On Tue, Aug 13, 2019 at 1:30 PM Nick Desaulniers
<ndesaulniers@xxxxxxxxxx> wrote:
>
> Hi Vaibhav,
> What LTS kernel are you basing your distro off of? IIRC, 4.19, or was
> it further back?
>
We are using 4.19.
> On Tue, Aug 13, 2019 at 11:40 AM <gregkh@xxxxxxxxxxxxxxxxxxx> wrote:
> >
> >
> > The patch below does not apply to the 4.9-stable tree.
> > If someone wants it applied there, or to any other stable or longterm
> > tree, then please email the backport, including the original git commit
> > id to <stable@xxxxxxxxxxxxxxx>.
> >
> > thanks,
> >
> > greg k-h
> >
> > ------------------ original commit in Linus's tree ------------------
> >
> > From b059f801a937d164e03b33c1848bb3dca67c0b04 Mon Sep 17 00:00:00 2001
> > From: Nick Desaulniers <ndesaulniers@xxxxxxxxxx>
> > Date: Wed, 7 Aug 2019 15:15:33 -0700
> > Subject: [PATCH] x86/purgatory: Use CFLAGS_REMOVE rather than reset
> > KBUILD_CFLAGS
> >
> > 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 = $(CC_FLAGS_FTRACE)` when
> > CONFIG_FUNCTION_TRACER is set. Prefer that pattern to wiping out all of
> > the important KBUILD_CFLAGS then manually having to re-add them. Seems
> > also that __stack_chk_fail references are generated when using
> > CONFIG_STACKPROTECTOR or CONFIG_STACKPROTECTOR_STRONG.
> >
> > Fixes: 8fc5b4d4121c ("purgatory: core purgatory functionality")
> > Reported-by: Vaibhav Rustagi <vaibhavrustagi@xxxxxxxxxx>
> > Suggested-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
> > Suggested-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> > Signed-off-by: Nick Desaulniers <ndesaulniers@xxxxxxxxxx>
> > Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> > Tested-by: Vaibhav Rustagi <vaibhavrustagi@xxxxxxxxxx>
> > Cc: stable@xxxxxxxxxxxxxxx
> > Link: https://lkml.kernel.org/r/20190807221539.94583-2-ndesaulniers@xxxxxxxxxx
> >
> > diff --git a/arch/x86/purgatory/Makefile b/arch/x86/purgatory/Makefile
> > index 91ef244026d2..8901a1f89cf5 100644
> > --- a/arch/x86/purgatory/Makefile
> > +++ b/arch/x86/purgatory/Makefile
> > @@ -20,11 +20,34 @@ KCOV_INSTRUMENT := n
> >
> > # Default KBUILD_CFLAGS can have -pg option set when FTRACE is enabled. That
> > # in turn leaves some undefined symbols like __fentry__ in purgatory and not
> > -# sure how to relocate those. Like kexec-tools, use custom flags.
> > -
> > -KBUILD_CFLAGS := -fno-strict-aliasing -Wall -Wstrict-prototypes -fno-zero-initialized-in-bss -fno-builtin -ffreestanding -c -Os -mcmodel=large
> > -KBUILD_CFLAGS += -m$(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
> > +
> > +ifdef CONFIG_RETPOLINE
> > +CFLAGS_REMOVE_sha256.o += $(RETPOLINE_CFLAGS)
> > +CFLAGS_REMOVE_purgatory.o += $(RETPOLINE_CFLAGS)
> > +CFLAGS_REMOVE_string.o += $(RETPOLINE_CFLAGS)
> > +CFLAGS_REMOVE_kexec-purgatory.o += $(RETPOLINE_CFLAGS)
> > +endif
> >
> > $(obj)/purgatory.ro: $(PURGATORY_OBJS) FORCE
> > $(call if_changed,ld)
> >
>
>
> --
> Thanks,
> ~Nick Desaulniers
