kbuild: soften modpost checks when doing cross builds

upstream commit: 4ce6efed48d736e3384c39ff87bda723e1f8e041

The module alias support in the kernel have a consistency
check where it is checked that the size of a structure
in the kernel and on the build host are the same.
For cross builds this check does not make sense so detect
when we do cross builds and silently skip the check in these
situations.
This fixes a build bug for a wireless driver when cross building
for arm.

Acked-by: Michael Buesch <mb@bu3sch.de>
Tested-by: Gordon Farquharson <gordonfarquharson@gmail.com>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
[chrisw@sous-sol.org: backport to 2.6.24.4]
Signed-off-by: Chris Wright <chrisw@sous-sol.org>

4 files changed, 14 insertions, 2 deletions

diff --git a/scripts/Makefile.modpost b/scripts/Makefile.modpost
index d988f5d21e3d..f6b332cc7cca 100644
--- a/scripts/Makefile.modpost
+++ b/scripts/Makefile.modpost
@@ -53,6 +53,9 @@ modules   := $(patsubst %.o,%.ko, $(wildcard $(__modules:.ko=.o)))
 # Stop after building .o files if NOFINAL is set. Makes compile tests quicker
 _modpost: $(if $(KBUILD_MODPOST_NOFINAL), $(modules:.ko:.o),$(modules))
 
+ifneq ($(KBUILD_BUILDHOST),$(ARCH))
+        cross_build := 1
+endif
 
 # Step 2), invoke modpost
 #  Includes step 3,4
@@ -62,7 +65,8 @@ modpost = scripts/mod/modpost                    \
  $(if $(KBUILD_EXTMOD),-i,-o) $(kernelsymfile)   \
  $(if $(KBUILD_EXTMOD),-I $(modulesymfile))      \
  $(if $(KBUILD_EXTMOD),-o $(modulesymfile))      \
- $(if $(KBUILD_EXTMOD)$(KBUILD_MODPOST_WARN),-w)
+ $(if $(KBUILD_EXTMOD)$(KBUILD_MODPOST_WARN),-w) \
+ $(if $(cross_build),-c)
 
 quiet_cmd_modpost = MODPOST $(words $(filter-out vmlinux FORCE, $^)) modules
       cmd_modpost = $(modpost) -s
diff --git a/scripts/mod/file2alias.c b/scripts/mod/file2alias.c
index 9ddf944cce29..348d8687b7c9 100644
--- a/scripts/mod/file2alias.c
+++ b/scripts/mod/file2alias.c
@@ -51,11 +51,13 @@ do {                                                            \
                 sprintf(str + strlen(str), "*");                \
 } while(0)
 
+unsigned int cross_build = 0;
 /**
  * Check that sizeof(device_id type) are consistent with size of section
  * in .o file. If in-consistent then userspace and kernel does not agree
  * on actual size which is a bug.
  * Also verify that the final entry in the table is all zeros.
+ * Ignore both checks if build host differ from target host and size differs.
  **/
 static void device_id_check(const char *modname, const char *device_id,
 			    unsigned long size, unsigned long id_size,
@@ -64,6 +66,8 @@ static void device_id_check(const char *modname, const char *device_id,
 	int i;
 
 	if (size % id_size || size < id_size) {
+		if (cross_build != 0)
+			return;
 		fatal("%s: sizeof(struct %s_device_id)=%lu is not a modulo "
 		      "of the size of section __mod_%s_device_table=%lu.\n"
 		      "Fix definition of struct %s_device_id "
diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
index 93ac52adb498..a99001102d15 100644
--- a/scripts/mod/modpost.c
+++ b/scripts/mod/modpost.c
@@ -1659,7 +1659,7 @@ int main(int argc, char **argv)
 	int opt;
 	int err;
 
-	while ((opt = getopt(argc, argv, "i:I:mso:aw")) != -1) {
+	while ((opt = getopt(argc, argv, "i:I:cmso:aw")) != -1) {
 		switch(opt) {
 			case 'i':
 				kernel_read = optarg;
@@ -1668,6 +1668,9 @@ int main(int argc, char **argv)
 				module_read = optarg;
 				external_module = 1;
 				break;
+		case 'c':
+			cross_build = 1;
+			break;
 			case 'm':
 				modversions = 1;
 				break;
diff --git a/scripts/mod/modpost.h b/scripts/mod/modpost.h
index 0ffed17ec20c..b50e3c90fa3e 100644
--- a/scripts/mod/modpost.h
+++ b/scripts/mod/modpost.h
@@ -130,6 +130,7 @@ struct elf_info {
 };
 
 /* file2alias.c */
+extern unsigned int cross_build;
 void handle_moddevtable(struct module *mod, struct elf_info *info,
 			Elf_Sym *sym, const char *symname);
 void add_moddevtable(struct buffer *buf, struct module *mod);