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 prequisites.
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/linux/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 prequisites.
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 * The algorithm to grep for "CONFIG_..." is bit unusual, but should
86 * be fast ;-) We don't even try to really parse the header files, but
87 * merely grep, i.e. if CONFIG_FOO is mentioned in a comment, it will
88 * be picked up as well. It's not a problem with respect to
89 * correctness, since that can only give too many dependencies, thus
90 * we cannot miss a rebuild. Since people tend to not mention totally
91 * unrelated CONFIG_ options all over the place, it's not an
92 * efficiency problem either.
93 *
94 * (Note: it'd be easy to port over the complete mkdep state machine,
95 *  but I don't think the added complexity is worth it)
96 */
97/*
98 * Note 2: if somebody writes HELLO_CONFIG_BOOM in a file, it will depend onto
99 * CONFIG_BOOM. This could seem a bug (not too hard to fix), but please do not
100 * fix it! Some UserModeLinux files (look at arch/um/) call CONFIG_BOOM as
101 * UML_CONFIG_BOOM, to avoid conflicts with /usr/include/linux/autoconf.h,
102 * through arch/um/include/uml-config.h; this fixdep "bug" makes sure that
103 * those files will have correct dependencies.
104 */
105
106#include <sys/types.h>
107#include <sys/stat.h>
108#include <sys/mman.h>
109#include <unistd.h>
110#include <fcntl.h>
111#include <string.h>
112#include <stdlib.h>
113#include <stdio.h>
114#include <limits.h>
115#include <ctype.h>
116#include <arpa/inet.h>
117
118#define INT_CONF ntohl(0x434f4e46)
119#define INT_ONFI ntohl(0x4f4e4649)
120#define INT_NFIG ntohl(0x4e464947)
121#define INT_FIG_ ntohl(0x4649475f)
122
123char *target;
124char *depfile;
125char *cmdline;
126
127static void usage(void)
128{
129	fprintf(stderr, "Usage: fixdep <depfile> <target> <cmdline>\n");
130	exit(1);
131}
132
133/*
134 * Print out the commandline prefixed with cmd_<target filename> :=
135 */
136static void print_cmdline(void)
137{
138	printf("cmd_%s := %s\n\n", target, cmdline);
139}
140
141struct item {
142	struct item	*next;
143	unsigned int	len;
144	unsigned int	hash;
145	char		name[0];
146};
147
148#define HASHSZ 256
149static struct item *hashtab[HASHSZ];
150
151static unsigned int strhash(const char *str, unsigned int sz)
152{
153	/* fnv32 hash */
154	unsigned int i, hash = 2166136261U;
155
156	for (i = 0; i < sz; i++)
157		hash = (hash ^ str[i]) * 0x01000193;
158	return hash;
159}
160
161/*
162 * Lookup a value in the configuration string.
163 */
164static int is_defined_config(const char *name, int len, unsigned int hash)
165{
166	struct item *aux;
167
168	for (aux = hashtab[hash % HASHSZ]; aux; aux = aux->next) {
169		if (aux->hash == hash && aux->len == len &&
170		    memcmp(aux->name, name, len) == 0)
171			return 1;
172	}
173	return 0;
174}
175
176/*
177 * Add a new value to the configuration string.
178 */
179static void define_config(const char *name, int len, unsigned int hash)
180{
181	struct item *aux = malloc(sizeof(*aux) + len);
182
183	if (!aux) {
184		perror("fixdep:malloc");
185		exit(1);
186	}
187	memcpy(aux->name, name, len);
188	aux->len = len;
189	aux->hash = hash;
190	aux->next = hashtab[hash % HASHSZ];
191	hashtab[hash % HASHSZ] = aux;
192}
193
194/*
195 * Clear the set of configuration strings.
196 */
197static void clear_config(void)
198{
199	struct item *aux, *next;
200	unsigned int i;
201
202	for (i = 0; i < HASHSZ; i++) {
203		for (aux = hashtab[i]; aux; aux = next) {
204			next = aux->next;
205			free(aux);
206		}
207		hashtab[i] = NULL;
208	}
209}
210
211/*
212 * Record the use of a CONFIG_* word.
213 */
214static void use_config(const char *m, int slen)
215{
216	unsigned int hash = strhash(m, slen);
217	int c, i;
218
219	if (is_defined_config(m, slen, hash))
220	    return;
221
222	define_config(m, slen, hash);
223
224	printf("    $(wildcard include/config/");
225	for (i = 0; i < slen; i++) {
226		c = m[i];
227		if (c == '_')
228			c = '/';
229		else
230			c = tolower(c);
231		putchar(c);
232	}
233	printf(".h) \\\n");
234}
235
236static void parse_config_file(const char *map, size_t len)
237{
238	const int *end = (const int *) (map + len);
239	/* start at +1, so that p can never be < map */
240	const int *m   = (const int *) map + 1;
241	const char *p, *q;
242
243	for (; m < end; m++) {
244		if (*m == INT_CONF) { p = (char *) m  ; goto conf; }
245		if (*m == INT_ONFI) { p = (char *) m-1; goto conf; }
246		if (*m == INT_NFIG) { p = (char *) m-2; goto conf; }
247		if (*m == INT_FIG_) { p = (char *) m-3; goto conf; }
248		continue;
249	conf:
250		if (p > map + len - 7)
251			continue;
252		if (memcmp(p, "CONFIG_", 7))
253			continue;
254		for (q = p + 7; q < map + len; q++) {
255			if (!(isalnum(*q) || *q == '_'))
256				goto found;
257		}
258		continue;
259
260	found:
261		if (!memcmp(q - 7, "_MODULE", 7))
262			q -= 7;
263		if( (q-p-7) < 0 )
264			continue;
265		use_config(p+7, q-p-7);
266	}
267}
268
269/* test is s ends in sub */
270static int strrcmp(char *s, char *sub)
271{
272	int slen = strlen(s);
273	int sublen = strlen(sub);
274
275	if (sublen > slen)
276		return 1;
277
278	return memcmp(s + slen - sublen, sub, sublen);
279}
280
281static void do_config_file(const char *filename)
282{
283	struct stat st;
284	int fd;
285	void *map;
286
287	fd = open(filename, O_RDONLY);
288	if (fd < 0) {
289		fprintf(stderr, "fixdep: error opening config file: ");
290		perror(filename);
291		exit(2);
292	}
293	fstat(fd, &st);
294	if (st.st_size == 0) {
295		close(fd);
296		return;
297	}
298	map = mmap(NULL, st.st_size, PROT_READ, MAP_PRIVATE, fd, 0);
299	if ((long) map == -1) {
300		perror("fixdep: mmap");
301		close(fd);
302		return;
303	}
304
305	parse_config_file(map, st.st_size);
306
307	munmap(map, st.st_size);
308
309	close(fd);
310}
311
312/*
313 * Important: The below generated source_foo.o and deps_foo.o variable
314 * assignments are parsed not only by make, but also by the rather simple
315 * parser in scripts/mod/sumversion.c.
316 */
317static void parse_dep_file(void *map, size_t len)
318{
319	char *m = map;
320	char *end = m + len;
321	char *p;
322	char s[PATH_MAX];
323	int is_target;
324	int saw_any_target = 0;
325	int is_first_dep = 0;
326
327	clear_config();
328
329	while (m < end) {
330		/* Skip any "white space" */
331		while (m < end && (*m == ' ' || *m == '\\' || *m == '\n'))
332			m++;
333		/* Find next "white space" */
334		p = m;
335		while (p < end && *p != ' ' && *p != '\\' && *p != '\n')
336			p++;
337		/* Is the token we found a target name? */
338		is_target = (*(p-1) == ':');
339		/* Don't write any target names into the dependency file */
340		if (is_target) {
341			/* The /next/ file is the first dependency */
342			is_first_dep = 1;
343		} else {
344			/* Save this token/filename */
345			memcpy(s, m, p-m);
346			s[p - m] = 0;
347
348			/* Ignore certain dependencies */
349			if (strrcmp(s, "include/generated/autoconf.h") &&
350			    strrcmp(s, "arch/um/include/uml-config.h") &&
351			    strrcmp(s, "include/linux/kconfig.h") &&
352			    strrcmp(s, ".ver")) {
353				/*
354				 * Do not list the source file as dependency,
355				 * so that kbuild is not confused if a .c file
356				 * is rewritten into .S or vice versa. Storing
357				 * it in source_* is needed for modpost to
358				 * compute srcversions.
359				 */
360				if (is_first_dep) {
361					/*
362					 * If processing the concatenation of
363					 * multiple dependency files, only
364					 * process the first target name, which
365					 * will be the original source name,
366					 * and ignore any other target names,
367					 * which will be intermediate temporary
368					 * files.
369					 */
370					if (!saw_any_target) {
371						saw_any_target = 1;
372						printf("source_%s := %s\n\n",
373							target, s);
374						printf("deps_%s := \\\n",
375							target);
376					}
377					is_first_dep = 0;
378				} else
379					printf("  %s \\\n", s);
380				do_config_file(s);
381			}
382		}
383		/*
384		 * Start searching for next token immediately after the first
385		 * "whitespace" character that follows this token.
386		 */
387		m = p + 1;
388	}
389
390	if (!saw_any_target) {
391		fprintf(stderr, "fixdep: parse error; no targets found\n");
392		exit(1);
393	}
394
395	printf("\n%s: $(deps_%s)\n\n", target, target);
396	printf("$(deps_%s):\n", target);
397}
398
399static void print_deps(void)
400{
401	struct stat st;
402	int fd;
403	void *map;
404
405	fd = open(depfile, O_RDONLY);
406	if (fd < 0) {
407		fprintf(stderr, "fixdep: error opening depfile: ");
408		perror(depfile);
409		exit(2);
410	}
411	if (fstat(fd, &st) < 0) {
412		fprintf(stderr, "fixdep: error fstat'ing depfile: ");
413		perror(depfile);
414		exit(2);
415	}
416	if (st.st_size == 0) {
417		fprintf(stderr,"fixdep: %s is empty\n",depfile);
418		close(fd);
419		return;
420	}
421	map = mmap(NULL, st.st_size, PROT_READ, MAP_PRIVATE, fd, 0);
422	if ((long) map == -1) {
423		perror("fixdep: mmap");
424		close(fd);
425		return;
426	}
427
428	parse_dep_file(map, st.st_size);
429
430	munmap(map, st.st_size);
431
432	close(fd);
433}
434
435static void traps(void)
436{
437	static char test[] __attribute__((aligned(sizeof(int)))) = "CONF";
438	int *p = (int *)test;
439
440	if (*p != INT_CONF) {
441		fprintf(stderr, "fixdep: sizeof(int) != 4 or wrong endianness? %#x\n",
442			*p);
443		exit(2);
444	}
445}
446
447int main(int argc, char *argv[])
448{
449	traps();
450
451	if (argc != 4)
452		usage();
453
454	depfile = argv[1];
455	target = argv[2];
456	cmdline = argv[3];
457
458	print_cmdline();
459	print_deps();
460
461	return 0;
462}
463