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

[Bradley Morgan]

On 30 September 2026 20:01:59 BST, Andrew Morton
<akpm@xxxxxxxxxxxxxxxxxxxx> wrote:
>On Wed, 30 Sep 2026 18:36:50 +0200 kernel test robot <lkp@xxxxxxxxx>
>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@xxxxxxxxx/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@xxxxxxxxx/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@xxxxxxxxx>
>> | Closes:
>https://lore.kernel.org/oe-kbuild-all/202609301826.MFaFMsmd-lkp@xxxxxxxxx/
>> 
>> 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