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 * We don't even try to really parse the header files, but
81 * merely grep, i.e. if CONFIG_FOO is mentioned in a comment, it will
82 * be picked up as well. It's not a problem with respect to
83 * correctness, since that can only give too many dependencies, thus
84 * we cannot miss a rebuild. Since people tend to not mention totally
85 * unrelated CONFIG_ options all over the place, it's not an
86 * efficiency problem either.
87 *
88 * (Note: it'd be easy to port over the complete mkdep state machine,
89 *  but I don't think the added complexity is worth it)
90 */
91
92#include <sys/types.h>
93#include <sys/stat.h>
94#include <unistd.h>
95#include <fcntl.h>
96#include <string.h>
97#include <stdarg.h>
98#include <stdlib.h>
99#include <stdio.h>
100#include <ctype.h>
101
102char tmp_buf[256]; /* hack for U-Boot */
103
104static void usage(void)
105{
106	fprintf(stderr, "Usage: fixdep <depfile> <target> <cmdline>\n");
107	exit(1);
108}
109
110/*
111 * In the intended usage of this program, the stdout is redirected to .*.cmd
112 * files. The return value of printf() and putchar() must be checked to catch
113 * any error, e.g. "No space left on device".
114 */
115static void xprintf(const char *format, ...)
116{
117	va_list ap;
118	int ret;
119
120	va_start(ap, format);
121	ret = vprintf(format, ap);
122	if (ret < 0) {
123		perror("fixdep");
124		exit(1);
125	}
126	va_end(ap);
127}
128
129static void xputchar(int c)
130{
131	int ret;
132
133	ret = putchar(c);
134	if (ret == EOF) {
135		perror("fixdep");
136		exit(1);
137	}
138}
139
140/*
141 * Print out a dependency path from a symbol name
142 */
143static void print_dep(const char *m, int slen, const char *dir)
144{
145	int c, prev_c = '/', i;
146
147	xprintf("    $(wildcard %s/", dir);
148	for (i = 0; i < slen; i++) {
149		c = m[i];
150		if (c == '_')
151			c = '/';
152		else
153			c = tolower(c);
154		if (c != '/' || prev_c != '/')
155			xputchar(c);
156		prev_c = c;
157	}
158	xprintf(".h) \\\n");
159}
160
161struct item {
162	struct item	*next;
163	unsigned int	len;
164	unsigned int	hash;
165	char		name[0];
166};
167
168#define HASHSZ 256
169static struct item *hashtab[HASHSZ];
170
171static unsigned int strhash(const char *str, unsigned int sz)
172{
173	/* fnv32 hash */
174	unsigned int i, hash = 2166136261U;
175
176	for (i = 0; i < sz; i++)
177		hash = (hash ^ str[i]) * 0x01000193;
178	return hash;
179}
180
181/*
182 * Lookup a value in the configuration string.
183 */
184static int is_defined_config(const char *name, int len, unsigned int hash)
185{
186	struct item *aux;
187
188	for (aux = hashtab[hash % HASHSZ]; aux; aux = aux->next) {
189		if (aux->hash == hash && aux->len == len &&
190		    memcmp(aux->name, name, len) == 0)
191			return 1;
192	}
193	return 0;
194}
195
196/*
197 * Add a new value to the configuration string.
198 */
199static void define_config(const char *name, int len, unsigned int hash)
200{
201	struct item *aux = malloc(sizeof(*aux) + len);
202
203	if (!aux) {
204		perror("fixdep:malloc");
205		exit(1);
206	}
207	memcpy(aux->name, name, len);
208	aux->len = len;
209	aux->hash = hash;
210	aux->next = hashtab[hash % HASHSZ];
211	hashtab[hash % HASHSZ] = aux;
212}
213
214/*
215 * Record the use of a CONFIG_* word.
216 */
217static void use_config(const char *m, int slen)
218{
219	unsigned int hash = strhash(m, slen);
220
221	if (is_defined_config(m, slen, hash))
222	    return;
223
224	define_config(m, slen, hash);
225	print_dep(m, slen, "include/config");
226}
227
228/* test if s ends in sub */
229static int str_ends_with(const char *s, int slen, const char *sub)
230{
231	int sublen = strlen(sub);
232
233	if (sublen > slen)
234		return 0;
235
236	return !memcmp(s + slen - sublen, sub, sublen);
237}
238
239static void parse_config_file(const char *p)
240{
241	const char *q, *r;
242	const char *start = p;
243
244	while ((p = strstr(p, "CONFIG_"))) {
245		if (p > start && (isalnum(p[-1]) || p[-1] == '_')) {
246			p += 7;
247			continue;
248		}
249		p += 7;
250		q = p;
251		while (isalnum(*q) || *q == '_')
252			q++;
253		if (str_ends_with(p, q - p, "_MODULE"))
254			r = q - 7;
255		else
256			r = q;
257		/*
258		 * U-Boot also handles
259		 *   CONFIG_IS_ENABLED(...)
260		 *   CONFIG_VAL(...)
261		 */
262		if ((q - p == 10 && !memcmp(p, "IS_ENABLED(", 11)) ||
263		    (q - p == 3 && !memcmp(p, "VAL(", 4))) {
264			p = q + 1;
265			q = p;
266			while (isalnum(*q) || *q == '_')
267				q++;
268			r = q;
269			if (r > p && tmp_buf[0]) {
270				memcpy(tmp_buf + 4, p, r - p);
271				r = tmp_buf + 4 + (r - p);
272				p = tmp_buf;
273			}
274		}
275		/* end U-Boot hack */
276
277		if (r > p)
278			use_config(p, r - p);
279		p = q;
280	}
281}
282
283static void *read_file(const char *filename)
284{
285	struct stat st;
286	int fd;
287	char *buf;
288
289	fd = open(filename, O_RDONLY);
290	if (fd < 0) {
291		fprintf(stderr, "fixdep: error opening file: ");
292		perror(filename);
293		exit(2);
294	}
295	if (fstat(fd, &st) < 0) {
296		fprintf(stderr, "fixdep: error fstat'ing file: ");
297		perror(filename);
298		exit(2);
299	}
300	buf = malloc(st.st_size + 1);
301	if (!buf) {
302		perror("fixdep: malloc");
303		exit(2);
304	}
305	if (read(fd, buf, st.st_size) != st.st_size) {
306		perror("fixdep: read");
307		exit(2);
308	}
309	buf[st.st_size] = '\0';
310	close(fd);
311
312	return buf;
313}
314
315/* Ignore certain dependencies */
316static int is_ignored_file(const char *s, int len)
317{
318	return str_ends_with(s, len, "include/generated/autoconf.h") ||
319	       str_ends_with(s, len, "include/generated/autoksyms.h");
320}
321
322/*
323 * Important: The below generated source_foo.o and deps_foo.o variable
324 * assignments are parsed not only by make, but also by the rather simple
325 * parser in scripts/mod/sumversion.c.
326 */
327static void parse_dep_file(char *m, const char *target)
328{
329	char *p;
330	int is_last, is_target;
331	int saw_any_target = 0;
332	int is_first_dep = 0;
333	void *buf;
334
335	while (1) {
336		/* Skip any "white space" */
337		while (*m == ' ' || *m == '\\' || *m == '\n')
338			m++;
339
340		if (!*m)
341			break;
342
343		/* Find next "white space" */
344		p = m;
345		while (*p && *p != ' ' && *p != '\\' && *p != '\n')
346			p++;
347		is_last = (*p == '\0');
348		/* Is the token we found a target name? */
349		is_target = (*(p-1) == ':');
350		/* Don't write any target names into the dependency file */
351		if (is_target) {
352			/* The /next/ file is the first dependency */
353			is_first_dep = 1;
354		} else if (!is_ignored_file(m, p - m)) {
355			*p = '\0';
356
357			/*
358			 * Do not list the source file as dependency, so that
359			 * kbuild is not confused if a .c file is rewritten
360			 * into .S or vice versa. Storing it in source_* is
361			 * needed for modpost to compute srcversions.
362			 */
363			if (is_first_dep) {
364				/*
365				 * If processing the concatenation of multiple
366				 * dependency files, only process the first
367				 * target name, which will be the original
368				 * source name, and ignore any other target
369				 * names, which will be intermediate temporary
370				 * files.
371				 */
372				if (!saw_any_target) {
373					saw_any_target = 1;
374					xprintf("source_%s := %s\n\n",
375						target, m);
376					xprintf("deps_%s := \\\n", target);
377				}
378				is_first_dep = 0;
379			} else {
380				xprintf("  %s \\\n", m);
381			}
382
383			buf = read_file(m);
384			parse_config_file(buf);
385			free(buf);
386		}
387
388		if (is_last)
389			break;
390
391		/*
392		 * Start searching for next token immediately after the first
393		 * "whitespace" character that follows this token.
394		 */
395		m = p + 1;
396	}
397
398	if (!saw_any_target) {
399		fprintf(stderr, "fixdep: parse error; no targets found\n");
400		exit(1);
401	}
402
403	xprintf("\n%s: $(deps_%s)\n\n", target, target);
404	xprintf("$(deps_%s):\n", target);
405}
406
407int main(int argc, char *argv[])
408{
409	const char *depfile, *target, *cmdline;
410	void *buf;
411
412	if (argc != 4)
413		usage();
414
415	depfile = argv[1];
416	target = argv[2];
417	cmdline = argv[3];
418
419	/* hack for U-Boot */
420	if (!strncmp(target, "spl/", 4))
421		strcpy(tmp_buf, "SPL_");
422	else if (!strncmp(target, "tpl/", 4))
423		strcpy(tmp_buf, "TPL_");
424	/* end U-Boot hack */
425
426	xprintf("cmd_%s := %s\n\n", target, cmdline);
427
428	buf = read_file(depfile);
429	parse_dep_file(buf, target);
430	free(buf);
431
432	return 0;
433}
434