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Diffstat (limited to '')
-rw-r--r-- | grub-core/commands/i386/pc/drivemap_int13h.S | 124 |
1 files changed, 124 insertions, 0 deletions
diff --git a/grub-core/commands/i386/pc/drivemap_int13h.S b/grub-core/commands/i386/pc/drivemap_int13h.S new file mode 100644 index 0000000..3c87521 --- /dev/null +++ b/grub-core/commands/i386/pc/drivemap_int13h.S @@ -0,0 +1,124 @@ +/* drivemap_int13h.S - interrupt handler for the BIOS drive remapper */ +/* + * GRUB -- GRand Unified Bootloader + * Copyright (C) 2008, 2009 Free Software Foundation, Inc. + * + * GRUB 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, either version 3 of the License, or + * (at your option) any later version. + * + * GRUB is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with GRUB. If not, see <http://www.gnu.org/licenses/>. + */ + +#include <grub/symbol.h> + +#define INT13H_OFFSET(x) ((x) - LOCAL (base)) + +.code16 + +/* Copy starts here. When deployed, this code must be segment-aligned. */ + +/* The replacement int13 handler. Preserve all registers. */ +FUNCTION(grub_drivemap_handler) +LOCAL (base): + /* Save %dx for future restore. */ + push %dx + /* Push flags. Used to simulate interrupt with original flags. */ + pushf + + /* Map the drive number (always in DL). */ + push %ax + push %bx +#ifdef __APPLE__ + LOCAL(mapstart_offset) = INT13H_OFFSET(LOCAL (mapstart)) + movw $LOCAL(mapstart_offset), %bx +#else + movw $INT13H_OFFSET(LOCAL (mapstart)), %bx +#endif + +more_remaining: + movw %cs:(%bx), %ax + cmpb %ah, %al + jz not_found /* DRV=DST => map end - drive not remapped, keep DL. */ + inc %bx + inc %bx + cmpb %dl, %al + jnz more_remaining /* Not found, but more remaining, loop. */ + movb %ah, %dl /* Found - drive remapped, modify DL. */ + +not_found: + pop %bx + pop %ax + + /* If the call isn't ah=0x8 or ah=0x15 we must restore %dx. */ + cmpb $0x8, %ah + jz norestore + cmpb $0x15, %ah + jz norestore + + /* Restore flags. */ + popf + pushf + +#ifdef __APPLE__ + LOCAL(oldhandler_offset) = INT13H_OFFSET (LOCAL (oldhandler)) + lcall *%cs:LOCAL(oldhandler_offset) +#else + lcall *%cs:INT13H_OFFSET (LOCAL (oldhandler)) +#endif + + push %bp + mov %sp, %bp + +tail: + /* Save new flags below %esp so the caller will recieve new flags. */ + pushf + pop %dx + mov %dx, 8(%bp) + + pop %bp + + /* Restore %dx. */ + pop %dx + iret + +norestore: + + /* Restore flags. */ + popf + pushf + +#ifdef __APPLE__ + lcall *%cs:LOCAL(oldhandler_offset) +#else + lcall *%cs:INT13H_OFFSET (LOCAL (oldhandler)) +#endif + + push %bp + mov %sp, %bp + + /* Save %dx. So it won't be restored to original value. */ + mov %dx, 2(%bp) + + jmp tail + +/* Far pointer to the old handler. Stored as a CS:IP in the style of real-mode + IVT entries (thus PI:SC in mem). */ +VARIABLE(grub_drivemap_oldhandler) +LOCAL (oldhandler): + .word 0x0, 0x0 + +/* This label MUST be at the end of the copied block, since the installer code + reserves additional space for mappings at runtime and copies them over it. */ + .align 2 + +VARIABLE(grub_drivemap_mapstart) +LOCAL (mapstart): + .byte 0 |