cscript.c

   1 /* SPDX-License-Identifier: GPL-2.0
   2  *
   3  * Copyright (C) 2018 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
   4  */
   5
   6 #define _GNU_SOURCE
   7
   8 #include <stdio.h>
   9 #include <stdlib.h>
  10 #include <string.h>
  11 #include <unistd.h>
  12 #include <errno.h>
  13 #include <sys/types.h>
  14 #include <sys/wait.h>
  15 #include <fcntl.h>
  16
  17 int main(int argc, char *argv[], char *envp[])
  18 {
  19         int fd, fd2, input = -1, pipes[2] = { 0 }, status;
  20         pid_t compiler_pid;
  21         char *output_path;
  22
  23         if (argc > 1 && argv[argc - 1][0] != '-') {
  24                 input = open(argv[1], O_RDONLY);
  25                 ++argv;
  26                 --argc;
  27                 if (input < 0) {
  28                         perror("Error: unable to open input file");
  29                         return 1;
  30                 }
  31                 if (pipe(pipes) < 0) {
  32                         perror("Error: unable to open filter pipe");
  33                         return 1;
  34                 }
  35         }
  36
  37         fd = open(getenv("HOME") ?: getenv("TMPDIR") ?: "/tmp", O_TMPFILE | O_EXCL | O_RDWR, S_IWUSR | S_IRUSR);
  38         if (fd < 0) {
  39                 perror("Error: unable to create temporary inode");
  40                 return 1;
  41         }
  42         if (asprintf(&output_path, "/proc/self/fd/%d", fd) < 0) {
  43                 perror("Error: unable to allocate memory for fd string");
  44                 return 1;
  45         }
  46
  47         compiler_pid = fork();
  48         if (compiler_pid < 0) {
  49                 perror("Error: unable to fork for compiler");
  50                 return 1;
  51         }
  52
  53         if (compiler_pid == 0) {
  54                 const char *cc = getenv("CC") ?: "gcc";
  55                 close(input);
  56                 if (pipes[0] != 0) {
  57                         close(pipes[1]);
  58                         if (dup2(pipes[0], 0) < 0) {
  59                                 perror("Error: unable to duplicate pipe fd");
  60                                 _exit(1);
  61                         }
  62                         close(pipes[0]);
  63                 }
  64                 execlp(cc, cc, "-xc", "-o", output_path, "-", NULL);
  65                 _exit(1);
  66         }
  67
  68         if (input != -1) {
  69                 char beginning[2];
  70                 ssize_t len;
  71
  72                 close(pipes[0]);
  73                 len = read(input, beginning, 2);
  74                 if (len < 0) {
  75                         perror("Error: unable to read from input file");
  76                         return 1;
  77                 } else if (len == 2 && beginning[0] == '#' && beginning[1] == '!')
  78                         len = write(pipes[1], "//", 2);
  79                 else if (len > 0)
  80                         len = write(pipes[1], beginning, len);
  81                 if (len < 0) {
  82                         perror("Error: unable to write input preamble");
  83                         return 1;
  84                 }
  85                 if (splice(input, NULL, pipes[1], NULL, 0x7fffffff, 0) < 0) {
  86                         perror("Error: unable to splice input to compiler child");
  87                         return 1;
  88                 }
  89                 close(pipes[1]);
  90         }
  91
  92         if (waitpid(compiler_pid, &status, 0) != compiler_pid || (!WIFEXITED(status) || WEXITSTATUS(status))) {
  93                 fprintf(stderr, "Error: compiler process did not complete successfully\n");
  94                 return 1;
  95         }
  96
  97         fd2 = open(output_path, O_RDONLY);
  98         if (fd2 < 0) {
  99                 perror("Error: unable to reopen temporary inode");
 100                 return 1;
 101         }
 102         close(fd);
 103
 104         if (fexecve(fd2, argv, envp) < 0) {
 105                 perror("Error: could not execute compiled program");
 106                 return 1;
 107         }
 108         return 0;
 109 }