minix/kernel/system/do_fork.c

   1 /* The kernel call implemented in this file:
   2  *   m_type:    SYS_FORK
   3  *
   4  * The parameters for this kernel call are:
   5  *   m_lsys_krn_sys_fork.endpt          (parent, process that forked)
   6  *   m_lsys_krn_sys_fork.slot           (child's process table slot)
   7  *   m_lsys_krn_sys_fork.flags          (fork flags)
   8  *   m_krn_lsys_sys_fork.endpt          (endpoint of the child)
   9  *   m_krn_lsys_sys_fork.msgaddr        (new memory map for the child)
  10  */
  11
  12 #include "kernel/system.h"
  13 #include "kernel/vm.h"
  14 #include <signal.h>
  15 #include <string.h>
  16 #include <assert.h>
  17
  18 #include <minix/endpoint.h>
  19 #include <minix/u64.h>
  20
  21 #if USE_FORK
  22
  23 /*===========================================================================*
  24  *                              do_fork                                      *
  25  *===========================================================================*/
  26 int do_fork(struct proc * caller, message * m_ptr)
  27 {
  28 /* Handle sys_fork().
  29  * m_lsys_krn_sys_fork.endpt has forked.
  30  * The child is m_lsys_krn_sys_fork.slot.
  31  */
  32 #if defined(__i386__)
  33   char *old_fpu_save_area_p;
  34 #endif
  35   register struct proc *rpc;            /* child process pointer */
  36   struct proc *rpp;                     /* parent process pointer */
  37   int gen;
  38   int p_proc;
  39   int namelen;
  40
  41   if(!isokendpt(m_ptr->m_lsys_krn_sys_fork.endpt, &p_proc))
  42         return EINVAL;
  43
  44   rpp = proc_addr(p_proc);
  45   rpc = proc_addr(m_ptr->m_lsys_krn_sys_fork.slot);
  46   if (isemptyp(rpp) || ! isemptyp(rpc)) return(EINVAL);
  47
  48   assert(!(rpp->p_misc_flags & MF_DELIVERMSG));
  49
  50   /* needs to be receiving so we know where the message buffer is */
  51   if(!RTS_ISSET(rpp, RTS_RECEIVING)) {
  52         printf("kernel: fork not done synchronously?\n");
  53         return EINVAL;
  54   }
  55
  56   /* make sure that the FPU context is saved in parent before copy */
  57   save_fpu(rpp);
  58   /* Copy parent 'proc' struct to child. And reinitialize some fields. */
  59   gen = _ENDPOINT_G(rpc->p_endpoint);
  60 #if defined(__i386__)
  61   old_fpu_save_area_p = rpc->p_seg.fpu_state;
  62 #endif
  63   *rpc = *rpp;                          /* copy 'proc' struct */
  64 #if defined(__i386__)
  65   rpc->p_seg.fpu_state = old_fpu_save_area_p;
  66   if(proc_used_fpu(rpp))
  67         memcpy(rpc->p_seg.fpu_state, rpp->p_seg.fpu_state, FPU_XFP_SIZE);
  68 #endif
  69   if(++gen >= _ENDPOINT_MAX_GENERATION) /* increase generation */
  70         gen = 1;                        /* generation number wraparound */
  71   rpc->p_nr = m_ptr->m_lsys_krn_sys_fork.slot;  /* this was obliterated by copy */
  72   rpc->p_endpoint = _ENDPOINT(gen, rpc->p_nr);  /* new endpoint of slot */
  73
  74   rpc->p_reg.retreg = 0;        /* child sees pid = 0 to know it is child */
  75   rpc->p_user_time = 0;         /* set all the accounting times to 0 */
  76   rpc->p_sys_time = 0;
  77
  78   rpc->p_misc_flags &=
  79         ~(MF_VIRT_TIMER | MF_PROF_TIMER | MF_SC_TRACE | MF_SPROF_SEEN | MF_STEP);
  80   rpc->p_virt_left = 0;         /* disable, clear the process-virtual timers */
  81   rpc->p_prof_left = 0;
  82
  83   /* Mark process name as being a forked copy */
  84   namelen = strlen(rpc->p_name);
  85 #define FORKSTR "*F"
  86   if(namelen+strlen(FORKSTR) < sizeof(rpc->p_name))
  87         strcat(rpc->p_name, FORKSTR);
  88
  89   /* the child process is not runnable until it's scheduled. */
  90   RTS_SET(rpc, RTS_NO_QUANTUM);
  91   reset_proc_accounting(rpc);
  92
  93   rpc->p_cpu_time_left = 0;
  94   rpc->p_cycles = 0;
  95   rpc->p_kcall_cycles = 0;
  96   rpc->p_kipc_cycles = 0;
  97
  98   rpc->p_tick_cycles = 0;
  99   cpuavg_init(&rpc->p_cpuavg);
 100
 101   /* If the parent is a privileged process, take away the privileges from the
 102    * child process and inhibit it from running by setting the NO_PRIV flag.
 103    * The caller should explicitly set the new privileges before executing.
 104    */
 105   if (priv(rpp)->s_flags & SYS_PROC) {
 106       rpc->p_priv = priv_addr(USER_PRIV_ID);
 107       rpc->p_rts_flags |= RTS_NO_PRIV;
 108   }
 109
 110   /* Calculate endpoint identifier, so caller knows what it is. */
 111   m_ptr->m_krn_lsys_sys_fork.endpt = rpc->p_endpoint;
 112   m_ptr->m_krn_lsys_sys_fork.msgaddr = rpp->p_delivermsg_vir;
 113
 114   /* Don't schedule process in VM mode until it has a new pagetable. */
 115   if(m_ptr->m_lsys_krn_sys_fork.flags & PFF_VMINHIBIT) {
 116         RTS_SET(rpc, RTS_VMINHIBIT);
 117   }
 118
 119   /*
 120    * Only one in group should have RTS_SIGNALED, child doesn't inherit tracing.
 121    */
 122   RTS_UNSET(rpc, (RTS_SIGNALED | RTS_SIG_PENDING | RTS_P_STOP));
 123   (void) sigemptyset(&rpc->p_pending);
 124
 125 #if defined(__i386__)
 126   rpc->p_seg.p_cr3 = 0;
 127   rpc->p_seg.p_cr3_v = NULL;
 128 #elif defined(__arm__)
 129   rpc->p_seg.p_ttbr = 0;
 130   rpc->p_seg.p_ttbr_v = NULL;
 131 #endif
 132
 133   return OK;
 134 }
 135
 136 #endif /* USE_FORK */