Le 07/12/2021 à 05:48, Nathan Chancellor a écrit : > On Tue, Dec 07, 2021 at 02:37:26PM +1100, Michael Ellerman wrote: >> Bill Wendling <mo...@google.com> writes: >>> On Tue, Nov 30, 2021 at 10:38 AM Bill Wendling <mo...@google.com> wrote: >>>> On Tue, Nov 30, 2021 at 10:17 AM Nathan Chancellor <nat...@kernel.org> >>>> wrote: >>>>> On Tue, Nov 30, 2021 at 10:25:43PM +1100, Michael Ellerman wrote: >>>>>> Christophe Leroy <christophe.le...@csgroup.eu> writes: >>>>>>> Le 29/11/2021 à 23:55, kernel test robot a écrit : >> ... >>>>>>>> All warnings (new ones prefixed by >>): >>>>>>>> >>>>>>>> In file included from arch/powerpc/kernel/asm-offsets.c:71: >>>>>>>> In file included from arch/powerpc/kernel/../xmon/xmon_bpts.h:7: >>>>>>>>>> arch/powerpc/include/asm/inst.h:165:20: warning: variable 'val' is >>>>>>>>>> uninitialized when used here [-Wuninitialized] >>>>>>>> *inst = ppc_inst(val); >>>>>>>> ^~~ >>>>>>>> arch/powerpc/include/asm/inst.h:53:22: note: expanded from macro >>>>>>>> 'ppc_inst' >>>>>>>> #define ppc_inst(x) (x) >>>>>>>> ^ >>>>>>>> arch/powerpc/include/asm/inst.h:155:18: note: initialize the >>>>>>>> variable 'val' to silence this warning >>>>>>>> unsigned int val, suffix; >>>>>>>> ^ >>>>>>>> = 0 >>>>>>> >>>>>>> I can't understand what's wrong here. >> ... >>>>>>> >>>>>>> I see no possibility, no alternative path where val wouldn't be set. The >>>>>>> asm clearly has *addr as an output param so it is always set. >>>>>> >>>>>> I guess clang can't convince itself of that? >> ... >>>>> >>>>> It certainly looks like there is something wrong with how clang is >>>>> tracking the initialization of the variable because it looks to me like >>>>> val is only used in the fallthrough path, which happens after it is >>>>> initialized via lwz. Perhaps something is wrong with the logic of >>>>> https://reviews.llvm.org/D71314? I've added Bill to CC (LLVM issues are >>>>> being migrated from Bugzilla to GitHub Issues right now so I cannot file >>>>> this upstream at the moment). >>>>> >>>> If I remove the casts of "val" the warning doesn't appear. I suspect >>>> that when I wrote that patch I forgot to remove those when checking. >>>> #include "Captain_Picard_facepalm.h" >>>> >>>> I'll look into it. >>>> >>> Small retraction. It's the "*(<cast>)&val" that's the issue. (I.e. the "*&") >> >> I guess for now I'll just squash this in as a workaround? >> >> >> diff --git a/arch/powerpc/include/asm/inst.h >> b/arch/powerpc/include/asm/inst.h >> index 631436f3f5c3..5b591c51fec9 100644 >> --- a/arch/powerpc/include/asm/inst.h >> +++ b/arch/powerpc/include/asm/inst.h >> @@ -157,6 +157,9 @@ static inline int >> copy_inst_from_kernel_nofault(ppc_inst_t *inst, u32 *src) >> if (unlikely(!is_kernel_addr((unsigned long)src))) >> return -ERANGE; > > Could we add a version check to this and a link to our bug tracker: > > /* https://github.com/ClangBuiltLinux/linux/issues/1521 */ > #if defined(CONFIG_CC_IS_CLANG) && CONFIG_CLANG_VERSION < 140000
The robot reported the problem on: compiler: clang version 14.0.0 (https://github.com/llvm/llvm-project df08b2fe8b35cb63dfb3b49738a3494b9b4e6f8e) Should it be CONFIG_CLANG_VERSION <= 140000 ? > >> +#ifdef CONFIG_CC_IS_CLANG >> + val = suffix = 0; >> +#endif >> __get_kernel_nofault(&val, src, u32, Efault); >> if (IS_ENABLED(CONFIG_PPC64) && get_op(val) == OP_PREFIX) { >> __get_kernel_nofault(&suffix, src + 1, u32, Efault); >> Christophe
