kern_syscalls.c

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    1 /*-
    2  * Copyright (c) 1999 Assar Westerlund
    3  * All rights reserved.
    4  *
    5  * Redistribution and use in source and binary forms, with or without
    6  * modification, are permitted provided that the following conditions
    7  * are met:
    8  * 1. Redistributions of source code must retain the above copyright
    9  *    notice, this list of conditions and the following disclaimer.
   10  * 2. Redistributions in binary form must reproduce the above copyright
   11  *    notice, this list of conditions and the following disclaimer in the
   12  *    documentation and/or other materials provided with the distribution.
   13  *
   14  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
   15  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   16  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   17  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
   18  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   19  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   20  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   21  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   22  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   23  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   24  * SUCH DAMAGE.
   25  *
   26  * $FreeBSD$
   27  */
   28 
   29 #include <sys/param.h>
   30 #include <sys/kernel.h>
   31 #include <sys/systm.h>
   32 #include <sys/malloc.h>
   33 #include <sys/sysproto.h>
   34 #include <sys/sysent.h>
   35 #include <sys/syscall.h>
   36 #include <sys/module.h>
   37 #include <sys/linker.h>
   38 #include <sys/proc.h>
   39 
   40 /*
   41  * Acts like "nosys" but can be identified in sysent for dynamic call 
   42  * number assignment for a limited number of calls. 
   43  * 
   44  * Place holder for system call slots reserved for loadable modules.
   45  */     
   46 int
   47 lkmnosys(struct proc *p, struct nosys_args *args)
   48 {
   49         return(nosys(p, args));
   50 }
   51 
   52 int
   53 syscall_register(int *offset, struct sysent *new_sysent,
   54                  struct sysent *old_sysent)
   55 {
   56        if (*offset == NO_SYSCALL) {
   57                int i;
   58 
   59                for (i = 1; i < SYS_MAXSYSCALL; ++i)
   60                        if (sysent[i].sy_call == (sy_call_t *)lkmnosys)
   61                                break;
   62                if (i == SYS_MAXSYSCALL)
   63                        return ENFILE;
   64                *offset = i;
   65        } else if (*offset < 0 || *offset >= SYS_MAXSYSCALL)
   66                return EINVAL;
   67        else if (sysent[*offset].sy_call != (sy_call_t *)lkmnosys)
   68                return EEXIST;
   69 
   70        *old_sysent = sysent[*offset];
   71        sysent[*offset] = *new_sysent;
   72        return 0;
   73 }
   74 
   75 int
   76 syscall_deregister(int *offset, struct sysent *old_sysent)
   77 {
   78        if (*offset)
   79                sysent[*offset] = *old_sysent;
   80        return 0;
   81 }
   82 
   83 int
   84 syscall_module_handler(struct module *mod, int what, void *arg)
   85 {
   86        struct syscall_module_data *data = (struct syscall_module_data*)arg;
   87        modspecific_t ms;
   88        int error;
   89 
   90        switch (what) {
   91        case MOD_LOAD :
   92                error = syscall_register(data->offset, data->new_sysent,
   93                                         &data->old_sysent);
   94                if (error)
   95                        return error;
   96                ms.intval = *data->offset;
   97                module_setspecific(mod, &ms);
   98                break;
   99        case MOD_UNLOAD :
  100                error = syscall_deregister(data->offset, &data->old_sysent);
  101                if (error)
  102                        return error;
  103                break;
  104        }
  105        if (data->chainevh)
  106                return data->chainevh(mod, what, data->chainarg);
  107        else
  108                return 0;
  109 }

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FreeBSD/Linux Kernel Cross Reference sys/kern/kern_syscalls.c

FreeBSD/Linux Kernel Cross Reference
sys/kern/kern_syscalls.c