123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100101102103104105106107108109110111112113114115116117118119120121122123124125126127128129130131132133134135136137138139140141142143144145146147148149150151152153154155156157158159160161162163164165166167168169170171172173174175176177178179180181182183184185186187188189190191192193194195196197198199200201202203204205206207208209210211212213214215216217218219220 |
- /* 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.
- */
-
- FILE_LICENCE ( GPL2_OR_LATER );
-
- #include <assert.h>
- #include <realmode.h>
- #include <biosint.h>
- #include <basemem.h>
- #include <fakee820.h>
- #include <ipxe/init.h>
- #include <ipxe/io.h>
- #include <ipxe/hidemem.h>
-
- /** Set to true if you want to test a fake E820 map */
- #define FAKE_E820 0
-
- /** Alignment for hidden memory regions */
- #define ALIGN_HIDDEN 4096 /* 4kB page alignment should be enough */
-
- /**
- * A hidden region of iPXE
- *
- * 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 */
- uint64_t start;
- /** Physical end address */
- uint64_t end;
- };
-
- /** Hidden base memory */
- extern struct hidden_region __data16 ( hidemem_base );
- #define hidemem_base __use_data16 ( hidemem_base )
-
- /** Hidden umalloc memory */
- extern struct hidden_region __data16 ( hidemem_umalloc );
- #define hidemem_umalloc __use_data16 ( hidemem_umalloc )
-
- /** Hidden text memory */
- extern struct hidden_region __data16 ( hidemem_textdata );
- #define hidemem_textdata __use_data16 ( hidemem_textdata )
-
- /** 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 )
-
- /* The linker defines these symbols for us */
- extern char _textdata[];
- extern char _etextdata[];
- extern char _text16_memsz[];
- #define _text16_memsz ( ( unsigned int ) _text16_memsz )
- extern char _data16_memsz[];
- #define _data16_memsz ( ( unsigned int ) _data16_memsz )
-
- /**
- * Hide region of memory from system memory map
- *
- * @v region Hidden memory region
- * @v start Start of region
- * @v end End of region
- */
- static void hide_region ( struct hidden_region *region,
- physaddr_t start, physaddr_t end ) {
-
- /* 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 [%llx,%llx)\n", region->start, region->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.
- */
- hidemem_base.start = ( get_fbms() * 1024 );
- }
-
- /**
- * Hide umalloc() region
- *
- */
- void hide_umalloc ( physaddr_t start, physaddr_t end ) {
- assert ( end <= virt_to_phys ( _textdata ) );
- hide_region ( &hidemem_umalloc, start, end );
- }
-
- /**
- * Hide .text and .data
- *
- */
- void hide_textdata ( void ) {
- hide_region ( &hidemem_textdata, virt_to_phys ( _textdata ),
- virt_to_phys ( _etextdata ) );
- }
-
- /**
- * Hide Etherboot
- *
- * Installs an INT 15 handler to edit Etherboot out of the memory map
- * returned by the BIOS.
- */
- static void hide_etherboot ( void ) {
- struct memory_map memmap;
- unsigned int rm_ds_top;
- unsigned int rm_cs_top;
- unsigned int fbms;
-
- /* Dump memory map before mangling */
- DBG ( "Hiding iPXE from system memory map\n" );
- get_memmap ( &memmap );
-
- /* Hook in fake E820 map, if we're testing one */
- if ( FAKE_E820 ) {
- DBG ( "Hooking in fake E820 map\n" );
- fake_e820();
- get_memmap ( &memmap );
- }
-
- /* Initialise the hidden regions */
- hide_basemem();
- hide_umalloc ( virt_to_phys ( _textdata ), virt_to_phys ( _textdata ) );
- hide_textdata();
-
- /* Some really moronic BIOSes bring up the PXE stack via the
- * UNDI loader entry point and then don't bother to unload it
- * before overwriting the code and data segments. If this
- * happens, we really don't want to leave INT 15 hooked,
- * because that will cause any loaded OS to die horribly as
- * soon as it attempts to fetch the system memory map.
- *
- * We use a heuristic to guess whether or not we are being
- * loaded sensibly.
- */
- rm_cs_top = ( ( ( rm_cs << 4 ) + _text16_memsz + 1024 - 1 ) >> 10 );
- rm_ds_top = ( ( ( rm_ds << 4 ) + _data16_memsz + 1024 - 1 ) >> 10 );
- fbms = get_fbms();
- if ( ( rm_cs_top < fbms ) && ( rm_ds_top < fbms ) ) {
- DBG ( "Detected potentially unsafe UNDI load at CS=%04x "
- "DS=%04x FBMS=%dkB\n", rm_cs, rm_ds, fbms );
- DBG ( "Disabling INT 15 memory hiding\n" );
- return;
- }
-
- /* Hook INT 15 */
- hook_bios_interrupt ( 0x15, ( unsigned int ) int15,
- &int15_vector );
-
- /* Dump memory map after mangling */
- DBG ( "Hidden iPXE from system memory map\n" );
- get_memmap ( &memmap );
- }
-
- /**
- * Unhide Etherboot
- *
- * Uninstalls the INT 15 handler installed by hide_etherboot(), if
- * possible.
- */
- static void unhide_etherboot ( int flags __unused ) {
-
- /* 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 );
-
- /* Unhook fake E820 map, if used */
- if ( FAKE_E820 )
- unfake_e820();
- }
-
- /** Hide Etherboot startup function */
- struct startup_fn hide_etherboot_startup_fn __startup_fn ( STARTUP_EARLY ) = {
- .startup = hide_etherboot,
- .shutdown = unhide_etherboot,
- };
|