| Message ID | 20190722213250.238685-2-ndesaulniers@google.com |
|---|---|
| State | New |
| Headers | show |
| Series | [v2,1/2] x86/purgatory: do not use __builtin_memcpy and __builtin_memset | expand |
On Mon, Jul 22, 2019 at 2:33 PM Nick Desaulniers <ndesaulniers@google.com> wrote: > > KBUILD_CFLAGS is very carefully built up in the top level Makefile, > particularly when cross compiling or using different build tools. > Resetting KBUILD_CFLAGS via := assignment is an antipattern. > > The comment above the reset mentions that -pg is problematic. Other > Makefiles like arch/x86/xen/vdso/Makefile use > `CFLAGS_REMOVE_file.o = -pg` when CONFIG_FUNCTION_TRACER is set. Prefer > that pattern to wiping out all of the important KBUILD_CFLAGS then > manually having to re-add them. > > Fixes: 8fc5b4d4121c ("purgatory: core purgatory functionality") > Reported-by: Vaibhav Rustagi <vaibhavrustagi@google.com> > Suggested-by: Peter Zijlstra <peterz@infradead.org> > Signed-off-by: Nick Desaulniers <ndesaulniers@google.com> > --- > Rather than manually add -mno-sse, -mno-mmx, -mno-sse2, prefer to filter > -pg flags. > > arch/x86/purgatory/Makefile | 12 +++++++----- > 1 file changed, 7 insertions(+), 5 deletions(-) > > diff --git a/arch/x86/purgatory/Makefile b/arch/x86/purgatory/Makefile > index 91ef244026d2..56bcabca283f 100644 > --- a/arch/x86/purgatory/Makefile > +++ b/arch/x86/purgatory/Makefile > @@ -20,11 +20,13 @@ KCOV_INSTRUMENT := n > > # Default KBUILD_CFLAGS can have -pg option set when FTRACE is enabled. That > # in turn leaves some undefined symbols like __fentry__ in purgatory and not > -# sure how to relocate those. Like kexec-tools, use custom flags. > - > -KBUILD_CFLAGS := -fno-strict-aliasing -Wall -Wstrict-prototypes -fno-zero-initialized-in-bss -fno-builtin -ffreestanding -c -Os -mcmodel=large > -KBUILD_CFLAGS += -m$(BITS) Is purgatory/kexec supported for CONFIG_X86_32? Should I be keeping `-m$(BITS)`? arch/x86/purgatory/Makefile mentions `setup-x86_$(BITS).o` which I assume is broken as there is no arch/x86/purgatory/setup-x86_32.S? > -KBUILD_CFLAGS += $(call cc-option,-fno-PIE) > +# sure how to relocate those. > +ifdef CONFIG_FUNCTION_TRACER > +CFLAGS_REMOVE_sha256.o = -pg > +CFLAGS_REMOVE_purgatory.o = -pg > +CFLAGS_REMOVE_string.o = -pg > +CFLAGS_REMOVE_kexec-purgatory.o = -pg > +endif > > $(obj)/purgatory.ro: $(PURGATORY_OBJS) FORCE > $(call if_changed,ld) > -- > 2.22.0.657.g960e92d24f-goog > -- Thanks, ~Nick Desaulniers
On Mon, Jul 22, 2019 at 3:10 PM Nick Desaulniers <ndesaulniers@google.com> wrote: > > On Mon, Jul 22, 2019 at 2:33 PM Nick Desaulniers > <ndesaulniers@google.com> wrote: > > > > KBUILD_CFLAGS is very carefully built up in the top level Makefile, > > particularly when cross compiling or using different build tools. > > Resetting KBUILD_CFLAGS via := assignment is an antipattern. > > > > The comment above the reset mentions that -pg is problematic. Other > > Makefiles like arch/x86/xen/vdso/Makefile use > > `CFLAGS_REMOVE_file.o = -pg` when CONFIG_FUNCTION_TRACER is set. Prefer > > that pattern to wiping out all of the important KBUILD_CFLAGS then > > manually having to re-add them. > > > > Fixes: 8fc5b4d4121c ("purgatory: core purgatory functionality") > > Reported-by: Vaibhav Rustagi <vaibhavrustagi@google.com> > > Suggested-by: Peter Zijlstra <peterz@infradead.org> > > Signed-off-by: Nick Desaulniers <ndesaulniers@google.com> > > --- > > Rather than manually add -mno-sse, -mno-mmx, -mno-sse2, prefer to filter > > -pg flags. > > > > arch/x86/purgatory/Makefile | 12 +++++++----- > > 1 file changed, 7 insertions(+), 5 deletions(-) > > > > diff --git a/arch/x86/purgatory/Makefile b/arch/x86/purgatory/Makefile > > index 91ef244026d2..56bcabca283f 100644 > > --- a/arch/x86/purgatory/Makefile > > +++ b/arch/x86/purgatory/Makefile > > @@ -20,11 +20,13 @@ KCOV_INSTRUMENT := n > > > > # Default KBUILD_CFLAGS can have -pg option set when FTRACE is enabled. That > > # in turn leaves some undefined symbols like __fentry__ in purgatory and not > > -# sure how to relocate those. Like kexec-tools, use custom flags. > > - > > -KBUILD_CFLAGS := -fno-strict-aliasing -Wall -Wstrict-prototypes -fno-zero-initialized-in-bss -fno-builtin -ffreestanding -c -Os -mcmodel=large > > -KBUILD_CFLAGS += -m$(BITS) > > Is purgatory/kexec supported for CONFIG_X86_32? Should I be keeping > `-m$(BITS)`? arch/x86/purgatory/Makefile mentions > `setup-x86_$(BITS).o` which I assume is broken as there is no > arch/x86/purgatory/setup-x86_32.S? > > > -KBUILD_CFLAGS += $(call cc-option,-fno-PIE) > > +# sure how to relocate those. > > +ifdef CONFIG_FUNCTION_TRACER > > +CFLAGS_REMOVE_sha256.o = -pg > > +CFLAGS_REMOVE_purgatory.o = -pg > > +CFLAGS_REMOVE_string.o = -pg > > +CFLAGS_REMOVE_kexec-purgatory.o = -pg > > +endif > > The changes suggested will cause undefined symbols while loading the new kernel. On doing 'nm purgatory.ro', I found below undefined symbols: U bmcp U __stack_chk_fail > > $(obj)/purgatory.ro: $(PURGATORY_OBJS) FORCE > > $(call if_changed,ld) > > -- > > 2.22.0.657.g960e92d24f-goog > > > > > -- > Thanks, > ~Nick Desaulniers
On Mon, Jul 22, 2019 at 3:59 PM Vaibhav Rustagi <vaibhavrustagi@google.com> wrote: > The changes suggested will cause undefined symbols while loading the new kernel. > On doing 'nm purgatory.ro', I found below undefined symbols: > > U bmcp > U __stack_chk_fail Thanks for the report, a v3: https://lkml.org/lkml/2019/7/23/864 (Tested v3 with defconfig, defconfig+CONFIG_FUNCTION_TRACER, +CONFIG_STACKPROTECTOR_STRONG, and allyesconfig) -- Thanks, ~Nick Desaulniers
diff --git a/arch/x86/purgatory/Makefile b/arch/x86/purgatory/Makefile index 91ef244026d2..56bcabca283f 100644 --- a/arch/x86/purgatory/Makefile +++ b/arch/x86/purgatory/Makefile @@ -20,11 +20,13 @@ KCOV_INSTRUMENT := n # Default KBUILD_CFLAGS can have -pg option set when FTRACE is enabled. That # in turn leaves some undefined symbols like __fentry__ in purgatory and not -# sure how to relocate those. Like kexec-tools, use custom flags. - -KBUILD_CFLAGS := -fno-strict-aliasing -Wall -Wstrict-prototypes -fno-zero-initialized-in-bss -fno-builtin -ffreestanding -c -Os -mcmodel=large -KBUILD_CFLAGS += -m$(BITS) -KBUILD_CFLAGS += $(call cc-option,-fno-PIE) +# sure how to relocate those. +ifdef CONFIG_FUNCTION_TRACER +CFLAGS_REMOVE_sha256.o = -pg +CFLAGS_REMOVE_purgatory.o = -pg +CFLAGS_REMOVE_string.o = -pg +CFLAGS_REMOVE_kexec-purgatory.o = -pg +endif $(obj)/purgatory.ro: $(PURGATORY_OBJS) FORCE $(call if_changed,ld)
KBUILD_CFLAGS is very carefully built up in the top level Makefile, particularly when cross compiling or using different build tools. Resetting KBUILD_CFLAGS via := assignment is an antipattern. The comment above the reset mentions that -pg is problematic. Other Makefiles like arch/x86/xen/vdso/Makefile use `CFLAGS_REMOVE_file.o = -pg` when CONFIG_FUNCTION_TRACER is set. Prefer that pattern to wiping out all of the important KBUILD_CFLAGS then manually having to re-add them. Fixes: 8fc5b4d4121c ("purgatory: core purgatory functionality") Reported-by: Vaibhav Rustagi <vaibhavrustagi@google.com> Suggested-by: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Nick Desaulniers <ndesaulniers@google.com> --- Rather than manually add -mno-sse, -mno-mmx, -mno-sse2, prefer to filter -pg flags. arch/x86/purgatory/Makefile | 12 +++++++----- 1 file changed, 7 insertions(+), 5 deletions(-) -- 2.22.0.657.g960e92d24f-goog