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Code to install the new E820 mangler (which doesn't require copying
down to base memory, since it is now in the base-memory-resident .text16 section).
This commit is contained in:
Michael Brown
parent
897313007b
commit
5e80847827
@ -1,94 +1,92 @@
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/* Utility functions to hide Etherboot by manipulating the E820 memory
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* map. These could go in memsizes.c, but are placed here because not
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* all images will need them.
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/* 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 "etherboot.h"
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#include "hidemem.h"
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#include <realmode.h>
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#include <biosint.h>
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#ifdef CODE16
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static int mangling = 0;
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static void *mangler = NULL;
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#define INSTALLED(x) ( (typeof(&x)) ( (void*)(&x) - (void*)e820mangler \
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+ mangler ) )
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#define intercept_int15 INSTALLED(_intercept_int15)
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#define intercepted_int15 INSTALLED(_intercepted_int15)
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#define hide_memory INSTALLED(_hide_memory)
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#define INT15_VECTOR ( (segoff_t*) ( phys_to_virt( 4 * 0x15 ) ) )
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int install_e820mangler ( void *new_mangler ) {
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if ( mangling ) return 0;
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memcpy ( new_mangler, &e820mangler, e820mangler_size );
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mangler = new_mangler;
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return 1;
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}
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/* Intercept INT15 calls and pass them through the mangler. The
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* mangler must have been copied to base memory before making this
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* call, and "mangler" must point to the base memory copy, which must
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* be 16-byte aligned.
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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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int hide_etherboot ( void ) {
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if ( mangling ) return 1;
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if ( !mangler ) return 0;
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struct hidden_region {
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/* Physical start address */
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uint32_t start;
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/* Physical end address */
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uint32_t end;
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};
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/* Hook INT15 handler */
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*intercepted_int15 = *INT15_VECTOR;
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(*hide_memory)[0].start = virt_to_phys(_text);
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(*hide_memory)[0].length = _end - _text;
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/* IMPORTANT, possibly even FIXME:
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*
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* Etherboot has a tendency to claim a very large area of
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* memory as possible heap; enough to make it impossible to
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* load an OS if we hide all of it. We hide only the portion
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* that's currently in use. This means that we MUST NOT
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* perform further allocations from the heap while the mangler
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* is active.
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*/
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(*hide_memory)[1].start = heap_ptr;
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(*hide_memory)[1].length = heap_bot - heap_ptr;
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INT15_VECTOR->segment = SEGMENT(mangler);
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INT15_VECTOR->offset = 0;
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/* Linker-defined symbols */
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extern char _text[];
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extern char _end[];
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mangling = 1;
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return 1;
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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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* Unique IDs for hidden regions
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*/
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enum {
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TEXT = 0,
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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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{ 0, 0, } /* Terminator */
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};
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#define hidden_regions __use_data16 ( hidden_regions )
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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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hidden_regions[TEXT].start = virt_to_phys ( _text );
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hidden_regions[TEXT].end = virt_to_phys ( _end );
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DBG ( "Hiding [%x,%x)\n", hidden_regions[TEXT].start,
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hidden_regions[TEXT].end );
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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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int unhide_etherboot ( void ) {
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if ( !mangling ) return 1;
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/* Restore original INT15 handler
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*/
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if ( VIRTUAL(INT15_VECTOR->segment,INT15_VECTOR->offset) != mangler ) {
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/* Oh dear... */
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#ifdef WORK_AROUND_BPBATCH_BUG
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/* BpBatch intercepts INT15, so can't unhook it, and
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* then proceeds to ignore our PXENV_KEEP_UNDI return
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* status, which means that it ends up zeroing out the
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* INT15 handler routine.
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*
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* This rather ugly hack involves poking into
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* BpBatch's code and changing it's stored value for
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* the "next handler" in the INT15 chain.
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*/
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segoff_t *bp_chain = VIRTUAL ( 0x0060, 0x8254 );
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if ( ( bp_chain->segment == SEGMENT(mangler) ) &&
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( bp_chain->offset == 0 ) ) {
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printf ( "\nBPBATCH bug workaround enabled\n" );
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*bp_chain = *intercepted_int15;
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}
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#endif /* WORK_AROUND_BPBATCH_BUG */
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return 0;
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}
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*INT15_VECTOR = *intercepted_int15;
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mangling = 0;
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return 1;
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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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unhook_bios_interrupt ( 0x15, ( unsigned int ) int15,
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&int15_vector );
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}
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#endif /* CODE16 */
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