第16章-建造工具

总结

  • 这一章仅仅基本的文件读写，也比较简单。

/projects/linux-0.12/docs/第16章-建造工具/1529198037191.png

/projects/linux-0.12/docs/第16章-建造工具/1529198118515.png

  • 分别打开三个文件，各种校验，然后写到标准输入1中。命令就是重定向到文件
  • 校验规则如下图

/projects/linux-0.12/docs/第16章-建造工具/1529198823641.png

代码

  1. /*
  2.  *  linux/tools/build.c
  3.  *
  4.  *  (C) 1991  Linus Torvalds
  5.  */
  7. /*
  8.  * This file builds a disk-image from three different files:
  9.  *
  10.  * - bootsect: max 510 bytes of 8086 machine code, loads the rest
  11.  * - setup: max 4 sectors of 8086 machine code, sets up system parm
  12.  * - system: 80386 code for actual system
  13.  *
  14.  * It does some checking that all files are of the correct type, and
  15.  * just writes the result to stdout, removing headers and padding to
  16.  * the right amount. It also writes some system data to stderr.
  17.  */
  19. /*
  20.  * Changes by tytso to allow root device specification
  21.  *
  22.  * Added swap-device specification: Linux 20.12.91
  23.  */
  25.  #include <stdio.h>    /* fprintf */
  26.  #include <string.h>
  27.  #include <stdlib.h>    /* contains exit */
  28.  #include <sys/types.h>    /* unistd.h needs this */
  29.  #include <sys/stat.h>
  30.  #include <linux/fs.h>
  31.  #include <unistd.h>    /* contains read/write */
  32.  #include <fcntl.h>
  34.  #define MINIX_HEADER 32
  35.  #define GCC_HEADER 1024
  37.  #define SYS_SIZE 0x3000
  39.  #define DEFAULT_MAJOR_ROOT 3
  40.  #define DEFAULT_MINOR_ROOT 6
  42.  #define DEFAULT_MAJOR_SWAP 0
  43.  #define DEFAULT_MINOR_SWAP 0
  45. /* max nr of sectors of setup: don't change unless you also change
  46.  * bootsect etc */
  47.  #define SETUP_SECTS 4
  49.  #define STRINGIFY(x) #x
  51. void die(char *str)
  52. {
  53.     fprintf(stderr, "%s\n", str);
  54.     exit(1);
  55. }
  57. void usage(void)
  58. {
  59.     die("Usage: build bootsect setup system [rootdev] [> image]");
  60. }
  62. int main(int argc, char **argv)
  63. {
  64.     int i, c, id;
  65.     char buf[1024];
  66.     char major_root, minor_root;
  67.     char major_swap, minor_swap;
  68.     struct stat sb;
  70.     if ((argc < 4) || (argc > 6))
  71.         usage();
  72.     if (argc > 4)
  73.     {
  74.         if (strcmp(argv[4], "FLOPPY"))
  75.         {
  76.             if (stat(argv[4], &sb))
  77.             {
  78.                 perror(argv[4]);
  79.                 die("Couldn't stat root device.");
  80.             }
  81.             major_root = MAJOR(sb.st_rdev);
  82.             minor_root = MINOR(sb.st_rdev);
  83.         }
  84.         else
  85.         {
  86.             major_root = 0;
  87.             minor_root = 0;
  88.         }
  89.     }
  90.     else
  91.     {
  92.         major_root = DEFAULT_MAJOR_ROOT;
  93.         minor_root = DEFAULT_MINOR_ROOT;
  94.     }
  95.     if (argc == 6)
  96.     {
  97.         if (strcmp(argv[5], "NONE"))
  98.         {
  99.             if (stat(argv[5], &sb))
  100.             {
  101.                 perror(argv[5]);
  102.                 die("Couldn't stat root device.");
  103.             }
  104.             major_swap = MAJOR(sb.st_rdev);
  105.             minor_swap = MINOR(sb.st_rdev);
  106.         }
  107.         else
  108.         {
  109.             major_swap = 0;
  110.             minor_swap = 0;
  111.         }
  112.     }
  113.     else
  114.     {
  115.         major_swap = DEFAULT_MAJOR_SWAP;
  116.         minor_swap = DEFAULT_MINOR_SWAP;
  117.     }
  118.     fprintf(stderr, "Root device is (%d, %d)\n", major_root, minor_root);
  119.     fprintf(stderr, "Swap device is (%d, %d)\n", major_swap, minor_swap);
  120.     if ((major_root != 2) && (major_root != 3) &&
  121.             (major_root != 0))
  122.     {
  123.         fprintf(stderr, "Illegal root device (major = %d)\n",
  124.                 major_root);
  125.         die("Bad root device --- major #");
  126.     }
  127.     if (major_swap && major_swap != 3)
  128.     {
  129.         fprintf(stderr, "Illegal swap device (major = %d)\n",
  130.                 major_swap);
  131.         die("Bad root device --- major #");
  132.     }
  133.     for (i = 0; i < sizeof buf; i++) buf[i] = 0;
  134.     if ((id = open(argv[1], O_RDONLY, 0)) < 0)
  135.         die("Unable to open 'boot'");
  136.     if (read(id, buf, MINIX_HEADER) != MINIX_HEADER)
  137.         die("Unable to read header of 'boot'");
  138.     if (((long *) buf)[0] != 0x04100301)
  139.         die("Non-Minix header of 'boot'");
  140.     if (((long *) buf)[1] != MINIX_HEADER)
  141.         die("Non-Minix header of 'boot'");
  142.     if (((long *) buf)[3] != 0)
  143.         die("Illegal data segment in 'boot'");
  144.     if (((long *) buf)[4] != 0)
  145.         die("Illegal bss in 'boot'");
  146.     if (((long *) buf)[5] != 0)
  147.         die("Non-Minix header of 'boot'");
  148.     if (((long *) buf)[7] != 0)
  149.         die("Illegal symbol table in 'boot'");
  150.     i = read(id, buf, sizeof buf);
  151.     fprintf(stderr, "Boot sector %d bytes.\n", i);
  152.     if (i != 512)
  153.         die("Boot block must be exactly 512 bytes");
  154.     if ((*(unsigned short *)(buf + 510)) != 0xAA55)
  155.         die("Boot block hasn't got boot flag (0xAA55)");
  156.     buf[506] = (char) minor_swap;
  157.     buf[507] = (char) major_swap;
  158.     buf[508] = (char) minor_root;
  159.     buf[509] = (char) major_root;
  160.     i = write(1, buf, 512);
  161.     if (i != 512)
  162.         die("Write call failed");
  163.     close (id);
  166.     if ((id = open(argv[2], O_RDONLY, 0)) < 0)
  167.         die("Unable to open 'setup'");
  168.     if (read(id, buf, MINIX_HEADER) != MINIX_HEADER)
  169.         die("Unable to read header of 'setup'");
  170.     if (((long *) buf)[0] != 0x04100301)
  171.         die("Non-Minix header of 'setup'");
  172.     if (((long *) buf)[1] != MINIX_HEADER)
  173.         die("Non-Minix header of 'setup'");
  174.     if (((long *) buf)[3] != 0)
  175.         die("Illegal data segment in 'setup'");
  176.     if (((long *) buf)[4] != 0)
  177.         die("Illegal bss in 'setup'");
  178.     if (((long *) buf)[5] != 0)
  179.         die("Non-Minix header of 'setup'");
  180.     if (((long *) buf)[7] != 0)
  181.         die("Illegal symbol table in 'setup'");
  182.     for (i = 0 ; (c = read(id, buf, sizeof buf)) > 0 ; i += c )
  183.         if (write(1, buf, c) != c)
  184.             die("Write call failed");
  185.     close (id);
  186.     if (i > SETUP_SECTS * 512)
  187.         die("Setup exceeds " STRINGIFY(SETUP_SECTS)
  188.             " sectors - rewrite build/boot/setup");
  189.     fprintf(stderr, "Setup is %d bytes.\n", i);
  190.     for (c = 0 ; c < sizeof(buf) ; c++)
  191.         buf[c] = '\0';
  192.     while (i < SETUP_SECTS * 512)
  193.     {
  194.         c = SETUP_SECTS * 512 - i;
  195.         if (c > sizeof(buf))
  196.             c = sizeof(buf);
  197.         if (write(1, buf, c) != c)
  198.             die("Write call failed");
  199.         i += c;
  200.     }
  202.     if ((id = open(argv[3], O_RDONLY, 0)) < 0)
  203.         die("Unable to open 'system'");
  204.     if (read(id, buf, GCC_HEADER) != GCC_HEADER)
  205.         die("Unable to read header of 'system'");
  206.     if (((long *) buf)[5] != 0)
  207.         die("Non-GCC header of 'system'");
  208.     for (i = 0 ; (c = read(id, buf, sizeof buf)) > 0 ; i += c )
  209.         if (write(1, buf, c) != c)
  210.             die("Write call failed");
  211.     close(id);
  212.     fprintf(stderr, "System is %d bytes.\n", i);
  213.     if (i > SYS_SIZE * 16)
  214.         die("System is too big");
  215.     return(0);
  216. }