Message ID | 20190911182049.77853-4-natechancellor@gmail.com (mailing list archive) |
---|---|
State | Superseded |
Headers | show |
Series | LLVM/Clang fixes for pseries_defconfig | expand |
Context | Check | Description |
---|---|---|
snowpatch_ozlabs/apply_patch | success | Successfully applied on branch next (c317052c95bef1f977b023158e5aa929215f443d) |
snowpatch_ozlabs/build-ppc64le | success | Build succeeded |
snowpatch_ozlabs/build-ppc64be | success | Build succeeded |
snowpatch_ozlabs/build-ppc64e | success | Build succeeded |
snowpatch_ozlabs/build-pmac32 | success | Build succeeded |
snowpatch_ozlabs/checkpatch | success | total: 0 errors, 0 warnings, 0 checks, 8 lines checked |
On Wed, Sep 11, 2019 at 11:21 AM Nathan Chancellor <natechancellor@gmail.com> wrote: > > r370454 gives LLVM the ability to convert certain loops into a reference > to bcmp as an optimization; this breaks prom_init_check.sh: > > CALL arch/powerpc/kernel/prom_init_check.sh > Error: External symbol 'bcmp' referenced from prom_init.c > make[2]: *** [arch/powerpc/kernel/Makefile:196: prom_init_check] Error 1 > > bcmp is defined in lib/string.c as a wrapper for memcmp so this could be > added to the whitelist. However, commit 450e7dd4001f ("powerpc/prom_init: > don't use string functions from lib/") copied memcmp as prom_memcmp to > avoid KASAN instrumentation so having bcmp be resolved to regular memcmp > would break that assumption. Furthermore, because the compiler is the > one that inserted bcmp, we cannot provide something like prom_bcmp. > > To prevent LLVM from being clever with optimizations like this, use > -ffreestanding to tell LLVM we are not hosted so it is not free to make > transformations like this. > > Link: https://github.com/ClangBuiltLinux/linux/issues/647 > Link: https://github.com/llvm/llvm-project/commit/5c9f3cfec78f9e9ae013de9a0d092a68e3e79e002 The above link doesn't work for me (HTTP 404). PEBKAC? https://github.com/llvm/llvm-project/commit/5c9f3cfec78f9e9ae013de9a0d092a68e3e79e002 > Signed-off-by: Nathan Chancellor <natechancellor@gmail.com> > --- > > New patch in the series so no previous version. > > arch/powerpc/kernel/Makefile | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/arch/powerpc/kernel/Makefile b/arch/powerpc/kernel/Makefile > index 19f19c8c874b..aa78b3f6271e 100644 > --- a/arch/powerpc/kernel/Makefile > +++ b/arch/powerpc/kernel/Makefile > @@ -21,7 +21,7 @@ CFLAGS_prom_init.o += $(DISABLE_LATENT_ENTROPY_PLUGIN) > CFLAGS_btext.o += $(DISABLE_LATENT_ENTROPY_PLUGIN) > CFLAGS_prom.o += $(DISABLE_LATENT_ENTROPY_PLUGIN) > > -CFLAGS_prom_init.o += $(call cc-option, -fno-stack-protector) > +CFLAGS_prom_init.o += $(call cc-option, -fno-stack-protector) -ffreestanding > > ifdef CONFIG_FUNCTION_TRACER > # Do not trace early boot code > -- > 2.23.0 >
On Wed, Sep 11, 2019 at 02:01:59PM -0700, Nick Desaulniers wrote: > On Wed, Sep 11, 2019 at 11:21 AM Nathan Chancellor > <natechancellor@gmail.com> wrote: > > > > r370454 gives LLVM the ability to convert certain loops into a reference > > to bcmp as an optimization; this breaks prom_init_check.sh: > > > > CALL arch/powerpc/kernel/prom_init_check.sh > > Error: External symbol 'bcmp' referenced from prom_init.c > > make[2]: *** [arch/powerpc/kernel/Makefile:196: prom_init_check] Error 1 > > > > bcmp is defined in lib/string.c as a wrapper for memcmp so this could be > > added to the whitelist. However, commit 450e7dd4001f ("powerpc/prom_init: > > don't use string functions from lib/") copied memcmp as prom_memcmp to > > avoid KASAN instrumentation so having bcmp be resolved to regular memcmp > > would break that assumption. Furthermore, because the compiler is the > > one that inserted bcmp, we cannot provide something like prom_bcmp. > > > > To prevent LLVM from being clever with optimizations like this, use > > -ffreestanding to tell LLVM we are not hosted so it is not free to make > > transformations like this. > > > > Link: https://github.com/ClangBuiltLinux/linux/issues/647 > > Link: https://github.com/llvm/llvm-project/commit/5c9f3cfec78f9e9ae013de9a0d092a68e3e79e002 > > The above link doesn't work for me (HTTP 404). PEBKAC? > https://github.com/llvm/llvm-project/commit/5c9f3cfec78f9e9ae013de9a0d092a68e3e79e002 Not really sure how an extra 2 got added on the end of that... Must have screwed up in vim somehow. Link: https://github.com/llvm/llvm-project/commit/5c9f3cfec78f9e9ae013de9a0d092a68e3e79e00 I can resend unless the maintainer is able to fix that up when it gets applied. Cheers, Nathan
On Wed, Sep 11, 2019 at 10:43 PM Nathan Chancellor <natechancellor@gmail.com> wrote: > > On Wed, Sep 11, 2019 at 02:01:59PM -0700, Nick Desaulniers wrote: > > On Wed, Sep 11, 2019 at 11:21 AM Nathan Chancellor > > <natechancellor@gmail.com> wrote: > > > > > > r370454 gives LLVM the ability to convert certain loops into a reference > > > to bcmp as an optimization; this breaks prom_init_check.sh: > > > > > > CALL arch/powerpc/kernel/prom_init_check.sh > > > Error: External symbol 'bcmp' referenced from prom_init.c > > > make[2]: *** [arch/powerpc/kernel/Makefile:196: prom_init_check] Error 1 > > > > > > bcmp is defined in lib/string.c as a wrapper for memcmp so this could be > > > added to the whitelist. However, commit 450e7dd4001f ("powerpc/prom_init: > > > don't use string functions from lib/") copied memcmp as prom_memcmp to > > > avoid KASAN instrumentation so having bcmp be resolved to regular memcmp > > > would break that assumption. Furthermore, because the compiler is the > > > one that inserted bcmp, we cannot provide something like prom_bcmp. > > > > > > To prevent LLVM from being clever with optimizations like this, use > > > -ffreestanding to tell LLVM we are not hosted so it is not free to make > > > transformations like this. > > > > > > Link: https://github.com/ClangBuiltLinux/linux/issues/647 > > > Link: https://github.com/llvm/llvm-project/commit/5c9f3cfec78f9e9ae013de9a0d092a68e3e79e002 > > > > The above link doesn't work for me (HTTP 404). PEBKAC? > > https://github.com/llvm/llvm-project/commit/5c9f3cfec78f9e9ae013de9a0d092a68e3e79e002 > > Not really sure how an extra 2 got added on the end of that... Must have > screwed up in vim somehow. > > Link: https://github.com/llvm/llvm-project/commit/5c9f3cfec78f9e9ae013de9a0d092a68e3e79e00 That looks better. Assuming Michael doesn't mind amending the link when applying: Reviewed-by: Nick Desaulneris <ndesaulniers@google.com> > > I can resend unless the maintainer is able to fix that up when it gets > applied. > > Cheers, > Nathan
diff --git a/arch/powerpc/kernel/Makefile b/arch/powerpc/kernel/Makefile index 19f19c8c874b..aa78b3f6271e 100644 --- a/arch/powerpc/kernel/Makefile +++ b/arch/powerpc/kernel/Makefile @@ -21,7 +21,7 @@ CFLAGS_prom_init.o += $(DISABLE_LATENT_ENTROPY_PLUGIN) CFLAGS_btext.o += $(DISABLE_LATENT_ENTROPY_PLUGIN) CFLAGS_prom.o += $(DISABLE_LATENT_ENTROPY_PLUGIN) -CFLAGS_prom_init.o += $(call cc-option, -fno-stack-protector) +CFLAGS_prom_init.o += $(call cc-option, -fno-stack-protector) -ffreestanding ifdef CONFIG_FUNCTION_TRACER # Do not trace early boot code
r370454 gives LLVM the ability to convert certain loops into a reference to bcmp as an optimization; this breaks prom_init_check.sh: CALL arch/powerpc/kernel/prom_init_check.sh Error: External symbol 'bcmp' referenced from prom_init.c make[2]: *** [arch/powerpc/kernel/Makefile:196: prom_init_check] Error 1 bcmp is defined in lib/string.c as a wrapper for memcmp so this could be added to the whitelist. However, commit 450e7dd4001f ("powerpc/prom_init: don't use string functions from lib/") copied memcmp as prom_memcmp to avoid KASAN instrumentation so having bcmp be resolved to regular memcmp would break that assumption. Furthermore, because the compiler is the one that inserted bcmp, we cannot provide something like prom_bcmp. To prevent LLVM from being clever with optimizations like this, use -ffreestanding to tell LLVM we are not hosted so it is not free to make transformations like this. Link: https://github.com/ClangBuiltLinux/linux/issues/647 Link: https://github.com/llvm/llvm-project/commit/5c9f3cfec78f9e9ae013de9a0d092a68e3e79e002 Signed-off-by: Nathan Chancellor <natechancellor@gmail.com> --- New patch in the series so no previous version. arch/powerpc/kernel/Makefile | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)