[kbuild-all] [linuxppc:next-test 146/147] arch/powerpc/kernel/process.c:1957:7: warning: variable 'val' is used uninitialized whenever 'if' condition is true

tree: https://github.com/linuxppc/linux next-test head: b86acbffee8165a25d69876c37b0a1bab8e4f66d commit: 887af0b0a569ff6f5af0ec24fcb1c6cde264a18a [146/147] powerpc/process: Remove useless #ifdef CONFIG_SPE config: powerpc-randconfig-r005-20200911 (attached as .config) compiler: clang version 12.0.0 (https://github.com/llvm/llvm-project 0a5dc7effb191eff740e0e7ae7bd8e1f6bdb3ad9) 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 powerpc cross compiling tool for clang build # apt-get install binutils-powerpc-linux-gnu git checkout 887af0b0a569ff6f5af0ec24fcb1c6cde264a18a # save the attached .config to linux build tree COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross ARCH=powerpc 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 >>): if (cpu_has_feature(CPU_FTR_SPE)) { ^~~~~~~~~~~~~~~~~~~~~~~~~~~~ arch/powerpc/kernel/process.c:1979:18: note: uninitialized use occurs here return put_user(val, (unsigned int __user *) adr); ^~~ arch/powerpc/include/asm/uaccess.h:90:40: note: expanded from macro 'put_user' __put_user_check((__typeof__(*(ptr)))(x), (ptr), sizeof(*(ptr))) ^ arch/powerpc/include/asm/uaccess.h:192:33: note: expanded from macro '__put_user_check' __typeof__(*(ptr)) __pu_val = (x); \ ^ arch/powerpc/kernel/process.c:1957:3: note: remove the 'if' if its condition is always false if (cpu_has_feature(CPU_FTR_SPE)) { ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ arch/powerpc/kernel/process.c:1954:18: note: initialize the variable 'val' to silence this warning unsigned int val; ^ = 0 1 warning generated. # https://github.com/linuxppc/linux/commit/887af0b0a569ff6f5af0ec24fcb1c6cd... git remote add linuxppc https://github.com/linuxppc/linux git fetch --no-tags linuxppc next-test git checkout 887af0b0a569ff6f5af0ec24fcb1c6cde264a18a vim +1957 arch/powerpc/kernel/process.c 14cf11af6cf608 Paul Mackerras 2005-09-26 1951 14cf11af6cf608 Paul Mackerras 2005-09-26 1952 int get_fpexc_mode(struct task_struct *tsk, unsigned long adr) 14cf11af6cf608 Paul Mackerras 2005-09-26 1953 { 14cf11af6cf608 Paul Mackerras 2005-09-26 1954 unsigned int val; 14cf11af6cf608 Paul Mackerras 2005-09-26 1955 887af0b0a569ff Christophe Leroy 2020-08-17 1956 if (tsk->thread.fpexc_mode & PR_FP_EXC_SW_ENABLE) { 640e922501103a Joseph Myers 2013-12-10 @1957 if (cpu_has_feature(CPU_FTR_SPE)) { 640e922501103a Joseph Myers 2013-12-10 1958 /* 640e922501103a Joseph Myers 2013-12-10 1959 * When the sticky exception bits are set 640e922501103a Joseph Myers 2013-12-10 1960 * directly by userspace, it must call prctl 640e922501103a Joseph Myers 2013-12-10 1961 * with PR_GET_FPEXC (with PR_FP_EXC_SW_ENABLE 640e922501103a Joseph Myers 2013-12-10 1962 * in the existing prctl settings) or 640e922501103a Joseph Myers 2013-12-10 1963 * PR_SET_FPEXC (with PR_FP_EXC_SW_ENABLE in 640e922501103a Joseph Myers 2013-12-10 1964 * the bits being set). <fenv.h> functions 640e922501103a Joseph Myers 2013-12-10 1965 * saving and restoring the whole 640e922501103a Joseph Myers 2013-12-10 1966 * floating-point environment need to do so 640e922501103a Joseph Myers 2013-12-10 1967 * anyway to restore the prctl settings from 640e922501103a Joseph Myers 2013-12-10 1968 * the saved environment. 640e922501103a Joseph Myers 2013-12-10 1969 */ 887af0b0a569ff Christophe Leroy 2020-08-17 1970 #ifdef CONFIG_SPE 640e922501103a Joseph Myers 2013-12-10 1971 tsk->thread.spefscr_last = mfspr(SPRN_SPEFSCR); 14cf11af6cf608 Paul Mackerras 2005-09-26 1972 val = tsk->thread.fpexc_mode; 887af0b0a569ff Christophe Leroy 2020-08-17 1973 #endif 640e922501103a Joseph Myers 2013-12-10 1974 } else 5e14d21e3f28a4 Kumar Gala 2007-09-13 1975 return -EINVAL; 887af0b0a569ff Christophe Leroy 2020-08-17 1976 } else { 14cf11af6cf608 Paul Mackerras 2005-09-26 1977 val = __unpack_fe01(tsk->thread.fpexc_mode); 887af0b0a569ff Christophe Leroy 2020-08-17 1978 } 14cf11af6cf608 Paul Mackerras 2005-09-26 1979 return put_user(val, (unsigned int __user *) adr); 14cf11af6cf608 Paul Mackerras 2005-09-26 1980 } 14cf11af6cf608 Paul Mackerras 2005-09-26 1981 :::::: The code at line 1957 was first introduced by commit :::::: 640e922501103aaf2e0abb4cf4de5d49fa8342f7 powerpc: fix exception clearing in e500 SPE float emulation :::::: TO: Joseph Myers <joseph(a)codesourcery.com&gt; :::::: CC: Scott Wood <scottwood(a)freescale.com&gt; --- 0-DAY CI Kernel Test Service, Intel Corporation https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org