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@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?