From a0db5a79c1dd9e6e7e454c2d0593f86e017757d4 Mon Sep 17 00:00:00 2001 From: "H. Peter Anvin" Date: Tue, 31 Mar 2009 16:37:56 -0700 Subject: [PATCH] chain.c32: remove loadbase < 0x7c00 hack Remove the special hack for loadbase < 0x7c00. We no longer need it, since the shuffler will relocate appropriately by magic. Signed-off-by: H. Peter Anvin --- com32/modules/chain.c | 77 +++++---------------------------------------------- 1 file changed, 7 insertions(+), 70 deletions(-) diff --git a/com32/modules/chain.c b/com32/modules/chain.c index 979ede2..9c2645c 100644 --- a/com32/modules/chain.c +++ b/com32/modules/chain.c @@ -1,6 +1,6 @@ /* ----------------------------------------------------------------------- * * - * Copyright 2003-2008 H. Peter Anvin - All Rights Reserved + * Copyright 2003-2009 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 @@ -446,79 +446,16 @@ static void do_boot(void *boot_sector, size_t boot_size, return; } - if (loadbase < 0x7c00) { - /* Special hack: if we are to be loaded below 0x7c00, we need to handle - the part that goes below 0x7c00 specially, since that's where the - shuffler lives. To deal with that, stuff the balance at the end - of low memory and put a small copy stub there. - - The only tricky bit is that we need to set up registers for our - move, and then restore them to what they should be at the end of - the code. */ - static uint8_t copy_down_code[] = { - 0xf3,0x66,0xa5, /* 00: rep movsd */ - 0xbe,0,0, /* 03: mov si,0 */ - 0xbf,0,0, /* 06: mov di,0 */ - 0x8e,0xde, /* 09: mov ds,si */ - 0x8e,0xc7, /* 0b: mov es,di */ - 0x66,0xb9,0,0,0,0, /* 0d: mov ecx,0 */ - 0x66,0xbe,0,0,0,0, /* 13: mov esi,0 */ - 0x66,0xbf,0,0,0,0, /* 19: mov edi,0 */ - 0xea,0,0,0,0, /* 1f: jmp 0:0 */ - /* pad out to segment boundary */ - 0x90,0x90,0x90,0x90, /* 24: ... */ - 0x90,0x90,0x90,0x90, /* 28: ... */ - 0x90,0x90,0x90,0x90, /* 2c: ... */ - }; - size_t low_size = min(boot_size, 0x7c00-loadbase); - size_t high_size = boot_size - low_size; - size_t low_addr = (0x7c00 + high_size + 15) & ~15; - size_t move_addr = (low_addr + low_size + 15) & ~15; - const size_t move_size = sizeof copy_down_code; - - if (move_addr+move_size >= dosmem-0x7c00) - goto too_big; - - *(uint16_t *)©_down_code[0x04] = regs->ds; - *(uint16_t *)©_down_code[0x07] = regs->es; - *(uint32_t *)©_down_code[0x0f] = regs->ecx.l; - *(uint32_t *)©_down_code[0x15] = regs->esi.l; - *(uint32_t *)©_down_code[0x1b] = regs->edi.l; - *(uint16_t *)©_down_code[0x20] = regs->ip; - *(uint16_t *)©_down_code[0x22] = regs->cs; - - regs->ecx.l = (low_size+3) >> 2; - regs->esi.l = 0; - regs->edi.l = loadbase & 15; - regs->ds = low_addr >> 4; - regs->es = loadbase >> 4; - regs->cs = move_addr >> 4; - regs->ip = 0; - - endimage = move_addr + move_size; - - if (high_size) - if (syslinux_add_movelist(&mlist, 0x7c00, - (addr_t)boot_sector+low_size, high_size)) - goto enomem; - if (syslinux_add_movelist(&mlist, low_addr, - (addr_t)boot_sector, low_size)) - goto enomem; - if (syslinux_add_movelist(&mlist, move_addr, - (addr_t)copy_down_code, move_size)) - goto enomem; - } else { - /* Nothing below 0x7c00, much simpler... */ + /* Nothing below 0x7c00, much simpler... */ + /* The 256 byte is a fudge factor... */ - if (boot_size >= dosmem-0x7c00) + if (boot_size >= dosmem - loadbase) goto too_big; - endimage = loadbase + boot_size; + endimage = loadbase + boot_size; - if (syslinux_add_movelist(&mlist, loadbase, (addr_t)boot_sector, - boot_size)) - goto enomem; - } + if (syslinux_add_movelist(&mlist, loadbase, (addr_t)boot_sector, boot_size)) + goto enomem; if (opt.swap && driveno != swapdrive) { static const uint8_t swapstub_master[] = { -- 2.7.4