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Diffstat (limited to 'bcopy32.inc')
| -rw-r--r-- | bcopy32.inc | 414 |
1 files changed, 414 insertions, 0 deletions
diff --git a/bcopy32.inc b/bcopy32.inc new file mode 100644 index 00000000..daa061e9 --- /dev/null +++ b/bcopy32.inc @@ -0,0 +1,414 @@ +;; $Id$ +;; ----------------------------------------------------------------------- +;; +;; Copyright 1994-2002 H. Peter Anvin - All Rights Reserved +;; +;; This program is free software; you can redistribute it and/or modify +;; it under the terms of the GNU General Public License as published by +;; the Free Software Foundation, Inc., 53 Temple Place Ste 330, +;; Bostom MA 02111-1307, USA; either version 2 of the License, or +;; (at your option) any later version; incorporated herein by reference. +;; +;; ----------------------------------------------------------------------- + +;; +;; bcopy32.inc +;; +;; 32-bit bcopy routine for real mode +;; + +; +; 32-bit bcopy routine for real mode +; +; We enter protected mode, set up a flat 32-bit environment, run rep movsd +; and then exit. IMPORTANT: This code assumes cs == 0. +; +; This code is probably excessively anal-retentive in its handling of +; segments, but this stuff is painful enough as it is without having to rely +; on everything happening "as it ought to." +; +; IMPORTANT: This code must be capable of operating when copied to the +; trackbuf area (1000h). The routine bcopy_over_self handles this mode +; of operation, including any necessary adjustments. +; + align 4 +__bcopy_start: + +bcopy_gdt: dw bcopy_gdt_size-1 ; Null descriptor - contains GDT +.adj1: dd bcopy_gdt ; pointer for LGDT instruction + dw 0 + dd 0000ffffh ; Code segment, use16, readable, + dd 00009b00h ; present, dpl 0, cover 64K + dd 0000ffffh ; Data segment, use16, read/write, + dd 008f9300h ; present, dpl 0, cover all 4G + dd 0000ffffh ; Data segment, use16, read/write, + dd 00009300h ; present, dpl 0, cover 64K +bcopy_gdt_size: equ $-bcopy_gdt + +bcopy: push eax + pushf ; Saves, among others, the IF flag + push gs + push fs + push ds + push es + mov [cs:SavedSSSP],sp + mov ax,ss + mov [cs:SavedSSSP+2],ax + + cli + call enable_a20 + +.adj2: o32 lgdt [cs:bcopy_gdt] + mov eax,cr0 + or al,1 + mov cr0,eax ; Enter protected mode + jmp 08h:.in_pm + +.in_pm: mov ax,10h ; Data segment selector + mov es,ax + mov ds,ax + + mov al,18h ; "Real-mode-like" data segment + mov ss,ax + mov fs,ax + mov gs,ax + + a32 rep movsd ; Do our business + + mov es,ax ; Set to "real-mode-like" + mov ds,ax + + mov eax,cr0 + and al,~1 + mov cr0,eax ; Disable protected mode +.adj3: jmp 0:.in_rm + +.in_rm: ; Back in real mode + lss sp,[cs:SavedSSSP] + pop es + pop ds + pop fs + pop gs + call disable_a20 + + popf ; Re-enables interrupts + pop eax + ret + +; +; Routines to enable and disable (yuck) A20. These routines are gathered +; from tips from a couple of sources, including the Linux kernel and +; http://www.x86.org/. The need for the delay to be as large as given here +; is indicated by Donnie Barnes of RedHat, the problematic system being an +; IBM ThinkPad 760EL. +; +; We typically toggle A20 twice for every 64K transferred. +; +%define io_delay call _io_delay +%define IO_DELAY_PORT 80h ; Invalid port (we hope!) +%define disable_wait 32 ; How long to wait for a disable + +%define A20_DUNNO 0 ; A20 type unknown +%define A20_NONE 1 ; A20 always on? +%define A20_BIOS 2 ; A20 BIOS enable +%define A20_KBC 3 ; A20 through KBC +%define A20_FAST 4 ; A20 through port 92h + + align 2 +A20List dw a20_dunno, a20_none, a20_bios, a20_kbc, a20_fast +A20DList dw a20d_dunno, a20d_none, a20d_bios, a20d_kbc, a20d_fast +a20_adjust_cnt equ ($-A20List)/2 +A20Type dw A20_DUNNO ; A20 type unknown + +slow_out: out dx, al ; Fall through + +_io_delay: out IO_DELAY_PORT,al + out IO_DELAY_PORT,al + ret + +enable_a20: + pushad + mov byte [cs:A20Tries],255 ; Times to try to make this work + +try_enable_a20: +; +; Flush the caches +; +; call try_wbinvd + +; +; If the A20 type is known, jump straight to type +; + mov bp,[cs:A20Type] + add bp,bp ; Convert to word offset +.adj4: jmp word [cs:bp+A20List] + +; +; First, see if we are on a system with no A20 gate +; +a20_dunno: +a20_none: + mov byte [cs:A20Type], A20_NONE + call a20_test + jnz a20_done + +; +; Next, try the BIOS (INT 15h AX=2401h) +; +a20_bios: + mov byte [cs:A20Type], A20_BIOS + mov ax,2401h + pushf ; Some BIOSes muck with IF + int 15h + popf + + call a20_test + jnz a20_done + +; +; Enable the keyboard controller A20 gate +; +a20_kbc: + mov dl, 1 ; Allow early exit + call empty_8042 + jnz a20_done ; A20 live, no need to use KBC + + mov byte [cs:A20Type], A20_KBC ; Starting KBC command sequence + + mov al,0D1h ; Command write + out 064h, al + call empty_8042_uncond + + mov al,0DFh ; A20 on + out 060h, al + call empty_8042_uncond + + ; Verify that A20 actually is enabled. Do that by + ; observing a word in low memory and the same word in + ; the HMA until they are no longer coherent. Note that + ; we don't do the same check in the disable case, because + ; we don't want to *require* A20 masking (SYSLINUX should + ; work fine without it, if the BIOS does.) +.kbc_wait: push cx + xor cx,cx +.kbc_wait_loop: + call a20_test + jnz a20_done_pop + loop .kbc_wait_loop + + pop cx +; +; Running out of options here. Final attempt: enable the "fast A20 gate" +; +a20_fast: + mov byte [cs:A20Type], A20_FAST ; Haven't used the KBC yet + in al, 092h + or al,02h + and al,~01h ; Don't accidentally reset the machine! + out 092h, al + +.fast_wait: push cx + xor cx,cx +.fast_wait_loop: + call a20_test + jnz a20_done_pop + loop .fast_wait_loop + + pop cx + +; +; Oh bugger. A20 is not responding. Try frobbing it again; eventually give up +; and report failure to the user. +; + + + dec byte [cs:A20Tries] + jnz try_enable_a20 + + mov si, err_a20 + jmp abort_load +; +; A20 unmasked, proceed... +; +a20_done_pop: pop cx +a20_done: popad + ret + +; +; This routine tests if A20 is enabled (ZF = 0). This routine +; must not destroy any register contents. +; +a20_test: + push es + push cx + push ax + mov cx,0FFFFh ; HMA = segment 0FFFFh + mov es,cx + mov cx,32 ; Loop count + mov ax,[cs:A20Test] +.a20_wait: inc ax + mov [cs:A20Test],ax + io_delay ; Serialize, and fix delay + cmp ax,[es:A20Test+10h] + loopz .a20_wait +.a20_done: pop ax + pop cx + pop es + ret + +disable_a20: + pushad +; +; Flush the caches +; +; call try_wbinvd + + mov bp,[cs:A20Type] + add bp,bp ; Convert to word offset +.adj5: jmp word [cs:bp+A20DList] + +a20d_bios: + mov ax,2400h + pushf ; Some BIOSes muck with IF + int 15h + popf + jmp short a20d_snooze + +; +; Disable the "fast A20 gate" +; +a20d_fast: + in al, 092h + and al,~03h + out 092h, al + jmp short a20d_snooze + +; +; Disable the keyboard controller A20 gate +; +a20d_kbc: + call empty_8042_uncond + mov al,0D1h + out 064h, al ; Command write + call empty_8042_uncond + mov al,0DDh ; A20 off + out 060h, al + call empty_8042_uncond + ; Wait a bit for it to take effect +a20d_snooze: + push cx + mov cx, disable_wait +.delayloop: call a20_test + jz .disabled + loop .delayloop +.disabled: pop cx +a20d_dunno: +a20d_none: + popad + ret + +; +; Routine to empty the 8042 KBC controller. If dl != 0 +; then we will test A20 in the loop and exit if A20 is +; suddenly enabled. +; +empty_8042_uncond: + xor dl,dl +empty_8042: + call a20_test + jz .a20_on + and dl,dl + jnz .done +.a20_on: io_delay + in al, 064h ; Status port + test al,1 + jz .no_output + io_delay + in al, 060h ; Read input + jmp short empty_8042 +.no_output: + test al,2 + jnz empty_8042 + io_delay +.done: ret + +; +; WBINVD instruction; gets auto-eliminated on 386 CPUs +; +try_wbinvd: + wbinvd + ret + +; +; bcopy_over_self: +; +; This routine is used to copy large blocks of code on top of +; conventional memory (to 0:7c00). We therefore have to move +; necessary code into the trackbuf area before doing the copy, +; and do adjustments to anything except BSS area references. +; +; After performing the copy, this routine resets the stack and +; jumps to 0:7c00. +; +; Inputs: +; ESI, EDI, ECX - same as bcopy +; EDX - edx on invocation +; EAX - esi on invocation +; +%define ADJUST (__bcopy_start - trackbuf) + + align 2 +adjlist dw bcopy_gdt.adj1 - ADJUST + dw bcopy.adj2 + 5 - ADJUST + dw bcopy.adj3 + 1 - ADJUST + dw try_enable_a20.adj4 + 3 - ADJUST + dw disable_a20.adj5 + 3 - ADJUST +adjlist_cnt equ ($-adjlist)/2 + +bcopy_over_self: + cli + cld + xor bx,bx + mov ds,bx + mov es,bx + mov ss,bx + mov sp,7c00h + + push eax + push edx + push esi + push edi + push ecx + + mov si,__bcopy_start + mov di,trackbuf + mov cx,(__bcopy_end - __bcopy_start + 3) >> 2 + rep movsd + + mov si,A20List - ADJUST + mov cx,a20_adjust_cnt +.adjust1: + sub word [si], ADJUST + inc si + inc si + loop .adjust1 + + mov si, adjlist + mov cx, adjlist_cnt +.adjust2: + lodsw + xchg di,ax + sub word [di], ADJUST + loop .adjust2 + + jmp .next-ADJUST +.next: + pop ecx + pop edi + pop esi + call bcopy + + pop edx + pop esi + jmp 0:7c00h +__bcopy_end: |