/* No copyright?! ** ** $Id: callback.c,v 1.3 1996/09/24 00:02:25 miff Exp $ */ #include <sys/queue.h> #include "doscmd.h" /* ** Callbacks are used for chaining interrupt handlers ** off interrupt vectors */ struct callback { LIST_ENTRY(callback) chain; u_long vec; callback_t func; char *name; }; LIST_HEAD(cbhead , callback) cbhead[127]; #define CBHASH(x) (((x) * 17) % 127) /* ** Register (func) as a handler for (vec) */ void register_callback(u_long vec, callback_t func, char *name) { struct cbhead *head; struct callback *elm; elm = malloc(sizeof(struct callback)); elm->vec = vec; elm->func = func; elm->name = name; head = &cbhead[CBHASH(vec)]; LIST_INSERT_HEAD(head, elm, chain); } /* ** Find a handler for (vec) */ callback_t find_callback(u_long vec) { struct cbhead *head; struct callback *elm; head = &cbhead[CBHASH(vec)]; for (elm = head->lh_first; elm; elm = elm->chain.le_next) if (elm->vec == vec) break; if (elm) { debug(D_TRAPS2, "callback %s\n", elm->name); return (elm->func); } else return ((callback_t)0); } u_long trampoline_rover = 0xF1000000; /* * Interrupts are disabled on an INTn call, so we must restore interrupts * before via STI returning. IRET is not used here because 1) some DOS * calls want to return status via the FLAGS register, and 2) external * routines which hook INTn calls do not always put a FLAGS image on the * stack which re-enables interrupts. */ u_char softint_trampoline[] = { 0xf4, /* HLT */ 0xfb, /* STI */ 0xca, /* RETF 2 */ 2, 0, }; u_char hardint_trampoline[] = { 0xf4, /* HLT */ 0xcf, /* IRET */ }; u_char null_trampoline[] = { 0xcf, /* IRET */ }; u_long insert_generic_trampoline(size_t len, u_char *p) { u_char *q; u_long where; where = trampoline_rover; q = (u_char *)VECPTR(where); memcpy(q, p, len); trampoline_rover += len; return (where); } u_long insert_softint_trampoline(void) { return (insert_generic_trampoline( sizeof(softint_trampoline), softint_trampoline)); } u_long insert_hardint_trampoline(void) { return (insert_generic_trampoline( sizeof(hardint_trampoline), hardint_trampoline)); } u_long insert_null_trampoline(void) { return (insert_generic_trampoline( sizeof(null_trampoline), null_trampoline)); }