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 * savedcmd_<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 *config_hashtab[HASHSZ], *file_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 * Add a new value to the configuration string.
131 static void add_to_hashtable(const char *name, int len, unsigned int hash,
132 struct item *hashtab[])
134 struct item *aux = malloc(sizeof(*aux) + len);
137 perror("fixdep:malloc");
140 memcpy(aux->name, name, len);
143 aux->next = hashtab[hash % HASHSZ];
144 hashtab[hash % HASHSZ] = aux;
148 * Lookup a string in the hash table. If found, just return true.
149 * If not, add it to the hashtable and return false.
151 static bool in_hashtable(const char *name, int len, struct item *hashtab[])
154 unsigned int hash = strhash(name, len);
156 for (aux = hashtab[hash % HASHSZ]; aux; aux = aux->next) {
157 if (aux->hash == hash && aux->len == len &&
158 memcmp(aux->name, name, len) == 0)
162 add_to_hashtable(name, len, hash, hashtab);
168 * Record the use of a CONFIG_* word.
170 static void use_config(const char *m, int slen)
172 if (in_hashtable(m, slen, config_hashtab))
175 /* Print out a dependency path from a symbol name. */
176 printf(" $(wildcard include/config/%.*s) \\\n", slen, m);
179 /* test if s ends in sub */
180 static int str_ends_with(const char *s, int slen, const char *sub)
182 int sublen = strlen(sub);
187 return !memcmp(s + slen - sublen, sub, sublen);
190 static void parse_config_file(const char *p)
193 const char *start = p;
195 while ((p = strstr(p, "CONFIG_"))) {
196 if (p > start && (isalnum(p[-1]) || p[-1] == '_')) {
202 while (isalnum(*q) || *q == '_')
204 if (str_ends_with(p, q - p, "_MODULE"))
209 use_config(p, r - p);
214 static void *read_file(const char *filename)
220 fd = open(filename, O_RDONLY);
222 fprintf(stderr, "fixdep: error opening file: ");
226 if (fstat(fd, &st) < 0) {
227 fprintf(stderr, "fixdep: error fstat'ing file: ");
231 buf = malloc(st.st_size + 1);
233 perror("fixdep: malloc");
236 if (read(fd, buf, st.st_size) != st.st_size) {
237 perror("fixdep: read");
240 buf[st.st_size] = '\0';
246 /* Ignore certain dependencies */
247 static int is_ignored_file(const char *s, int len)
249 return str_ends_with(s, len, "include/generated/autoconf.h") ||
250 str_ends_with(s, len, "include/generated/autoksyms.h");
253 /* Do not parse these files */
254 static int is_no_parse_file(const char *s, int len)
256 /* rustc may list binary files in dep-info */
257 return str_ends_with(s, len, ".rlib") ||
258 str_ends_with(s, len, ".rmeta") ||
259 str_ends_with(s, len, ".so");
263 * Important: The below generated source_foo.o and deps_foo.o variable
264 * assignments are parsed not only by make, but also by the rather simple
265 * parser in scripts/mod/sumversion.c.
267 static void parse_dep_file(char *p, const char *target)
269 bool saw_any_target = false;
270 bool is_target = true;
271 bool is_source = false;
276 /* handle some special characters first. */
281 * rustc may emit comments to dep-info.
284 while (*p != '\0' && *p != '\n') {
286 * escaped newlines continue the comment across
296 /* skip whitespaces */
301 * backslash/newline combinations continue the
302 * statement. Skip it just like a whitespace.
304 if (*(p + 1) == '\n') {
311 * Makefiles use a line-based syntax, where the newline
312 * is the end of a statement. After seeing a newline,
313 * we expect the next token is a target.
320 * assume the first dependency after a colon as the
329 /* find the end of the token */
331 while (*q != ' ' && *q != '\t' && *q != '\n' && *q != '#' && *q != ':') {
334 * backslash/newline combinations work like as
335 * a whitespace, so this is the end of token.
337 if (*(q + 1) == '\n')
340 /* escaped special characters */
341 if (*(q + 1) == '#' || *(q + 1) == ':') {
342 memmove(p + 1, p, q - p);
354 /* Just discard the target */
365 * Do not list the source file as dependency, so that kbuild is
366 * not confused if a .c file is rewritten into .S or vice versa.
367 * Storing it in source_* is needed for modpost to compute
372 * The DT build rule concatenates multiple dep files.
373 * When processing them, only process the first source
374 * name, which will be the original one, and ignore any
375 * other source names, which will be intermediate
378 * rustc emits the same dependency list for each
379 * emission type. It is enough to list the source name
382 if (!saw_any_target) {
383 saw_any_target = true;
384 printf("source_%s := %s\n\n", target, p);
385 printf("deps_%s := \\\n", target);
388 } else if (!is_ignored_file(p, q - p) &&
389 !in_hashtable(p, q - p, file_hashtab)) {
390 printf(" %s \\\n", p);
394 if (need_parse && !is_no_parse_file(p, q - p)) {
398 parse_config_file(buf);
407 if (!saw_any_target) {
408 fprintf(stderr, "fixdep: parse error; no targets found\n");
412 printf("\n%s: $(deps_%s)\n\n", target, target);
413 printf("$(deps_%s):\n", target);
416 int main(int argc, char *argv[])
418 const char *depfile, *target, *cmdline;
428 printf("savedcmd_%s := %s\n\n", target, cmdline);
430 buf = read_file(depfile);
431 parse_dep_file(buf, target);
437 * In the intended usage, the stdout is redirected to .*.cmd files.
438 * Call ferror() to catch errors such as "No space left on device".
440 if (ferror(stdout)) {
441 fprintf(stderr, "fixdep: not all data was written to the output\n");