289 lines
11 KiB
C
289 lines
11 KiB
C
/* This file deals with creating processes (via FORK) and deleting them (via
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* EXIT/WAIT). When a process forks, a new slot in the 'mproc' table is
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* allocated for it, and a copy of the parent's core image is made for the
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* child. Then the kernel and file system are informed. A process is removed
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* from the 'mproc' table when two events have occurred: (1) it has exited or
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* been killed by a signal, and (2) the parent has done a WAIT. If the process
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* exits first, it continues to occupy a slot until the parent does a WAIT.
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*
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* The entry points into this file are:
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* do_fork: perform the FORK system call
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* do_mm_exit: perform the EXIT system call (by calling mm_exit())
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* mm_exit: actually do the exiting
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* do_wait: perform the WAITPID or WAIT system call
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*/
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#include "mm.h"
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#include <sys/wait.h>
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#include <minix/callnr.h>
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#include <minix/com.h>
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#include <minix/utils.h>
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#include <signal.h>
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#include "mproc.h"
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#include "param.h"
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#define LAST_FEW 2 /* last few slots reserved for superuser */
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PRIVATE pid_t next_pid = INIT_PID+1; /* next pid to be assigned */
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FORWARD _PROTOTYPE (void cleanup, (register struct mproc *child) );
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/*===========================================================================*
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* do_fork *
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*===========================================================================*/
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PUBLIC int do_fork()
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{
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/* The process pointed to by 'mp' has forked. Create a child process. */
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register struct mproc *rmp; /* pointer to parent */
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register struct mproc *rmc; /* pointer to child */
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int i, child_nr, t;
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phys_clicks prog_clicks, child_base;
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phys_bytes prog_bytes, parent_abs, child_abs; /* Intel only */
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/* If tables might fill up during FORK, don't even start since recovery half
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* way through is such a nuisance.
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*/
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rmp = mp;
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if ((procs_in_use == NR_PROCS) ||
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(procs_in_use >= NR_PROCS-LAST_FEW && rmp->mp_effuid != 0))
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{
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printf("MM: proc table full!\n");
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return(EAGAIN);
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}
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/* Determine how much memory to allocate. Only the data and stack need to
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* be copied, because the text segment is either shared or of zero length.
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*/
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prog_clicks = (phys_clicks) rmp->mp_seg[S].mem_len;
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prog_clicks += (rmp->mp_seg[S].mem_vir - rmp->mp_seg[D].mem_vir);
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prog_bytes = (phys_bytes) prog_clicks << CLICK_SHIFT;
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if ( (child_base = alloc_mem(prog_clicks)) == NO_MEM) return(ENOMEM);
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/* Create a copy of the parent's core image for the child. */
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child_abs = (phys_bytes) child_base << CLICK_SHIFT;
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parent_abs = (phys_bytes) rmp->mp_seg[D].mem_phys << CLICK_SHIFT;
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i = sys_abscopy(parent_abs, child_abs, prog_bytes);
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if (i < 0) panic("do_fork can't copy", i);
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/* Find a slot in 'mproc' for the child process. A slot must exist. */
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for (rmc = &mproc[0]; rmc < &mproc[NR_PROCS]; rmc++)
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if ( (rmc->mp_flags & IN_USE) == 0) break;
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/* Set up the child and its memory map; copy its 'mproc' slot from parent. */
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child_nr = (int)(rmc - mproc); /* slot number of the child */
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procs_in_use++;
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*rmc = *rmp; /* copy parent's process slot to child's */
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rmc->mp_parent = who; /* record child's parent */
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rmc->mp_flags &= (IN_USE|SEPARATE); /* inherit only these flags */
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/* A separate I&D child keeps the parents text segment. The data and stack
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* segments must refer to the new copy.
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*/
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if (!(rmc->mp_flags & SEPARATE)) rmc->mp_seg[T].mem_phys = child_base;
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rmc->mp_seg[D].mem_phys = child_base;
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rmc->mp_seg[S].mem_phys = rmc->mp_seg[D].mem_phys +
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(rmp->mp_seg[S].mem_vir - rmp->mp_seg[D].mem_vir);
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rmc->mp_exitstatus = 0;
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rmc->mp_sigstatus = 0;
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/* Find a free pid for the child and put it in the table. */
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do {
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t = 0; /* 't' = 0 means pid still free */
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next_pid = (next_pid < 30000 ? next_pid + 1 : INIT_PID + 1);
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for (rmp = &mproc[0]; rmp < &mproc[NR_PROCS]; rmp++)
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if (rmp->mp_pid == next_pid || rmp->mp_procgrp == next_pid) {
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t = 1;
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break;
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}
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rmc->mp_pid = next_pid; /* assign pid to child */
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} while (t);
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/* Tell kernel and file system about the (now successful) FORK. */
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sys_fork(who, child_nr, rmc->mp_pid);
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tell_fs(FORK, who, child_nr, rmc->mp_pid);
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/* Report child's memory map to kernel. */
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sys_newmap(child_nr, rmc->mp_seg);
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/* Reply to child to wake it up. */
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setreply(child_nr, 0);
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return(next_pid); /* child's pid */
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}
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/*===========================================================================*
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* do_mm_exit *
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*===========================================================================*/
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PUBLIC int do_mm_exit()
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{
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/* Perform the exit(status) system call. The real work is done by mm_exit(),
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* which is also called when a process is killed by a signal.
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*/
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mm_exit(mp, m_in.status);
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return(SUSPEND); /* can't communicate from beyond the grave */
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}
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/*===========================================================================*
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* mm_exit *
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*===========================================================================*/
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PUBLIC void mm_exit(rmp, exit_status)
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register struct mproc *rmp; /* pointer to the process to be terminated */
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int exit_status; /* the process' exit status (for parent) */
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{
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/* A process is done. Release most of the process' possessions. If its
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* parent is waiting, release the rest, else keep the process slot and
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* become a zombie.
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*/
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register int proc_nr;
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int parent_waiting, right_child;
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pid_t pidarg, procgrp;
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struct mproc *p_mp;
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proc_nr = (int) (rmp - mproc); /* get process slot number */
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/* Remember a session leader's process group. */
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procgrp = (rmp->mp_pid == mp->mp_procgrp) ? mp->mp_procgrp : 0;
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/* If the exited process has a timer pending, kill it. */
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if (rmp->mp_flags & ALARM_ON) set_alarm(proc_nr, (unsigned) 0);
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/* Tell the kernel and FS that the process is no longer runnable. */
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tell_fs(EXIT, proc_nr, 0, 0); /* file system can free the proc slot */
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sys_xit(rmp->mp_parent, proc_nr);
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/* Release the memory occupied by the child. */
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if (find_share(rmp, rmp->mp_ino, rmp->mp_dev, rmp->mp_ctime) == NULL) {
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/* No other process shares the text segment, so free it. */
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free_mem(rmp->mp_seg[T].mem_phys, rmp->mp_seg[T].mem_len);
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}
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/* Free the data and stack segments. */
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free_mem(rmp->mp_seg[D].mem_phys,
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rmp->mp_seg[S].mem_vir + rmp->mp_seg[S].mem_len - rmp->mp_seg[D].mem_vir);
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/* The process slot can only be freed if the parent has done a WAIT. */
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rmp->mp_exitstatus = (char) exit_status;
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p_mp = &mproc[rmp->mp_parent]; /* process' parent */
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pidarg = p_mp->mp_wpid; /* who's being waited for? */
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parent_waiting = p_mp->mp_flags & WAITING;
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right_child = /* child meets one of the 3 tests? */
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(pidarg == -1 || pidarg == rmp->mp_pid || -pidarg == rmp->mp_procgrp);
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if (parent_waiting && right_child) {
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cleanup(rmp); /* tell parent and release child slot */
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} else {
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rmp->mp_flags = IN_USE|ZOMBIE; /* parent not waiting, zombify child */
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sig_proc(p_mp, SIGCHLD); /* send parent a "child died" signal */
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}
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/* If the process has children, disinherit them. INIT is the new parent. */
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for (rmp = &mproc[0]; rmp < &mproc[NR_PROCS]; rmp++) {
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if (rmp->mp_flags & IN_USE && rmp->mp_parent == proc_nr) {
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/* 'rmp' now points to a child to be disinherited. */
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rmp->mp_parent = INIT_PROC_NR;
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parent_waiting = mproc[INIT_PROC_NR].mp_flags & WAITING;
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if (parent_waiting && (rmp->mp_flags & ZOMBIE)) cleanup(rmp);
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}
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}
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/* Send a hangup to the process' process group if it was a session leader. */
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if (procgrp != 0) check_sig(-procgrp, SIGHUP);
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}
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/*===========================================================================*
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* do_waitpid *
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*===========================================================================*/
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PUBLIC int do_waitpid()
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{
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/* A process wants to wait for a child to terminate. If one is already waiting,
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* go clean it up and let this WAIT call terminate. Otherwise, really wait.
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* Both WAIT and WAITPID are handled by this code.
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*/
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register struct mproc *rp;
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int pidarg, options, children;
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/* A process calling WAIT never gets a reply in the usual way at the end
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* of the main loop (unless WNOHANG is set or no qualifying child exists).
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* If a child has already exited, the routine cleanup() sends the reply
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* to awaken the caller.
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*/
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/* Set internal variables, depending on whether this is WAIT or WAITPID. */
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pidarg = (call_nr == WAIT ? -1 : m_in.pid); /* 1st param of waitpid */
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options = (call_nr == WAIT ? 0 : m_in.sig_nr); /* 3rd param of waitpid */
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if (pidarg == 0) pidarg = -mp->mp_procgrp; /* pidarg < 0 ==> proc grp */
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/* Is there a child waiting to be collected? At this point, pidarg != 0:
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* pidarg > 0 means pidarg is pid of a specific process to wait for
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* pidarg == -1 means wait for any child
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* pidarg < -1 means wait for any child whose process group = -pidarg
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*/
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children = 0;
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for (rp = &mproc[0]; rp < &mproc[NR_PROCS]; rp++) {
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if ( (rp->mp_flags & IN_USE) && rp->mp_parent == who) {
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/* The value of pidarg determines which children qualify. */
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if (pidarg > 0 && pidarg != rp->mp_pid) continue;
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if (pidarg < -1 && -pidarg != rp->mp_procgrp) continue;
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children++; /* this child is acceptable */
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if (rp->mp_flags & ZOMBIE) {
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/* This child meets the pid test and has exited. */
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cleanup(rp); /* this child has already exited */
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return(SUSPEND);
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}
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if ((rp->mp_flags & STOPPED) && rp->mp_sigstatus) {
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/* This child meets the pid test and is being traced.*/
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mp->mp_reply.reply_res2 = 0177|(rp->mp_sigstatus << 8);
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rp->mp_sigstatus = 0;
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return(rp->mp_pid);
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}
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}
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}
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/* No qualifying child has exited. Wait for one, unless none exists. */
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if (children > 0) {
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/* At least 1 child meets the pid test exists, but has not exited. */
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if (options & WNOHANG) return(0); /* parent does not want to wait */
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mp->mp_flags |= WAITING; /* parent wants to wait */
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mp->mp_wpid = (pid_t) pidarg; /* save pid for later */
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return(SUSPEND); /* do not reply, let it wait */
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} else {
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/* No child even meets the pid test. Return error immediately. */
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return(ECHILD); /* no - parent has no children */
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}
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}
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/*===========================================================================*
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* cleanup *
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*===========================================================================*/
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PRIVATE void cleanup(child)
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register struct mproc *child; /* tells which process is exiting */
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{
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/* Finish off the exit of a process. The process has exited or been killed
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* by a signal, and its parent is waiting.
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*/
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struct mproc *parent = &mproc[child->mp_parent];
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int exitstatus;
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/* Wake up the parent. */
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exitstatus = (child->mp_exitstatus << 8) | (child->mp_sigstatus & 0377);
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parent->mp_reply.reply_res2 = exitstatus;
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setreply(child->mp_parent, child->mp_pid);
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parent->mp_flags &= ~WAITING; /* parent no longer waiting */
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/* Release the process table entry. */
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child->mp_flags = 0;
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procs_in_use--;
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}
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