lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
Open Source and information security mailing list archives
| ||
|
Date: Fri, 3 Nov 2017 18:09:13 +0000 From: Mark Rutland <mark.rutland@....com> To: Sami Tolvanen <samitolvanen@...gle.com> Cc: Kees Cook <keescook@...omium.org>, Nick Desaulniers <ndesaulniers@...gle.com>, linux-kernel@...r.kernel.org, Greg Hackmann <ghackmann@...gle.com>, Matthias Kaehlcke <mka@...omium.org>, linux-arm-kernel@...ts.infradead.org Subject: Re: [PATCH 00/15] Add support for clang LTO On Fri, Nov 03, 2017 at 05:51:56PM +0000, Mark Rutland wrote: > Hi, > > On Fri, Nov 03, 2017 at 10:11:44AM -0700, Sami Tolvanen wrote: > > This series adds build system support for compiling the kernel with clang > > Link Time Optimization (LTO), using GNU gold with the LLVMgold plug-in > > for linking. Some background for clang's LTO support is available here: > > > > https://llvm.org/docs/LinkTimeOptimization.html > > > > With -flto, clang produces LLVM bitcode instead of object files, and > > the compilation to native code happens at link time. In addition, clang > > cannot use an external assembler for inline assembly when LTO is enabled, > > which causes further compatibility issues. > > > > The patches in this series remove intermediate linking steps when LTO is > > used, postpone processing done on object files until after the LTO link > > step, add workarounds for GNU gold incompatibilities, and address inline > > assembly incompatibilities for arm64. > > > > These changes allow arm64 defconfig to be compiled with LTO, but other > > architectures are not enabled until compatibility issues have been > > addressed. In particular, x86 inline assembly doesn't currently compile > > with clang's integrated assembler due to this LLVM bug: > > > > https://bugs.llvm.org/show_bug.cgi?id=24487 > > > > Due to recent bug fixes in the toolchain, it's recommended to use clang > > 5.0 or later, and GNU gold from binutils 2.27 or later > > Which tree are you testing with? > > I had a go building the arm64 for/next/core branch defconfig using clang > 5.0.0 from llvm.org, with the Linaro 17.05 toolchain's binutils > (2.27.0.20161019), and I hit what appears to be a compiler bug quite > quickly. So as per my reply to patch 7, it looks like this series addresses this case. What's the minimum set of patches necessary to work with clang (ignoring LTO)? Thanks, Mark.
Powered by blists - more mailing lists