Date: Fri, 4 Sep 2020 00:14:11 -0700 From: Nathan Chancellor <natechancellor@...il.com> To: Arvind Sankar <nivedita@...m.mit.edu> Cc: Kees Cook <keescook@...omium.org>, Sami Tolvanen <samitolvanen@...gle.com>, Masahiro Yamada <masahiroy@...nel.org>, Will Deacon <will@...nel.org>, Peter Zijlstra <peterz@...radead.org>, Steven Rostedt <rostedt@...dmis.org>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>, "Paul E. McKenney" <paulmck@...nel.org>, Nick Desaulniers <ndesaulniers@...gle.com>, clang-built-linux@...glegroups.com, kernel-hardening@...ts.openwall.com, linux-arch@...r.kernel.org, linux-arm-kernel@...ts.infradead.org, linux-kbuild@...r.kernel.org, linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org, x86@...nel.org Subject: Re: [PATCH v2 01/28] x86/boot/compressed: Disable relocation relaxation On Thu, Sep 03, 2020 at 07:42:15PM -0400, Arvind Sankar wrote: > On Thu, Sep 03, 2020 at 02:44:41PM -0700, Kees Cook wrote: > > On Thu, Sep 03, 2020 at 01:30:26PM -0700, Sami Tolvanen wrote: > > > From: Arvind Sankar <nivedita@...m.mit.edu> > > > > > > Patch series  is a solution to allow the compressed kernel to be > > > linked with -pie unconditionally, but even if merged is unlikely to be > > > backported. As a simple solution that can be applied to stable as well, > > > prevent the assembler from generating the relaxed relocation types using > > > the -mrelax-relocations=no option. For ease of backporting, do this > > > unconditionally. > > > > > >  https://gitlab.com/x86-psABIs/x86-64-ABI/-/blob/master/x86-64-ABI/linker-optimization.tex#L65 > > >  https://email@example.com/ > > >  https://github.com/ClangBuiltLinux/linux/issues/1121 > > >  https://reviews.llvm.org/rGc41a18cf61790fc898dcda1055c3efbf442c14c0 > > >  https://firstname.lastname@example.org/ > > > > > > Reported-by: Nick Desaulniers <ndesaulniers@...gle.com> > > > Signed-off-by: Arvind Sankar <nivedita@...m.mit.edu> > > > > Reviewed-by: Kees Cook <keescook@...omium.org> > > > > -- > > Kees Cook > > Note that since  is now in tip, assuming it doesn't get dropped for > some reason, this patch isn't necessary unless you need to backport this > LTO series to 5.9 or below. > > Thanks. It is still necessary for tip of tree LLVM to work properly (specifically clang and ld.lld) regardless of whether or not LTO is used.  also fixes it but I don't think it can be backported to stable so it would still be nice to get it picked up so that it can be sent back there. We have been carrying it in our CI for a decent amount of time... Cheers, Nathan
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