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- #include <errno.h>
- #include <realmode.h>
- #include <biosint.h>
-
- /**
- * @file BIOS interrupts
- *
- */
-
- FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
-
- /**
- * Hook INT vector
- *
- * @v interrupt INT number
- * @v handler Offset within .text16 to interrupt handler
- * @v chain_vector Vector for chaining to previous handler
- *
- * Hooks in an i386 INT handler. The handler itself must reside
- * within the .text16 segment. @c chain_vector will be filled in with
- * the address of the previously-installed handler for this interrupt;
- * the handler should probably exit by ljmping via this vector.
- */
- void hook_bios_interrupt ( unsigned int interrupt, unsigned int handler,
- struct segoff *chain_vector ) {
- struct segoff vector = {
- .segment = rm_cs,
- .offset = handler,
- };
-
- DBG ( "Hooking INT %#02x to %04x:%04x\n",
- interrupt, rm_cs, handler );
-
- if ( ( chain_vector->segment != 0 ) ||
- ( chain_vector->offset != 0 ) ) {
- /* Already hooked; do nothing */
- DBG ( "...already hooked\n" );
- return;
- }
-
- copy_from_real ( chain_vector, 0, ( interrupt * 4 ),
- sizeof ( *chain_vector ) );
- DBG ( "...chaining to %04x:%04x\n",
- chain_vector->segment, chain_vector->offset );
- if ( DBG_LOG ) {
- char code[64];
- copy_from_real ( code, chain_vector->segment,
- chain_vector->offset, sizeof ( code ) );
- DBG_HDA ( *chain_vector, code, sizeof ( code ) );
- }
-
- copy_to_real ( 0, ( interrupt * 4 ), &vector, sizeof ( vector ) );
- hooked_bios_interrupts++;
- }
-
- /**
- * Unhook INT vector
- *
- * @v interrupt INT number
- * @v handler Offset within .text16 to interrupt handler
- * @v chain_vector Vector containing address of previous handler
- *
- * Unhooks an i386 interrupt handler hooked by hook_i386_vector().
- * Note that this operation may fail, if some external code has hooked
- * the vector since we hooked in our handler. If it fails, it means
- * that it is not possible to unhook our handler, and we must leave it
- * (and its chaining vector) resident in memory.
- */
- int unhook_bios_interrupt ( unsigned int interrupt, unsigned int handler,
- struct segoff *chain_vector ) {
- struct segoff vector;
-
- DBG ( "Unhooking INT %#02x from %04x:%04x\n",
- interrupt, rm_cs, handler );
-
- copy_from_real ( &vector, 0, ( interrupt * 4 ), sizeof ( vector ) );
- if ( ( vector.segment != rm_cs ) || ( vector.offset != handler ) ) {
- DBG ( "...cannot unhook; vector points to %04x:%04x\n",
- vector.segment, vector.offset );
- return -EBUSY;
- }
-
- DBG ( "...restoring to %04x:%04x\n",
- chain_vector->segment, chain_vector->offset );
- copy_to_real ( 0, ( interrupt * 4 ), chain_vector,
- sizeof ( *chain_vector ) );
-
- chain_vector->segment = 0;
- chain_vector->offset = 0;
- hooked_bios_interrupts--;
- return 0;
- }
-
- /**
- * Dump changes to interrupt vector table (for debugging)
- *
- */
- void check_bios_interrupts ( void ) {
- static struct segoff vectors[256];
- static uint8_t initialised;
- struct segoff vector;
- unsigned int i;
-
- /* Print any changed interrupt vectors */
- for ( i = 0; i < ( sizeof ( vectors ) / sizeof ( vectors[0] ) ); i++ ) {
- copy_from_real ( &vector, 0, ( i * sizeof ( vector ) ),
- sizeof ( vector ) );
- if ( memcmp ( &vector, &vectors[i], sizeof ( vector ) ) == 0 )
- continue;
- if ( initialised ) {
- dbg_printf ( "INT %02x changed %04x:%04x => "
- "%04x:%04x\n", i, vectors[i].segment,
- vectors[i].offset, vector.segment,
- vector.offset );
- }
- memcpy ( &vectors[i], &vector, sizeof ( vectors[i] ) );
- }
- initialised = 1;
- }
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