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