minix/kernel/system/do_fork.c
2010-04-01 22:22:33 +00:00

135 lines
4.4 KiB
C

/* The kernel call implemented in this file:
* m_type: SYS_FORK
*
* The parameters for this kernel call are:
* m1_i1: PR_ENDPT (parent, process that forked)
* m1_i2: PR_SLOT (child's process table slot)
* m1_p1: PR_MEM_PTR (new memory map for the child)
* m1_i3: PR_FORK_FLAGS (fork flags)
*/
#include "kernel/system.h"
#include "kernel/vm.h"
#include <signal.h>
#include <string.h>
#include <assert.h>
#include <minix/endpoint.h>
#if USE_FORK
/*===========================================================================*
* do_fork *
*===========================================================================*/
PUBLIC int do_fork(struct proc * caller, message * m_ptr)
{
/* Handle sys_fork(). PR_ENDPT has forked. The child is PR_SLOT. */
#if (_MINIX_CHIP == _CHIP_INTEL)
reg_t old_ldt_sel;
void *old_fpu_save_area_p;
#endif
register struct proc *rpc; /* child process pointer */
struct proc *rpp; /* parent process pointer */
struct mem_map *map_ptr; /* virtual address of map inside caller (PM) */
int gen, r;
int p_proc;
if(!isokendpt(m_ptr->PR_ENDPT, &p_proc))
return EINVAL;
rpp = proc_addr(p_proc);
rpc = proc_addr(m_ptr->PR_SLOT);
if (isemptyp(rpp) || ! isemptyp(rpc)) return(EINVAL);
assert(!(rpp->p_misc_flags & MF_DELIVERMSG));
/* needs to be receiving so we know where the message buffer is */
if(!RTS_ISSET(rpp, RTS_RECEIVING)) {
printf("kernel: fork not done synchronously?\n");
return EINVAL;
}
map_ptr= (struct mem_map *) m_ptr->PR_MEM_PTR;
/* Copy parent 'proc' struct to child. And reinitialize some fields. */
gen = _ENDPOINT_G(rpc->p_endpoint);
#if (_MINIX_CHIP == _CHIP_INTEL)
old_ldt_sel = rpc->p_seg.p_ldt_sel; /* backup local descriptors */
old_fpu_save_area_p = rpc->p_fpu_state.fpu_save_area_p;
#endif
*rpc = *rpp; /* copy 'proc' struct */
#if (_MINIX_CHIP == _CHIP_INTEL)
rpc->p_seg.p_ldt_sel = old_ldt_sel; /* restore descriptors */
rpc->p_fpu_state.fpu_save_area_p = old_fpu_save_area_p;
if(rpp->p_misc_flags & MF_FPU_INITIALIZED)
memcpy(rpc->p_fpu_state.fpu_save_area_p,
rpp->p_fpu_state.fpu_save_area_p,
FPU_XFP_SIZE);
#endif
if(++gen >= _ENDPOINT_MAX_GENERATION) /* increase generation */
gen = 1; /* generation number wraparound */
rpc->p_nr = m_ptr->PR_SLOT; /* this was obliterated by copy */
rpc->p_endpoint = _ENDPOINT(gen, rpc->p_nr); /* new endpoint of slot */
rpc->p_reg.retreg = 0; /* child sees pid = 0 to know it is child */
rpc->p_user_time = 0; /* set all the accounting times to 0 */
rpc->p_sys_time = 0;
rpc->p_reg.psw &= ~TRACEBIT; /* clear trace bit */
rpc->p_misc_flags &= ~(MF_VIRT_TIMER | MF_PROF_TIMER | MF_SC_TRACE);
rpc->p_virt_left = 0; /* disable, clear the process-virtual timers */
rpc->p_prof_left = 0;
/* Parent and child have to share the quantum that the forked process had,
* so that queued processes do not have to wait longer because of the fork.
*/
/*
* we want to avoid having processes that loose their quantum without going
* through the standard path where the "out of quantum" is handled. We add
* some more time to such processes.
*
* This is a temporary solution until we are able to handle this in the
* userspace
*/
if (rpp->p_ticks_left < 2)
rpp->p_ticks_left = 2;
rpc->p_ticks_left = rpp->p_ticks_left / 2;
rpp->p_ticks_left = rpp->p_ticks_left / 2;
assert(rpc->p_ticks_left > 0 && rpp->p_ticks_left > 0);
/* If the parent is a privileged process, take away the privileges from the
* child process and inhibit it from running by setting the NO_PRIV flag.
* The caller should explicitely set the new privileges before executing.
*/
if (priv(rpp)->s_flags & SYS_PROC) {
rpc->p_priv = priv_addr(USER_PRIV_ID);
rpc->p_rts_flags |= RTS_NO_PRIV;
}
/* Calculate endpoint identifier, so caller knows what it is. */
m_ptr->PR_ENDPT = rpc->p_endpoint;
m_ptr->PR_FORK_MSGADDR = (char *) rpp->p_delivermsg_vir;
/* Install new map */
r = newmap(caller, rpc, map_ptr);
FIXLINMSG(rpc);
/* Don't schedule process in VM mode until it has a new pagetable. */
if(m_ptr->PR_FORK_FLAGS & PFF_VMINHIBIT) {
RTS_SET(rpc, RTS_VMINHIBIT);
}
/*
* Only one in group should have RTS_SIGNALED, child doesn't inherit tracing.
*/
RTS_UNSET(rpc, (RTS_SIGNALED | RTS_SIG_PENDING | RTS_P_STOP));
sigemptyset(&rpc->p_pending);
return r;
}
#endif /* USE_FORK */