131 lines
3.3 KiB
C
131 lines
3.3 KiB
C
#include <sys/types.h>
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#include <sys/wait.h>
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#include <assert.h>
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#include <ctype.h>
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#include <errno.h>
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#include <fcntl.h>
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#include <limits.h>
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#include <math.h>
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#include <poll.h>
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#include <setjmp.h>
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#include <stdarg.h>
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#include <stdint.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <unistd.h>
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#include "scheme.h"
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static void warn(const char *msg) { fprintf(stderr, "%s\n", msg); }
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static void warnsys(const char *msg)
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{
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fprintf(stderr, "%s: %s\n", msg, strerror(errno));
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}
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static void diesys(const char *msg)
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{
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warnsys(msg);
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exit(1);
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}
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static void set_close_on_exec(int fd)
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{
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int flags;
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if ((flags = fcntl(fd, F_GETFD)) == -1) {
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diesys("cannot get file descriptor flags");
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}
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flags |= FD_CLOEXEC;
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if (fcntl(fd, F_SETFD, flags) == -1) {
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diesys("cannot set close-on-exec");
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}
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}
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value_t builtin_spawn(value_t *args, uint32_t nargs)
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{
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pid_t child;
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int status, exec_errno;
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int fds[2];
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struct pollfd pollfd;
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ssize_t nbyte;
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value_t exec_args;
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char *exec_argv[16];
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size_t exec_argv_fill = 0;
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argcount("spawn", nargs, 1);
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exec_args = args[0];
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if (exec_args == FL_NIL) {
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lerror(ArgError, "executable argument list is empty");
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}
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for (;;) {
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if (!iscons(exec_args)) {
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lerror(ArgError, "executable arguments not a proper list");
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}
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exec_argv[exec_argv_fill++] =
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tostring(car_(exec_args), "executable argument");
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if ((exec_args = cdr_(exec_args)) == FL_NIL) {
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break;
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}
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}
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exec_argv[exec_argv_fill++] = 0;
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// TODO: Signal mask for the child process.
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if (pipe(fds) == -1) {
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diesys("cannot create pipe");
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}
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set_close_on_exec(fds[0]);
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set_close_on_exec(fds[1]);
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if ((child = fork()) == -1) {
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diesys("cannot fork");
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}
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if (!child) {
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// We are in the new child process.
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close(fds[0]);
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execvp(exec_argv[0], exec_argv);
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exec_errno = errno;
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nbyte = write(fds[1], &exec_errno, sizeof(exec_errno));
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if (nbyte == (ssize_t)-1) {
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warnsys("completely borked (child)");
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} else if (nbyte != (ssize_t)sizeof(exec_errno)) {
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warn("completely borked (child)");
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}
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_exit(126);
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}
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// We are in the old parent process.
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close(fds[1]);
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memset(&pollfd, 0, sizeof(pollfd));
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pollfd.fd = fds[0];
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pollfd.events = POLLIN;
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if (poll(&pollfd, 1, -1) == -1) {
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diesys("cannot poll");
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}
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exec_errno = 0;
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if (pollfd.revents & POLLIN) {
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nbyte = read(pollfd.fd, &exec_errno, sizeof(exec_errno));
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if (nbyte == 0) {
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// We don't get any data, means the pipe was closed.
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} else if (nbyte == (ssize_t)-1) {
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warnsys("completely borked (parent)");
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} else if (nbyte != (ssize_t)sizeof(exec_errno)) {
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warn("completely borked (parent)");
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}
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}
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if (waitpid(child, &status, 0) == -1) {
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warnsys("cannot wait for child process");
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return FL_NIL;
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}
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if (!WIFEXITED(status)) {
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warn("child process did not exit normally");
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return FL_NIL;
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}
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if (exec_errno != 0) {
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errno = exec_errno;
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warnsys("cannot execute command");
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return FL_NIL;
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}
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return fixnum(WEXITSTATUS(status));
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}
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