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https://github.com/xcat2/xNBA.git
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Michael Brown
cba22d36b7
Commit 238050d ("[build] Work around bug in gcc >= 4.8") works around
one instance of a bug in recent versions of gcc, in which "ebp" cannot
be specified within an asm clobber list.
Some versions of gcc seem to exhibit the same bug on other points in
the codebase. Fix by changing all instances of "ebp" in a clobber
list to use the push/pop %ebp workaround instead.
Originally-implemented-by: Víctor Román Archidona <contacto@victor-roman.es>
Signed-off-by: Michael Brown <mcb30@ipxe.org>
134 lines
4.0 KiB
C
134 lines
4.0 KiB
C
/*
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* Copyright (C) 2007 Michael Brown <mbrown@fensystems.co.uk>.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License as
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* published by the Free Software Foundation; either version 2 of the
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* License, or any later version.
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*
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* This program is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
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* 02110-1301, USA.
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*/
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FILE_LICENCE ( GPL2_OR_LATER );
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/**
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* @file
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*
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* x86 bootsector image format
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*
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*/
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#include <errno.h>
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#include <realmode.h>
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#include <biosint.h>
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#include <bootsector.h>
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/** Vector for storing original INT 18 handler
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*
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* We do not chain to this vector, so there is no need to place it in
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* .text16.
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*/
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static struct segoff int18_vector;
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/** Vector for storing original INT 19 handler
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*
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* We do not chain to this vector, so there is no need to place it in
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* .text16.
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*/
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static struct segoff int19_vector;
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/** Restart point for INT 18 or 19 */
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extern void bootsector_exec_fail ( void );
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/**
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* Jump to preloaded bootsector
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*
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* @v segment Real-mode segment
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* @v offset Real-mode offset
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* @v drive Drive number to pass to boot sector
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* @ret rc Return status code
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*/
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int call_bootsector ( unsigned int segment, unsigned int offset,
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unsigned int drive ) {
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int discard_b, discard_D, discard_d;
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DBG ( "Booting from boot sector at %04x:%04x\n", segment, offset );
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/* Hook INTs 18 and 19 to capture failure paths */
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hook_bios_interrupt ( 0x18, ( unsigned int ) bootsector_exec_fail,
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&int18_vector );
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hook_bios_interrupt ( 0x19, ( unsigned int ) bootsector_exec_fail,
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&int19_vector );
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/* Boot the loaded sector
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*
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* We assume that the boot sector may completely destroy our
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* real-mode stack, so we preserve everything we need in
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* static storage.
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*/
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__asm__ __volatile__ ( REAL_CODE ( /* Save return address off-stack */
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"popw %%cs:saved_retaddr\n\t"
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/* Save stack pointer */
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"movw %%ss, %%ax\n\t"
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"movw %%ax, %%cs:saved_ss\n\t"
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"movw %%sp, %%cs:saved_sp\n\t"
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/* Save frame pointer (gcc bug) */
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"movl %%ebp, %%cs:saved_ebp\n\t"
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/* Prepare jump to boot sector */
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"pushw %%bx\n\t"
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"pushw %%di\n\t"
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/* Clear all registers */
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"xorl %%eax, %%eax\n\t"
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"xorl %%ebx, %%ebx\n\t"
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"xorl %%ecx, %%ecx\n\t"
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/* %edx contains drive number */
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"xorl %%esi, %%esi\n\t"
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"xorl %%edi, %%edi\n\t"
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"xorl %%ebp, %%ebp\n\t"
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"movw %%ax, %%ds\n\t"
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"movw %%ax, %%es\n\t"
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"movw %%ax, %%fs\n\t"
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"movw %%ax, %%gs\n\t"
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/* Jump to boot sector */
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"sti\n\t"
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"lret\n\t"
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/* Preserved variables */
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"\nsaved_ebp: .long 0\n\t"
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"\nsaved_ss: .word 0\n\t"
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"\nsaved_sp: .word 0\n\t"
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"\nsaved_retaddr: .word 0\n\t"
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/* Boot failure return point */
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"\nbootsector_exec_fail:\n\t"
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/* Restore frame pointer (gcc bug) */
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"movl %%cs:saved_ebp, %%ebp\n\t"
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/* Restore stack pointer */
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"movw %%cs:saved_ss, %%ax\n\t"
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"movw %%ax, %%ss\n\t"
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"movw %%cs:saved_sp, %%sp\n\t"
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/* Return via saved address */
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"jmp *%%cs:saved_retaddr\n\t" )
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: "=b" ( discard_b ), "=D" ( discard_D ),
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"=d" ( discard_d )
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: "b" ( segment ), "D" ( offset ),
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"d" ( drive )
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: "eax", "ecx", "esi" );
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DBG ( "Booted disk returned via INT 18 or 19\n" );
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/* Unhook INTs 18 and 19 */
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unhook_bios_interrupt ( 0x18, ( unsigned int ) bootsector_exec_fail,
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&int18_vector );
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unhook_bios_interrupt ( 0x19, ( unsigned int ) bootsector_exec_fail,
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&int19_vector );
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return -ECANCELED;
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}
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