diff options
Diffstat (limited to 'qemu/roms/ipxe/src/arch/i386/image/bootsector.c')
| -rw-r--r-- | qemu/roms/ipxe/src/arch/i386/image/bootsector.c | 137 |
1 files changed, 137 insertions, 0 deletions
diff --git a/qemu/roms/ipxe/src/arch/i386/image/bootsector.c b/qemu/roms/ipxe/src/arch/i386/image/bootsector.c new file mode 100644 index 000000000..9a089e6bb --- /dev/null +++ b/qemu/roms/ipxe/src/arch/i386/image/bootsector.c @@ -0,0 +1,137 @@ +/* + * Copyright (C) 2007 Michael Brown <mbrown@fensystems.co.uk>. + * + * 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; either version 2 of the + * License, or any later version. + * + * This program 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 this program; if not, write to the Free Software + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA + * 02110-1301, USA. + */ + +FILE_LICENCE ( GPL2_OR_LATER ); + +/** + * @file + * + * x86 bootsector image format + * + */ + +#include <errno.h> +#include <realmode.h> +#include <biosint.h> +#include <bootsector.h> +#include <ipxe/console.h> + +/** Vector for storing original INT 18 handler + * + * We do not chain to this vector, so there is no need to place it in + * .text16. + */ +static struct segoff int18_vector; + +/** Vector for storing original INT 19 handler + * + * We do not chain to this vector, so there is no need to place it in + * .text16. + */ +static struct segoff int19_vector; + +/** Restart point for INT 18 or 19 */ +extern void bootsector_exec_fail ( void ); + +/** + * Jump to preloaded bootsector + * + * @v segment Real-mode segment + * @v offset Real-mode offset + * @v drive Drive number to pass to boot sector + * @ret rc Return status code + */ +int call_bootsector ( unsigned int segment, unsigned int offset, + unsigned int drive ) { + int discard_b, discard_D, discard_d; + + /* Reset console, since boot sector will probably use it */ + console_reset(); + + DBG ( "Booting from boot sector at %04x:%04x\n", segment, offset ); + + /* Hook INTs 18 and 19 to capture failure paths */ + hook_bios_interrupt ( 0x18, ( unsigned int ) bootsector_exec_fail, + &int18_vector ); + hook_bios_interrupt ( 0x19, ( unsigned int ) bootsector_exec_fail, + &int19_vector ); + + /* Boot the loaded sector + * + * We assume that the boot sector may completely destroy our + * real-mode stack, so we preserve everything we need in + * static storage. + */ + __asm__ __volatile__ ( REAL_CODE ( /* Save return address off-stack */ + "popw %%cs:saved_retaddr\n\t" + /* Save stack pointer */ + "movw %%ss, %%ax\n\t" + "movw %%ax, %%cs:saved_ss\n\t" + "movw %%sp, %%cs:saved_sp\n\t" + /* Save frame pointer (gcc bug) */ + "movl %%ebp, %%cs:saved_ebp\n\t" + /* Prepare jump to boot sector */ + "pushw %%bx\n\t" + "pushw %%di\n\t" + /* Clear all registers */ + "xorl %%eax, %%eax\n\t" + "xorl %%ebx, %%ebx\n\t" + "xorl %%ecx, %%ecx\n\t" + /* %edx contains drive number */ + "xorl %%esi, %%esi\n\t" + "xorl %%edi, %%edi\n\t" + "xorl %%ebp, %%ebp\n\t" + "movw %%ax, %%ds\n\t" + "movw %%ax, %%es\n\t" + "movw %%ax, %%fs\n\t" + "movw %%ax, %%gs\n\t" + /* Jump to boot sector */ + "sti\n\t" + "lret\n\t" + /* Preserved variables */ + "\nsaved_ebp: .long 0\n\t" + "\nsaved_ss: .word 0\n\t" + "\nsaved_sp: .word 0\n\t" + "\nsaved_retaddr: .word 0\n\t" + /* Boot failure return point */ + "\nbootsector_exec_fail:\n\t" + /* Restore frame pointer (gcc bug) */ + "movl %%cs:saved_ebp, %%ebp\n\t" + /* Restore stack pointer */ + "movw %%cs:saved_ss, %%ax\n\t" + "movw %%ax, %%ss\n\t" + "movw %%cs:saved_sp, %%sp\n\t" + /* Return via saved address */ + "jmp *%%cs:saved_retaddr\n\t" ) + : "=b" ( discard_b ), "=D" ( discard_D ), + "=d" ( discard_d ) + : "b" ( segment ), "D" ( offset ), + "d" ( drive ) + : "eax", "ecx", "esi" ); + + DBG ( "Booted disk returned via INT 18 or 19\n" ); + + /* Unhook INTs 18 and 19 */ + unhook_bios_interrupt ( 0x18, ( unsigned int ) bootsector_exec_fail, + &int18_vector ); + unhook_bios_interrupt ( 0x19, ( unsigned int ) bootsector_exec_fail, + &int19_vector ); + + return -ECANCELED; +} |