scripts/basic/fixdep.c

   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 <stdlib.h>
 103 #include <stdio.h>
 104 #include <ctype.h>
 105
 106 static void usage(void)
 107 {
 108         fprintf(stderr, "Usage: fixdep [-e] <depfile> <target> <cmdline>\n");
 109         fprintf(stderr, " -e  insert extra dependencies given on stdin\n");
 110         exit(1);
 111 }
 112
 113 /*
 114  * Print out a dependency path from a symbol name
 115  */
 116 static void print_dep(const char *m, int slen, const char *dir)
 117 {
 118         int c, prev_c = '/', i;
 119
 120         printf("    $(wildcard %s/", dir);
 121         for (i = 0; i < slen; i++) {
 122                 c = m[i];
 123                 if (c == '_')
 124                         c = '/';
 125                 else
 126                         c = tolower(c);
 127                 if (c != '/' || prev_c != '/')
 128                         putchar(c);
 129                 prev_c = c;
 130         }
 131         printf(".h) \\\n");
 132 }
 133
 134 static void do_extra_deps(void)
 135 {
 136         char buf[80];
 137
 138         while (fgets(buf, sizeof(buf), stdin)) {
 139                 int len = strlen(buf);
 140
 141                 if (len < 2 || buf[len - 1] != '\n') {
 142                         fprintf(stderr, "fixdep: bad data on stdin\n");
 143                         exit(1);
 144                 }
 145                 print_dep(buf, len - 1, "include/ksym");
 146         }
 147 }
 148
 149 struct item {
 150         struct item     *next;
 151         unsigned int    len;
 152         unsigned int    hash;
 153         char            name[0];
 154 };
 155
 156 #define HASHSZ 256
 157 static struct item *hashtab[HASHSZ];
 158
 159 static unsigned int strhash(const char *str, unsigned int sz)
 160 {
 161         /* fnv32 hash */
 162         unsigned int i, hash = 2166136261U;
 163
 164         for (i = 0; i < sz; i++)
 165                 hash = (hash ^ str[i]) * 0x01000193;
 166         return hash;
 167 }
 168
 169 /*
 170  * Lookup a value in the configuration string.
 171  */
 172 static int is_defined_config(const char *name, int len, unsigned int hash)
 173 {
 174         struct item *aux;
 175
 176         for (aux = hashtab[hash % HASHSZ]; aux; aux = aux->next) {
 177                 if (aux->hash == hash && aux->len == len &&
 178                     memcmp(aux->name, name, len) == 0)
 179                         return 1;
 180         }
 181         return 0;
 182 }
 183
 184 /*
 185  * Add a new value to the configuration string.
 186  */
 187 static void define_config(const char *name, int len, unsigned int hash)
 188 {
 189         struct item *aux = malloc(sizeof(*aux) + len);
 190
 191         if (!aux) {
 192                 perror("fixdep:malloc");
 193                 exit(1);
 194         }
 195         memcpy(aux->name, name, len);
 196         aux->len = len;
 197         aux->hash = hash;
 198         aux->next = hashtab[hash % HASHSZ];
 199         hashtab[hash % HASHSZ] = aux;
 200 }
 201
 202 /*
 203  * Record the use of a CONFIG_* word.
 204  */
 205 static void use_config(const char *m, int slen)
 206 {
 207         unsigned int hash = strhash(m, slen);
 208
 209         if (is_defined_config(m, slen, hash))
 210             return;
 211
 212         define_config(m, slen, hash);
 213         print_dep(m, slen, "include/config");
 214 }
 215
 216 /* test if s ends in sub */
 217 static int str_ends_with(const char *s, int slen, const char *sub)
 218 {
 219         int sublen = strlen(sub);
 220
 221         if (sublen > slen)
 222                 return 0;
 223
 224         return !memcmp(s + slen - sublen, sub, sublen);
 225 }
 226
 227 static void parse_config_file(const char *p)
 228 {
 229         const char *q, *r;
 230         const char *start = p;
 231
 232         while ((p = strstr(p, "CONFIG_"))) {
 233                 if (p > start && (isalnum(p[-1]) || p[-1] == '_')) {
 234                         p += 7;
 235                         continue;
 236                 }
 237                 p += 7;
 238                 q = p;
 239                 while (*q && (isalnum(*q) || *q == '_'))
 240                         q++;
 241                 if (str_ends_with(p, q - p, "_MODULE"))
 242                         r = q - 7;
 243                 else
 244                         r = q;
 245                 if (r > p)
 246                         use_config(p, r - p);
 247                 p = q;
 248         }
 249 }
 250
 251 static void *read_file(const char *filename)
 252 {
 253         struct stat st;
 254         int fd;
 255         char *buf;
 256
 257         fd = open(filename, O_RDONLY);
 258         if (fd < 0) {
 259                 fprintf(stderr, "fixdep: error opening file: ");
 260                 perror(filename);
 261                 exit(2);
 262         }
 263         if (fstat(fd, &st) < 0) {
 264                 fprintf(stderr, "fixdep: error fstat'ing file: ");
 265                 perror(filename);
 266                 exit(2);
 267         }
 268         buf = malloc(st.st_size + 1);
 269         if (!buf) {
 270                 perror("fixdep: malloc");
 271                 exit(2);
 272         }
 273         if (read(fd, buf, st.st_size) != st.st_size) {
 274                 perror("fixdep: read");
 275                 exit(2);
 276         }
 277         buf[st.st_size] = '\0';
 278         close(fd);
 279
 280         return buf;
 281 }
 282
 283 /* Ignore certain dependencies */
 284 static int is_ignored_file(const char *s, int len)
 285 {
 286         return str_ends_with(s, len, "include/generated/autoconf.h") ||
 287                str_ends_with(s, len, "include/generated/autoksyms.h") ||
 288                str_ends_with(s, len, ".ver");
 289 }
 290
 291 /*
 292  * Important: The below generated source_foo.o and deps_foo.o variable
 293  * assignments are parsed not only by make, but also by the rather simple
 294  * parser in scripts/mod/sumversion.c.
 295  */
 296 static void parse_dep_file(char *m, const char *target, int insert_extra_deps)
 297 {
 298         char *p;
 299         int is_last, is_target;
 300         int saw_any_target = 0;
 301         int is_first_dep = 0;
 302         void *buf;
 303
 304         while (1) {
 305                 /* Skip any "white space" */
 306                 while (*m == ' ' || *m == '\\' || *m == '\n')
 307                         m++;
 308
 309                 if (!*m)
 310                         break;
 311
 312                 /* Find next "white space" */
 313                 p = m;
 314                 while (*p && *p != ' ' && *p != '\\' && *p != '\n')
 315                         p++;
 316                 is_last = (*p == '\0');
 317                 /* Is the token we found a target name? */
 318                 is_target = (*(p-1) == ':');
 319                 /* Don't write any target names into the dependency file */
 320                 if (is_target) {
 321                         /* The /next/ file is the first dependency */
 322                         is_first_dep = 1;
 323                 } else if (!is_ignored_file(m, p - m)) {
 324                         *p = '\0';
 325
 326                         /*
 327                          * Do not list the source file as dependency, so that
 328                          * kbuild is not confused if a .c file is rewritten
 329                          * into .S or vice versa. Storing it in source_* is
 330                          * needed for modpost to compute srcversions.
 331                          */
 332                         if (is_first_dep) {
 333                                 /*
 334                                  * If processing the concatenation of multiple
 335                                  * dependency files, only process the first
 336                                  * target name, which will be the original
 337                                  * source name, and ignore any other target
 338                                  * names, which will be intermediate temporary
 339                                  * files.
 340                                  */
 341                                 if (!saw_any_target) {
 342                                         saw_any_target = 1;
 343                                         printf("source_%s := %s\n\n",
 344                                                target, m);
 345                                         printf("deps_%s := \\\n", target);
 346                                 }
 347                                 is_first_dep = 0;
 348                         } else {
 349                                 printf("  %s \\\n", m);
 350                         }
 351
 352                         buf = read_file(m);
 353                         parse_config_file(buf);
 354                         free(buf);
 355                 }
 356
 357                 if (is_last)
 358                         break;
 359
 360                 /*
 361                  * Start searching for next token immediately after the first
 362                  * "whitespace" character that follows this token.
 363                  */
 364                 m = p + 1;
 365         }
 366
 367         if (!saw_any_target) {
 368                 fprintf(stderr, "fixdep: parse error; no targets found\n");
 369                 exit(1);
 370         }
 371
 372         if (insert_extra_deps)
 373                 do_extra_deps();
 374
 375         printf("\n%s: $(deps_%s)\n\n", target, target);
 376         printf("$(deps_%s):\n", target);
 377 }
 378
 379 int main(int argc, char *argv[])
 380 {
 381         const char *depfile, *target, *cmdline;
 382         int insert_extra_deps = 0;
 383         void *buf;
 384
 385         if (argc == 5 && !strcmp(argv[1], "-e")) {
 386                 insert_extra_deps = 1;
 387                 argv++;
 388         } else if (argc != 4)
 389                 usage();
 390
 391         depfile = argv[1];
 392         target = argv[2];
 393         cmdline = argv[3];
 394
 395         printf("cmd_%s := %s\n\n", target, cmdline);
 396
 397         buf = read_file(depfile);
 398         parse_dep_file(buf, target, insert_extra_deps);
 399         free(buf);
 400
 401         return 0;
 402 }