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Date: Fri, 13 Nov 2020 11:34:11 -0800 From: Nick Desaulniers <ndesaulniers@...gle.com> To: Ard Biesheuvel <ardb@...nel.org> Cc: Nathan Chancellor <natechancellor@...il.com>, Masahiro Yamada <masahiroy@...nel.org>, Michal Marek <michal.lkml@...kovi.net>, Catalin Marinas <catalin.marinas@....com>, Will Deacon <will@...nel.org>, Russell King <linux@...linux.org.uk>, Florian Fainelli <f.fainelli@...il.com>, Arnd Bergmann <arnd@...db.de>, Abbott Liu <liuwenliang@...wei.com>, Linus Walleij <linus.walleij@...aro.org>, Jian Cai <jiancai@...gle.com>, Andrey Ryabinin <aryabinin@...tuozzo.com>, Mike Rapoport <rppt@...ux.ibm.com>, Linux Kbuild mailing list <linux-kbuild@...r.kernel.org>, LKML <linux-kernel@...r.kernel.org>, Linux ARM <linux-arm-kernel@...ts.infradead.org> Subject: Re: [PATCH] kbuild: Always link with '-z norelro' On Thu, Nov 12, 2020 at 10:06 PM Ard Biesheuvel <ardb@...nel.org> wrote: > > On Fri, 13 Nov 2020 at 01:53, Nathan Chancellor > <natechancellor@...il.com> wrote: > > > > On Thu, Nov 12, 2020 at 04:44:46PM -0800, Nick Desaulniers wrote: > > > On Thu, Nov 12, 2020 at 10:41 AM Nathan Chancellor > > > <natechancellor@...il.com> wrote: > > > > > > > > Commit 3bbd3db86470 ("arm64: relocatable: fix inconsistencies in linker > > > > script and options") added '-z norelro' to the arm64 Makefile when > > > > CONFIG_RELOCATABLE was set to help support ld.lld because ld.lld > > > > defaults to '-z relro' but the kernel does not use program headers or > > > > adhere to the section layout that is required for RELRO to work. > > > > > > > > Commit 3b92fa7485eb ("arm64: link with -z norelro regardless of > > > > CONFIG_RELOCATABLE") unconditionally added it to LDFLAGS_vmlinux because > > > > an error occurs with CONFIG_KASAN set even when CONFIG_RELOCATABLE is > > > > unset. > > > > > > > > As it turns out, ARM experiences the same error after CONFIG_KASAN was > > > > implemented, meaning that '-z norelro' needs to be added to that > > > > Makefile as well (multi_v7_defconfig + CONFIG_KASAN=y + LD=ld.lld): > > > > > > > > $ make ARCH=arm CROSS_COMPILE=arm-linux-gnueabi- LLVM=1 zImage > > > > ld.lld: error: section: .exit.data is not contiguous with other relro sections > > > > > > > > To avoid playing whack-a-mole with different architectures over time, > > > > hoist '-z norelro' into the main Makefile. This does not affect ld.bfd > > > > because '-z norelro' is the default for it. > > > > > > > > Link: https://github.com/ClangBuiltLinux/linux/issues/1189 > > > > Suggested-by: Nick Desaulniers <ndesaulniers@...gle.com> > > > > Signed-off-by: Nathan Chancellor <natechancellor@...il.com> > > > > > > Why not add it additionally to KBUILD_LDFLAGS_MODULE a la > > > `--build-id=sha1` a few lines above? (or `LDFLAGS_MODULE`, but that > > > looks unused?) We probably don't want this for modules either. In > > > that case, you could add -z norelo to the two existing lines with > > > `--build-id=sha1` above? > > > > Yes, I can do that. I will send a v2 along tomorrow morning to let > > others comment. > > > > Modules are partially linked objects, so there is no point in passing > -z options for them. Ok then. Reviewed-by: Nick Desaulniers <ndesaulniers@...gle.com> Tested-by: Nick Desaulniers <ndesaulniers@...gle.com> More work to be done to boot this config, but at least we can link without error. -- Thanks, ~Nick Desaulniers
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