usr.bin/doscmd/callback.c

   1 /*
   2  * No copyright?!
   3  *
   4  * $FreeBSD: src/usr.bin/doscmd/callback.c,v 1.2.2.2 2002/04/25 11:04:50 tg Exp $
   5  * $DragonFly: src/usr.bin/doscmd/callback.c,v 1.2 2003/06/17 04:29:25 dillon Exp $
   6  */
   7
   8 #include <sys/queue.h>
   9 #include "doscmd.h"
  10
  11 /*
  12 ** Callbacks are used for chaining interrupt handlers
  13 ** off interrupt vectors
  14 */
  15
  16 struct callback {
  17     LIST_ENTRY(callback) chain;
  18     u_long vec;
  19     callback_t func;
  20     const char *name;
  21 };
  22
  23 LIST_HEAD(cbhead , callback) cbhead[127];
  24
  25 #define CBHASH(x)       (((x) * 17) % 127)
  26
  27 /*
  28 ** Register (func) as a handler for (vec)
  29 */
  30 void
  31 register_callback(u_long vec, callback_t func, const char *name)
  32 {
  33     struct cbhead *head;
  34     struct callback *elm;
  35
  36     elm = malloc(sizeof(struct callback));
  37     elm->vec = vec;
  38     elm->func = func;
  39     elm->name = name;
  40
  41     head = &cbhead[CBHASH(vec)];
  42     LIST_INSERT_HEAD(head, elm, chain);
  43 }
  44
  45 /*
  46 ** Find a handler for (vec)
  47 */
  48 callback_t
  49 find_callback(u_long vec)
  50 {
  51     struct cbhead *head;
  52     struct callback *elm;
  53
  54     head = &cbhead[CBHASH(vec)];
  55     LIST_FOREACH(elm, head, chain)
  56         if (elm->vec == vec)
  57             break;
  58     if (elm) {
  59         debug(D_TRAPS2, "callback %s\n", elm->name);
  60         return (elm->func);
  61     } else
  62         return ((callback_t)0);
  63 }
  64
  65 u_long trampoline_rover = 0xF1000000;
  66
  67 /*
  68  * Interrupts are disabled on an INTn call, so we must restore interrupts
  69  * before via STI returning.  IRET is not used here because 1) some DOS
  70  * calls want to return status via the FLAGS register, and 2) external
  71  * routines which hook INTn calls do not always put a FLAGS image on the
  72  * stack which re-enables interrupts.
  73  */
  74 u_char softint_trampoline[] = {
  75     0xf4,       /* HLT */
  76     0xfb,       /* STI */
  77     0xca,       /* RETF 2 */
  78     2,
  79     0,
  80 };
  81 u_char hardint_trampoline[] = {
  82     0xf4,       /* HLT */
  83     0xcf,       /* IRET */
  84 };
  85 u_char null_trampoline[] = {
  86     0xcf,       /* IRET */
  87 };
  88
  89 u_long
  90 insert_generic_trampoline(size_t len, u_char *p)
  91 {
  92     u_char *q;
  93     u_long where;
  94
  95     where = trampoline_rover;
  96     q = (u_char *)VECPTR(where);
  97     memcpy(q, p, len);
  98     trampoline_rover += len;
  99     return (where);
 100 }
 101
 102 u_long
 103 insert_softint_trampoline(void)
 104 {
 105     return (insert_generic_trampoline(
 106         sizeof(softint_trampoline), softint_trampoline));
 107 }
 108
 109 u_long
 110 insert_hardint_trampoline(void)
 111 {
 112     return (insert_generic_trampoline(
 113         sizeof(hardint_trampoline), hardint_trampoline));
 114 }
 115
 116 u_long
 117 insert_null_trampoline(void)
 118 {
 119     return (insert_generic_trampoline(
 120         sizeof(null_trampoline), null_trampoline));
 121 }