2 * "Optimize" a list of dependencies as spit out by gcc -MD
4 * ===========================================================================
6 * Author Kai Germaschewski
7 * Copyright 2002 by Kai Germaschewski <kai.germaschewski@gmx.de>
9 * This software may be used and distributed according to the terms
10 * of the GNU General Public License, incorporated herein by reference.
15 * gcc produces a very nice and correct list of dependencies which
16 * tells make when to remake a file.
18 * To use this list as-is however has the drawback that virtually
19 * every file in the kernel includes autoconf.h.
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.
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.
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.
36 * So if the user changes his CONFIG_HIS_DRIVER option, only the objects
37 * which depend on "include/config/HIS_DRIVER" will be rebuilt,
38 * so most likely only his driver ;-)
40 * The idea above dates, by the way, back to Michael E Chastain, AFAIK.
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.
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.
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.
56 * This code here has been based partially based on mkdep.c, which
57 * says the following about its history:
59 * Copyright abandoned, Michael Chastain, <mailto:mec@shout.net>.
60 * This is a C version of syncdep.pl by Werner Almesberger.
65 * fixdep <depfile> <target> <cmdline>
67 * and will read the dependency file <depfile>
69 * The transformed dependency snipped is written to stdout.
71 * It first generates a line
73 * cmd_<target> = <cmdline>
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 for every
78 * CONFIG_MY_OPTION encountered in any of the prerequisites.
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.
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)
92 #include <sys/types.h>
102 static void usage(void)
104 fprintf(stderr, "Usage: fixdep <depfile> <target> <cmdline>\n");
116 static struct item *hashtab[HASHSZ];
118 static unsigned int strhash(const char *str, unsigned int sz)
121 unsigned int i, hash = 2166136261U;
123 for (i = 0; i < sz; i++)
124 hash = (hash ^ str[i]) * 0x01000193;
129 * Lookup a value in the configuration string.
131 static int is_defined_config(const char *name, int len, unsigned int hash)
135 for (aux = hashtab[hash % HASHSZ]; aux; aux = aux->next) {
136 if (aux->hash == hash && aux->len == len &&
137 memcmp(aux->name, name, len) == 0)
144 * Add a new value to the configuration string.
146 static void define_config(const char *name, int len, unsigned int hash)
148 struct item *aux = malloc(sizeof(*aux) + len);
151 perror("fixdep:malloc");
154 memcpy(aux->name, name, len);
157 aux->next = hashtab[hash % HASHSZ];
158 hashtab[hash % HASHSZ] = aux;
162 * Record the use of a CONFIG_* word.
164 static void use_config(const char *m, int slen)
166 unsigned int hash = strhash(m, slen);
168 if (is_defined_config(m, slen, hash))
171 define_config(m, slen, hash);
172 /* Print out a dependency path from a symbol name. */
173 printf(" $(wildcard include/config/%.*s) \\\n", slen, m);
176 /* test if s ends in sub */
177 static int str_ends_with(const char *s, int slen, const char *sub)
179 int sublen = strlen(sub);
184 return !memcmp(s + slen - sublen, sub, sublen);
187 static void parse_config_file(const char *p)
190 const char *start = p;
192 while ((p = strstr(p, "CONFIG_"))) {
193 if (p > start && (isalnum(p[-1]) || p[-1] == '_')) {
199 while (isalnum(*q) || *q == '_')
201 if (str_ends_with(p, q - p, "_MODULE"))
206 use_config(p, r - p);
211 static void *read_file(const char *filename)
217 fd = open(filename, O_RDONLY);
219 fprintf(stderr, "fixdep: error opening file: ");
223 if (fstat(fd, &st) < 0) {
224 fprintf(stderr, "fixdep: error fstat'ing file: ");
228 buf = malloc(st.st_size + 1);
230 perror("fixdep: malloc");
233 if (read(fd, buf, st.st_size) != st.st_size) {
234 perror("fixdep: read");
237 buf[st.st_size] = '\0';
243 /* Ignore certain dependencies */
244 static int is_ignored_file(const char *s, int len)
246 return str_ends_with(s, len, "include/generated/autoconf.h") ||
247 str_ends_with(s, len, "include/generated/autoksyms.h");
251 * Important: The below generated source_foo.o and deps_foo.o variable
252 * assignments are parsed not only by make, but also by the rather simple
253 * parser in scripts/mod/sumversion.c.
255 static void parse_dep_file(char *m, const char *target)
258 int is_last, is_target;
259 int saw_any_target = 0;
260 int is_first_dep = 0;
264 /* Skip any "white space" */
265 while (*m == ' ' || *m == '\\' || *m == '\n')
271 /* Find next "white space" */
273 while (*p && *p != ' ' && *p != '\\' && *p != '\n')
275 is_last = (*p == '\0');
276 /* Is the token we found a target name? */
277 is_target = (*(p-1) == ':');
278 /* Don't write any target names into the dependency file */
280 /* The /next/ file is the first dependency */
282 } else if (!is_ignored_file(m, p - m)) {
286 * Do not list the source file as dependency, so that
287 * kbuild is not confused if a .c file is rewritten
288 * into .S or vice versa. Storing it in source_* is
289 * needed for modpost to compute srcversions.
293 * If processing the concatenation of multiple
294 * dependency files, only process the first
295 * target name, which will be the original
296 * source name, and ignore any other target
297 * names, which will be intermediate temporary
300 if (!saw_any_target) {
302 printf("source_%s := %s\n\n",
304 printf("deps_%s := \\\n", target);
308 printf(" %s \\\n", m);
312 parse_config_file(buf);
320 * Start searching for next token immediately after the first
321 * "whitespace" character that follows this token.
326 if (!saw_any_target) {
327 fprintf(stderr, "fixdep: parse error; no targets found\n");
331 printf("\n%s: $(deps_%s)\n\n", target, target);
332 printf("$(deps_%s):\n", target);
335 int main(int argc, char *argv[])
337 const char *depfile, *target, *cmdline;
347 printf("cmd_%s := %s\n\n", target, cmdline);
349 buf = read_file(depfile);
350 parse_dep_file(buf, target);
356 * In the intended usage, the stdout is redirected to .*.cmd files.
357 * Call ferror() to catch errors such as "No space left on device".
359 if (ferror(stdout)) {
360 fprintf(stderr, "fixdep: not all data was written to the output\n");