kbuild: link symbol CRCs at final link, removing CONFIG_MODULE_REL_CRCS

include/{linux,asm-generic}/export.h defines a weak symbol, __crc_*
as a placeholder.

Genksyms writes the version CRCs into the linker script, which will be
used for filling the __crc_* symbols. The linker script format depends
on CONFIG_MODULE_REL_CRCS. If it is enabled, __crc_* holds the offset
to the reference of CRC.

It is time to get rid of this complexity.

Now that modpost parses text files (.*.cmd) to collect all the CRCs,
it can generate C code that will be linked to the vmlinux or modules.

Generate a new C file, .vmlinux.export.c, which contains the CRCs of
symbols exported by vmlinux. It is compiled and linked to vmlinux in
scripts/link-vmlinux.sh.

Put the CRCs of symbols exported by modules into the existing *.mod.c
files. No additional build step is needed for modules. As before,
*.mod.c are compiled and linked to *.ko in scripts/Makefile.modfinal.

No linker magic is used here. The new C implementation works in the
same way, whether CONFIG_RELOCATABLE is enabled or not.
CONFIG_MODULE_REL_CRCS is no longer needed.

Previously, Kbuild invoked additional $(LD) to update the CRCs in
objects, but this step is unneeded too.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Tested-by: Nathan Chancellor <nathan@kernel.org>
Tested-by: Nicolas Schier <nicolas@fjasle.eu>
Reviewed-by: Nicolas Schier <nicolas@fjasle.eu>
Tested-by: Sedat Dilek <sedat.dilek@gmail.com> # LLVM-14 (x86-64)

1 files changed, 4 insertions, 14 deletions

diff --git a/scripts/genksyms/genksyms.c b/scripts/genksyms/genksyms.c
index 4827c5abe5b7..67b23cc0df0f 100644
--- a/scripts/genksyms/genksyms.c
+++ b/scripts/genksyms/genksyms.c
@@ -33,7 +33,7 @@ char *cur_filename;
 int in_source_file;
 
 static int flag_debug, flag_dump_defs, flag_reference, flag_dump_types,
-	   flag_preserve, flag_warnings, flag_rel_crcs;
+	   flag_preserve, flag_warnings;
 
 static int errors;
 static int nsyms;
@@ -680,11 +680,7 @@ void export_symbol(const char *name)
 		if (flag_dump_defs)
 			fputs(">\n", debugfile);
 
-		/* Used as a linker script. */
-		printf(!flag_rel_crcs ? "__crc_%s = 0x%08lx;\n" :
-		       "SECTIONS { .rodata : ALIGN(4) { "
-		       "__crc_%s = .; LONG(0x%08lx); } }\n",
-		       name, crc);
+		printf("__crc_%s = 0x%08lx;\n", name, crc);
 	}
 }
 
@@ -733,7 +729,6 @@ static void genksyms_usage(void)
 	      "  -q, --quiet           Disable warnings (default)\n"
 	      "  -h, --help            Print this message\n"
 	      "  -V, --version         Print the release version\n"
-	      "  -R, --relative-crc    Emit section relative symbol CRCs\n"
 #else				/* __GNU_LIBRARY__ */
 	      "  -s                    Select symbol prefix\n"
 	      "  -d                    Increment the debug level (repeatable)\n"
@@ -745,7 +740,6 @@ static void genksyms_usage(void)
 	      "  -q                    Disable warnings (default)\n"
 	      "  -h                    Print this message\n"
 	      "  -V                    Print the release version\n"
-	      "  -R                    Emit section relative symbol CRCs\n"
 #endif				/* __GNU_LIBRARY__ */
 	      , stderr);
 }
@@ -766,14 +760,13 @@ int main(int argc, char **argv)
 		{"preserve", 0, 0, 'p'},
 		{"version", 0, 0, 'V'},
 		{"help", 0, 0, 'h'},
-		{"relative-crc", 0, 0, 'R'},
 		{0, 0, 0, 0}
 	};
 
-	while ((o = getopt_long(argc, argv, "s:dwqVDr:T:phR",
+	while ((o = getopt_long(argc, argv, "s:dwqVDr:T:ph",
 				&long_opts[0], NULL)) != EOF)
 #else				/* __GNU_LIBRARY__ */
-	while ((o = getopt(argc, argv, "s:dwqVDr:T:phR")) != EOF)
+	while ((o = getopt(argc, argv, "s:dwqVDr:T:ph")) != EOF)
 #endif				/* __GNU_LIBRARY__ */
 		switch (o) {
 		case 'd':
@@ -813,9 +806,6 @@ int main(int argc, char **argv)
 		case 'h':
 			genksyms_usage();
 			return 0;
-		case 'R':
-			flag_rel_crcs = 1;
-			break;
 		default:
 			genksyms_usage();
 			return 1;