| Message ID | 20190723212418.36379-2-ndesaulniers@google.com |
|---|---|
| State | New |
| Headers | show |
| Series | None | expand |
On Tue, 23 Jul 2019, Nick Desaulniers wrote: > +ifdef CONFIG_FUNCTION_TRACER > +CFLAGS_REMOVE_sha256.o += $(CC_FLAGS_FTRACE) > +CFLAGS_REMOVE_purgatory.o += $(CC_FLAGS_FTRACE) > +CFLAGS_REMOVE_string.o += $(CC_FLAGS_FTRACE) > +CFLAGS_REMOVE_kexec-purgatory.o += $(CC_FLAGS_FTRACE) Nit. Can you please make that tabular? CFLAGS_REMOVE_sha256.o += $(CC_FLAGS_FTRACE) CFLAGS_REMOVE_purgatory.o += $(CC_FLAGS_FTRACE) CFLAGS_REMOVE_string.o += $(CC_FLAGS_FTRACE) CFLAGS_REMOVE_kexec-purgatory.o += $(CC_FLAGS_FTRACE) The above confused my pattern recognition engine :) Thanks, tglx
On Tue, Jul 23, 2019 at 2:24 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 use `CFLAGS_REMOVE_file.o = $(CC_FLAGS_FTRACE)` 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. Seems > also that __stack_chk_fail references are generated when using > CONFIG_STACKPROTECTOR or CONFIG_STACKPROTECTOR_STRONG. > > Cc: stable@vger.kernel.org > 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> > --- > Alternatively, we could put these in all in one variable and remove it > without any conditional checks (I think that's ok to do so with > CFLAGS_REMOVE). > > Changes v2 -> v3: > * Prefer $(CC_FLAGS_FTRACE) which is exported to -pg. > * Also check CONFIG_STACKPROTECTOR and CONFIG_STACKPROTECTOR_STRONG. > * Cc stable. > Changes v1 -> v2: > Rather than manually add -mno-sse, -mno-mmx, -mno-sse2, prefer to filter > -pg flags. > > arch/x86/purgatory/Makefile | 26 +++++++++++++++++++++----- > 1 file changed, 21 insertions(+), 5 deletions(-) > > diff --git a/arch/x86/purgatory/Makefile b/arch/x86/purgatory/Makefile > index 91ef244026d2..6ef0ced59b9c 100644 > --- a/arch/x86/purgatory/Makefile > +++ b/arch/x86/purgatory/Makefile > @@ -20,11 +20,27 @@ KCOV_INSTRUMENT := n > > # Default KBUILD_CFLAGS can have -pg option set when FTRACE is enabled. That > # in turn leaves some undefined symbols like __fentry__ in purgatory and not > -# sure how to relocate those. Like kexec-tools, use custom flags. > - > -KBUILD_CFLAGS := -fno-strict-aliasing -Wall -Wstrict-prototypes -fno-zero-initialized-in-bss -fno-builtin -ffreestanding -c -Os -mcmodel=large > -KBUILD_CFLAGS += -m$(BITS) > -KBUILD_CFLAGS += $(call cc-option,-fno-PIE) > +# sure how to relocate those. > +ifdef CONFIG_FUNCTION_TRACER > +CFLAGS_REMOVE_sha256.o += $(CC_FLAGS_FTRACE) > +CFLAGS_REMOVE_purgatory.o += $(CC_FLAGS_FTRACE) > +CFLAGS_REMOVE_string.o += $(CC_FLAGS_FTRACE) > +CFLAGS_REMOVE_kexec-purgatory.o += $(CC_FLAGS_FTRACE) > +endif > + > +ifdef CONFIG_STACKPROTECTOR > +CFLAGS_REMOVE_sha256.o += -fstack-protector > +CFLAGS_REMOVE_purgatory.o += -fstack-protector > +CFLAGS_REMOVE_string.o += -fstack-protector > +CFLAGS_REMOVE_kexec-purgatory.o += -fstack-protector > +endif > + > +ifdef CONFIG_STACKPROTECTOR_STRONG > +CFLAGS_REMOVE_sha256.o += -fstack-protector-strong > +CFLAGS_REMOVE_purgatory.o += -fstack-protector-strong > +CFLAGS_REMOVE_string.o += -fstack-protector-strong > +CFLAGS_REMOVE_kexec-purgatory.o += -fstack-protector-strong > +endif > > $(obj)/purgatory.ro: $(PURGATORY_OBJS) FORCE > $(call if_changed,ld) > -- > 2.22.0.709.g102302147b-goog > Tested-by: Vaibhav Rustagi <vaibhavrustagi@google.com> I tested the v3 patch series with clang compiled kernel for below scenarios: 1. kexec'ing into a new kernel. 2. Purposely crashing the running kernel to generate kdump logs. Thanks, Vaibhav
diff --git a/arch/x86/purgatory/Makefile b/arch/x86/purgatory/Makefile index 91ef244026d2..6ef0ced59b9c 100644 --- a/arch/x86/purgatory/Makefile +++ b/arch/x86/purgatory/Makefile @@ -20,11 +20,27 @@ KCOV_INSTRUMENT := n # Default KBUILD_CFLAGS can have -pg option set when FTRACE is enabled. That # in turn leaves some undefined symbols like __fentry__ in purgatory and not -# sure how to relocate those. Like kexec-tools, use custom flags. - -KBUILD_CFLAGS := -fno-strict-aliasing -Wall -Wstrict-prototypes -fno-zero-initialized-in-bss -fno-builtin -ffreestanding -c -Os -mcmodel=large -KBUILD_CFLAGS += -m$(BITS) -KBUILD_CFLAGS += $(call cc-option,-fno-PIE) +# sure how to relocate those. +ifdef CONFIG_FUNCTION_TRACER +CFLAGS_REMOVE_sha256.o += $(CC_FLAGS_FTRACE) +CFLAGS_REMOVE_purgatory.o += $(CC_FLAGS_FTRACE) +CFLAGS_REMOVE_string.o += $(CC_FLAGS_FTRACE) +CFLAGS_REMOVE_kexec-purgatory.o += $(CC_FLAGS_FTRACE) +endif + +ifdef CONFIG_STACKPROTECTOR +CFLAGS_REMOVE_sha256.o += -fstack-protector +CFLAGS_REMOVE_purgatory.o += -fstack-protector +CFLAGS_REMOVE_string.o += -fstack-protector +CFLAGS_REMOVE_kexec-purgatory.o += -fstack-protector +endif + +ifdef CONFIG_STACKPROTECTOR_STRONG +CFLAGS_REMOVE_sha256.o += -fstack-protector-strong +CFLAGS_REMOVE_purgatory.o += -fstack-protector-strong +CFLAGS_REMOVE_string.o += -fstack-protector-strong +CFLAGS_REMOVE_kexec-purgatory.o += -fstack-protector-strong +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 use `CFLAGS_REMOVE_file.o = $(CC_FLAGS_FTRACE)` 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. Seems also that __stack_chk_fail references are generated when using CONFIG_STACKPROTECTOR or CONFIG_STACKPROTECTOR_STRONG. Cc: stable@vger.kernel.org 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> --- Alternatively, we could put these in all in one variable and remove it without any conditional checks (I think that's ok to do so with CFLAGS_REMOVE). Changes v2 -> v3: * Prefer $(CC_FLAGS_FTRACE) which is exported to -pg. * Also check CONFIG_STACKPROTECTOR and CONFIG_STACKPROTECTOR_STRONG. * Cc stable. Changes v1 -> v2: Rather than manually add -mno-sse, -mno-mmx, -mno-sse2, prefer to filter -pg flags. arch/x86/purgatory/Makefile | 26 +++++++++++++++++++++----- 1 file changed, 21 insertions(+), 5 deletions(-) -- 2.22.0.709.g102302147b-goog