95 lines
2.7 KiB
C
95 lines
2.7 KiB
C
/* 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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*/
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#include "etherboot.h"
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#include "hidemem.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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int hide_etherboot ( void ) {
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if ( mangling ) return 1;
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if ( !mangler ) return 0;
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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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mangling = 1;
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return 1;
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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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#endif /* CODE16 */
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