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Date: Tue, 11 Aug 2020 20:41:58 -0400 From: Arvind Sankar <nivedita@...m.mit.edu> To: Nick Desaulniers <ndesaulniers@...gle.com> Cc: Arvind Sankar <nivedita@...m.mit.edu>, Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>, Fangrui Song <maskray@...gle.com>, clang-built-linux <clang-built-linux@...glegroups.com>, e5ten.arch@...il.com, "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" <x86@...nel.org>, "H. Peter Anvin" <hpa@...or.com>, Masahiro Yamada <masahiroy@...nel.org>, Ard Biesheuvel <ardb@...nel.org>, Kees Cook <keescook@...omium.org>, LKML <linux-kernel@...r.kernel.org>, "# 3.4.x" <stable@...r.kernel.org> Subject: Re: [PATCH] x86/boot/compressed: Disable relocation relaxation for non-pie link On Tue, Aug 11, 2020 at 04:51:23PM -0700, Nick Desaulniers wrote: > On Tue, Aug 11, 2020 at 4:43 PM Arvind Sankar <nivedita@...m.mit.edu> wrote: > > > > On Tue, Aug 11, 2020 at 04:04:40PM -0700, Nick Desaulniers wrote: > > > On Tue, Aug 11, 2020 at 3:44 PM Arvind Sankar <nivedita@...m.mit.edu> wrote: > > > > > > > > On Tue, Aug 11, 2020 at 10:58:40AM -0700, Nick Desaulniers wrote: > > > > > > Cc: stable@...r.kernel.org # 4.19.x > > > > > > > > > > Thanks Arvind, good write up. Just curious about this stable tag, how > > > > > come you picked 4.19? I can see boot failures in our CI for x86+LLD > > > > > back to 4.9. Can we amend that tag to use `# 4.9`? I'd be happy to > > > > > help submit backports should they fail to apply cleanly. > > > > > https://travis-ci.com/github/ClangBuiltLinux/continuous-integration/builds/179237488 > > > > > > > > > > > > > 4.19 renamed LDFLAGS to KBUILD_LDFLAGS. For 4.4, 4.9 and 4.14 the patch > > > > needs to be modified, KBUILD_LDFLAGS -> LDFLAGS, so I figured we should > > > > submit backports separately. For 4.19 onwards, it should apply without > > > > changes I think. > > > > > > Cool, sounds good. I'll keep an eye out for when stable goes to pick this up. > > > > > > tglx, Ingo, BP, can we pretty please get this in tip/urgent for > > > inclusion into 5.9? > > > -- > > > Thanks, > > > ~Nick Desaulniers > > > > Another alternative is to just do this unconditionally instead of even > > checking for the -pie flag. None of the GOTPCRELs are in the > > decompressor, so they shouldn't be performance-sensitive at all. > > > > It still wouldn't apply cleanly to all the stable versions, but > > backporting would be even simpler. > > > > What do you think? > > > > diff --git a/arch/x86/boot/compressed/Makefile b/arch/x86/boot/compressed/Makefile > > index 3962f592633d..10c2ba59d192 100644 > > --- a/arch/x86/boot/compressed/Makefile > > +++ b/arch/x86/boot/compressed/Makefile > > @@ -43,6 +43,7 @@ KBUILD_CFLAGS += -Wno-pointer-sign > > KBUILD_CFLAGS += $(call cc-option,-fmacro-prefix-map=$(srctree)/=) > > KBUILD_CFLAGS += -fno-asynchronous-unwind-tables > > KBUILD_CFLAGS += -D__DISABLE_EXPORTS > > +KBUILD_CFLAGS += $(call as-option,-Wa$(comma)-mrelax-relocations=no) > > We'd still want it for KBUILD_AFLAGS, too, just to be safe. Maybe a KBUILD_CFLAGS gets included into KBUILD_AFLAGS, so this already does that. > one line comment to the effect of `# remove me once we can link as > -pie` would help us rip off this band-aid in the future? It's more > obvious that the added hunk can be reverted once -pie linkage is > achieved with the current patch; either are fine by me. Thanks! > > > > > KBUILD_AFLAGS := $(KBUILD_CFLAGS) -D__ASSEMBLY__ > > GCOV_PROFILE := n > > > > -- > Thanks, > ~Nick Desaulniers
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