jai@lab.ultra.nyu.edu (Benchiao Jai) (02/26/91)
code segment assume cs:code, ds:code, ss:code org 100h start: mov dx, cs ; set up registers mov ds, dx cli mov ss, dx mov sp, offset stack sti mov ax, offset tail ; calculate my size add ax, 0fh ; round to multiple mov cl, 4 ; of 16 shr ax, cl add ax, dx ; add to my origin mov loadpos, ax ; is the first load position mov bp, offset k_struct call load ; load kernel mov bp, offset m_struct call load ; load mm mov bp, offset f_struct call load ; load fs mov bp, offset i_struct call load ; load init mov bx, k_struct+4 ; kernel data mov es, k_struct+2 ; kernel segment mov ax, k_struct+6 ; kernel size mov es:[bx+2], ax ; ---> size table of kernel mov ax, m_struct+6 ; mm size mov es:[bx+6], ax ; ---> size table of kernel mov ax, f_struct+6 ; fs size mov es:[bx+10], ax ; ---> size table of kernel mov ax, i_struct+6 ; init size mov es:[bx+14], ax ; ---> size table of kernel mov bx, f_struct+4 ; fs data mov es, f_struct+2 ; fs segment mov es:[bx+8], ax ; init size ---> fs table mov ax, i_struct+2 ; init origin mov es:[bx+4], ax ; ---> fs table mov bx, 13 ; scan code of '=' xor ax, ax mov k_struct, ax call dword ptr k_struct mov ax,4c00h int 21h ; load: mov dx, [bp] ; filename mov ax, 3d00h ; open the file int 21h jc error_open mov handle, ax ; save for later use mov bx, ax ; read the file mov cx, 0ffffh ; all you can read mov dx, loadpos ; to this segment mov 2[bp], dx ; store text origin segment push ds mov ds, dx mov es, dx ; for later use to clear bss xor dx, dx mov ah, 3fh int 21h mov bx, ds:[2] ; 2 is begdata mov dx, ds:[4] ; 4 is endbss pop ds jc error_read mov 4[bp], bx ; store data origin offset mov cx, dx sub cx, ax ; bss size = endbss - enddata (in AX by READ) shr cx, 1 ; words inc cx ; just in case mov di, ax ; starts here xor ax, ax ; use zero rep stosw ; to clear bss add dx, 0fh ; round to multiple mov cl, 4 ; of 16 shr dx, cl mov 6[bp], dx ; store total size in paragraphs add loadpos, dx ; advance for next load mov bx, handle ; close the file mov ah, 3eh int 21h ret ; print: lodsb and al, al jz finish mov dl, al mov ah, 2 int 21h jmp print finish: ret ; error_open: mov si, offset unable_open call print jmp short error error_read: mov si, offset unable_read call print error: mov si, [bp] call print mov ax, 4c01h int 21h ; handle dw 0 unable_open db 'Unable to open ', 0 unable_read db 'Unable to read ', 0 ; loadpos dw 0 kernelname db 'KERNEL.BIN', 0 mmname db 'MM.BIN', 0 fsname db 'FS.BIN', 0 initname db 'INIT.BIN', 0 k_struct dw kernelname, 0, 0, 0 m_struct dw mmname, 0, 0, 0 f_struct dw fsname, 0, 0, 0 i_struct dw initname, 0, 0, 0 ; db 64 dup (0) stack label byte tail label byte ; code ends end start