Follow @Openwall on Twitter for new release announcements and other news
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date: Sat, 11 Jul 2020 18:32:41 +0200
From: Paul Menzel <>
To: Sami Tolvanen <>,
 Masahiro Yamada <>, Will Deacon <>
Cc: Greg Kroah-Hartman <>,
 "Paul E. McKenney" <>, Kees Cook <>,
 Nick Desaulniers <>,,,,,,,,
Subject: Re: [PATCH 00/22] add support for Clang LTO

Dear Sami,

Am 24.06.20 um 22:31 schrieb Sami Tolvanen:
> This patch series adds support for building x86_64 and arm64 kernels
> with Clang's Link Time Optimization (LTO).
> In addition to performance, the primary motivation for LTO is to allow
> Clang's Control-Flow Integrity (CFI) to be used in the kernel. Google's
> Pixel devices have shipped with LTO+CFI kernels since 2018.
> Most of the patches are build system changes for handling LLVM bitcode,
> which Clang produces with LTO instead of ELF object files, postponing
> ELF processing until a later stage, and ensuring initcall ordering.
> Note that first objtool patch in the series is already in linux-next,
> but as it's needed with LTO, I'm including it also here to make testing
> easier.


Thank you very much for sending these changes.

Do you have a branch, where your current work can be pulled from? Your 
branch on GitHub [1] seems 15 months old.

Out of curiosity, I applied the changes, allowed the selection for i386 
(x86), and with Clang 1:11~++20200701093119+ffee8040534-1~exp1 from 
Debian experimental, it failed with `Invalid absolute R_386_32 
relocation: KERNEL_PAGES`:

> make -f ./scripts/ obj=arch/x86/boot arch/x86/boot/bzImage
> make -f ./scripts/ obj=arch/x86/boot/compressed arch/x86/boot/compressed/vmlinux
>   llvm-nm vmlinux | sed -n -e 's/^\([0-9a-fA-F]*\) [ABCDGRSTVW] \(_text\|__bss_start\|_end\)$/#define VO_ _AC(0x,UL)/p' > arch/x86/boot/compressed/../voffset.h
>   clang -Wp,-MMD,arch/x86/boot/compressed/.misc.o.d -nostdinc -isystem /usr/lib/llvm-11/lib/clang/11.0.0/include -I./arch/x86/include -I./arch/x86/include/generated  -I./include -I./arch/x86/include/uapi -I./arch/x86/include/generated/uapi -I./include/uapi -I./include/generated/uapi -include ./include/linux/kconfig.h -include ./include/linux/compiler_types.h -D__KERNEL__ -Qunused-arguments -m32 -O2 -fno-strict-aliasing -fPIE -DDISABLE_BRANCH_PROFILING -march=i386 -mno-mmx -mno-sse -ffreestanding -fno-stack-protector -Wno-address-of-packed-member -Wno-gnu -Wno-pointer-sign -fmacro-prefix-map=./= -fno-asynchronous-unwind-tables    -DKBUILD_MODFILE='"arch/x86/boot/compressed/misc"' -DKBUILD_BASENAME='"misc"' -DKBUILD_MODNAME='"misc"' -D__KBUILD_MODNAME=misc -c -o arch/x86/boot/compressed/misc.o arch/x86/boot/compressed/misc.c
>   llvm-objcopy  -R .comment -S vmlinux arch/x86/boot/compressed/vmlinux.bin
>   arch/x86/tools/relocs vmlinux > arch/x86/boot/compressed/vmlinux.relocs;arch/x86/tools/relocs --abs-relocs vmlinux
> Invalid absolute R_386_32 relocation: KERNEL_PAGES
> make[2]: *** [arch/x86/boot/compressed/Makefile:134: arch/x86/boot/compressed/vmlinux.relocs] Error 1
> make[2]: *** Deleting file 'arch/x86/boot/compressed/vmlinux.relocs'
> make[1]: *** [arch/x86/boot/Makefile:115: arch/x86/boot/compressed/vmlinux] Error 2
> make: *** [arch/x86/Makefile:268: bzImage] Error 2

Kind regards,



Powered by blists - more mailing lists

Confused about mailing lists and their use? Read about mailing lists on Wikipedia and check out these guidelines on proper formatting of your messages.