@@ -1,32 +1,32 @@ -global loader ; making entry point visible to linker -extern kmain ; main is defined elsewhere +global loader ; making entry point visible to linker +extern kmain ; main is defined elsewhere ; setting up the Multiboot header - see GRUB docs for details -MODULEALIGN equ 1<<0 ; align loaded modules on page boundaries -MEMINFO equ 1<<1 ; provide memory map -FLAGS equ MODULEALIGN | MEMINFO ; this is the Multiboot 'flag' field -MAGIC equ 0x1BADB002 ; 'magic number' lets bootloader find the header -CHECKSUM equ -(MAGIC + FLAGS) ; checksum required +MODULEALIGN equ 1<<0 ; align loaded modules on page boundaries +MEMINFO equ 1<<1 ; provide memory map +FLAGS equ MODULEALIGN | MEMINFO ; this is the Multiboot 'flag' field +MAGIC equ 0x1BADB002 ; 'magic number' lets bootloader find the header +CHECKSUM equ -(MAGIC + FLAGS) ; checksum required section .text align 4 MultiBootHeader: - dd MAGIC - dd FLAGS - dd CHECKSUM + dd MAGIC + dd FLAGS + dd CHECKSUM ; reserve initial kernel stack space -STACKSIZE equ 0x4000 ; that's 16k. +STACKSIZE equ 0x4000 ; that's 16k. loader: - mov esp, stack+STACKSIZE ; set up the stack - push eax ; pass Multiboot magic number - push ebx ; pass Multiboot info structure - - call kmain ; call kernel proper - hlt ; halt machine should kernel return + mov esp, stack+STACKSIZE ; set up the stack + push eax ; pass Multiboot magic number + push ebx ; pass Multiboot info structure + + call kmain ; call kernel proper + hlt ; halt machine should kernel return section .bss align 32 stack: - resb STACKSIZE ; reserve 16k stack on a quadword boundary \ No newline at end of file + resb STACKSIZE ; reserve 16k stack on a quadword boundary hello_world/kstart.asm @@ -3,16 +3,16 @@ ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; ; macros to handle leading underscores added by DOS/Windows compilers -%macro IMP 1 +%macro IMP 1 %ifdef UNDERBARS - EXTERN _%1 - %define %1 _%1 + EXTERN _%1 + %define %1 _%1 %else - EXTERN %1 + EXTERN %1 %endif %endmacro -DS_MAGIC equ 3544DA2Ah +DS_MAGIC equ 3544DA2Ah SECTION .text BITS 32 @@ -23,41 +23,42 @@ BITS 32 GLOBAL entry entry: -; check if data segment linked, located, and loaded properly - mov eax,[ds_magic] - cmp eax,DS_MAGIC - je ds_ok - -; display a blinking white-on-blue 'D' and freeze - mov word [0B8000h],9F44h - jmp short $ -ds_ok: + ; check if data segment linked, located, and loaded properly + mov eax,[ds_magic] + cmp eax,DS_MAGIC + je ds_ok + + ; display a blinking white-on-blue 'D' and freeze + mov word [0B8000h],9F44h + jmp short $ -; stop using bootloader GDT, and load new GDT - lgdt [gdt_ptr] +ds_ok: + ; stop using bootloader GDT, and load new GDT + lgdt [gdt_ptr] + + mov ax,LINEAR_DATA_SEL + mov ds,ax + mov es,ax + mov ss,ax + mov fs,ax + mov gs,ax + jmp LINEAR_CODE_SEL:sbat - mov ax,LINEAR_DATA_SEL - mov ds,ax - mov es,ax - mov ss,ax - mov fs,ax - mov gs,ax - jmp LINEAR_CODE_SEL:sbat sbat: - -; zero the C language BSS -; 'bss' and 'end' are defined in the linker script file + ; zero the C language BSS + ; 'bss' and 'end' are defined in the linker script file EXTERN bss, end - mov edi,bss - mov ecx,end - sub ecx,edi - xor eax,eax - rep stosb - - mov esp,stack + mov edi,bss + mov ecx,end + sub ecx,edi + xor eax,eax + rep stosb + + mov esp,stack + IMP main - call main ; call C code - jmp $ ; freeze + call main ; call C code + jmp $ ; freeze ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; ; Multiboot header for GRUB bootloader. This must be in the first 8K @@ -65,76 +66,78 @@ IMP main ; DJGPP COFF, Win32 PE, or other formats. ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; -MULTIBOOT_PAGE_ALIGN equ 1<<0 -MULTIBOOT_MEMORY_INFO equ 1<<1 -MULTIBOOT_AOUT_KLUDGE equ 1<<16 -MULTIBOOT_HEADER_MAGIC equ 0x1BADB002 -MULTIBOOT_HEADER_FLAGS equ MULTIBOOT_PAGE_ALIGN | MULTIBOOT_MEMORY_INFO | MULTIBOOT_AOUT_KLUDGE -MULTIBOOT_CHECKSUM equ -(MULTIBOOT_HEADER_MAGIC + MULTIBOOT_HEADER_FLAGS) +MULTIBOOT_PAGE_ALIGN equ 1<<0 +MULTIBOOT_MEMORY_INFO equ 1<<1 +MULTIBOOT_AOUT_KLUDGE equ 1<<16 +MULTIBOOT_HEADER_MAGIC equ 0x1BADB002 +MULTIBOOT_HEADER_FLAGS equ MULTIBOOT_PAGE_ALIGN | MULTIBOOT_MEMORY_INFO | MULTIBOOT_AOUT_KLUDGE +MULTIBOOT_CHECKSUM equ -(MULTIBOOT_HEADER_MAGIC + MULTIBOOT_HEADER_FLAGS) ; these are in the linker script file EXTERN code, bss, end ALIGN 4 mboot: - dd MULTIBOOT_HEADER_MAGIC - dd MULTIBOOT_HEADER_FLAGS - dd MULTIBOOT_CHECKSUM -; aout kludge. These must be PHYSICAL addresses - dd mboot - dd code - dd bss - dd end - dd entry + dd MULTIBOOT_HEADER_MAGIC + dd MULTIBOOT_HEADER_FLAGS + dd MULTIBOOT_CHECKSUM + + ; aout kludge. These must be PHYSICAL addresses + dd mboot + dd code + dd bss + dd end + dd entry ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; SECTION .data ds_magic: - dd DS_MAGIC + dd DS_MAGIC gdt: ; NULL descriptor - dw 0 ; limit 15:0 - dw 0 ; base 15:0 - db 0 ; base 23:16 - db 0 ; type - db 0 ; limit 19:16, flags - db 0 ; base 31:24 + dw 0 ; limit 15:0 + dw 0 ; base 15:0 + db 0 ; base 23:16 + db 0 ; type + db 0 ; limit 19:16, flags + db 0 ; base 31:24 ; unused descriptor - dw 0 - dw 0 - db 0 - db 0 - db 0 - db 0 - -LINEAR_DATA_SEL equ $-gdt - dw 0FFFFh - dw 0 - db 0 - db 92h ; present, ring 0, data, expand-up, writable - db 0CFh ; page-granular (4 gig limit), 32-bit - db 0 - -LINEAR_CODE_SEL equ $-gdt - dw 0FFFFh - dw 0 - db 0 - db 9Ah ; present,ring 0,code,non-conforming,readable - db 0CFh ; page-granular (4 gig limit), 32-bit - db 0 + dw 0 + dw 0 + db 0 + db 0 + db 0 + db 0 + +LINEAR_DATA_SEL equ $-gdt + dw 0FFFFh + dw 0 + db 0 + db 92h ; present, ring 0, data, expand-up, writable + db 0CFh ; page-granular (4 gig limit), 32-bit + db 0 + +LINEAR_CODE_SEL equ $-gdt + dw 0FFFFh + dw 0 + db 0 + db 9Ah ; present,ring 0,code,non-conforming,readable + db 0CFh ; page-granular (4 gig limit), 32-bit + db 0 + gdt_end: gdt_ptr: - dw gdt_end - gdt - 1 - dd gdt + dw gdt_end - gdt - 1 + dd gdt ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; SECTION .bss + resd 1024 - resd 1024 stack: oneplusone/kstart.asm 500fa00906aafea742b4c49cec2f208407565a3d James Tauber jtauber@jtauber.com http://github.com/jtauber/cleese/commit/e7f6026b45a0162dc9495988ce0350c94c62fc25 e7f6026b45a0162dc9495988ce0350c94c62fc25 2009-10-11T11:01:06-07:00 2009-10-11T11:01:06-07:00 a bit of cleanup in kstart.asm formatting 9cf64665e359f637e7f019d82049f8dbd5637a2b James Tauber jtauber@jtauber.com