From 9b7a6adfd10bb04f58f98f460efa31238e07f912 Mon Sep 17 00:00:00 2001
From: dfr <dfr@FreeBSD.org>
Date: Sat, 9 Jan 1999 14:15:41 +0000
Subject: Implement support for adding syscalls in KLD modules.

Submitted by: Assar Westerlund <assar@sics.se>
---
 sys/kern/kern_syscalls.c | 94 ++++++++++++++++++++++++++++++++++++++++++++++++
 sys/sys/sysent.h         | 34 ++++++++++++++++--
 2 files changed, 126 insertions(+), 2 deletions(-)
 create mode 100644 sys/kern/kern_syscalls.c

diff --git a/sys/kern/kern_syscalls.c b/sys/kern/kern_syscalls.c
new file mode 100644
index 0000000..e8dc83b
--- /dev/null
+++ b/sys/kern/kern_syscalls.c
@@ -0,0 +1,94 @@
+/*-
+ * Copyright (c) 1999 Assar Westerlund
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ *
+ *     $Id: kern_syscalls.c,v 1.1 1999/01/03 06:00:55 root Exp root $
+ */
+
+#include <sys/param.h>
+#include <sys/kernel.h>
+#include <sys/systm.h>
+#include <sys/malloc.h>
+#include <sys/sysproto.h>
+#include <sys/sysent.h>
+#include <sys/syscall.h>
+#include <sys/module.h>
+#include <sys/linker.h>
+#include <sys/proc.h>
+
+int
+syscall_register(int *offset, struct sysent *new_sysent,
+		 struct sysent *old_sysent)
+{
+       if (*offset == NO_SYSCALL) {
+               int i;
+
+               for (i = 1; i < SYS_MAXSYSCALL; ++i)
+                       if (sysent[i].sy_call == (sy_call_t *)lkmnosys)
+                               break;
+               if (i == SYS_MAXSYSCALL)
+                       return ENFILE;
+               *offset = i;
+       } else if (*offset < 0 || *offset >= SYS_MAXSYSCALL)
+               return EINVAL;
+       else if (sysent[*offset].sy_call != (sy_call_t *)lkmnosys)
+               return EEXIST;
+
+       *old_sysent = sysent[*offset];
+       sysent[*offset] = *new_sysent;
+       return 0;
+}
+
+int
+syscall_deregister(int *offset, struct sysent *old_sysent)
+{
+       if (*offset)
+               sysent[*offset] = *old_sysent;
+       return 0;
+}
+
+int
+syscall_module_handler(struct module *mod, int what, void *arg)
+{
+       struct syscall_module_data *data = (struct syscall_module_data*)arg;
+       int error;
+
+       switch (what) {
+       case MOD_LOAD :
+               error = syscall_register(data->offset, data->new_sysent,
+                                        &data->old_sysent);
+               if (error)
+                       return error;
+               break;
+       case MOD_UNLOAD :
+               error = syscall_deregister(data->offset, &data->old_sysent);
+               if (error)
+                       return error;
+               break;
+       }
+       if (data->chainevh)
+               return data->chainevh(mod, what, data->chainarg);
+       else
+               return 0;
+}
diff --git a/sys/sys/sysent.h b/sys/sys/sysent.h
index 114fe35..9bfc978 100644
--- a/sys/sys/sysent.h
+++ b/sys/sys/sysent.h
@@ -30,7 +30,7 @@
  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  * SUCH DAMAGE.
  *
- *	$Id: sysent.h,v 1.18 1998/06/07 17:13:03 dfr Exp $
+ *	$Id: sysent.h,v 1.19 1998/09/14 05:36:51 jdp Exp $
  */
 
 #ifndef _SYS_SYSENT_H_
@@ -76,6 +76,36 @@ struct sysentvec {
 #ifdef KERNEL
 extern struct sysentvec aout_sysvec;
 extern struct sysent sysent[];
-#endif
+
+#define NO_SYSCALL (-1)
+
+struct module;
+
+struct syscall_module_data {
+       int     (*chainevh)(struct module *, int, void *); /* next handler */
+       void    *chainarg;      /* arg for next event handler */
+       int     *offset;         /* offset into sysent */
+       struct  sysent *new_sysent; /* new sysent */
+       struct  sysent old_sysent; /* old sysent */
+};
+
+#define SYSCALL_MODULE(name, offset, new_sysent, evh, arg)     \
+static struct syscall_module_data name##_syscall_mod = {       \
+       evh, arg, offset, new_sysent                            \
+};                                                             \
+                                                               \
+static moduledata_t name##_mod = {                             \
+       #name,                                                  \
+       syscall_module_handler,                                 \
+       &name##_syscall_mod                                     \
+};                                                             \
+DECLARE_MODULE(name, name##_mod, SI_SUB_DRIVERS, SI_ORDER_MIDDLE)
+
+int    syscall_register __P((int *offset, struct sysent *new_sysent,
+                             struct sysent *old_sysent));
+int    syscall_deregister __P((int *offset, struct sysent *old_sysent));
+int    syscall_module_handler __P((struct module *mod, int what, void *arg));
+
+#endif /* KERNEL */
 
 #endif /* !_SYS_SYSENT_H_ */
-- 
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