Re: [PATCH] nios2: ksyms: Declare __mulsi3 export
From: Vineet Gupta
Date: Sat Oct 31 2026 - 19:57:24 EST
On 10/19/26 04:16, Arnd Bergmann wrote:
On Mon, Oct 19, 2026, at 11:49, Thomas Weißschuh wrote:
GCC may emit libcalls to __mulsi3(). As modpost is not aware that thisAcked-by: Arnd Bergmann <arnd@xxxxxxxx>
function is provided through the linked in libgcc, it fails:
ERROR: modpost: kernel/locking/test-ww_mutex.ko: symbol '__mulsi3' undefined!
ERROR: modpost: kernel/time/test_udelay.ko: symbol '__mulsi3' undefined!
ERROR: modpost: kernel/resource_kunit.ko: symbol '__mulsi3' undefined!
ERROR: modpost: fs/fuse/virtiofs.ko: symbol '__mulsi3' undefined!
etc.
Make sure modpost can see the symbol from libgcc.
Reported-by: kernel test robot <lkp@xxxxxxxxx>
Closes:
https://lore.kernel.org/oe-kbuild-all/202610171933.J4bFOfL8-lkp@xxxxxxxxx/
Fixes: 2fc8483fdcde ("nios2: Build infrastructure")
Signed-off-by: Thomas Weißschuh <thomas.weissschuh@xxxxxxxxxxxxx>
The patch looks correct to me, but it would also be nice to not use
libgcc at all. What I see is that only arc, nios2, openrisc and
parisc still link against the toolchain-provided libgcc, everything
else uses the kernel's own runtime.
It's probably not even that hard to do right, here is what I found
is imported from libgcc.
And seems like ARC is the biggest offender, what a shame.
* Generic library helper exists, can be enabled through Kconfig:
=== __lshrdi3 ===
arch/arc/kernel/arcksyms.c
arch/nios2/kernel/nios2_ksyms.c
arch/openrisc/kernel/or32_ksyms.c
arch/parisc/kernel/parisc_ksyms.c
-> lib/lshrdi3.c
=== __ashldi3 ===
arch/arc/kernel/arcksyms.c
arch/nios2/kernel/nios2_ksyms.c
arch/openrisc/kernel/or32_ksyms.c
arch/parisc/kernel/parisc_ksyms.c
-> lib/ashldi3.c
=== __ashrdi3 ===
arch/arc/kernel/arcksyms.c
arch/nios2/kernel/nios2_ksyms.c
arch/openrisc/kernel/or32_ksyms.c
arch/parisc/kernel/parisc_ksyms.c
-> lib/ashrdi3.c
=== __cmpdi2 ===
arch/arc/kernel/arcksyms.c
-> lib/cmpdi2.c
=== __muldi3 ===
arch/arc/kernel/arcksyms.c
arch/nios2/kernel/nios2_ksyms.c
arch/openrisc/kernel/or32_ksyms.c
arch/parisc/kernel/parisc_ksyms.c
-> lib/muldi3.c
=== __ucmpdi2 ===
arch/arc/kernel/arcksyms.c
arch/nios2/kernel/nios2_ksyms.c
arch/openrisc/kernel/or32_ksyms.c
arch/parisc/kernel/parisc_ksyms.c
-> lib/ucmpdi2.c
It seems Palmer added those back in 2018 which ARC was still developed actively, I totally missed them.
I now have a patch to switch ARC to generic helpers for those.
* 64-bit division probably should not be provided on arc or
nios2 (and sparc32, which has a private copy).
parisc64 should get these from libgcc/libgcc2.c.
=== __divdi3 ===
arch/parisc/kernel/parisc_ksyms.c
=== __udivmoddi4 ===
arch/nios2/kernel/nios2_ksyms.c
=== __udivdi3 ===
arch/arc/kernel/arcksyms.c
It seems in some of the old binaries I have, dw mmc driver was at some point calling 64/64 divide which eventually got fixed.
But agree as of today there are no callers of 64-bit div/mod. I will get rid of ?div*di* from ARC.
arch/parisc/kernel/parisc_ksyms.c
=== __umoddi3 ===
arch/nios2/kernel/nios2_ksyms.c
arch/parisc/kernel/parisc_ksyms.c
=== __moddi3 ===
arch/nios2/kernel/nios2_ksyms.c
arch/parisc/kernel/parisc_ksyms.c
* floating-point math should not be provided by kernel:
=== __divdf3 ===
arch/arc/kernel/arcksyms.c
=== __divsf3 ===
arch/arc/kernel/arcksyms.c
=== __fixunsdfsi ===
arch/arc/kernel/arcksyms.c
=== __floatunsidf ===
arch/arc/kernel/arcksyms.c
=== __floatunsisf ===
arch/arc/kernel/arcksyms.c
=== __muldf3 ===
arch/arc/kernel/arcksyms.c
And a second patch gets rid of those. FWIW back in the day some ARCAngel board's HDD driver needed those. Crazy times.
* no generic implementation in kernel, need to copy from
libgcc/lib1funcs.S code:
=== __divsi3 ===
arch/arc/kernel/arcksyms.c
arch/nios2/kernel/nios2_ksyms.c
arch/openrisc/kernel/or32_ksyms.c
-> arch/arm/lib/lib1funcs.S
arch/m68k/lib/divsi3.S
arch/microblaze/lib/divsi3.S
arch/xtensa/lib/divsi3.S
=== __modsi3 ===
arch/arc/kernel/arcksyms.c
arch/nios2/kernel/nios2_ksyms.c
arch/openrisc/kernel/or32_ksyms.c
-> arch/m68k/lib/modsi3.S
arch/microblaze/lib/modsi3.S
arch/xtensa/lib/modsi3.S
=== __udivsi3 ===
arch/arc/kernel/arcksyms.c
arch/nios2/kernel/nios2_ksyms.c
arch/openrisc/kernel/or32_ksyms.c
-> arch/arm/lib/lib1funcs.S
arch/m68k/lib/udivsi3.S
arch/microblaze/lib/udivsi3.S
arch/sh/lib/udivsi3.S
arch/xtensa/lib/udivsi3.S
=== __umodsi3 ===
arch/arc/kernel/arcksyms.c
arch/nios2/kernel/nios2_ksyms.c
arch/openrisc/kernel/or32_ksyms.c
-> arch/arm/lib/lib1funcs.S
arch/m68k/lib/umodsi3.S
arch/microblaze/lib/umodsi3.S
arch/xtensa/lib/umodsi3.S
ARCv2 has hardware divide so these are not needed, but ARC700 doesn't and there's a ton of calls for those.
┌───────────┬───────┬───────────┐
│ routine │ calls │ functions │
├───────────┼───────┼───────────┤
│ __udivsi3 │ 415 │ 238 │
├───────────┼───────┼───────────┤
│ __umodsi3 │ 203 │ 131 │
├───────────┼───────┼───────────┤
│ __divsi3 │ 77 │ 57 │
├───────────┼───────┼───────────┤
│ __modsi3 │ 41 │ 33 │
└───────────┴───────┴───────────┘
I can take a stab at providing the generic libgcc implementation in lib/* but I only expect the arches using libgcc version to switch.
Thx,
-Vineet