xref: /openbmc/linux/scripts/basic/fixdep.c (revision 68198dca)
1 /*
2  * "Optimize" a list of dependencies as spit out by gcc -MD
3  * for the kernel build
4  * ===========================================================================
5  *
6  * Author       Kai Germaschewski
7  * Copyright    2002 by Kai Germaschewski  <kai.germaschewski@gmx.de>
8  *
9  * This software may be used and distributed according to the terms
10  * of the GNU General Public License, incorporated herein by reference.
11  *
12  *
13  * Introduction:
14  *
15  * gcc produces a very nice and correct list of dependencies which
16  * tells make when to remake a file.
17  *
18  * To use this list as-is however has the drawback that virtually
19  * every file in the kernel includes autoconf.h.
20  *
21  * If the user re-runs make *config, autoconf.h will be
22  * regenerated.  make notices that and will rebuild every file which
23  * includes autoconf.h, i.e. basically all files. This is extremely
24  * annoying if the user just changed CONFIG_HIS_DRIVER from n to m.
25  *
26  * So we play the same trick that "mkdep" played before. We replace
27  * the dependency on autoconf.h by a dependency on every config
28  * option which is mentioned in any of the listed prerequisites.
29  *
30  * kconfig populates a tree in include/config/ with an empty file
31  * for each config symbol and when the configuration is updated
32  * the files representing changed config options are touched
33  * which then let make pick up the changes and the files that use
34  * the config symbols are rebuilt.
35  *
36  * So if the user changes his CONFIG_HIS_DRIVER option, only the objects
37  * which depend on "include/config/his/driver.h" will be rebuilt,
38  * so most likely only his driver ;-)
39  *
40  * The idea above dates, by the way, back to Michael E Chastain, AFAIK.
41  *
42  * So to get dependencies right, there are two issues:
43  * o if any of the files the compiler read changed, we need to rebuild
44  * o if the command line given to the compile the file changed, we
45  *   better rebuild as well.
46  *
47  * The former is handled by using the -MD output, the later by saving
48  * the command line used to compile the old object and comparing it
49  * to the one we would now use.
50  *
51  * Again, also this idea is pretty old and has been discussed on
52  * kbuild-devel a long time ago. I don't have a sensibly working
53  * internet connection right now, so I rather don't mention names
54  * without double checking.
55  *
56  * This code here has been based partially based on mkdep.c, which
57  * says the following about its history:
58  *
59  *   Copyright abandoned, Michael Chastain, <mailto:mec@shout.net>.
60  *   This is a C version of syncdep.pl by Werner Almesberger.
61  *
62  *
63  * It is invoked as
64  *
65  *   fixdep <depfile> <target> <cmdline>
66  *
67  * and will read the dependency file <depfile>
68  *
69  * The transformed dependency snipped is written to stdout.
70  *
71  * It first generates a line
72  *
73  *   cmd_<target> = <cmdline>
74  *
75  * and then basically copies the .<target>.d file to stdout, in the
76  * process filtering out the dependency on autoconf.h and adding
77  * dependencies on include/config/my/option.h for every
78  * CONFIG_MY_OPTION encountered in any of the prerequisites.
79  *
80  * It will also filter out all the dependencies on *.ver. We need
81  * to make sure that the generated version checksum are globally up
82  * to date before even starting the recursive build, so it's too late
83  * at this point anyway.
84  *
85  * We don't even try to really parse the header files, but
86  * merely grep, i.e. if CONFIG_FOO is mentioned in a comment, it will
87  * be picked up as well. It's not a problem with respect to
88  * correctness, since that can only give too many dependencies, thus
89  * we cannot miss a rebuild. Since people tend to not mention totally
90  * unrelated CONFIG_ options all over the place, it's not an
91  * efficiency problem either.
92  *
93  * (Note: it'd be easy to port over the complete mkdep state machine,
94  *  but I don't think the added complexity is worth it)
95  */
96 /*
97  * Note 2: if somebody writes HELLO_CONFIG_BOOM in a file, it will depend onto
98  * CONFIG_BOOM. This could seem a bug (not too hard to fix), but please do not
99  * fix it! Some UserModeLinux files (look at arch/um/) call CONFIG_BOOM as
100  * UML_CONFIG_BOOM, to avoid conflicts with /usr/include/linux/autoconf.h,
101  * through arch/um/include/uml-config.h; this fixdep "bug" makes sure that
102  * those files will have correct dependencies.
103  */
104 
105 #include <sys/types.h>
106 #include <sys/stat.h>
107 #include <sys/mman.h>
108 #include <unistd.h>
109 #include <fcntl.h>
110 #include <string.h>
111 #include <stdlib.h>
112 #include <stdio.h>
113 #include <limits.h>
114 #include <ctype.h>
115 #include <arpa/inet.h>
116 
117 int insert_extra_deps;
118 char *target;
119 char *depfile;
120 char *cmdline;
121 
122 static void usage(void)
123 {
124 	fprintf(stderr, "Usage: fixdep [-e] <depfile> <target> <cmdline>\n");
125 	fprintf(stderr, " -e  insert extra dependencies given on stdin\n");
126 	exit(1);
127 }
128 
129 /*
130  * Print out the commandline prefixed with cmd_<target filename> :=
131  */
132 static void print_cmdline(void)
133 {
134 	printf("cmd_%s := %s\n\n", target, cmdline);
135 }
136 
137 /*
138  * Print out a dependency path from a symbol name
139  */
140 static void print_config(const char *m, int slen)
141 {
142 	int c, i;
143 
144 	printf("    $(wildcard include/config/");
145 	for (i = 0; i < slen; i++) {
146 		c = m[i];
147 		if (c == '_')
148 			c = '/';
149 		else
150 			c = tolower(c);
151 		putchar(c);
152 	}
153 	printf(".h) \\\n");
154 }
155 
156 static void do_extra_deps(void)
157 {
158 	if (insert_extra_deps) {
159 		char buf[80];
160 		while(fgets(buf, sizeof(buf), stdin)) {
161 			int len = strlen(buf);
162 			if (len < 2 || buf[len-1] != '\n') {
163 				fprintf(stderr, "fixdep: bad data on stdin\n");
164 				exit(1);
165 			}
166 			print_config(buf, len-1);
167 		}
168 	}
169 }
170 
171 struct item {
172 	struct item	*next;
173 	unsigned int	len;
174 	unsigned int	hash;
175 	char		name[0];
176 };
177 
178 #define HASHSZ 256
179 static struct item *hashtab[HASHSZ];
180 
181 static unsigned int strhash(const char *str, unsigned int sz)
182 {
183 	/* fnv32 hash */
184 	unsigned int i, hash = 2166136261U;
185 
186 	for (i = 0; i < sz; i++)
187 		hash = (hash ^ str[i]) * 0x01000193;
188 	return hash;
189 }
190 
191 /*
192  * Lookup a value in the configuration string.
193  */
194 static int is_defined_config(const char *name, int len, unsigned int hash)
195 {
196 	struct item *aux;
197 
198 	for (aux = hashtab[hash % HASHSZ]; aux; aux = aux->next) {
199 		if (aux->hash == hash && aux->len == len &&
200 		    memcmp(aux->name, name, len) == 0)
201 			return 1;
202 	}
203 	return 0;
204 }
205 
206 /*
207  * Add a new value to the configuration string.
208  */
209 static void define_config(const char *name, int len, unsigned int hash)
210 {
211 	struct item *aux = malloc(sizeof(*aux) + len);
212 
213 	if (!aux) {
214 		perror("fixdep:malloc");
215 		exit(1);
216 	}
217 	memcpy(aux->name, name, len);
218 	aux->len = len;
219 	aux->hash = hash;
220 	aux->next = hashtab[hash % HASHSZ];
221 	hashtab[hash % HASHSZ] = aux;
222 }
223 
224 /*
225  * Record the use of a CONFIG_* word.
226  */
227 static void use_config(const char *m, int slen)
228 {
229 	unsigned int hash = strhash(m, slen);
230 
231 	if (is_defined_config(m, slen, hash))
232 	    return;
233 
234 	define_config(m, slen, hash);
235 	print_config(m, slen);
236 }
237 
238 static void parse_config_file(const char *p)
239 {
240 	const char *q, *r;
241 
242 	while ((p = strstr(p, "CONFIG_"))) {
243 		p += 7;
244 		q = p;
245 		while (*q && (isalnum(*q) || *q == '_'))
246 			q++;
247 		if (memcmp(q - 7, "_MODULE", 7) == 0)
248 			r = q - 7;
249 		else
250 			r = q;
251 		if (r > p)
252 			use_config(p, r - p);
253 		p = q;
254 	}
255 }
256 
257 /* test if s ends in sub */
258 static int strrcmp(const char *s, const char *sub)
259 {
260 	int slen = strlen(s);
261 	int sublen = strlen(sub);
262 
263 	if (sublen > slen)
264 		return 1;
265 
266 	return memcmp(s + slen - sublen, sub, sublen);
267 }
268 
269 static void do_config_file(const char *filename)
270 {
271 	struct stat st;
272 	int fd;
273 	char *map;
274 
275 	fd = open(filename, O_RDONLY);
276 	if (fd < 0) {
277 		fprintf(stderr, "fixdep: error opening config file: ");
278 		perror(filename);
279 		exit(2);
280 	}
281 	if (fstat(fd, &st) < 0) {
282 		fprintf(stderr, "fixdep: error fstat'ing config file: ");
283 		perror(filename);
284 		exit(2);
285 	}
286 	if (st.st_size == 0) {
287 		close(fd);
288 		return;
289 	}
290 	map = malloc(st.st_size + 1);
291 	if (!map) {
292 		perror("fixdep: malloc");
293 		close(fd);
294 		return;
295 	}
296 	if (read(fd, map, st.st_size) != st.st_size) {
297 		perror("fixdep: read");
298 		close(fd);
299 		return;
300 	}
301 	map[st.st_size] = '\0';
302 	close(fd);
303 
304 	parse_config_file(map);
305 
306 	free(map);
307 }
308 
309 /*
310  * Important: The below generated source_foo.o and deps_foo.o variable
311  * assignments are parsed not only by make, but also by the rather simple
312  * parser in scripts/mod/sumversion.c.
313  */
314 static void parse_dep_file(void *map, size_t len)
315 {
316 	char *m = map;
317 	char *end = m + len;
318 	char *p;
319 	char s[PATH_MAX];
320 	int is_target;
321 	int saw_any_target = 0;
322 	int is_first_dep = 0;
323 
324 	while (m < end) {
325 		/* Skip any "white space" */
326 		while (m < end && (*m == ' ' || *m == '\\' || *m == '\n'))
327 			m++;
328 		/* Find next "white space" */
329 		p = m;
330 		while (p < end && *p != ' ' && *p != '\\' && *p != '\n')
331 			p++;
332 		/* Is the token we found a target name? */
333 		is_target = (*(p-1) == ':');
334 		/* Don't write any target names into the dependency file */
335 		if (is_target) {
336 			/* The /next/ file is the first dependency */
337 			is_first_dep = 1;
338 		} else {
339 			/* Save this token/filename */
340 			memcpy(s, m, p-m);
341 			s[p - m] = 0;
342 
343 			/* Ignore certain dependencies */
344 			if (strrcmp(s, "include/generated/autoconf.h") &&
345 			    strrcmp(s, "include/generated/autoksyms.h") &&
346 			    strrcmp(s, "arch/um/include/uml-config.h") &&
347 			    strrcmp(s, "include/linux/kconfig.h") &&
348 			    strrcmp(s, ".ver")) {
349 				/*
350 				 * Do not list the source file as dependency,
351 				 * so that kbuild is not confused if a .c file
352 				 * is rewritten into .S or vice versa. Storing
353 				 * it in source_* is needed for modpost to
354 				 * compute srcversions.
355 				 */
356 				if (is_first_dep) {
357 					/*
358 					 * If processing the concatenation of
359 					 * multiple dependency files, only
360 					 * process the first target name, which
361 					 * will be the original source name,
362 					 * and ignore any other target names,
363 					 * which will be intermediate temporary
364 					 * files.
365 					 */
366 					if (!saw_any_target) {
367 						saw_any_target = 1;
368 						printf("source_%s := %s\n\n",
369 							target, s);
370 						printf("deps_%s := \\\n",
371 							target);
372 					}
373 					is_first_dep = 0;
374 				} else
375 					printf("  %s \\\n", s);
376 				do_config_file(s);
377 			}
378 		}
379 		/*
380 		 * Start searching for next token immediately after the first
381 		 * "whitespace" character that follows this token.
382 		 */
383 		m = p + 1;
384 	}
385 
386 	if (!saw_any_target) {
387 		fprintf(stderr, "fixdep: parse error; no targets found\n");
388 		exit(1);
389 	}
390 
391 	do_extra_deps();
392 
393 	printf("\n%s: $(deps_%s)\n\n", target, target);
394 	printf("$(deps_%s):\n", target);
395 }
396 
397 static void print_deps(void)
398 {
399 	struct stat st;
400 	int fd;
401 	void *map;
402 
403 	fd = open(depfile, O_RDONLY);
404 	if (fd < 0) {
405 		fprintf(stderr, "fixdep: error opening depfile: ");
406 		perror(depfile);
407 		exit(2);
408 	}
409 	if (fstat(fd, &st) < 0) {
410 		fprintf(stderr, "fixdep: error fstat'ing depfile: ");
411 		perror(depfile);
412 		exit(2);
413 	}
414 	if (st.st_size == 0) {
415 		fprintf(stderr,"fixdep: %s is empty\n",depfile);
416 		close(fd);
417 		return;
418 	}
419 	map = mmap(NULL, st.st_size, PROT_READ, MAP_PRIVATE, fd, 0);
420 	if ((long) map == -1) {
421 		perror("fixdep: mmap");
422 		close(fd);
423 		return;
424 	}
425 
426 	parse_dep_file(map, st.st_size);
427 
428 	munmap(map, st.st_size);
429 
430 	close(fd);
431 }
432 
433 int main(int argc, char *argv[])
434 {
435 	if (argc == 5 && !strcmp(argv[1], "-e")) {
436 		insert_extra_deps = 1;
437 		argv++;
438 	} else if (argc != 4)
439 		usage();
440 
441 	depfile = argv[1];
442 	target = argv[2];
443 	cmdline = argv[3];
444 
445 	print_cmdline();
446 	print_deps();
447 
448 	return 0;
449 }
450