kbuild: simplify dependency generation for CONFIG_TRIM_UNUSED_KSYMS

My main motivation of this commit is to clean up scripts/Kbuild.include
and scripts/Makefile.build.

Currently, CONFIG_TRIM_UNUSED_KSYMS works with a tricky gimmick;
possibly exported symbols are detected by letting $(CPP) replace
EXPORT_SYMBOL* with a special string '=== __KSYM_*===', which is
post-processed by sed, and passed to fixdep. The extra preprocessing
is costly, and hacking cmd_and_fixdep is ugly.

I came up with a new way to find exported symbols; insert a dummy
symbol __ksym_marker_* to each potentially exported symbol. Those
dummy symbols are picked up by $(NM), post-processed by sed, then
appended to .*.cmd files. I collected the post-process part to a
new shell script scripts/gen_ksymdeps.sh for readability. The dummy
symbols are put into the .discard.* section so that the linker
script rips them off the final vmlinux or modules.

A nice side-effect is building with CONFIG_TRIM_UNUSED_KSYMS will
be much faster.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Reviewed-by: Nicolas Pitre <nico@linaro.org>

1 files changed, 4 insertions, 27 deletions

diff --git a/scripts/basic/fixdep.c b/scripts/basic/fixdep.c
index 850966f3d602..facbd603adf6 100644
--- a/scripts/basic/fixdep.c
+++ b/scripts/basic/fixdep.c
@@ -105,8 +105,7 @@
 
 static void usage(void)
 {
-        fprintf(stderr, "Usage: fixdep [-e] <depfile> <target> <cmdline>\n");
-        fprintf(stderr, " -e  insert extra dependencies given on stdin\n");
+        fprintf(stderr, "Usage: fixdep <depfile> <target> <cmdline>\n");
         exit(1);
 }
 
@@ -131,21 +130,6 @@ static void print_dep(const char *m, int slen, const char *dir)
         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;
@@ -293,7 +277,7 @@ static int is_ignored_file(const char *s, int len)
  * 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)
+static void parse_dep_file(char *m, const char *target)
 {
         char *p;
         int is_last, is_target;
@@ -369,9 +353,6 @@ static void parse_dep_file(char *m, const char *target, int insert_extra_deps)
                 exit(1);
         }
 
-        if (insert_extra_deps)
-                do_extra_deps();
-
         printf("\n%s: $(deps_%s)\n\n", target, target);
         printf("$(deps_%s):\n", target);
 }
@@ -379,13 +360,9 @@ static void parse_dep_file(char *m, const char *target, int insert_extra_deps)
 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)
+        if (argc != 4)
                 usage();
 
         depfile = argv[1];
@@ -395,7 +372,7 @@ int main(int argc, char *argv[])
         printf("cmd_%s := %s\n\n", target, cmdline);
 
         buf = read_file(depfile);
-        parse_dep_file(buf, target, insert_extra_deps);
+        parse_dep_file(buf, target);
         free(buf);
 
         return 0;