 0
+	mov edi, [dataptr+4]		; clear BSS
+	mov ecx, [dataptr+8]
+	rep stosb
 
 	mov dx, 0xCFC			; restore smramc
 	mov al, [esp-5]
 	out dx, al
+	
+	mov eax, [dataptr+12]
+	call eax
 
 	mov dx, 0xCF8			; restore the old config value
 	mov eax, [esp-4]
@@ -123,8 +115,12 @@ gdt:
 	db 0xFF, 0xFF, 0x00, 0x00, 0x00, 0x9B, 0xCF, 0x00	; code segment
 	db 0xFF, 0xFF, 0x00, 0x80, 0x0A, 0x9B, 0xCF, 0x00	; code segment for trampoline
 
-TIMES   512-($-$$) DB 0
-status:
-	dd 0xAA55AA55
 cstat:
 	db 0x00
+
+TIMES   512-($-$$) DB 0
+dataptr:
+	; 4 bytes of stack top
+	; 4 bytes of BSS start
+	; 4 bytes of BSS length
+	; 4 bytes of C entry point
\ No newline at end of file
diff --git a/aseg/aseg.lds b/aseg/aseg.lds
index 2d805bb..a3a8ece 100644
--- a/aseg/aseg.lds
+++ b/aseg/aseg.lds
@@ -3,9 +3,27 @@ OUTPUT_ARCH(i386)
 SECTIONS
 {
 	. = 0xA8000;
-	
-	.aseg 0xA8000 : {
+	.aseg : {
 		_start = .;
 		aseg.o
+		LONG(_stacktop);
+		LONG(_bss);
+		LONG(_bssend - _bss);
+		LONG(__start);
+		*(.text);
+		*(.data);
+		*(.rodata);
+	}
+
+	. = 0x1FF80000;
+	.bss : {
+		_bss = .;
+		*(.bss);
+		_bssend = .;
+	}
+	.stack : { 
+		. = . + 0x10000;
+		. = ALIGN(0x10);
+		_stacktop = .;
 	}
 }
diff --git a/aseg/counter.c b/aseg/counter.c
new file mode 100644
index 0000000..891c075
--- /dev/null
+++ b/aseg/counter.c
@@ -0,0 +1,10 @@
+char counter = 0;
+
+#define outb(port, val) \
+({ asm volatile("outb %0, %%dx" : : "a" ((unsigned char)(val)) , "d" ((unsigned short)(port))); })
+
+void __start (void) {
+	counter++;
+	outb (0x80, counter);
+}
+
-- 
2.43.0