tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master head: 051143e1602d90ea71887d92363edd539d411de5 commit: 305d60012304684bd59ea1f67703e51662e4906a powerpc/kasan: add missing/lost Makefile config: powerpc-randconfig-r024-20200522 (attached as .config) compiler: powerpc-linux-gcc (GCC) 9.3.0 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 git checkout 305d60012304684bd59ea1f67703e51662e4906a # save the attached .config to linux build tree COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-9.3.0 make.cross ARCH=powerpc If you fix the issue, kindly add following tag as appropriate Reported-by: kbuild test robot <lkp(a)intel.com&gt; All error/warnings (new ones prefixed by >>, old ones prefixed by <<): arch/powerpc/mm/kasan/kasan_init_32.c:135:7: warning: no previous prototype for 'module_alloc' [-Wmissing-prototypes] 135 | void *module_alloc(unsigned long size) | ^~~~~~~~~~~~ In file included from include/linux/kernel.h:11, from arch/powerpc/include/asm/page.h:15, from arch/powerpc/include/asm/kasan.h:17, from include/linux/kasan.h:14, from arch/powerpc/mm/kasan/kasan_init_32.c:5: arch/powerpc/mm/kasan/kasan_init_32.c: In function 'kasan_early_init': 344 | _compiletime_assert(condition, msg, __compiletime_assert_, __LINE__) | ^ include/linux/compiler.h:325:4: note: in definition of macro '__compiletime_assert' 325 | prefix ## suffix(); | ^~~~~~ include/linux/compiler.h:344:2: note: in expansion of macro '_compiletime_assert' 344 | _compiletime_assert(condition, msg, __compiletime_assert_, __LINE__) | ^~~~~~~~~~~~~~~~~~~ include/linux/build_bug.h:39:37: note: in expansion of macro 'compiletime_assert' 39 | #define BUILD_BUG_ON_MSG(cond, msg) compiletime_assert(!(cond), msg) | ^~~~~~~~~~~~~~~~~~ include/linux/build_bug.h:50:2: note: in expansion of macro 'BUILD_BUG_ON_MSG' 50 | BUILD_BUG_ON_MSG(condition, "BUILD_BUG_ON failed: " #condition) | ^~~~~~~~~~~~~~~~ 172 | BUILD_BUG_ON(KASAN_SHADOW_START & ~PGDIR_MASK); | ^~~~~~~~~~~~ # 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 remote update linus git checkout 305d60012304684bd59ea1f67703e51662e4906a vim +/__compiletime_assert_172 +344 include/linux/compiler.h 9a8ab1c39970a4 Daniel Santos 2013-02-21 330 9a8ab1c39970a4 Daniel Santos 2013-02-21 331 #define _compiletime_assert(condition, msg, prefix, suffix) \ 9a8ab1c39970a4 Daniel Santos 2013-02-21 332 __compiletime_assert(condition, msg, prefix, suffix) 9a8ab1c39970a4 Daniel Santos 2013-02-21 333 9a8ab1c39970a4 Daniel Santos 2013-02-21 334 /** 9a8ab1c39970a4 Daniel Santos 2013-02-21 335 * compiletime_assert - break build and emit msg if condition is false 9a8ab1c39970a4 Daniel Santos 2013-02-21 336 * @condition: a compile-time constant condition to check 9a8ab1c39970a4 Daniel Santos 2013-02-21 337 * @msg: a message to emit if condition is false 9a8ab1c39970a4 Daniel Santos 2013-02-21 338 * 9a8ab1c39970a4 Daniel Santos 2013-02-21 339 * In tradition of POSIX assert, this macro will break the build if the 9a8ab1c39970a4 Daniel Santos 2013-02-21 340 * supplied condition is *false*, emitting the supplied error message if the 9a8ab1c39970a4 Daniel Santos 2013-02-21 341 * compiler has support to do so. 9a8ab1c39970a4 Daniel Santos 2013-02-21 342 */ 9a8ab1c39970a4 Daniel Santos 2013-02-21 343 #define compiletime_assert(condition, msg) \ 9a8ab1c39970a4 Daniel Santos 2013-02-21 @344 _compiletime_assert(condition, msg, __compiletime_assert_, __LINE__) 9a8ab1c39970a4 Daniel Santos 2013-02-21 345 :::::: The code at line 344 was first introduced by commit :::::: 9a8ab1c39970a4938a72d94e6fd13be88a797590 bug.h, compiler.h: introduce compiletime_assert & BUILD_BUG_ON_MSG :::::: TO: Daniel Santos <daniel.santos(a)pobox.com&gt; :::::: CC: Linus Torvalds <torvalds(a)linux-foundation.org&gt; --- 0-DAY CI Kernel Test Service, Intel Corporation https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org