Root/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 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, ".ver")) {
349            /*
350             * Do not list the source file as dependency, so that
351             * kbuild is not confused if a .c file is rewritten
352             * into .S or vice versa. Storing it in source_* is
353             * needed for modpost to compute srcversions.
354             */
355            if (first) {
356                printf("source_%s := %s\n\n", target, s);
357                printf("deps_%s := \\\n", target);
358            } else
359                printf(" %s \\\n", s);
360            do_config_file(s);
361        }
362        first = 0;
363        m = p + 1;
364    }
365    printf("\n%s: $(deps_%s)\n\n", target, target);
366    printf("$(deps_%s):\n", target);
367}
368
369static void print_deps(void)
370{
371    struct stat st;
372    int fd;
373    void *map;
374
375    fd = open(depfile, O_RDONLY);
376    if (fd < 0) {
377        fprintf(stderr, "fixdep: error opening depfile: ");
378        perror(depfile);
379        exit(2);
380    }
381    if (fstat(fd, &st) < 0) {
382                fprintf(stderr, "fixdep: error fstat'ing depfile: ");
383                perror(depfile);
384                exit(2);
385        }
386    if (st.st_size == 0) {
387        fprintf(stderr,"fixdep: %s is empty\n",depfile);
388        close(fd);
389        return;
390    }
391    map = mmap(NULL, st.st_size, PROT_READ, MAP_PRIVATE, fd, 0);
392    if ((long) map == -1) {
393        perror("fixdep: mmap");
394        close(fd);
395        return;
396    }
397
398    parse_dep_file(map, st.st_size);
399
400    munmap(map, st.st_size);
401
402    close(fd);
403}
404
405static void traps(void)
406{
407    static char test[] __attribute__((aligned(sizeof(int)))) = "CONF";
408    int *p = (int *)test;
409
410    if (*p != INT_CONF) {
411        fprintf(stderr, "fixdep: sizeof(int) != 4 or wrong endianess? %#x\n",
412            *p);
413        exit(2);
414    }
415}
416
417int main(int argc, char *argv[])
418{
419    traps();
420
421    if (argc != 4)
422        usage();
423
424    depfile = argv[1];
425    target = argv[2];
426    cmdline = argv[3];
427
428    print_cmdline();
429    print_deps();
430
431    return 0;
432}
433

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