128 lines
2.7 KiB
C
128 lines
2.7 KiB
C
#include <u.h>
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#include <sys/wait.h>
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#include <signal.h>
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#include <libc.h>
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#undef rfork
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static void
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nop(int x)
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{
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USED(x);
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}
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int
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p9rfork(int flags)
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{
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int pid, status;
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int p[2];
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int n;
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char buf[128], *q;
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extern char **environ;
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struct sigaction oldchld;
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memset(&oldchld, 0, sizeof oldchld);
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if((flags&(RFPROC|RFFDG|RFMEM)) == (RFPROC|RFFDG)){
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/* check other flags before we commit */
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flags &= ~(RFPROC|RFFDG|RFENVG);
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n = (flags & ~(RFNOTEG|RFNAMEG|RFNOWAIT|RFCENVG));
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if(n){
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werrstr("unknown flags %08ux in rfork", n);
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return -1;
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}
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if(flags&RFNOWAIT){
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sigaction(SIGCHLD, nil, &oldchld);
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signal(SIGCHLD, nop);
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if(pipe(p) < 0)
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return -1;
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}
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pid = fork();
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if(pid == -1)
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return -1;
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if(flags&RFNOWAIT){
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flags &= ~RFNOWAIT;
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if(pid){
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/*
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* Parent - wait for child to fork wait-free child.
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* Then read pid from pipe. Assume pipe buffer can absorb the write.
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*/
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close(p[1]);
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status = 0;
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if(wait4(pid, &status, 0, 0) < 0){
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werrstr("pipe dance - wait4 - %r");
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close(p[0]);
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return -1;
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}
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n = readn(p[0], buf, sizeof buf-1);
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close(p[0]);
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if(!WIFEXITED(status) || WEXITSTATUS(status)!=0 || n <= 0){
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if(!WIFEXITED(status))
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werrstr("pipe dance - !exited 0x%ux", status);
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else if(WEXITSTATUS(status) != 0)
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werrstr("pipe dance - non-zero status 0x%ux", status);
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else if(n < 0)
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werrstr("pipe dance - pipe read error - %r");
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else if(n == 0)
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werrstr("pipe dance - pipe read eof");
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else
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werrstr("pipe dance - unknown failure");
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return -1;
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}
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buf[n] = 0;
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if(buf[0] == 'x'){
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werrstr("%s", buf+2);
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return -1;
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}
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pid = strtol(buf, &q, 0);
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}else{
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/*
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* Child - fork a new child whose wait message can't
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* get back to the parent because we're going to exit!
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*/
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signal(SIGCHLD, SIG_IGN);
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close(p[0]);
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pid = fork();
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if(pid){
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/* Child parent - send status over pipe and exit. */
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if(pid > 0)
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fprint(p[1], "%d", pid);
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else
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fprint(p[1], "x %r");
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close(p[1]);
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_exit(0);
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}else{
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/* Child child - close pipe. */
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close(p[1]);
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}
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}
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sigaction(SIGCHLD, &oldchld, nil);
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}
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if(pid != 0)
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return pid;
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if(flags&RFCENVG)
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if(environ)
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*environ = nil;
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}
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if(flags&RFPROC){
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werrstr("cannot use rfork for shared memory -- use libthread");
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return -1;
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}
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if(flags&RFNAMEG){
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/* XXX set $NAMESPACE to a new directory */
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flags &= ~RFNAMEG;
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}
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if(flags&RFNOTEG){
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setpgid(0, getpid());
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flags &= ~RFNOTEG;
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}
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if(flags&RFNOWAIT){
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werrstr("cannot use RFNOWAIT without RFPROC");
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return -1;
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}
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if(flags){
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werrstr("unknown flags %08ux in rfork", flags);
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return -1;
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}
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return 0;
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}
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