linux/scripts/basic/fixdep.c
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   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 prequisites.
  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/linux/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 prequisites.
  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 * The algorithm to grep for "CONFIG_..." is bit unusual, but should
  86 * be fast ;-) We don't even try to really parse the header files, but
  87 * merely grep, i.e. if CONFIG_FOO is mentioned in a comment, it will
  88 * be picked up as well. It's not a problem with respect to
  89 * correctness, since that can only give too many dependencies, thus
  90 * we cannot miss a rebuild. Since people tend to not mention totally
  91 * unrelated CONFIG_ options all over the place, it's not an
  92 * efficiency problem either.
  93 *
  94 * (Note: it'd be easy to port over the complete mkdep state machine,
  95 *  but I don't think the added complexity is worth it)
  96 */
  97/*
  98 * Note 2: if somebody writes HELLO_CONFIG_BOOM in a file, it will depend onto
  99 * CONFIG_BOOM. This could seem a bug (not too hard to fix), but please do not
 100 * fix it! Some UserModeLinux files (look at arch/um/) call CONFIG_BOOM as
 101 * UML_CONFIG_BOOM, to avoid conflicts with /usr/include/linux/autoconf.h,
 102 * through arch/um/include/uml-config.h; this fixdep "bug" makes sure that
 103 * those files will have correct dependencies.
 104 */
 105
 106#include <sys/types.h>
 107#include <sys/stat.h>
 108#include <sys/mman.h>
 109#include <unistd.h>
 110#include <fcntl.h>
 111#include <string.h>
 112#include <stdlib.h>
 113#include <stdio.h>
 114#include <limits.h>
 115#include <ctype.h>
 116#include <arpa/inet.h>
 117
 118#define INT_CONF ntohl(0x434f4e46)
 119#define INT_ONFI ntohl(0x4f4e4649)
 120#define INT_NFIG ntohl(0x4e464947)
 121#define INT_FIG_ ntohl(0x4649475f)
 122
 123char *target;
 124char *depfile;
 125char *cmdline;
 126
 127static void usage(void)
 128{
 129        fprintf(stderr, "Usage: fixdep <depfile> <target> <cmdline>\n");
 130        exit(1);
 131}
 132
 133/*
 134 * Print out the commandline prefixed with cmd_<target filename> :=
 135 */
 136static void print_cmdline(void)
 137{
 138        printf("cmd_%s := %s\n\n", target, cmdline);
 139}
 140
 141struct item {
 142        struct item     *next;
 143        unsigned int    len;
 144        unsigned int    hash;
 145        char            name[0];
 146};
 147
 148#define HASHSZ 256
 149static struct item *hashtab[HASHSZ];
 150
 151static unsigned int strhash(const char *str, unsigned int sz)
 152{
 153        /* fnv32 hash */
 154        unsigned int i, hash = 2166136261U;
 155
 156        for (i = 0; i < sz; i++)
 157                hash = (hash ^ str[i]) * 0x01000193;
 158        return hash;
 159}
 160
 161/*
 162 * Lookup a value in the configuration string.
 163 */
 164static int is_defined_config(const char *name, int len, unsigned int hash)
 165{
 166        struct item *aux;
 167
 168        for (aux = hashtab[hash % HASHSZ]; aux; aux = aux->next) {
 169                if (aux->hash == hash && aux->len == len &&
 170                    memcmp(aux->name, name, len) == 0)
 171                        return 1;
 172        }
 173        return 0;
 174}
 175
 176/*
 177 * Add a new value to the configuration string.
 178 */
 179static void define_config(const char *name, int len, unsigned int hash)
 180{
 181        struct item *aux = malloc(sizeof(*aux) + len);
 182
 183        if (!aux) {
 184                perror("fixdep:malloc");
 185                exit(1);
 186        }
 187        memcpy(aux->name, name, len);
 188        aux->len = len;
 189        aux->hash = hash;
 190        aux->next = hashtab[hash % HASHSZ];
 191        hashtab[hash % HASHSZ] = aux;
 192}
 193
 194/*
 195 * Clear the set of configuration strings.
 196 */
 197static void clear_config(void)
 198{
 199        struct item *aux, *next;
 200        unsigned int i;
 201
 202        for (i = 0; i < HASHSZ; i++) {
 203                for (aux = hashtab[i]; aux; aux = next) {
 204                        next = aux->next;
 205                        free(aux);
 206                }
 207                hashtab[i] = NULL;
 208        }
 209}
 210
 211/*
 212 * Record the use of a CONFIG_* word.
 213 */
 214static void use_config(const char *m, int slen)
 215{
 216        unsigned int hash = strhash(m, slen);
 217        int c, i;
 218
 219        if (is_defined_config(m, slen, hash))
 220            return;
 221
 222        define_config(m, slen, hash);
 223
 224        printf("    $(wildcard include/config/");
 225        for (i = 0; i < slen; i++) {
 226                c = m[i];
 227                if (c == '_')
 228                        c = '/';
 229                else
 230                        c = tolower(c);
 231                putchar(c);
 232        }
 233        printf(".h) \\\n");
 234}
 235
 236static void parse_config_file(const char *map, size_t len)
 237{
 238        const int *end = (const int *) (map + len);
 239        /* start at +1, so that p can never be < map */
 240        const int *m   = (const int *) map + 1;
 241        const char *p, *q;
 242
 243        for (; m < end; m++) {
 244                if (*m == INT_CONF) { p = (char *) m  ; goto conf; }
 245                if (*m == INT_ONFI) { p = (char *) m-1; goto conf; }
 246                if (*m == INT_NFIG) { p = (char *) m-2; goto conf; }
 247                if (*m == INT_FIG_) { p = (char *) m-3; goto conf; }
 248                continue;
 249        conf:
 250                if (p > map + len - 7)
 251                        continue;
 252                if (memcmp(p, "CONFIG_", 7))
 253                        continue;
 254                for (q = p + 7; q < map + len; q++) {
 255                        if (!(isalnum(*q) || *q == '_'))
 256                                goto found;
 257                }
 258                continue;
 259
 260        found:
 261                if (!memcmp(q - 7, "_MODULE", 7))
 262                        q -= 7;
 263                if( (q-p-7) < 0 )
 264                        continue;
 265                use_config(p+7, q-p-7);
 266        }
 267}
 268
 269/* test is s ends in sub */
 270static int strrcmp(char *s, char *sub)
 271{
 272        int slen = strlen(s);
 273        int sublen = strlen(sub);
 274
 275        if (sublen > slen)
 276                return 1;
 277
 278        return memcmp(s + slen - sublen, sub, sublen);
 279}
 280
 281static void do_config_file(const char *filename)
 282{
 283        struct stat st;
 284        int fd;
 285        void *map;
 286
 287        fd = open(filename, O_RDONLY);
 288        if (fd < 0) {
 289                fprintf(stderr, "fixdep: error opening config file: ");
 290                perror(filename);
 291                exit(2);
 292        }
 293        fstat(fd, &st);
 294        if (st.st_size == 0) {
 295                close(fd);
 296                return;
 297        }
 298        map = mmap(NULL, st.st_size, PROT_READ, MAP_PRIVATE, fd, 0);
 299        if ((long) map == -1) {
 300                perror("fixdep: mmap");
 301                close(fd);
 302                return;
 303        }
 304
 305        parse_config_file(map, st.st_size);
 306
 307        munmap(map, st.st_size);
 308
 309        close(fd);
 310}
 311
 312/*
 313 * Important: The below generated source_foo.o and deps_foo.o variable
 314 * assignments are parsed not only by make, but also by the rather simple
 315 * parser in scripts/mod/sumversion.c.
 316 */
 317static void parse_dep_file(void *map, size_t len)
 318{
 319        char *m = map;
 320        char *end = m + len;
 321        char *p;
 322        char s[PATH_MAX];
 323        int first;
 324
 325        p = strchr(m, ':');
 326        if (!p) {
 327                fprintf(stderr, "fixdep: parse error\n");
 328                exit(1);
 329        }
 330        memcpy(s, m, p-m); s[p-m] = 0;
 331        m = p+1;
 332
 333        clear_config();
 334
 335        first = 1;
 336        while (m < end) {
 337                while (m < end && (*m == ' ' || *m == '\\' || *m == '\n'))
 338                        m++;
 339                p = m;
 340                while (p < end && *p != ' ') p++;
 341                if (p == end) {
 342                        do p--; while (!isalnum(*p));
 343                        p++;
 344                }
 345                memcpy(s, m, p-m); s[p-m] = 0;
 346                if (strrcmp(s, "include/generated/autoconf.h") &&
 347                    strrcmp(s, "arch/um/include/uml-config.h") &&
 348                    strrcmp(s, "include/linux/kconfig.h") &&
 349                    strrcmp(s, ".ver")) {
 350                        /*
 351                         * Do not list the source file as dependency, so that
 352                         * kbuild is not confused if a .c file is rewritten
 353                         * into .S or vice versa. Storing it in source_* is
 354                         * needed for modpost to compute srcversions.
 355                         */
 356                        if (first) {
 357                                printf("source_%s := %s\n\n", target, s);
 358                                printf("deps_%s := \\\n", target);
 359                        } else
 360                                printf("  %s \\\n", s);
 361                        do_config_file(s);
 362                }
 363                first = 0;
 364                m = p + 1;
 365        }
 366        printf("\n%s: $(deps_%s)\n\n", target, target);
 367        printf("$(deps_%s):\n", target);
 368}
 369
 370static void print_deps(void)
 371{
 372        struct stat st;
 373        int fd;
 374        void *map;
 375
 376        fd = open(depfile, O_RDONLY);
 377        if (fd < 0) {
 378                fprintf(stderr, "fixdep: error opening depfile: ");
 379                perror(depfile);
 380                exit(2);
 381        }
 382        if (fstat(fd, &st) < 0) {
 383                fprintf(stderr, "fixdep: error fstat'ing depfile: ");
 384                perror(depfile);
 385                exit(2);
 386        }
 387        if (st.st_size == 0) {
 388                fprintf(stderr,"fixdep: %s is empty\n",depfile);
 389                close(fd);
 390                return;
 391        }
 392        map = mmap(NULL, st.st_size, PROT_READ, MAP_PRIVATE, fd, 0);
 393        if ((long) map == -1) {
 394                perror("fixdep: mmap");
 395                close(fd);
 396                return;
 397        }
 398
 399        parse_dep_file(map, st.st_size);
 400
 401        munmap(map, st.st_size);
 402
 403        close(fd);
 404}
 405
 406static void traps(void)
 407{
 408        static char test[] __attribute__((aligned(sizeof(int)))) = "CONF";
 409        int *p = (int *)test;
 410
 411        if (*p != INT_CONF) {
 412                fprintf(stderr, "fixdep: sizeof(int) != 4 or wrong endianess? %#x\n",
 413                        *p);
 414                exit(2);
 415        }
 416}
 417
 418int main(int argc, char *argv[])
 419{
 420        traps();
 421
 422        if (argc != 4)
 423                usage();
 424
 425        depfile = argv[1];
 426        target = argv[2];
 427        cmdline = argv[3];
 428
 429        print_cmdline();
 430        print_deps();
 431
 432        return 0;
 433}
 434
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