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