| 1 | #include <errno.h> |
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| 2 | #include <realmode.h> |
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| 3 | #include <biosint.h> |
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| 4 | |
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| 5 | /** |
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| 6 | * @file BIOS interrupts |
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| 7 | * |
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| 8 | */ |
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| 9 | |
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| 10 | FILE_LICENCE ( GPL2_OR_LATER ); |
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| 11 | |
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| 12 | /** |
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| 13 | * Hook INT vector |
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| 14 | * |
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| 15 | * @v interrupt INT number |
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| 16 | * @v handler Offset within .text16 to interrupt handler |
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| 17 | * @v chain_vector Vector for chaining to previous handler |
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| 18 | * |
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| 19 | * Hooks in an i386 INT handler. The handler itself must reside |
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| 20 | * within the .text16 segment. @c chain_vector will be filled in with |
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| 21 | * the address of the previously-installed handler for this interrupt; |
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| 22 | * the handler should probably exit by ljmping via this vector. |
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| 23 | */ |
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| 24 | void hook_bios_interrupt ( unsigned int interrupt, unsigned int handler, |
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| 25 | struct segoff *chain_vector ) { |
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| 26 | struct segoff vector = { |
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| 27 | .segment = rm_cs, |
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| 28 | .offset = handler, |
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| 29 | }; |
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| 30 | |
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| 31 | DBG ( "Hooking INT %#02x to %04x:%04x\n", |
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| 32 | interrupt, rm_cs, handler ); |
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| 33 | |
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| 34 | if ( ( chain_vector->segment != 0 ) || |
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| 35 | ( chain_vector->offset != 0 ) ) { |
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| 36 | /* Already hooked; do nothing */ |
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| 37 | DBG ( "...already hooked\n" ); |
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| 38 | return; |
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| 39 | } |
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| 40 | |
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| 41 | copy_from_real ( chain_vector, 0, ( interrupt * 4 ), |
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| 42 | sizeof ( *chain_vector ) ); |
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| 43 | DBG ( "...chaining to %04x:%04x\n", |
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| 44 | chain_vector->segment, chain_vector->offset ); |
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| 45 | if ( DBG_LOG ) { |
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| 46 | char code[64]; |
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| 47 | copy_from_real ( code, chain_vector->segment, |
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| 48 | chain_vector->offset, sizeof ( code ) ); |
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| 49 | DBG_HDA ( *chain_vector, code, sizeof ( code ) ); |
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| 50 | } |
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| 51 | |
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| 52 | copy_to_real ( 0, ( interrupt * 4 ), &vector, sizeof ( vector ) ); |
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| 53 | hooked_bios_interrupts++; |
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| 54 | } |
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| 55 | |
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| 56 | /** |
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| 57 | * Unhook INT vector |
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| 58 | * |
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| 59 | * @v interrupt INT number |
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| 60 | * @v handler Offset within .text16 to interrupt handler |
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| 61 | * @v chain_vector Vector containing address of previous handler |
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| 62 | * |
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| 63 | * Unhooks an i386 interrupt handler hooked by hook_i386_vector(). |
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| 64 | * Note that this operation may fail, if some external code has hooked |
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| 65 | * the vector since we hooked in our handler. If it fails, it means |
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| 66 | * that it is not possible to unhook our handler, and we must leave it |
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| 67 | * (and its chaining vector) resident in memory. |
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| 68 | */ |
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| 69 | int unhook_bios_interrupt ( unsigned int interrupt, unsigned int handler, |
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| 70 | struct segoff *chain_vector ) { |
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| 71 | struct segoff vector; |
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| 72 | |
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| 73 | DBG ( "Unhooking INT %#02x from %04x:%04x\n", |
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| 74 | interrupt, rm_cs, handler ); |
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| 75 | |
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| 76 | copy_from_real ( &vector, 0, ( interrupt * 4 ), sizeof ( vector ) ); |
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| 77 | if ( ( vector.segment != rm_cs ) || ( vector.offset != handler ) ) { |
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| 78 | DBG ( "...cannot unhook; vector points to %04x:%04x\n", |
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| 79 | vector.segment, vector.offset ); |
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| 80 | return -EBUSY; |
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| 81 | } |
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| 82 | |
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| 83 | DBG ( "...restoring to %04x:%04x\n", |
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| 84 | chain_vector->segment, chain_vector->offset ); |
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| 85 | copy_to_real ( 0, ( interrupt * 4 ), chain_vector, |
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| 86 | sizeof ( *chain_vector ) ); |
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| 87 | |
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| 88 | chain_vector->segment = 0; |
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| 89 | chain_vector->offset = 0; |
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| 90 | hooked_bios_interrupts--; |
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| 91 | return 0; |
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| 92 | } |
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