8 extern boot_mem_map_size
19 mov fs, ax ; this will store the original real mode segment
21 ; modify the return to real mode jump segment
22 mov [.jmpcs16 + 3], ax
27 ; check for VM86 and abort
41 ; calculate GDT linear address
48 ; set tmp segment bases to match the linear address of our current seg
52 mov word [gdt + 18h + 2], ax ; tmp pm code base
53 mov word [gdt + 20h + 2], ax ; tmp pm data base
54 mov word [gdt + 28h + 2], ax ; ret-to-realmode code
56 mov byte [gdt + 18h + 4], al
57 mov byte [gdt + 20h + 4], al
58 mov byte [gdt + 28h + 4], al
72 .pm: mov ax, 20h ; tmp data selector
74 mov ax, 10h ; dest data selector
77 ; copy main program high
79 mov esi, _ldr_main_start
81 mov ecx, _main_size + 3
86 mov eax, [mem_map_size]
87 mov [es:boot_mem_map_size], eax
90 mov ecx, 32 ; 128 bytes
101 ; return to real mode
109 jmp 42h:.loadcs16 ; 42 seg is modifed at the start
116 ; restore real-mode IVT
125 str_errvm86 db 'Error: memory manager detected! Stop it and try again (e.g. emm386 off)',10,0
126 str_enterpm db 'Entering 32bit protected mode ...',10,0
133 call printstr ; print "Enable A20 line ... "
145 .done: mov si, .okstr
149 .infomsg db 'Enable A20 line:',0
150 .failstr db ' failed.',10,0
151 .okstr db ' success.',10,0
153 ; CF = 1 if A20 test fails (not enabled)
172 .done: mov [ds:si], dl
185 .info db ' fast ...',0
187 KBC_DATA_PORT equ 0x60
188 KBC_CMD_PORT equ 0x64
189 KBC_STATUS_PORT equ 0x64
190 KBC_CMD_WR_OUTPORT equ 0xd1
192 KBC_STAT_IN_FULL equ 2
198 mov al, KBC_CMD_WR_OUTPORT
202 out KBC_DATA_PORT, al
204 .info db ' kbd ...',0
207 in al, KBC_STATUS_PORT
208 and al, KBC_STAT_IN_FULL
213 ; ---------------------- memory detection -----------------------
216 mov si, memdet_e820_msg
223 mov si, memdet_e801_msg
230 mov esi, memdet_88_msg
237 mov esi, memdet_cmos_msg
244 mov si, memdet_fail_msg
253 str_fail db 'failed',10,0
254 memdet_fail_msg db 'Failed to detect available memory!',10,0
255 memdet_e820_msg db 'Detecting RAM (BIOS 15h/0xe820)... ',0
256 memdet_e801_msg db 'Detecting RAM (BIOS 15h/0xe801)... ',0
257 memdet_88_msg db 'Detecting RAM (BIOS 15h/0x88, max 64mb)... ',0
258 memdet_cmos_msg db 'Detecting RAM (CMOS)...',0
260 ; detect extended memory using BIOS call 15h/e820
262 mov dword [mem_map_size], 0
276 ; skip areas starting above 4GB as we won't be able to use them
277 cmp dword [di + 4], 0
280 ; only care for type 1 (usable ram), otherwise ignore
281 cmp dword [di + 16], 1
286 mov ebp, [mem_map_size]
287 mov [ebp * 8 + esi], eax
289 ; skip areas with 0 size (also clamp size to 4gb)
291 cmp dword [edi + 12], 0
293 ; high part is non-zero, make low part ffffffff
299 ; if both high and low parts are zero, ignore
304 .skiph0:mov [ebp * 8 + esi + 4], eax
305 inc dword [mem_map_size]
308 ; terminate the loop if ebx was reset to 0
316 .fail: ; if size > 0, then it's not a failure, just the end
317 cmp dword [mem_map_size], 0
322 .buffer times 32 db 0
324 ; detect extended memory using BIOS call 15h/e801
327 mov ebp, [mem_map_size]
343 .foo1: mov dword [si], 100000h
345 ; first size is in KB, convert to bytes
348 ; overflow means it's >4GB, clamp to 4GB
350 .foo2: mov [si + 4], eax
351 inc dword [mem_map_size]
354 mov dword [si + 8], 1000000h
356 ; second size is in 64kb blocks, convert to bytes
359 ; overflow means it's >4GB, clamp to 4GB
361 .foo3: mov [si + 12], eax
362 inc dword [mem_map_size]
371 ; reportedly some BIOS implementations fail to clear CF on success
380 ; ax has size in KB, convert to bytes in eax
385 mov dword [si], 100000h
388 mov dword [mem_map_size], 1
406 ; ax has size in KB, convert to bytes in eax
411 mov dword [si], 100000h
413 mov dword [mem_map_size], 1
422 mem_map times 128 db 0
425 ; ----------------------- serial console ------------------------
429 mov dx, UART_BASE + 3 ; LCTL
432 mov dx, UART_BASE ; DIVLO
433 mov al, UART_DIVISOR & 0xff
436 mov al, UART_DIVISOR >> 8
438 mov dx, UART_BASE + 3 ; LCTL
442 mov al, 0xb ; DTR/RTS/OUT2
460 .nolf: call ser_putchar
468 cmp al, 10 ; check for line-feed and insert CR before it
477 .nolf: call ser_putchar
497 call ser_putchar_pmode
499 .nolf: call ser_putchar_pmode
505 enterpm dd 0xbad00d ; space for linear address for far jump to pmode
506 enterpm_sel dw 8 ; selector for far jump to protected mode
508 gdt_lim dw 47 ; GDT limit
509 gdt_base dd 0xbadf00d ; space for GDT linear address
512 gdt: ; 0: null segment
515 ; 1: code - 0/lim:4g, G:4k, 32bit, avl, pres|app, dpl:0, type:code/non-conf/rd (sel: 8)
518 ; 2: data - 0/lim:4g, G:4k, 32bit, avl, pres|app, dpl:0, type:data/rw (sel: 10h)
521 ; 3: tmp code (will set base before entering pmode) (sel: 18h)
524 ; 4: tmp data (will set base before entering pmode) (sel: 20h)
527 ; 5: return to real-mode 16bit code segment (sel: 28h)
531 ; pseudo IDTR descriptor for real-mode IVT at address 0
534 rmidt: dw 3ffh ; IVT limit (1kb / 256 entries)
537 ; vi:set ts=8 sts=8 sw=8 ft=nasm: