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/* Utility functions to hide Etherboot by manipulating the E820 memory
* map. These could go in memsizes.c, but are placed here because not
* all images will need them.
*/
#include "etherboot.h"
#include "hidemem.h"
#ifdef CODE16
static int mangling = 0;
static void *mangler = NULL;
#define INSTALLED(x) ( (typeof(&x)) ( (void*)(&x) - (void*)e820mangler \
+ mangler ) )
#define intercept_int15 INSTALLED(_intercept_int15)
#define intercepted_int15 INSTALLED(_intercepted_int15)
#define hide_memory INSTALLED(_hide_memory)
#define INT15_VECTOR ( (segoff_t*) ( phys_to_virt( 4 * 0x15 ) ) )
int install_e820mangler ( void *new_mangler ) {
if ( mangling ) return 0;
memcpy ( new_mangler, &e820mangler, e820mangler_size );
mangler = new_mangler;
return 1;
}
/* Intercept INT15 calls and pass them through the mangler. The
* mangler must have been copied to base memory before making this
* call, and "mangler" must point to the base memory copy, which must
* be 16-byte aligned.
*/
int hide_etherboot ( void ) {
if ( mangling ) return 1;
if ( !mangler ) return 0;
/* Hook INT15 handler */
*intercepted_int15 = *INT15_VECTOR;
(*hide_memory)[0].start = virt_to_phys(_text);
(*hide_memory)[0].length = _end - _text;
/* IMPORTANT, possibly even FIXME:
*
* Etherboot has a tendency to claim a very large area of
* memory as possible heap; enough to make it impossible to
* load an OS if we hide all of it. We hide only the portion
* that's currently in use. This means that we MUST NOT
* perform further allocations from the heap while the mangler
* is active.
*/
(*hide_memory)[1].start = heap_ptr;
(*hide_memory)[1].length = heap_bot - heap_ptr;
INT15_VECTOR->segment = SEGMENT(mangler);
INT15_VECTOR->offset = 0;
mangling = 1;
return 1;
}
int unhide_etherboot ( void ) {
if ( !mangling ) return 1;
/* Restore original INT15 handler
*/
if ( VIRTUAL(INT15_VECTOR->segment,INT15_VECTOR->offset) != mangler ) {
/* Oh dear... */
#ifdef WORK_AROUND_BPBATCH_BUG
/* BpBatch intercepts INT15, so can't unhook it, and
* then proceeds to ignore our PXENV_KEEP_UNDI return
* status, which means that it ends up zeroing out the
* INT15 handler routine.
*
* This rather ugly hack involves poking into
* BpBatch's code and changing it's stored value for
* the "next handler" in the INT15 chain.
*/
segoff_t *bp_chain = VIRTUAL ( 0x0060, 0x8254 );
if ( ( bp_chain->segment == SEGMENT(mangler) ) &&
( bp_chain->offset == 0 ) ) {
printf ( "\nBPBATCH bug workaround enabled\n" );
*bp_chain = *intercepted_int15;
}
#endif /* WORK_AROUND_BPBATCH_BUG */
return 0;
}
*INT15_VECTOR = *intercepted_int15;
mangling = 0;
return 1;
}
#endif /* CODE16 */
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