Files in the arch/s390/boot directory reuse logic from the rest of the
kernel by including certain C and assembly files from the kernel and lib
directories. Some of these included files contain EXPORT_SYMBOL directives.
For instance, arch/s390/boot/cmdline.c includes lib/cmdline.c, which
exports the get_option() function.

This inclusion triggers genksyms processing for the files in
arch/s390/boot, which is unnecessary and slows down the build.
Additionally, when KBUILD_SYMTYPES=1 is set, the generated symtypes data
contain exported symbols that are duplicated with the main kernel. This
duplication can confuse external kABI tools that process the symtypes data.

Address this issue by compiling the files in arch/s390/boot with
-D__DISABLE_EXPORTS.

Signed-off-by: Petr Pavlu <petr.pavlu@suse.com>
---
 arch/s390/boot/Makefile | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/s390/boot/Makefile b/arch/s390/boot/Makefile
index bee49626be4b..0986c7c67eaf 100644
--- a/arch/s390/boot/Makefile
+++ b/arch/s390/boot/Makefile
@@ -19,8 +19,8 @@ CC_FLAGS_MARCH_MINIMUM := -march=z10
 
 KBUILD_AFLAGS := $(filter-out $(CC_FLAGS_MARCH),$(KBUILD_AFLAGS_DECOMPRESSOR))
 KBUILD_CFLAGS := $(filter-out $(CC_FLAGS_MARCH),$(KBUILD_CFLAGS_DECOMPRESSOR))
-KBUILD_AFLAGS += $(CC_FLAGS_MARCH_MINIMUM)
-KBUILD_CFLAGS += $(CC_FLAGS_MARCH_MINIMUM)
+KBUILD_AFLAGS += $(CC_FLAGS_MARCH_MINIMUM) -D__DISABLE_EXPORTS
+KBUILD_CFLAGS += $(CC_FLAGS_MARCH_MINIMUM) -D__DISABLE_EXPORTS
 
 CFLAGS_sclp_early_core.o += -I$(srctree)/drivers/s390/char
 

base-commit: 75f5f23f8787c5e184fcb2fbcd02d8e9317dc5e7
-- 
2.49.0

On Fri, Jun 20, 2025 at 05:45:49PM +0200, Petr Pavlu wrote:
> Files in the arch/s390/boot directory reuse logic from the rest of the
> kernel by including certain C and assembly files from the kernel and lib
> directories. Some of these included files contain EXPORT_SYMBOL directives.
> For instance, arch/s390/boot/cmdline.c includes lib/cmdline.c, which
> exports the get_option() function.
> 
> This inclusion triggers genksyms processing for the files in
> arch/s390/boot, which is unnecessary and slows down the build.
> Additionally, when KBUILD_SYMTYPES=1 is set, the generated symtypes data
> contain exported symbols that are duplicated with the main kernel. This
> duplication can confuse external kABI tools that process the symtypes data.
> 
> Address this issue by compiling the files in arch/s390/boot with
> -D__DISABLE_EXPORTS.
> 
> Signed-off-by: Petr Pavlu <petr.pavlu@suse.com>
> ---
>  arch/s390/boot/Makefile | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)

Applied, thanks!

On Fri, Jun 20, 2025 at 05:45:49PM +0200, Petr Pavlu wrote:
> Files in the arch/s390/boot directory reuse logic from the rest of the
> kernel by including certain C and assembly files from the kernel and lib
> directories. Some of these included files contain EXPORT_SYMBOL directives.
> For instance, arch/s390/boot/cmdline.c includes lib/cmdline.c, which
> exports the get_option() function.
> 
> This inclusion triggers genksyms processing for the files in
> arch/s390/boot, which is unnecessary and slows down the build.
> Additionally, when KBUILD_SYMTYPES=1 is set, the generated symtypes data
> contain exported symbols that are duplicated with the main kernel. This
> duplication can confuse external kABI tools that process the symtypes data.
> 
> Address this issue by compiling the files in arch/s390/boot with
> -D__DISABLE_EXPORTS.
> 
> Signed-off-by: Petr Pavlu <petr.pavlu@suse.com>
> ---
>  arch/s390/boot/Makefile | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)

Reviewed-by: Heiko Carstens <hca@linux.ibm.com>