90 lines
2.9 KiB
C
90 lines
2.9 KiB
C
/* The kernel call implemented in this file:
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* m_type: SYS_FORK
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*
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* The parameters for this kernel call are:
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* m1_i1: PR_SLOT (child's process table slot)
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* m1_i2: PR_ENDPT (parent, process that forked)
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*/
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#include "../system.h"
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#include <signal.h>
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#if (CHIP == INTEL)
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#include "../protect.h"
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#endif
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#include <minix/endpoint.h>
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#if USE_FORK
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/*===========================================================================*
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* do_fork *
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*===========================================================================*/
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PUBLIC int do_fork(m_ptr)
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register message *m_ptr; /* pointer to request message */
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{
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/* Handle sys_fork(). PR_ENDPT has forked. The child is PR_SLOT. */
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#if (CHIP == INTEL)
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reg_t old_ldt_sel;
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#endif
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register struct proc *rpc; /* child process pointer */
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struct proc *rpp; /* parent process pointer */
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struct mem_map *map_ptr; /* virtual address of map inside caller (PM) */
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int i, gen;
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int p_proc;
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if(!isokendpt(m_ptr->PR_ENDPT, &p_proc))
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return EINVAL;
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rpp = proc_addr(p_proc);
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rpc = proc_addr(m_ptr->PR_SLOT);
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if (isemptyp(rpp) || ! isemptyp(rpc)) return(EINVAL);
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map_ptr= (struct mem_map *) m_ptr->PR_MEM_PTR;
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/* Copy parent 'proc' struct to child. And reinitialize some fields. */
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gen = _ENDPOINT_G(rpc->p_endpoint);
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#if (CHIP == INTEL)
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old_ldt_sel = rpc->p_ldt_sel; /* backup local descriptors */
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*rpc = *rpp; /* copy 'proc' struct */
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rpc->p_ldt_sel = old_ldt_sel; /* restore descriptors */
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#else
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*rpc = *rpp; /* copy 'proc' struct */
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#endif
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if(++gen >= _ENDPOINT_MAX_GENERATION) /* increase generation */
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gen = 1; /* generation number wraparound */
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rpc->p_nr = m_ptr->PR_SLOT; /* this was obliterated by copy */
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rpc->p_endpoint = _ENDPOINT(gen, rpc->p_nr); /* new endpoint of slot */
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/* Only one in group should have SIGNALED, child doesn't inherit tracing. */
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rpc->p_rts_flags &= ~(SIGNALED | SIG_PENDING | P_STOP);
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sigemptyset(&rpc->p_pending);
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rpc->p_reg.retreg = 0; /* child sees pid = 0 to know it is child */
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rpc->p_user_time = 0; /* set all the accounting times to 0 */
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rpc->p_sys_time = 0;
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/* Parent and child have to share the quantum that the forked process had,
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* so that queued processes do not have to wait longer because of the fork.
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* If the time left is odd, the child gets an extra tick.
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*/
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rpc->p_ticks_left = (rpc->p_ticks_left + 1) / 2;
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rpp->p_ticks_left = rpp->p_ticks_left / 2;
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/* If the parent is a privileged process, take away the privileges from the
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* child process and inhibit it from running by setting the NO_PRIV flag.
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* The caller should explicitely set the new privileges before executing.
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*/
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if (priv(rpp)->s_flags & SYS_PROC) {
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rpc->p_priv = priv_addr(USER_PRIV_ID);
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rpc->p_rts_flags |= NO_PRIV;
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}
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/* Calculate endpoint identifier, so caller knows what it is. */
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m_ptr->PR_ENDPT = rpc->p_endpoint;
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/* Install new map */
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return newmap(rpc, map_ptr);
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}
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#endif /* USE_FORK */
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