1 // SPDX-License-Identifier: GPL-2.0
3 * Copyright (C) 1991, 1992 Linus Torvalds
4 * Copyright (C) 1997 Martin Mares
8 * This file builds a disk-image from three different files:
10 * - bootsect: exactly 512 bytes of 8086 machine code, loads the rest
11 * - setup: 8086 machine code, sets up system parm
12 * - system: 80386 code for actual system
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.
20 * Changes by tytso to allow root device specification
21 * High loaded stuff by Hans Lermen & Werner Almesberger, Feb. 1996
22 * Cross compiling fixes by Gertjan van Wingerde, July 1996
23 * Rewritten by Martin Mares, April 1997
30 #include <sys/types.h>
32 #include <sys/sysmacros.h>
37 #define DEFAULT_MAJOR_ROOT 0
38 #define DEFAULT_MINOR_ROOT 0
40 /* Minimal number of setup sectors (see also bootsect.S) */
47 __attribute__((noreturn))
48 void die(const char *str, ...)
52 vfprintf(stderr, str, args);
57 void file_open(const char *name)
59 fd = open(name, O_RDONLY, 0);
61 die("Unable to open `%s': %m", name);
64 __attribute__((noreturn))
67 die("Usage: build [-b] bootsect setup system [rootdev] [> image]");
70 int main(int argc, char **argv)
72 unsigned int i, c, sz, setup_sectors;
74 uint8_t major_root, minor_root;
77 if (argc > 2 && !strcmp(argv[1], "-b")) {
81 if ((argc < 4) || (argc > 5))
84 if (!strcmp(argv[4], "CURRENT")) {
87 die("Couldn't stat /");
89 major_root = major(sb.st_dev);
90 minor_root = minor(sb.st_dev);
91 } else if (strcmp(argv[4], "FLOPPY")) {
92 if (stat(argv[4], &sb)) {
94 die("Couldn't stat root device.");
96 major_root = major(sb.st_rdev);
97 minor_root = minor(sb.st_rdev);
103 major_root = DEFAULT_MAJOR_ROOT;
104 minor_root = DEFAULT_MINOR_ROOT;
106 fprintf(stderr, "Root device is (%d, %d)\n", major_root, minor_root);
109 i = read(fd, buf, sizeof(buf));
110 fprintf(stderr, "Boot sector %d bytes.\n", i);
112 die("Boot block must be exactly 512 bytes");
113 if (buf[510] != 0x55 || buf[511] != 0xaa)
114 die("Boot block hasn't got boot flag (0xAA55)");
115 buf[508] = minor_root;
116 buf[509] = major_root;
117 if (write(1, buf, 512) != 512)
118 die("Write call failed");
121 /* Copy the setup code */
123 for (i = 0; (c = read(fd, buf, sizeof(buf))) > 0; i += c)
124 if (write(1, buf, c) != c)
125 die("Write call failed");
127 die("read-error on `setup'");
130 /* Pad unused space with zeros */
131 setup_sectors = (i + 511) / 512;
132 /* for compatibility with ancient versions of LILO. */
133 if (setup_sectors < SETUP_SECTS)
134 setup_sectors = SETUP_SECTS;
135 fprintf(stderr, "Setup is %d bytes.\n", i);
136 memset(buf, 0, sizeof(buf));
137 while (i < setup_sectors * 512) {
138 c = setup_sectors * 512 - i;
141 if (write(1, buf, c) != c)
142 die("Write call failed");
148 die("Unable to stat `%s': %m", argv[3]);
150 fprintf(stderr, "System is %d kB\n", sz / 1024);
151 sys_size = (sz + 15) / 16;
152 /* 0x28000*16 = 2.5 MB, conservative estimate for the current maximum */
153 if (sys_size > (is_big_kernel ? 0x28000 : DEF_SYSSIZE))
154 die("System is too big. Try using %smodules.",
155 is_big_kernel ? "" : "bzImage or ");
156 if (sys_size > 0xffff)
158 "warning: kernel is too big for standalone boot "
163 l = (sz > sizeof(buf)) ? sizeof(buf) : sz;
164 n = read(fd, buf, l);
167 die("Error reading %s: %m", argv[3]);
169 die("%s: Unexpected EOF", argv[3]);
171 if (write(1, buf, l) != l)
177 /* Write sizes to the bootsector */
178 if (lseek(1, 497, SEEK_SET) != 497)
179 die("Output: seek failed");
180 buf[0] = setup_sectors;
181 if (write(1, buf, 1) != 1)
182 die("Write of setup sector count failed");
183 if (lseek(1, 500, SEEK_SET) != 500)
184 die("Output: seek failed");
185 buf[0] = (sys_size & 0xff);
186 buf[1] = ((sys_size >> 8) & 0xff);
187 if (write(1, buf, 2) != 2)
188 die("Write of image length failed");