1 files changed, 120 insertions, 0 deletions

diff --git a/usr.bin/doscmd/callback.c b/usr.bin/doscmd/callback.c
new file mode 100644
index 000000000000..4b333ecc7c37
--- /dev/null
+++ b/usr.bin/doscmd/callback.c
@@ -0,0 +1,120 @@
+/* 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));
+}