mirror of https://github.com/ipxe/ipxe.git
150 lines
4.0 KiB
C
150 lines
4.0 KiB
C
/* Copyright (C) 2006 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., 675 Mass Ave, Cambridge, MA 02139, USA.
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*/
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#include <realmode.h>
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#include <biosint.h>
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#include <basemem.h>
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#include <gpxe/hidemem.h>
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/** Alignment for hidden memory regions */
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#define ALIGN_HIDDEN 4096 /* 4kB page alignment should be enough */
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/**
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* A hidden region of Etherboot
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*
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* This represents a region that will be edited out of the system's
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* memory map.
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*
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* This structure is accessed by assembly code, so must not be
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* changed.
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*/
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struct hidden_region {
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/* Physical start address */
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physaddr_t start;
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/* Physical end address */
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physaddr_t end;
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};
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/**
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* List of hidden regions
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*
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* Must be terminated by a zero entry.
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*/
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struct hidden_region __data16_array ( hidden_regions, [] ) = {
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[TEXT] = { 0, 0 },
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[BASEMEM] = { ( 640 * 1024 ), ( 640 * 1024 ) },
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[EXTMEM] = { 0, 0 },
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{ 0, 0, } /* Terminator */
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};
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#define hidden_regions __use_data16 ( hidden_regions )
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/** Assembly routine in e820mangler.S */
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extern void int15();
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/** Vector for storing original INT 15 handler */
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extern struct segoff __text16 ( int15_vector );
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#define int15_vector __use_text16 ( int15_vector )
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/**
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* Hide region of memory from system memory map
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*
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* @v start Start of region
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* @v end End of region
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*/
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void hide_region ( unsigned int region_id, physaddr_t start, physaddr_t end ) {
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struct hidden_region *region = &hidden_regions[region_id];
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/* Some operating systems get a nasty shock if a region of the
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* E820 map seems to start on a non-page boundary. Make life
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* safer by rounding out our edited region.
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*/
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region->start = ( start & ~( ALIGN_HIDDEN - 1 ) );
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region->end = ( ( end + ALIGN_HIDDEN - 1 ) & ~( ALIGN_HIDDEN - 1 ) );
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DBG ( "Hiding region %d [%lx,%lx)\n",
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region_id, region->start, region->end );
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}
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/**
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* Hide Etherboot text
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*
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*/
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static void hide_text ( void ) {
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/* The linker defines these symbols for us */
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extern char _text[];
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extern char _end[];
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hide_region ( TEXT, virt_to_phys ( _text ), virt_to_phys ( _end ) );
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}
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/**
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* Hide used base memory
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*
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*/
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void hide_basemem ( void ) {
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/* Hide from the top of free base memory to 640kB. Don't use
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* hide_region(), because we don't want this rounded to the
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* nearest page boundary.
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*/
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hidden_regions[BASEMEM].start = ( get_fbms() * 1024 );
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}
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/**
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* Hide Etherboot
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*
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* Installs an INT 15 handler to edit Etherboot out of the memory map
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* returned by the BIOS.
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*/
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void hide_etherboot ( void ) {
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/* Initialise the hidden regions */
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hide_text();
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hide_basemem();
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/* Hook INT 15 */
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hook_bios_interrupt ( 0x15, ( unsigned int ) int15,
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&int15_vector );
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}
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/**
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* Unhide Etherboot
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*
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* Uninstalls the INT 15 handler installed by hide_etherboot(), if
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* possible.
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*/
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void unhide_etherboot ( void ) {
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/* If we have more than one hooked interrupt at this point, it
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* means that some other vector is still hooked, in which case
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* we can't safely unhook INT 15 because we need to keep our
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* memory protected. (We expect there to be at least one
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* hooked interrupt, because INT 15 itself is still hooked).
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*/
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if ( hooked_bios_interrupts > 1 ) {
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DBG ( "Cannot unhide: %d interrupt vectors still hooked\n",
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hooked_bios_interrupts );
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return;
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}
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/* Try to unhook INT 15. If it fails, then just leave it
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* hooked; it takes care of protecting itself. :)
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*/
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unhook_bios_interrupt ( 0x15, ( unsigned int ) int15,
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&int15_vector );
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}
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