Hi Paul, First bad commit (maybe != root cause): tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master head: 7acac4b3196caee5e21fb5ea53f8bc124e6a16fc commit: a510b616131f85215ba156ed67e5ed1c0701f80f MIPS: Add support for ZSTD-compressed kernels date: 7 months ago config: mips-randconfig-r011-20210322 (attached as .config) compiler: clang version 13.0.0 (https://github.com/llvm/llvm-project 14696baaf4c43fe53f738bc292bbe169eed93d5d) reproduce (this is a W=1 build): wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross chmod +x ~/bin/make.cross # install mips cross compiling tool for clang build # apt-get install binutils-mips-linux-gnu # https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit... git remote add linus https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git git fetch --no-tags linus master git checkout a510b616131f85215ba156ed67e5ed1c0701f80f # save the attached .config to linux build tree COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross ARCH=mips If you fix the issue, kindly add following tag as appropriate Reported-by: kernel test robot <lkp(a)intel.com&gt; All warnings (new ones prefixed by >>): arch/mips/boot/compressed/decompress.c:38:6: warning: no previous prototype for function 'error' [-Wmissing-prototypes] void error(char *x) ^ arch/mips/boot/compressed/decompress.c:38:1: note: declare 'static' if the function is not intended to be used outside of this translation unit void error(char *x) ^ static In file included from arch/mips/boot/compressed/decompress.c:76: In file included from arch/mips/boot/compressed/../../../../lib/decompress_unzstd.c:75: ZSTD_DCtx *ZSTD_createDCtx_advanced(ZSTD_customMem customMem) ^ arch/mips/boot/compressed/../../../../lib/zstd/decompress.c:126:1: note: declare 'static' if the function is not intended to be used outside of this translation unit ZSTD_DCtx *ZSTD_createDCtx_advanced(ZSTD_customMem customMem) ^ static size_t ZSTD_getcBlockSize(const void *src, size_t srcSize, blockProperties_t *bpPtr) ^ arch/mips/boot/compressed/../../../../lib/zstd/decompress.c:394:1: note: declare 'static' if the function is not intended to be used outside of this translation unit size_t ZSTD_getcBlockSize(const void *src, size_t srcSize, blockProperties_t *bpPtr) ^ static size_t ZSTD_decodeLiteralsBlock(ZSTD_DCtx *dctx, const void *src, size_t srcSize) /* note : srcSize < BLOCKSIZE */ ^ arch/mips/boot/compressed/../../../../lib/zstd/decompress.c:432:1: note: declare 'static' if the function is not intended to be used outside of this translation unit size_t ZSTD_decodeLiteralsBlock(ZSTD_DCtx *dctx, const void *src, size_t srcSize) /* note : srcSize < BLOCKSIZE */ ^ static size_t ZSTD_decodeSeqHeaders(ZSTD_DCtx *dctx, int *nbSeqPtr, const void *src, size_t srcSize) ^ arch/mips/boot/compressed/../../../../lib/zstd/decompress.c:794:1: note: declare 'static' if the function is not intended to be used outside of this translation unit size_t ZSTD_decodeSeqHeaders(ZSTD_DCtx *dctx, int *nbSeqPtr, const void *src, size_t srcSize) ^ static size_t ZSTD_generateNxBytes(void *dst, size_t dstCapacity, BYTE byte, size_t length) ^ arch/mips/boot/compressed/../../../../lib/zstd/decompress.c:1497:1: note: declare 'static' if the function is not intended to be used outside of this translation unit size_t ZSTD_generateNxBytes(void *dst, size_t dstCapacity, BYTE byte, size_t length) ^ static arch/mips/boot/compressed/decompress.c:81:6: warning: no previous prototype for function '__stack_chk_fail' [-Wmissing-prototypes] void __stack_chk_fail(void) ^ arch/mips/boot/compressed/decompress.c:81:1: note: declare 'static' if the function is not intended to be used outside of this translation unit void __stack_chk_fail(void) ^ static arch/mips/boot/compressed/decompress.c:86:6: warning: no previous prototype for function 'decompress_kernel' [-Wmissing-prototypes] void decompress_kernel(unsigned long boot_heap_start) ^ arch/mips/boot/compressed/decompress.c:86:1: note: declare 'static' if the function is not intended to be used outside of this translation unit void decompress_kernel(unsigned long boot_heap_start) ^ static 8 warnings generated. Kconfig warnings: (for reference only) WARNING: unmet direct dependencies detected for SSB_EMBEDDED Depends on SSB && SSB_DRIVER_MIPS && SSB_PCICORE_HOSTMODE Selected by - BCM47XX_SSB && BCM47XX vim +/ZSTD_createDCtx_advanced +126 arch/mips/boot/compressed/../../../../lib/zstd/decompress.c 73f3d1b48f5069 Nick Terrell 2017-08-09 125 73f3d1b48f5069 Nick Terrell 2017-08-09 @126 ZSTD_DCtx *ZSTD_createDCtx_advanced(ZSTD_customMem customMem) 73f3d1b48f5069 Nick Terrell 2017-08-09 127 { 73f3d1b48f5069 Nick Terrell 2017-08-09 128 ZSTD_DCtx *dctx; 73f3d1b48f5069 Nick Terrell 2017-08-09 129 73f3d1b48f5069 Nick Terrell 2017-08-09 130 if (!customMem.customAlloc || !customMem.customFree) 73f3d1b48f5069 Nick Terrell 2017-08-09 131 return NULL; 73f3d1b48f5069 Nick Terrell 2017-08-09 132 73f3d1b48f5069 Nick Terrell 2017-08-09 133 dctx = (ZSTD_DCtx *)ZSTD_malloc(sizeof(ZSTD_DCtx), customMem); 73f3d1b48f5069 Nick Terrell 2017-08-09 134 if (!dctx) 73f3d1b48f5069 Nick Terrell 2017-08-09 135 return NULL; 73f3d1b48f5069 Nick Terrell 2017-08-09 136 memcpy(&dctx->customMem, &customMem, sizeof(customMem)); 73f3d1b48f5069 Nick Terrell 2017-08-09 137 ZSTD_decompressBegin(dctx); 73f3d1b48f5069 Nick Terrell 2017-08-09 138 return dctx; 73f3d1b48f5069 Nick Terrell 2017-08-09 139 } 73f3d1b48f5069 Nick Terrell 2017-08-09 140 :::::: The code at line 126 was first introduced by commit :::::: 73f3d1b48f5069d46ba48aa28c2898dc93185560 lib: Add zstd modules :::::: TO: Nick Terrell <terrelln(a)fb.com&gt; :::::: CC: Chris Mason <clm(a)fb.com&gt; --- 0-DAY CI Kernel Test Service, Intel Corporation https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org