minix/lib/libc/sys/__sysctl.c

   1 #include <sys/cdefs.h>
   2 #include <lib.h>
   3 #include "namespace.h"
   4 #include "extern.h"
   5 #include <string.h>
   6
   7 /*
   8  * The sysctl(2) system call, handled by the MIB service.
   9  */
  10 int
  11 __sysctl(const int * name, unsigned int namelen, void * oldp, size_t * oldlenp,
  12         const void * newp, size_t newlen)
  13 {
  14         message m;
  15         int r;
  16
  17         memset(&m, 0, sizeof(m));
  18         m.m_lc_mib_sysctl.oldp = (vir_bytes)oldp;
  19         m.m_lc_mib_sysctl.oldlen = (oldlenp != NULL) ? *oldlenp : 0;
  20         m.m_lc_mib_sysctl.newp = (vir_bytes)newp;
  21         m.m_lc_mib_sysctl.newlen = newlen;
  22         m.m_lc_mib_sysctl.namelen = namelen;
  23         m.m_lc_mib_sysctl.namep = (vir_bytes)name;
  24         if (namelen <= CTL_SHORTNAME)
  25                 memcpy(m.m_lc_mib_sysctl.name, name, sizeof(*name) * namelen);
  26
  27         r = _syscall(MIB_PROC_NR, MIB_SYSCTL, &m);
  28
  29         /*
  30          * We copy the NetBSD behavior of replying with the old length also if
  31          * the call failed, typically with ENOMEM.  This is undocumented
  32          * behavior, but unfortunately relied on by sysctl(8) and other NetBSD
  33          * userland code.  If the call failed at the IPC level, the resulting
  34          * value will be garbage, but it should then not be used anyway.
  35          */
  36         if (oldlenp != NULL)
  37                 *oldlenp = m.m_mib_lc_sysctl.oldlen;
  38
  39         return r;
  40 }