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