Hi Nick,

I love your patch! Yet something to improve:

[auto build test ERROR on 4de593fb965fc2bd11a0b767e0c65ff43540a6e4]

url:    https://github.com/0day-ci/linux/commits/Nick-Desaulniers/kallsyms-strip-LTO-suffixes-from-static-functions/20211002-035956
base:   4de593fb965fc2bd11a0b767e0c65ff43540a6e4
config: i386-randconfig-m021-20211002 (attached as .config)
compiler: gcc-9 (Debian 9.3.0-22) 9.3.0
reproduce (this is a W=1 build):
        # https://github.com/0day-ci/linux/commit/b73f738c48b304c633f9ff079fd8de572ffc6eb0
        git remote add linux-review https://github.com/0day-ci/linux
        git fetch --no-tags linux-review Nick-Desaulniers/kallsyms-strip-LTO-suffixes-from-static-functions/20211002-035956
        git checkout b73f738c48b304c633f9ff079fd8de572ffc6eb0
        # save the attached .config to linux build tree
        mkdir build_dir
        make W=1 O=build_dir ARCH=i386 SHELL=/bin/bash

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@intel.com>

All errors (new ones prefixed by >>):

   kernel/kallsyms.c: In function 'cleanup_symbol_name':
>> kernel/kallsyms.c:190:6: error: '__clang_major__' undeclared (first use in this function)
     190 |      __clang_major__ >= 13)
         |      ^~~~~~~~~~~~~~~
   kernel/kallsyms.c:190:6: note: each undeclared identifier is reported only once for each function it appears in
   kernel/kallsyms.c: At top level:
   kernel/kallsyms.c:585:12: warning: no previous prototype for 'arch_get_kallsym' [-Wmissing-prototypes]
     585 | int __weak arch_get_kallsym(unsigned int symnum, unsigned long *value,
         |            ^~~~~~~~~~~~~~~~


vim +/__clang_major__ +190 kernel/kallsyms.c

   166	
   167	static bool cleanup_symbol_name(char *s)
   168	{
   169		char *res;
   170	
   171		if (!IS_ENABLED(CONFIG_LTO_CLANG))
   172			return false;
   173	
   174		/*
   175		 * LLVM appends various suffixes for local functions and variables that must
   176		 * be promoted to global scope as part of LTO.  This can break hooking of
   177		 * static functions with kprobes. '.' is not a valid character in an
   178		 * identifier in C. Suffixes observed:
   179		 * - foo.llvm.[0-9a-f]+
   180		 * - foo.[0-9a-f]+
   181		 * - foo.[0-9a-f]+.cfi_jt
   182		 */
   183		res = strchr(s, '.');
   184		if (res) {
   185			*res = '\0';
   186			return true;
   187		}
   188	
   189		if (!IS_ENABLED(CONFIG_CFI_CLANG) || !IS_ENABLED(CONFIG_LTO_CLANG_THIN) ||
 > 190		    __clang_major__ >= 13)
   191			return false;
   192	
   193		/*
   194		 * Prior to LLVM 13, the following suffixes were observed when thinLTO
   195		 * and CFI are both enabled:
   196		 * - foo$[0-9]+
   197		 */
   198		res = strrchr(s, '$');
   199		if (res) {
   200			*res = '\0';
   201			return true;
   202		}
   203	
   204		return false;
   205	}
   206	

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0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all(a)lists.01.org