ERROR: modpost: lib/kunit/kunit-example-test.ko: symbol '__mulsi3' undefined!

ERROR: modpost: lib/kunit/kunit-example-test.ko: symbol '__mulsi3' undefined!

[kernel test robot]

Hi Karl,

First bad commit (maybe != root cause):

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
head:   c339f4010dea8b0d754f84ace70cd1b089878ef8
commit: 7c3f4d699f34535285d0ceb184927d71543d0064 resource, kunit: stop selecting GET_FREE_REGION
date:   2 weeks ago
config: openrisc-randconfig-r2306-20261028 (https://download.01.org/0day-ci/archive/20261029/202610290106.o8Fs3NvO-lkp@intel.com/config)
compiler: or1k-linux-gcc (GCC) 16.2.0
sparse: v0.6.5-rc1-1-gc4640450
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20261029/202610290106.o8Fs3NvO-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Fixes: 7c3f4d699f34 ("resource, kunit: stop selecting GET_FREE_REGION")
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202610290106.o8Fs3NvO-lkp@intel.com/

All errors (new ones prefixed by >>, old ones prefixed by <<):

ERROR: modpost: kernel/rcu/rcutorture.ko: symbol '__mulsi3' undefined!
ERROR: modpost: fs/fuse/virtiofs.ko: symbol '__mulsi3' undefined!
ERROR: modpost: fs/pstore/ramoops.ko: symbol '__mulsi3' undefined!
ERROR: modpost: fs/ecryptfs/ecryptfs.ko: symbol '__mulsi3' undefined!
ERROR: modpost: fs/overlayfs/overlay.ko: symbol '__mulsi3' undefined!
ERROR: modpost: crypto/asymmetric_keys/pkcs8_key_parser.ko: symbol '__mulsi3' undefined!
ERROR: modpost: crypto/ccm.ko: symbol '__mulsi3' undefined!
ERROR: modpost: lib/kunit/kunit.ko: symbol '__mulsi3' undefined!
ERROR: modpost: lib/kunit/kunit-test.ko: symbol '__mulsi3' undefined!
>> ERROR: modpost: lib/kunit/kunit-example-test.ko: symbol '__mulsi3' undefined!
WARNING: modpost: suppressed 1014 unresolved symbol warnings because there were too many)

--
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki

Re: ERROR: modpost: lib/kunit/kunit-example-test.ko: symbol '__mulsi3' undefined!

[Andrew Morton]

On Thu, 29 Oct 2026 01:59:13 +0100 kernel test robot <lkp@intel.com> wrote:

> Hi Karl,
> 
> First bad commit (maybe != root cause):
> 
> tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
> head:   c339f4010dea8b0d754f84ace70cd1b089878ef8
> commit: 7c3f4d699f34535285d0ceb184927d71543d0064 resource, kunit: stop selecting GET_FREE_REGION
> date:   2 weeks ago
> config: openrisc-randconfig-r2306-20261028 (https://download.01.org/0day-ci/archive/20261029/202610290106.o8Fs3NvO-lkp@intel.com/config)
> compiler: or1k-linux-gcc (GCC) 16.2.0
> sparse: v0.6.5-rc1-1-gc4640450
> reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20261029/202610290106.o8Fs3NvO-lkp@intel.com/reproduce)
> 
> If you fix the issue in a separate patch/commit (i.e. not just a new version of
> the same patch/commit), kindly add following tags
> | Fixes: 7c3f4d699f34 ("resource, kunit: stop selecting GET_FREE_REGION")
> | Reported-by: kernel test robot <lkp@intel.com>
> | Closes: https://lore.kernel.org/oe-kbuild-all/202610290106.o8Fs3NvO-lkp@intel.com/
> 
> All errors (new ones prefixed by >>, old ones prefixed by <<):
> 
> ERROR: modpost: kernel/rcu/rcutorture.ko: symbol '__mulsi3' undefined!
> ERROR: modpost: fs/fuse/virtiofs.ko: symbol '__mulsi3' undefined!
> ERROR: modpost: fs/pstore/ramoops.ko: symbol '__mulsi3' undefined!
> ERROR: modpost: fs/ecryptfs/ecryptfs.ko: symbol '__mulsi3' undefined!
> ERROR: modpost: fs/overlayfs/overlay.ko: symbol '__mulsi3' undefined!
> ERROR: modpost: crypto/asymmetric_keys/pkcs8_key_parser.ko: symbol '__mulsi3' undefined!
> ERROR: modpost: crypto/ccm.ko: symbol '__mulsi3' undefined!
> ERROR: modpost: lib/kunit/kunit.ko: symbol '__mulsi3' undefined!
> ERROR: modpost: lib/kunit/kunit-test.ko: symbol '__mulsi3' undefined!
> >> ERROR: modpost: lib/kunit/kunit-example-test.ko: symbol '__mulsi3' undefined!
> WARNING: modpost: suppressed 1014 unresolved symbol warnings because there were too many)

Thanks.

#syz test

From: Andrew Morton <akpm@linux-foundation.org>
Subject: openrisc: export __mulsi3 for modules
Date: Wed Oct 28 06:24:22 PM PDT 2026

OpenRISC configurations without hardware multiplication fail to build
modules which contain compiler-generated calls to __mulsi3.  The failure
is widespread, affecting filesystems, drivers and KUnit tests at modpost.

When CONFIG_OPENRISC_HAVE_INST_MUL is disabled, the architecture Makefile
passes -msoft-mul to GCC.  The multiplication helper is supplied by the
libgcc archive linked into vmlinux, but or32_ksyms.c does not export it. 
Built-in callers can therefore link while module callers cannot resolve
the symbol.

Export __mulsi3 alongside the other compiler-generated helpers.

The omission predates 7c3f4d699f34 ("resource, kunit: stop selecting
GET_FREE_REGION"), which the robot identified when reporting an additional
failing module.  It was already present in the initial OpenRISC export
list.

Fixes: 616257669e1a ("OpenRISC: Miscellaneous")
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202610290106.o8Fs3NvO-lkp@intel.com/
Assisted-by: LLM
Cc: Jonas Bonn <jonas@southpole.se>
Cc: Stefan Kristiansson <stefan.kristiansson@saunalahti.fi>
Cc: Stafford Horne <shorne@gmail.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Karl Mehltretter <kmehltretter@gmail.com>
Cc: <stable@vger.kernel.org>
---

 arch/openrisc/kernel/or32_ksyms.c |    1 +
 1 file changed, 1 insertion(+)

--- a/arch/openrisc/kernel/or32_ksyms.c~openrisc-export-mulsi3
+++ a/arch/openrisc/kernel/or32_ksyms.c
@@ -35,6 +35,7 @@ DECLARE_EXPORT(__divsi3);
 DECLARE_EXPORT(__umodsi3);
 DECLARE_EXPORT(__modsi3);
 DECLARE_EXPORT(__muldi3);
+DECLARE_EXPORT(__mulsi3);
 DECLARE_EXPORT(__ashrdi3);
 DECLARE_EXPORT(__ashldi3);
 DECLARE_EXPORT(__lshrdi3);
_