From: Sami Tolvanen <samitolvanen@google.com>
To: Masahiro Yamada <masahiroy@kernel.org>,
Steven Rostedt <rostedt@goodmis.org>,
Will Deacon <will@kernel.org>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>,
Peter Zijlstra <peterz@infradead.org>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
"Paul E. McKenney" <paulmck@kernel.org>,
Kees Cook <keescook@chromium.org>,
Nick Desaulniers <ndesaulniers@google.com>,
clang-built-linux@googlegroups.com,
kernel-hardening@lists.openwall.com, linux-arch@vger.kernel.org,
linux-arm-kernel@lists.infradead.org,
linux-kbuild@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-pci@vger.kernel.org,
Sami Tolvanen <samitolvanen@google.com>
Subject: [PATCH v9 00/16] Add support for Clang LTO
Date: Fri, 11 Dec 2020 10:46:17 -0800 [thread overview]
Message-ID: <20201211184633.3213045-1-samitolvanen@google.com> (raw)
This patch series adds support for building the kernel 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 has shipped millions of Pixel
devices running three major kernel versions with LTO+CFI 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 arm64 support depends on Will's memory ordering patches
[1]. I will post x86_64 patches separately after we have fixed the
remaining objtool warnings [2][3].
[1] https://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git/log/?h=for-next/lto
[2] https://lore.kernel.org/lkml/20201120040424.a3wctajzft4ufoiw@treble/
[3] https://git.kernel.org/pub/scm/linux/kernel/git/jpoimboe/linux.git/log/?h=objtool-vmlinux
You can also pull this series from
https://github.com/samitolvanen/linux.git lto-v9
---
Changes in v9:
- Added HAS_LTO_CLANG dependencies to LLVM=1 and LLVM_IAS=1 to avoid
issues with mismatched toolchains.
- Dropped the .mod patch as Masahiro landed a better solution to
the split line issue in commit 7d32358be8ac ("kbuild: avoid split
lines in .mod files").
- Updated CC_FLAGS_LTO to use -fvisibility=hidden to avoid weak symbol
visibility issues with ThinLTO on x86.
- Changed LTO_CLANG_FULL to depend on !COMPILE_TEST to prevent
timeouts in automated testing.
- Added a dependency to CPU_LITTLE_ENDIAN to ARCH_SUPPORTS_LTO_CLANG
in arch/arm64/Kconfig.
- Added a default symbol list to fix an issue with TRIM_UNUSED_KSYMS.
Changes in v8:
- Cleaned up the LTO Kconfig options based on suggestions from
Nick and Kees.
- Dropped the patch to disable LTO for the arm64 nVHE KVM code as
David pointed out it's not needed anymore.
Changes in v7:
- Rebased to master again.
- Added back arm64 patches as the prerequisites are now staged,
and dropped x86_64 support until the remaining objtool issues
are resolved.
- Dropped ifdefs from module.lds.S.
Changes in v6:
- Added the missing --mcount flag to patch 5.
- Dropped the arm64 patches from this series and will repost them
later.
Changes in v5:
- Rebased on top of tip/master.
- Changed the command line for objtool to use --vmlinux --duplicate
to disable warnings about retpoline thunks and to fix .orc_unwind
generation for vmlinux.o.
- Added --noinstr flag to objtool, so we can use --vmlinux without
also enabling noinstr validation.
- Disabled objtool's unreachable instruction warnings with LTO to
disable false positives for the int3 padding in vmlinux.o.
- Added ANNOTATE_RETPOLINE_SAFE annotations to the indirect jumps
in x86 assembly code to fix objtool warnings with retpoline.
- Fixed modpost warnings about missing version information with
CONFIG_MODVERSIONS.
- Included Makefile.lib into Makefile.modpost for ld_flags. Thanks
to Sedat for pointing this out.
- Updated the help text for ThinLTO to better explain the trade-offs.
- Updated commit messages with better explanations.
Changes in v4:
- Fixed a typo in Makefile.lib to correctly pass --no-fp to objtool.
- Moved ftrace configs related to generating __mcount_loc to Kconfig,
so they are available also in Makefile.modfinal.
- Dropped two prerequisite patches that were merged to Linus' tree.
Changes in v3:
- Added a separate patch to remove the unused DISABLE_LTO treewide,
as filtering out CC_FLAGS_LTO instead is preferred.
- Updated the Kconfig help to explain why LTO is behind a choice
and disabled by default.
- Dropped CC_FLAGS_LTO_CLANG, compiler-specific LTO flags are now
appended directly to CC_FLAGS_LTO.
- Updated $(AR) flags as KBUILD_ARFLAGS was removed earlier.
- Fixed ThinLTO cache handling for external module builds.
- Rebased on top of Masahiro's patch for preprocessing modules.lds,
and moved the contents of module-lto.lds to modules.lds.S.
- Moved objtool_args to Makefile.lib to avoid duplication of the
command line parameters in Makefile.modfinal.
- Clarified in the commit message for the initcall ordering patch
that the initcall order remains the same as without LTO.
- Changed link-vmlinux.sh to use jobserver-exec to control the
number of jobs started by generate_initcall_ordering.pl.
- Dropped the x86/relocs patch to whitelist L4_PAGE_OFFSET as it's
no longer needed with ToT kernel.
- Disabled LTO for arch/x86/power/cpu.c to work around a Clang bug
with stack protector attributes.
Changes in v2:
- Fixed -Wmissing-prototypes warnings with W=1.
- Dropped cc-option from -fsplit-lto-unit and added .thinlto-cache
scrubbing to make distclean.
- Added a comment about Clang >=11 being required.
- Added a patch to disable LTO for the arm64 KVM nVHE code.
- Disabled objtool's noinstr validation with LTO unless enabled.
- Included Peter's proposed objtool mcount patch in the series
and replaced recordmcount with the objtool pass to avoid
whitelisting relocations that are not calls.
- Updated several commit messages with better explanations.
Sami Tolvanen (16):
tracing: move function tracer options to Kconfig
kbuild: add support for Clang LTO
kbuild: lto: fix module versioning
kbuild: lto: limit inlining
kbuild: lto: merge module sections
kbuild: lto: add a default list of used symbols
init: lto: ensure initcall ordering
init: lto: fix PREL32 relocations
PCI: Fix PREL32 relocations for LTO
modpost: lto: strip .lto from module names
scripts/mod: disable LTO for empty.c
efi/libstub: disable LTO
drivers/misc/lkdtm: disable LTO for rodata.o
arm64: vdso: disable LTO
arm64: disable recordmcount with DYNAMIC_FTRACE_WITH_REGS
arm64: allow LTO to be selected
.gitignore | 1 +
Makefile | 45 +++--
arch/Kconfig | 90 +++++++++
arch/arm64/Kconfig | 4 +
arch/arm64/kernel/vdso/Makefile | 3 +-
drivers/firmware/efi/libstub/Makefile | 2 +
drivers/misc/lkdtm/Makefile | 1 +
include/asm-generic/vmlinux.lds.h | 11 +-
include/linux/init.h | 79 +++++++-
include/linux/pci.h | 19 +-
init/Kconfig | 1 +
kernel/trace/Kconfig | 16 ++
scripts/Makefile.build | 48 ++++-
scripts/Makefile.lib | 6 +-
scripts/Makefile.modfinal | 9 +-
scripts/Makefile.modpost | 25 ++-
scripts/generate_initcall_order.pl | 270 ++++++++++++++++++++++++++
scripts/link-vmlinux.sh | 70 ++++++-
scripts/lto-used-symbollist | 5 +
scripts/mod/Makefile | 1 +
scripts/mod/modpost.c | 16 +-
scripts/mod/modpost.h | 9 +
scripts/mod/sumversion.c | 6 +-
scripts/module.lds.S | 24 +++
24 files changed, 696 insertions(+), 65 deletions(-)
create mode 100755 scripts/generate_initcall_order.pl
create mode 100644 scripts/lto-used-symbollist
base-commit: 33dc9614dc208291d0c4bcdeb5d30d481dcd2c4c
--
2.29.2.576.ga3fc446d84-goog
next reply other threads:[~2020-12-11 18:46 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-11 18:46 Sami Tolvanen [this message]
2020-12-11 18:46 ` [PATCH v9 01/16] tracing: move function tracer options to Kconfig Sami Tolvanen
2021-02-24 20:17 ` [PATCH v9 01/16] tracing: move function tracer options to Kconfig (causing parisc build failures) Guenter Roeck
2021-02-24 20:38 ` Kees Cook
2021-02-24 20:54 ` Sami Tolvanen
2021-02-24 22:29 ` Guenter Roeck
2021-02-24 22:28 ` Guenter Roeck
2021-02-24 22:42 ` Kees Cook
2020-12-11 18:46 ` [PATCH v9 02/16] kbuild: add support for Clang LTO Sami Tolvanen
2020-12-11 18:46 ` [PATCH v9 03/16] kbuild: lto: fix module versioning Sami Tolvanen
2020-12-11 18:46 ` [PATCH v9 04/16] kbuild: lto: limit inlining Sami Tolvanen
2020-12-11 18:46 ` [PATCH v9 05/16] kbuild: lto: merge module sections Sami Tolvanen
2021-02-16 21:37 ` Stephen Boyd
2020-12-11 18:46 ` [PATCH v9 06/16] kbuild: lto: add a default list of used symbols Sami Tolvanen
2020-12-11 19:32 ` Kees Cook
2020-12-11 19:40 ` Sami Tolvanen
2020-12-11 19:45 ` Nick Desaulniers
2020-12-11 18:46 ` [PATCH v9 07/16] init: lto: ensure initcall ordering Sami Tolvanen
2020-12-11 18:46 ` [PATCH v9 08/16] init: lto: fix PREL32 relocations Sami Tolvanen
2020-12-11 18:46 ` [PATCH v9 09/16] PCI: Fix PREL32 relocations for LTO Sami Tolvanen
2020-12-11 18:46 ` [PATCH v9 10/16] modpost: lto: strip .lto from module names Sami Tolvanen
2020-12-11 18:46 ` [PATCH v9 11/16] scripts/mod: disable LTO for empty.c Sami Tolvanen
2020-12-11 18:46 ` [PATCH v9 12/16] efi/libstub: disable LTO Sami Tolvanen
2020-12-11 18:46 ` [PATCH v9 13/16] drivers/misc/lkdtm: disable LTO for rodata.o Sami Tolvanen
2020-12-11 18:46 ` [PATCH v9 14/16] arm64: vdso: disable LTO Sami Tolvanen
2020-12-11 18:46 ` [PATCH v9 15/16] arm64: disable recordmcount with DYNAMIC_FTRACE_WITH_REGS Sami Tolvanen
2020-12-11 18:46 ` [PATCH v9 16/16] arm64: allow LTO to be selected Sami Tolvanen
2020-12-11 19:38 ` [PATCH v9 00/16] Add support for Clang LTO Kees Cook
2021-01-09 0:27 ` Kees Cook
2021-01-09 14:54 ` Sedat Dilek
2021-01-09 15:36 ` Josh Poimboeuf
2021-01-09 15:46 ` Sedat Dilek
2021-01-09 16:07 ` Josh Poimboeuf
2021-01-09 16:21 ` Sedat Dilek
2021-01-09 16:32 ` Josh Poimboeuf
2021-01-09 16:45 ` Sedat Dilek
2021-01-09 17:03 ` Josh Poimboeuf
2021-01-09 17:05 ` Josh Poimboeuf
2021-01-09 17:33 ` Sedat Dilek
2021-01-09 23:44 ` Sedat Dilek
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