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+/*
+ * "Optimize" a list of dependencies as spit out by gcc -MD
+ * for the kernel build
+ * ===========================================================================
+ *
+ * Author Kai Germaschewski
+ * Copyright 2002 by Kai Germaschewski <kai.germaschewski@gmx.de>
+ *
+ * This software may be used and distributed according to the terms
+ * of the GNU General Public License, incorporated herein by reference.
+ *
+ *
+ * Introduction:
+ *
+ * gcc produces a very nice and correct list of dependencies which
+ * tells make when to remake a file.
+ *
+ * To use this list as-is however has the drawback that virtually
+ * every file in the kernel includes autoconf.h.
+ *
+ * If the user re-runs make *config, autoconf.h will be
+ * regenerated. make notices that and will rebuild every file which
+ * includes autoconf.h, i.e. basically all files. This is extremely
+ * annoying if the user just changed CONFIG_HIS_DRIVER from n to m.
+ *
+ * So we play the same trick that "mkdep" played before. We replace
+ * the dependency on autoconf.h by a dependency on every config
+ * option which is mentioned in any of the listed prerequisites.
+ *
+ * kconfig populates a tree in include/config/ with an empty file
+ * for each config symbol and when the configuration is updated
+ * the files representing changed config options are touched
+ * which then let make pick up the changes and the files that use
+ * the config symbols are rebuilt.
+ *
+ * So if the user changes his CONFIG_HIS_DRIVER option, only the objects
+ * which depend on "include/config/his/driver.h" will be rebuilt,
+ * so most likely only his driver ;-)
+ *
+ * The idea above dates, by the way, back to Michael E Chastain, AFAIK.
+ *
+ * So to get dependencies right, there are two issues:
+ * o if any of the files the compiler read changed, we need to rebuild
+ * o if the command line given to the compile the file changed, we
+ * better rebuild as well.
+ *
+ * The former is handled by using the -MD output, the later by saving
+ * the command line used to compile the old object and comparing it
+ * to the one we would now use.
+ *
+ * Again, also this idea is pretty old and has been discussed on
+ * kbuild-devel a long time ago. I don't have a sensibly working
+ * internet connection right now, so I rather don't mention names
+ * without double checking.
+ *
+ * This code here has been based partially based on mkdep.c, which
+ * says the following about its history:
+ *
+ * Copyright abandoned, Michael Chastain, <mailto:mec@shout.net>.
+ * This is a C version of syncdep.pl by Werner Almesberger.
+ *
+ *
+ * It is invoked as
+ *
+ * fixdep <depfile> <target> <cmdline>
+ *
+ * and will read the dependency file <depfile>
+ *
+ * The transformed dependency snipped is written to stdout.
+ *
+ * It first generates a line
+ *
+ * cmd_<target> = <cmdline>
+ *
+ * and then basically copies the .<target>.d file to stdout, in the
+ * process filtering out the dependency on autoconf.h and adding
+ * dependencies on include/config/my/option.h for every
+ * CONFIG_MY_OPTION encountered in any of the prerequisites.
+ *
+ * It will also filter out all the dependencies on *.ver. We need
+ * to make sure that the generated version checksum are globally up
+ * to date before even starting the recursive build, so it's too late
+ * at this point anyway.
+ *
+ * We don't even try to really parse the header files, but
+ * merely grep, i.e. if CONFIG_FOO is mentioned in a comment, it will
+ * be picked up as well. It's not a problem with respect to
+ * correctness, since that can only give too many dependencies, thus
+ * we cannot miss a rebuild. Since people tend to not mention totally
+ * unrelated CONFIG_ options all over the place, it's not an
+ * efficiency problem either.
+ *
+ * (Note: it'd be easy to port over the complete mkdep state machine,
+ * but I don't think the added complexity is worth it)
+ */
+
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <string.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <ctype.h>
+
+static void usage(void)
+{
+ fprintf(stderr, "Usage: fixdep [-e] <depfile> <target> <cmdline>\n");
+ fprintf(stderr, " -e insert extra dependencies given on stdin\n");
+ exit(1);
+}
+
+/*
+ * Print out a dependency path from a symbol name
+ */
+static void print_dep(const char *m, int slen, const char *dir)
+{
+ int c, prev_c = '/', i;
+
+ printf(" $(wildcard %s/", dir);
+ for (i = 0; i < slen; i++) {
+ c = m[i];
+ if (c == '_')
+ c = '/';
+ else
+ c = tolower(c);
+ if (c != '/' || prev_c != '/')
+ putchar(c);
+ prev_c = c;
+ }
+ printf(".h) \\\n");
+}
+
+static void do_extra_deps(void)
+{
+ char buf[80];
+
+ while (fgets(buf, sizeof(buf), stdin)) {
+ int len = strlen(buf);
+
+ if (len < 2 || buf[len - 1] != '\n') {
+ fprintf(stderr, "fixdep: bad data on stdin\n");
+ exit(1);
+ }
+ print_dep(buf, len - 1, "include/ksym");
+ }
+}
+
+struct item {
+ struct item *next;
+ unsigned int len;
+ unsigned int hash;
+ char name[0];
+};
+
+#define HASHSZ 256
+static struct item *hashtab[HASHSZ];
+
+static unsigned int strhash(const char *str, unsigned int sz)
+{
+ /* fnv32 hash */
+ unsigned int i, hash = 2166136261U;
+
+ for (i = 0; i < sz; i++)
+ hash = (hash ^ str[i]) * 0x01000193;
+ return hash;
+}
+
+/*
+ * Lookup a value in the configuration string.
+ */
+static int is_defined_config(const char *name, int len, unsigned int hash)
+{
+ struct item *aux;
+
+ for (aux = hashtab[hash % HASHSZ]; aux; aux = aux->next) {
+ if (aux->hash == hash && aux->len == len &&
+ memcmp(aux->name, name, len) == 0)
+ return 1;
+ }
+ return 0;
+}
+
+/*
+ * Add a new value to the configuration string.
+ */
+static void define_config(const char *name, int len, unsigned int hash)
+{
+ struct item *aux = malloc(sizeof(*aux) + len);
+
+ if (!aux) {
+ perror("fixdep:malloc");
+ exit(1);
+ }
+ memcpy(aux->name, name, len);
+ aux->len = len;
+ aux->hash = hash;
+ aux->next = hashtab[hash % HASHSZ];
+ hashtab[hash % HASHSZ] = aux;
+}
+
+/*
+ * Record the use of a CONFIG_* word.
+ */
+static void use_config(const char *m, int slen)
+{
+ unsigned int hash = strhash(m, slen);
+
+ if (is_defined_config(m, slen, hash))
+ return;
+
+ define_config(m, slen, hash);
+ print_dep(m, slen, "include/config");
+}
+
+/* test if s ends in sub */
+static int str_ends_with(const char *s, int slen, const char *sub)
+{
+ int sublen = strlen(sub);
+
+ if (sublen > slen)
+ return 0;
+
+ return !memcmp(s + slen - sublen, sub, sublen);
+}
+
+static void parse_config_file(const char *p)
+{
+ const char *q, *r;
+ const char *start = p;
+
+ while ((p = strstr(p, "CONFIG_"))) {
+ if (p > start && (isalnum(p[-1]) || p[-1] == '_')) {
+ p += 7;
+ continue;
+ }
+ p += 7;
+ q = p;
+ while (*q && (isalnum(*q) || *q == '_'))
+ q++;
+ if (str_ends_with(p, q - p, "_MODULE"))
+ r = q - 7;
+ else
+ r = q;
+ if (r > p)
+ use_config(p, r - p);
+ p = q;
+ }
+}
+
+static void *read_file(const char *filename)
+{
+ struct stat st;
+ int fd;
+ char *buf;
+
+ fd = open(filename, O_RDONLY);
+ if (fd < 0) {
+ fprintf(stderr, "fixdep: error opening file: ");
+ perror(filename);
+ exit(2);
+ }
+ if (fstat(fd, &st) < 0) {
+ fprintf(stderr, "fixdep: error fstat'ing file: ");
+ perror(filename);
+ exit(2);
+ }
+ buf = malloc(st.st_size + 1);
+ if (!buf) {
+ perror("fixdep: malloc");
+ exit(2);
+ }
+ if (read(fd, buf, st.st_size) != st.st_size) {
+ perror("fixdep: read");
+ exit(2);
+ }
+ buf[st.st_size] = '\0';
+ close(fd);
+
+ return buf;
+}
+
+/* Ignore certain dependencies */
+static int is_ignored_file(const char *s, int len)
+{
+ return str_ends_with(s, len, "include/generated/autoconf.h") ||
+ str_ends_with(s, len, "include/generated/autoksyms.h") ||
+ str_ends_with(s, len, ".ver");
+}
+
+/*
+ * Important: The below generated source_foo.o and deps_foo.o variable
+ * assignments are parsed not only by make, but also by the rather simple
+ * parser in scripts/mod/sumversion.c.
+ */
+static void parse_dep_file(char *m, const char *target, int insert_extra_deps)
+{
+ char *p;
+ int is_last, is_target;
+ int saw_any_target = 0;
+ int is_first_dep = 0;
+ void *buf;
+
+ while (1) {
+ /* Skip any "white space" */
+ while (*m == ' ' || *m == '\\' || *m == '\n')
+ m++;
+
+ if (!*m)
+ break;
+
+ /* Find next "white space" */
+ p = m;
+ while (*p && *p != ' ' && *p != '\\' && *p != '\n')
+ p++;
+ is_last = (*p == '\0');
+ /* Is the token we found a target name? */
+ is_target = (*(p-1) == ':');
+ /* Don't write any target names into the dependency file */
+ if (is_target) {
+ /* The /next/ file is the first dependency */
+ is_first_dep = 1;
+ } else if (!is_ignored_file(m, p - m)) {
+ *p = '\0';
+
+ /*
+ * Do not list the source file as dependency, so that
+ * kbuild is not confused if a .c file is rewritten
+ * into .S or vice versa. Storing it in source_* is
+ * needed for modpost to compute srcversions.
+ */
+ if (is_first_dep) {
+ /*
+ * If processing the concatenation of multiple
+ * dependency files, only process the first
+ * target name, which will be the original
+ * source name, and ignore any other target
+ * names, which will be intermediate temporary
+ * files.
+ */
+ if (!saw_any_target) {
+ saw_any_target = 1;
+ printf("source_%s := %s\n\n",
+ target, m);
+ printf("deps_%s := \\\n", target);
+ }
+ is_first_dep = 0;
+ } else {
+ printf(" %s \\\n", m);
+ }
+
+ buf = read_file(m);
+ parse_config_file(buf);
+ free(buf);
+ }
+
+ if (is_last)
+ break;
+
+ /*
+ * Start searching for next token immediately after the first
+ * "whitespace" character that follows this token.
+ */
+ m = p + 1;
+ }
+
+ if (!saw_any_target) {
+ fprintf(stderr, "fixdep: parse error; no targets found\n");
+ exit(1);
+ }
+
+ if (insert_extra_deps)
+ do_extra_deps();
+
+ printf("\n%s: $(deps_%s)\n\n", target, target);
+ printf("$(deps_%s):\n", target);
+}
+
+int main(int argc, char *argv[])
+{
+ const char *depfile, *target, *cmdline;
+ int insert_extra_deps = 0;
+ void *buf;
+
+ if (argc == 5 && !strcmp(argv[1], "-e")) {
+ insert_extra_deps = 1;
+ argv++;
+ } else if (argc != 4)
+ usage();
+
+ depfile = argv[1];
+ target = argv[2];
+ cmdline = argv[3];
+
+ printf("cmd_%s := %s\n\n", target, cmdline);
+
+ buf = read_file(depfile);
+ parse_dep_file(buf, target, insert_extra_deps);
+ free(buf);
+
+ return 0;
+}
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