1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3    Simple utility to make a single-image install kernel with initial ramdisk
4    for Sparc tftpbooting without need to set up nfs.
5 
6    Copyright (C) 1996,1997 Jakub Jelinek (jj@sunsite.mff.cuni.cz)
7    Pete Zaitcev <zaitcev@yahoo.com> endian fixes for cross-compiles, 2000.
8    Copyright (C) 2011 Sam Ravnborg <sam@ravnborg.org>
9 
10  */
11 
12 #include <dirent.h>
13 #include <stdlib.h>
14 #include <string.h>
15 #include <unistd.h>
16 #include <ctype.h>
17 #include <errno.h>
18 #include <fcntl.h>
19 #include <stdio.h>
20 
21 #include <sys/types.h>
22 #include <sys/stat.h>
23 
24 /*
25  * Note: run this on an a.out kernel (use elftoaout for it),
26  * as PROM looks for a.out image only.
27  */
28 
29 #define AOUT_TEXT_OFFSET   32
30 
31 static int is64bit = 0;
32 
33 /* align to power-of-two size */
align(int n)34 static int align(int n)
35 {
36 	if (is64bit)
37 		return (n + 0x1fff) & ~0x1fff;
38 	else
39 		return (n + 0xfff) & ~0xfff;
40 }
41 
42 /* read two bytes as big endian */
ld2(char * p)43 static unsigned short ld2(char *p)
44 {
45 	return (p[0] << 8) | p[1];
46 }
47 
48 /* save 4 bytes as big endian */
st4(char * p,unsigned int x)49 static void st4(char *p, unsigned int x)
50 {
51 	p[0] = x >> 24;
52 	p[1] = x >> 16;
53 	p[2] = x >> 8;
54 	p[3] = x;
55 }
56 
die(const char * str)57 static void die(const char *str)
58 {
59 	perror(str);
60 	exit(1);
61 }
62 
usage(void)63 static void usage(void)
64 {
65 	/* fs_img.gz is an image of initial ramdisk. */
66 	fprintf(stderr, "Usage: piggyback bits vmlinux.aout System.map fs_img.gz\n");
67 	fprintf(stderr, "\tKernel image will be modified in place.\n");
68 	exit(1);
69 }
70 
start_line(const char * line)71 static int start_line(const char *line)
72 {
73 	if (strcmp(line + 10, " _start\n") == 0)
74 		return 1;
75 	else if (strcmp(line + 18, " _start\n") == 0)
76 		return 1;
77 	return 0;
78 }
79 
end_line(const char * line)80 static int end_line(const char *line)
81 {
82 	if (strcmp(line + 10, " _end\n") == 0)
83 		return 1;
84 	else if (strcmp (line + 18, " _end\n") == 0)
85 		return 1;
86 	return 0;
87 }
88 
89 /*
90  * Find address for start and end in System.map.
91  * The file looks like this:
92  * f0004000 ... _start
93  * f0379f79 ... _end
94  * 1234567890123456
95  * ^coloumn 1
96  * There is support for 64 bit addresses too.
97  *
98  * Return 0 if either start or end is not found
99  */
get_start_end(const char * filename,unsigned int * start,unsigned int * end)100 static int get_start_end(const char *filename, unsigned int *start,
101                                                unsigned int *end)
102 {
103 	FILE *map;
104 	char buffer[1024];
105 
106 	*start = 0;
107 	*end = 0;
108 	map = fopen(filename, "r");
109 	if (!map)
110 		die(filename);
111 	while (fgets(buffer, 1024, map)) {
112 		if (start_line(buffer))
113 			*start = strtoul(buffer, NULL, 16);
114 		else if (end_line(buffer))
115 			*end = strtoul(buffer, NULL, 16);
116 	}
117 	fclose (map);
118 
119 	if (*start == 0 || *end == 0)
120 		return 0;
121 
122 	return 1;
123 }
124 
125 #define LOOKBACK (128 * 4)
126 #define BUFSIZE 1024
127 /*
128  * Find the HdrS entry from head_32/head_64.
129  * We check if it is at the beginning of the file (sparc64 case)
130  * and if not we search for it.
131  * When we search do so in steps of 4 as HdrS is on a 4-byte aligned
132  * address (it is on same alignment as sparc instructions)
133  * Return the offset to the HdrS entry (as off_t)
134  */
get_hdrs_offset(int kernelfd,const char * filename)135 static off_t get_hdrs_offset(int kernelfd, const char *filename)
136 {
137 	char buffer[BUFSIZE];
138 	off_t offset;
139 	int i;
140 
141 	if (lseek(kernelfd, 0, SEEK_SET) < 0)
142 		die("lseek");
143 	if (read(kernelfd, buffer, BUFSIZE) != BUFSIZE)
144 		die(filename);
145 
146 	if (buffer[40] == 'H' && buffer[41] == 'd' &&
147 	    buffer[42] == 'r' && buffer[43] == 'S') {
148 		return 40;
149 	} else {
150 		/*  Find the gokernel label */
151 		/* Decode offset from branch instruction */
152 		offset = ld2(buffer + AOUT_TEXT_OFFSET + 2) << 2;
153 		/* Go back 512 bytes so we do not miss HdrS */
154 		offset -= LOOKBACK;
155 		/* skip a.out header */
156 		offset += AOUT_TEXT_OFFSET;
157 		if (offset < 0) {
158 			errno = -EINVAL;
159 			die("Calculated a negative offset, probably elftoaout generated an invalid image. Did you use a recent elftoaout ?");
160 		}
161 		if (lseek(kernelfd, offset, SEEK_SET) < 0)
162 			die("lseek");
163 		if (read(kernelfd, buffer, BUFSIZE) != BUFSIZE)
164 			die(filename);
165 
166 		for (i = 0; i < LOOKBACK; i += 4) {
167 			if (buffer[i + 0] == 'H' && buffer[i + 1] == 'd' &&
168 			    buffer[i + 2] == 'r' && buffer[i + 3] == 'S') {
169 				return offset + i;
170 			}
171 		}
172 	}
173 	fprintf (stderr, "Couldn't find headers signature in %s\n", filename);
174 	exit(1);
175 }
176 
main(int argc,char ** argv)177 int main(int argc,char **argv)
178 {
179 	static char aout_magic[] = { 0x01, 0x03, 0x01, 0x07 };
180 	char buffer[1024];
181 	unsigned int i, start, end;
182 	off_t offset;
183 	struct stat s;
184 	int image, tail;
185 
186 	if (argc != 5)
187 		usage();
188 	if (strcmp(argv[1], "64") == 0)
189 		is64bit = 1;
190 	if (stat (argv[4], &s) < 0)
191 		die(argv[4]);
192 
193 	if (!get_start_end(argv[3], &start, &end)) {
194 		fprintf(stderr, "Could not determine start and end from %s\n",
195 		        argv[3]);
196 		exit(1);
197 	}
198 	if ((image = open(argv[2], O_RDWR)) < 0)
199 		die(argv[2]);
200 	if (read(image, buffer, 512) != 512)
201 		die(argv[2]);
202 	if (memcmp(buffer, aout_magic, 4) != 0) {
203 		fprintf (stderr, "Not a.out. Don't blame me.\n");
204 		exit(1);
205 	}
206 	/*
207 	 * We need to fill in values for
208 	 * sparc_ramdisk_image + sparc_ramdisk_size
209 	 * To locate these symbols search for the "HdrS" text which appear
210 	 * in the image a little before the gokernel symbol.
211 	 * See definition of these in init_32.S
212 	 */
213 
214 	offset = get_hdrs_offset(image, argv[2]);
215 	/* skip HdrS + LINUX_VERSION_CODE + HdrS version */
216 	offset += 10;
217 
218 	if (lseek(image, offset, 0) < 0)
219 		die("lseek");
220 
221 	/*
222 	 * root_flags = 0
223 	 * root_dev = 1 (RAMDISK_MAJOR)
224 	 * ram_flags = 0
225 	 * sparc_ramdisk_image = "PAGE aligned address after _end")
226 	 * sparc_ramdisk_size = size of image
227 	 */
228 	st4(buffer, 0);
229 	st4(buffer + 4, 0x01000000);
230 	st4(buffer + 8, align(end + 32));
231 	st4(buffer + 12, s.st_size);
232 
233 	if (write(image, buffer + 2, 14) != 14)
234 		die(argv[2]);
235 
236 	/* For sparc64 update a_text and clear a_data + a_bss */
237 	if (is64bit)
238 	{
239 		if (lseek(image, 4, 0) < 0)
240 			die("lseek");
241 		/* a_text */
242 		st4(buffer, align(end + 32 + 8191) - (start & ~0x3fffffUL) +
243 		            s.st_size);
244 		/* a_data */
245 		st4(buffer + 4, 0);
246 		/* a_bss */
247 		st4(buffer + 8, 0);
248 		if (write(image, buffer, 12) != 12)
249 			die(argv[2]);
250 	}
251 
252 	/* seek page aligned boundary in the image file and add boot image */
253 	if (lseek(image, AOUT_TEXT_OFFSET - start + align(end + 32), 0) < 0)
254 		die("lseek");
255 	if ((tail = open(argv[4], O_RDONLY)) < 0)
256 		die(argv[4]);
257 	while ((i = read(tail, buffer, 1024)) > 0)
258 		if (write(image, buffer, i) != i)
259 			die(argv[2]);
260 	if (close(image) < 0)
261 		die("close");
262 	if (close(tail) < 0)
263 		die("close");
264 	return 0;
265 }
266