arch/mips/boot/compressed/decompress.c:undefined reference to `__ashldi3'

arch/mips/boot/compressed/decompress.c:undefined reference to `__ashldi3'

[kernel test robot]

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
head:   551c722f40809618230001baccf219193e22fc5a
commit: d4dba3b9c03a326cfa73833d6b166aeb442f82b5 lib: decompress_bunzip2: fix 32-bit shift undefined behavior
date:   6 months ago
config: mips-randconfig-r2300-20260930 (https://download.01.org/0day-ci/archive/20260930/202609301826.MFaFMsmd-lkp@intel.com/config)
compiler: mips-linux-gcc (GCC) 15.2.0
sparse: v0.6.5-rc1
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260930/202609301826.MFaFMsmd-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: d4dba3b9c03a ("lib: decompress_bunzip2: fix 32-bit shift undefined behavior")
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202609301826.MFaFMsmd-lkp@intel.com/

All errors (new ones prefixed by >>):

   mips-linux-ld: arch/mips/boot/compressed/decompress.o: in function `get_bits':
>> arch/mips/boot/compressed/decompress.c:(.text+0xf4): undefined reference to `__ashldi3'
>> mips-linux-ld: arch/mips/boot/compressed/decompress.c:(.text+0x168): undefined reference to `__ashldi3'

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

Re: arch/mips/boot/compressed/decompress.c:undefined reference to `__ashldi3'

[Andrew Morton]

On Wed, 30 Sep 2026 18:36:50 +0200 kernel test robot <lkp@intel.com> wrote:

> tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
> head:   551c722f40809618230001baccf219193e22fc5a
> commit: d4dba3b9c03a326cfa73833d6b166aeb442f82b5 lib: decompress_bunzip2: fix 32-bit shift undefined behavior
> date:   6 months ago
> config: mips-randconfig-r2300-20260930 (https://download.01.org/0day-ci/archive/20260930/202609301826.MFaFMsmd-lkp@intel.com/config)
> compiler: mips-linux-gcc (GCC) 15.2.0
> sparse: v0.6.5-rc1
> reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260930/202609301826.MFaFMsmd-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: d4dba3b9c03a ("lib: decompress_bunzip2: fix 32-bit shift undefined behavior")
> | Reported-by: kernel test robot <lkp@intel.com>
> | Closes: https://lore.kernel.org/oe-kbuild-all/202609301826.MFaFMsmd-lkp@intel.com/
> 
> All errors (new ones prefixed by >>):
> 
>    mips-linux-ld: arch/mips/boot/compressed/decompress.o: in function `get_bits':
> >> arch/mips/boot/compressed/decompress.c:(.text+0xf4): undefined reference to `__ashldi3'
> >> mips-linux-ld: arch/mips/boot/compressed/decompress.c:(.text+0x168): undefined reference to `__ashldi3'

I dunno, I'd be suspecting a toolchain issue here?

--- a/lib/decompress_bunzip2.c
+++ b/lib/decompress_bunzip2.c
@@ -135,7 +135,7 @@ static unsigned int INIT get_bits(struct bunzip_data *bd, char bits_wanted)
 		}
 		/* Avoid 32-bit overflow (dump bit buffer to top of output) */
 		if (bd->inbufBitCount >= 24) {
-			bits = bd->inbufBits&((1 << bd->inbufBitCount)-1);
+			bits = bd->inbufBits & ((1ULL << bd->inbufBitCount) - 1);
 			bits_wanted -= bd->inbufBitCount;
 			bits <<= bits_wanted;
 			bd->inbufBitCount = 0;
@@ -146,7 +146,7 @@ static unsigned int INIT get_bits(struct bunzip_data *bd, char bits_wanted)
 	}
 	/* Calculate result */
 	bd->inbufBitCount -= bits_wanted;
-	bits |= (bd->inbufBits >> bd->inbufBitCount)&((1 << bits_wanted)-1);
+	bits |= (bd->inbufBits >> bd->inbufBitCount) & ((1ULL << bits_wanted) - 1);
 
 	return bits;
 }

32-bit MIPS should be able to do this?

Re: arch/mips/boot/compressed/decompress.c:undefined reference to `__ashldi3'

[Bradley Morgan]

On 30 September 2026 20:01:59 BST, Andrew Morton
<akpm@linux-foundation.org> wrote:
>On Wed, 30 Sep 2026 18:36:50 +0200 kernel test robot <lkp@intel.com>
>wrote:
>
>> tree:  
>https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
>> head:   551c722f40809618230001baccf219193e22fc5a
>> commit: d4dba3b9c03a326cfa73833d6b166aeb442f82b5 lib:
>decompress_bunzip2: fix 32-bit shift undefined behavior
>> date:   6 months ago
>> config: mips-randconfig-r2300-20260930
>(https://download.01.org/0day-ci/archive/20260930/202609301826.MFaFMsmd-lkp@intel.com/config)
>> compiler: mips-linux-gcc (GCC) 15.2.0
>> sparse: v0.6.5-rc1
>> reproduce (this is a W=1 build):
>(https://download.01.org/0day-ci/archive/20260930/202609301826.MFaFMsmd-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: d4dba3b9c03a ("lib: decompress_bunzip2: fix 32-bit shift
>undefined behavior")
>> | Reported-by: kernel test robot <lkp@intel.com>
>> | Closes:
>https://lore.kernel.org/oe-kbuild-all/202609301826.MFaFMsmd-lkp@intel.com/
>> 
>> All errors (new ones prefixed by >>):
>> 
>>    mips-linux-ld: arch/mips/boot/compressed/decompress.o: in function
>`get_bits':
>> >> arch/mips/boot/compressed/decompress.c:(.text+0xf4): undefined
>reference to `__ashldi3'
>> >> mips-linux-ld: arch/mips/boot/compressed/decompress.c:(.text+0x168):
>undefined reference to `__ashldi3'
>
>I dunno, I'd be suspecting a toolchain issue here?
>
>--- a/lib/decompress_bunzip2.c
>+++ b/lib/decompress_bunzip2.c
>@@ -135,7 +135,7 @@ static unsigned int INIT get_bits(struct bunzip_data *bd, char bits_wanted)
> 		}
> 		/* Avoid 32-bit overflow (dump bit buffer to top of output) */
> 		if (bd->inbufBitCount >= 24) {
>-			bits = bd->inbufBits&((1 << bd->inbufBitCount)-1);
>+			bits = bd->inbufBits & ((1ULL << bd->inbufBitCount) - 1);
> 			bits_wanted -= bd->inbufBitCount;
> 			bits <<= bits_wanted;
> 			bd->inbufBitCount = 0;
>@@ -146,7 +146,7 @@ static unsigned int INIT get_bits(struct bunzip_data *bd, char bits_wanted)
> 	}
> 	/* Calculate result */
> 	bd->inbufBitCount -= bits_wanted;
>-	bits |= (bd->inbufBits >> bd->inbufBitCount)&((1 << bits_wanted)-1);
>+	bits |= (bd->inbufBits >> bd->inbufBitCount) & ((1ULL << bits_wanted) - 1);
> 
> 	return bits;
> }
>
>32-bit MIPS should be able to do this?
May I ask why I got CCed in this..??
--- Thanks!
"I'm not a very positive person" - Linus torvalds

Re: arch/mips/boot/compressed/decompress.c:undefined reference to `__ashldi3'

[Pedro Falcato]

On Wed, Sep 30, 2026 at 12:01:59PM -0700, Andrew Morton wrote:
> On Wed, 30 Sep 2026 18:36:50 +0200 kernel test robot <lkp@intel.com> wrote:
> 
> > tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
> > head:   551c722f40809618230001baccf219193e22fc5a
> > commit: d4dba3b9c03a326cfa73833d6b166aeb442f82b5 lib: decompress_bunzip2: fix 32-bit shift undefined behavior
> > date:   6 months ago
> > config: mips-randconfig-r2300-20260930 (https://download.01.org/0day-ci/archive/20260930/202609301826.MFaFMsmd-lkp@intel.com/config)
> > compiler: mips-linux-gcc (GCC) 15.2.0
> > sparse: v0.6.5-rc1
> > reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260930/202609301826.MFaFMsmd-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: d4dba3b9c03a ("lib: decompress_bunzip2: fix 32-bit shift undefined behavior")
> > | Reported-by: kernel test robot <lkp@intel.com>
> > | Closes: https://lore.kernel.org/oe-kbuild-all/202609301826.MFaFMsmd-lkp@intel.com/
> > 
> > All errors (new ones prefixed by >>):
> > 
> >    mips-linux-ld: arch/mips/boot/compressed/decompress.o: in function `get_bits':
> > >> arch/mips/boot/compressed/decompress.c:(.text+0xf4): undefined reference to `__ashldi3'
> > >> mips-linux-ld: arch/mips/boot/compressed/decompress.c:(.text+0x168): undefined reference to `__ashldi3'
> 
> I dunno, I'd be suspecting a toolchain issue here?
> 
> --- a/lib/decompress_bunzip2.c
> +++ b/lib/decompress_bunzip2.c
> @@ -135,7 +135,7 @@ static unsigned int INIT get_bits(struct bunzip_data *bd, char bits_wanted)
>  		}
>  		/* Avoid 32-bit overflow (dump bit buffer to top of output) */
>  		if (bd->inbufBitCount >= 24) {
> -			bits = bd->inbufBits&((1 << bd->inbufBitCount)-1);
> +			bits = bd->inbufBits & ((1ULL << bd->inbufBitCount) - 1);
>  			bits_wanted -= bd->inbufBitCount;
>  			bits <<= bits_wanted;
>  			bd->inbufBitCount = 0;
> @@ -146,7 +146,7 @@ static unsigned int INIT get_bits(struct bunzip_data *bd, char bits_wanted)
>  	}
>  	/* Calculate result */
>  	bd->inbufBitCount -= bits_wanted;
> -	bits |= (bd->inbufBits >> bd->inbufBitCount)&((1 << bits_wanted)-1);
> +	bits |= (bd->inbufBits >> bd->inbufBitCount) & ((1ULL << bits_wanted) - 1);
>  
>  	return bits;
>  }
> 
> 32-bit MIPS should be able to do this?

FWIW the patch seems entirely bogus. I don't think you can have inbufBitCount >=
32. If you could, then the patch would still not fix anything, because
bd->inbufBits is an (32-bit) unsigned int.

As per MIPS itself, MIPS does not link ashldi3.o into the decompressor for BZ2.
It only does so for XZ and ZSTD.

Changing arch/mips/boot/compressed/Makefile would work, but since the change is
entirely wrong I would suggest perhaps reverting?


-- 
Pedro

Re: arch/mips/boot/compressed/decompress.c:undefined reference to `__ashldi3'

[Andrew Morton]

On Thu, 1 Oct 2026 11:30:09 +0100 Pedro Falcato <pfalcato@suse.de> wrote:

> > -	bits |= (bd->inbufBits >> bd->inbufBitCount)&((1 << bits_wanted)-1);
> > +	bits |= (bd->inbufBits >> bd->inbufBitCount) & ((1ULL << bits_wanted) - 1);
> >  
> >  	return bits;
> >  }
> > 
> > 32-bit MIPS should be able to do this?
> 
> FWIW the patch seems entirely bogus. I don't think you can have inbufBitCount >=
> 32. If you could, then the patch would still not fix anything, because
> bd->inbufBits is an (32-bit) unsigned int.
> 
> As per MIPS itself, MIPS does not link ashldi3.o into the decompressor for BZ2.
> It only does so for XZ and ZSTD.
> 
> Changing arch/mips/boot/compressed/Makefile would work, but since the change is
> entirely wrong I would suggest perhaps reverting?

Sure, thanks.  Do you have time to send a formal patch?

Re: arch/mips/boot/compressed/decompress.c:undefined reference to `__ashldi3'

[David Laight]

On Thu, 1 Oct 2026 11:30:09 +0100
Pedro Falcato <pfalcato@suse.de> wrote:

> On Wed, Sep 30, 2026 at 12:01:59PM -0700, Andrew Morton wrote:
> > On Wed, 30 Sep 2026 18:36:50 +0200 kernel test robot <lkp@intel.com> wrote:
> >   
> > > tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
> > > head:   551c722f40809618230001baccf219193e22fc5a
> > > commit: d4dba3b9c03a326cfa73833d6b166aeb442f82b5 lib: decompress_bunzip2: fix 32-bit shift undefined behavior
> > > date:   6 months ago
> > > config: mips-randconfig-r2300-20260930 (https://download.01.org/0day-ci/archive/20260930/202609301826.MFaFMsmd-lkp@intel.com/config)
> > > compiler: mips-linux-gcc (GCC) 15.2.0
> > > sparse: v0.6.5-rc1
> > > reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260930/202609301826.MFaFMsmd-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: d4dba3b9c03a ("lib: decompress_bunzip2: fix 32-bit shift undefined behavior")
> > > | Reported-by: kernel test robot <lkp@intel.com>
> > > | Closes: https://lore.kernel.org/oe-kbuild-all/202609301826.MFaFMsmd-lkp@intel.com/
> > > 
> > > All errors (new ones prefixed by >>):
> > > 
> > >    mips-linux-ld: arch/mips/boot/compressed/decompress.o: in function `get_bits':  
> > > >> arch/mips/boot/compressed/decompress.c:(.text+0xf4): undefined reference to `__ashldi3'
> > > >> mips-linux-ld: arch/mips/boot/compressed/decompress.c:(.text+0x168): undefined reference to `__ashldi3'  
> > 
> > I dunno, I'd be suspecting a toolchain issue here?
> > 
> > --- a/lib/decompress_bunzip2.c
> > +++ b/lib/decompress_bunzip2.c
> > @@ -135,7 +135,7 @@ static unsigned int INIT get_bits(struct bunzip_data *bd, char bits_wanted)
> >  		}
> >  		/* Avoid 32-bit overflow (dump bit buffer to top of output) */
> >  		if (bd->inbufBitCount >= 24) {
> > -			bits = bd->inbufBits&((1 << bd->inbufBitCount)-1);
> > +			bits = bd->inbufBits & ((1ULL << bd->inbufBitCount) - 1);
> >  			bits_wanted -= bd->inbufBitCount;
> >  			bits <<= bits_wanted;
> >  			bd->inbufBitCount = 0;
> > @@ -146,7 +146,7 @@ static unsigned int INIT get_bits(struct bunzip_data *bd, char bits_wanted)
> >  	}
> >  	/* Calculate result */
> >  	bd->inbufBitCount -= bits_wanted;
> > -	bits |= (bd->inbufBits >> bd->inbufBitCount)&((1 << bits_wanted)-1);
> > +	bits |= (bd->inbufBits >> bd->inbufBitCount) & ((1ULL << bits_wanted) - 1);
> >  
> >  	return bits;
> >  }
> > 
> > 32-bit MIPS should be able to do this?  
> 
> FWIW the patch seems entirely bogus. I don't think you can have inbufBitCount >=
> 32. If you could, then the patch would still not fix anything, because
> bd->inbufBits is an (32-bit) unsigned int.

The 1 should probably be 1U (or possibly 1UL is 64bit values can happen on
64bit) rather than 1ULL.

Wasn't the problem being solved '1 << 31' being undefined (or UB) and one of
the static checkers deciding that should never shift a signed value left?
That is entirely bogus anyway.
It is only non-portable because C allows 1's compliment and sign overpunch
for negative integers, gcc supports neither (and I think the next C standard
mandates 2's compliment).

That is separate from shift right of negative values being UB to allow for
cpu that don't have a sign replicating shift (all modern ones do).
Think about it, for a shift/rotate left you need one of 0/carry/high-bit and
for shift right 0/carry/low-bit so two instruction bits can select one of
0/carry/low-bit/high-bit (giving the often implemented but undocumented shift
left that replicates the low bit).

David

> 
> As per MIPS itself, MIPS does not link ashldi3.o into the decompressor for BZ2.
> It only does so for XZ and ZSTD.
> 
> Changing arch/mips/boot/compressed/Makefile would work, but since the change is
> entirely wrong I would suggest perhaps reverting?
> 
> 

arch/mips/boot/compressed/decompress.c:undefined reference to `__ashldi3'

[kernel test robot]

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
head:   4539944e515183668109bdf4d0c3d7d228383d88
commit: d4dba3b9c03a326cfa73833d6b166aeb442f82b5 lib: decompress_bunzip2: fix 32-bit shift undefined behavior
date:   4 months ago
config: mips-randconfig-r134-20260724 (https://download.01.org/0day-ci/archive/20260724/202607242144.ZsfAPGBh-lkp@intel.com/config)
compiler: mips-linux-gcc (GCC) 8.5.0
sparse: v0.6.5-rc1
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260724/202607242144.ZsfAPGBh-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: d4dba3b9c03a ("lib: decompress_bunzip2: fix 32-bit shift undefined behavior")
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202607242144.ZsfAPGBh-lkp@intel.com/

All errors (new ones prefixed by >>):

   mips-linux-ld: arch/mips/boot/compressed/decompress.o: in function `$L13':
>> arch/mips/boot/compressed/decompress.c:(.text+0xfc): undefined reference to `__ashldi3'
   mips-linux-ld: arch/mips/boot/compressed/decompress.o: in function `$L12':
   arch/mips/boot/compressed/decompress.c:(.text+0x168): undefined reference to `__ashldi3'

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