From: Sami Tolvanen <samitolvanen@google.com>
To: Masahiro Yamada <masahiroy@kernel.org>,
Steven Rostedt <rostedt@goodmis.org>
Cc: Will Deacon <will@kernel.org>,
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, x86@kernel.org,
Sami Tolvanen <samitolvanen@google.com>
Subject: [PATCH v6 00/25] Add support for Clang LTO
Date: Mon, 12 Oct 2020 17:31:38 -0700 [thread overview]
Message-ID: <20201013003203.4168817-1-samitolvanen@google.com> (raw)
This patch series adds support for building the x86_64 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 this version is based on tip/master to reduce the number
of prerequisite patches, and to make it easier to manage changes to
objtool. Patch 1 is from Masahiro's kbuild tree, and while it's not
directly related to LTO, it makes the module linker script changes
cleaner.
Furthermore, patches 2-6 include Peter's patch for generating
__mcount_loc with objtool, and build system changes to enable it on
x86. With these patches, we no longer need to annotate functions
that have non-call references to __fentry__ with LTO, which greatly
simplifies supporting dynamic ftrace.
You can also pull this series from
https://github.com/samitolvanen/linux.git lto-v6
---
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.
Masahiro Yamada (1):
kbuild: preprocess module linker script
Peter Zijlstra (1):
objtool: Add a pass for generating __mcount_loc
Sami Tolvanen (23):
objtool: Don't autodetect vmlinux.o
tracing: move function tracer options to Kconfig
tracing: add support for objtool mcount
x86, build: use objtool mcount
treewide: remove DISABLE_LTO
kbuild: add support for Clang LTO
kbuild: lto: fix module versioning
objtool: Split noinstr validation from --vmlinux
kbuild: lto: postpone objtool
kbuild: lto: limit inlining
kbuild: lto: merge module sections
kbuild: lto: remove duplicate dependencies from .mod files
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
x86/asm: annotate indirect jumps
x86, vdso: disable LTO only for vDSO
x86, cpu: disable LTO for cpu.c
x86, build: allow LTO_CLANG and THINLTO to be selected
.gitignore | 1 +
Makefile | 68 +++--
arch/Kconfig | 74 +++++
arch/arm/Makefile | 4 -
.../module.lds => include/asm/module.lds.h} | 2 +
arch/arm64/Makefile | 4 -
.../module.lds => include/asm/module.lds.h} | 2 +
arch/arm64/kernel/vdso/Makefile | 1 -
arch/ia64/Makefile | 1 -
.../{module.lds => include/asm/module.lds.h} | 0
arch/m68k/Makefile | 1 -
.../module.lds => include/asm/module.lds.h} | 0
arch/powerpc/Makefile | 1 -
.../module.lds => include/asm/module.lds.h} | 0
arch/riscv/Makefile | 3 -
.../module.lds => include/asm/module.lds.h} | 3 +-
arch/sparc/vdso/Makefile | 2 -
arch/um/include/asm/Kbuild | 1 +
arch/x86/Kconfig | 3 +
arch/x86/Makefile | 5 +
arch/x86/entry/vdso/Makefile | 5 +-
arch/x86/kernel/acpi/wakeup_64.S | 2 +
arch/x86/platform/pvh/head.S | 2 +
arch/x86/power/Makefile | 4 +
arch/x86/power/hibernate_asm_64.S | 3 +
drivers/firmware/efi/libstub/Makefile | 2 +
drivers/misc/lkdtm/Makefile | 1 +
include/asm-generic/Kbuild | 1 +
include/asm-generic/module.lds.h | 10 +
include/asm-generic/vmlinux.lds.h | 11 +-
include/linux/init.h | 79 ++++-
include/linux/pci.h | 19 +-
kernel/Makefile | 3 -
kernel/trace/Kconfig | 29 ++
scripts/.gitignore | 1 +
scripts/Makefile | 3 +
scripts/Makefile.build | 69 +++--
scripts/Makefile.lib | 17 +-
scripts/Makefile.modfinal | 29 +-
scripts/Makefile.modpost | 25 +-
scripts/generate_initcall_order.pl | 270 ++++++++++++++++++
scripts/link-vmlinux.sh | 98 ++++++-
scripts/mod/Makefile | 1 +
scripts/mod/modpost.c | 16 +-
scripts/mod/modpost.h | 9 +
scripts/mod/sumversion.c | 6 +-
scripts/{module-common.lds => module.lds.S} | 31 ++
scripts/package/builddeb | 2 +-
tools/objtool/builtin-check.c | 10 +-
tools/objtool/builtin.h | 2 +-
tools/objtool/check.c | 84 +++++-
tools/objtool/check.h | 1 +
tools/objtool/objtool.c | 1 +
tools/objtool/objtool.h | 1 +
54 files changed, 895 insertions(+), 128 deletions(-)
rename arch/arm/{kernel/module.lds => include/asm/module.lds.h} (72%)
rename arch/arm64/{kernel/module.lds => include/asm/module.lds.h} (76%)
rename arch/ia64/{module.lds => include/asm/module.lds.h} (100%)
rename arch/m68k/{kernel/module.lds => include/asm/module.lds.h} (100%)
rename arch/powerpc/{kernel/module.lds => include/asm/module.lds.h} (100%)
rename arch/riscv/{kernel/module.lds => include/asm/module.lds.h} (84%)
create mode 100644 include/asm-generic/module.lds.h
create mode 100755 scripts/generate_initcall_order.pl
rename scripts/{module-common.lds => module.lds.S} (59%)
base-commit: a292570e9f694ed50d3e69afd6d54272fd40deca
--
2.28.0.1011.ga647a8990f-goog
next reply other threads:[~2020-10-13 2:42 UTC|newest]
Thread overview: 73+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-13 0:31 Sami Tolvanen [this message]
2020-10-13 0:31 ` [PATCH v6 01/25] kbuild: preprocess module linker script Sami Tolvanen
2020-10-13 0:31 ` [PATCH v6 02/25] objtool: Add a pass for generating __mcount_loc Sami Tolvanen
2020-10-14 16:50 ` Ingo Molnar
2020-10-14 18:21 ` Peter Zijlstra
2020-10-15 20:10 ` Josh Poimboeuf
2020-10-13 0:31 ` [PATCH v6 03/25] objtool: Don't autodetect vmlinux.o Sami Tolvanen
2020-10-13 0:31 ` [PATCH v6 04/25] tracing: move function tracer options to Kconfig Sami Tolvanen
2020-10-13 0:31 ` [PATCH v6 05/25] tracing: add support for objtool mcount Sami Tolvanen
2020-10-13 0:31 ` [PATCH v6 06/25] x86, build: use " Sami Tolvanen
2020-10-13 0:31 ` [PATCH v6 07/25] treewide: remove DISABLE_LTO Sami Tolvanen
2020-10-14 22:43 ` Kees Cook
2020-10-17 1:46 ` Masahiro Yamada
2020-10-13 0:31 ` [PATCH v6 08/25] kbuild: add support for Clang LTO Sami Tolvanen
2020-10-13 0:31 ` [PATCH v6 09/25] kbuild: lto: fix module versioning Sami Tolvanen
2020-10-13 0:31 ` [PATCH v6 10/25] objtool: Split noinstr validation from --vmlinux Sami Tolvanen
2020-10-13 0:31 ` [PATCH v6 11/25] kbuild: lto: postpone objtool Sami Tolvanen
2020-10-13 0:31 ` [PATCH v6 12/25] kbuild: lto: limit inlining Sami Tolvanen
2020-10-13 0:31 ` [PATCH v6 13/25] kbuild: lto: merge module sections Sami Tolvanen
2020-10-14 22:49 ` Kees Cook
2020-10-20 16:42 ` Sami Tolvanen
2020-10-13 0:31 ` [PATCH v6 14/25] kbuild: lto: remove duplicate dependencies from .mod files Sami Tolvanen
2020-10-14 22:50 ` Kees Cook
2020-12-03 17:59 ` Masahiro Yamada
2020-12-03 18:47 ` Sami Tolvanen
2020-10-13 0:31 ` [PATCH v6 15/25] init: lto: ensure initcall ordering Sami Tolvanen
2020-10-13 0:31 ` [PATCH v6 16/25] init: lto: fix PREL32 relocations Sami Tolvanen
2020-10-14 22:53 ` Kees Cook
2020-10-15 0:12 ` Jann Horn
2020-10-13 0:31 ` [PATCH v6 17/25] PCI: Fix PREL32 relocations for LTO Sami Tolvanen
2020-10-14 22:58 ` Kees Cook
2020-10-13 0:31 ` [PATCH v6 18/25] modpost: lto: strip .lto from module names Sami Tolvanen
2020-10-13 0:31 ` [PATCH v6 19/25] scripts/mod: disable LTO for empty.c Sami Tolvanen
2020-10-13 0:31 ` [PATCH v6 20/25] efi/libstub: disable LTO Sami Tolvanen
2020-10-13 0:31 ` [PATCH v6 21/25] drivers/misc/lkdtm: disable LTO for rodata.o Sami Tolvanen
2020-10-13 0:32 ` [PATCH v6 22/25] x86/asm: annotate indirect jumps Sami Tolvanen
2020-10-14 22:46 ` Kees Cook
2020-10-14 23:23 ` Jann Horn
2020-10-15 10:22 ` Peter Zijlstra
2020-10-15 20:39 ` Josh Poimboeuf
2020-10-20 16:45 ` Sami Tolvanen
2020-10-20 18:52 ` Josh Poimboeuf
2020-10-20 19:24 ` Sami Tolvanen
2020-10-21 8:56 ` Peter Zijlstra
2020-10-21 9:08 ` Peter Zijlstra
2020-10-21 9:32 ` Peter Zijlstra
2020-10-21 21:27 ` Josh Poimboeuf
2020-10-22 7:25 ` Peter Zijlstra
2020-10-23 17:48 ` Sami Tolvanen
2020-10-23 18:04 ` Nick Desaulniers
2020-10-21 15:01 ` Sami Tolvanen
2020-10-22 0:22 ` Sami Tolvanen
2020-10-23 17:36 ` Sami Tolvanen
2020-11-09 23:11 ` Sami Tolvanen
2020-11-10 2:29 ` Josh Poimboeuf
2020-11-10 3:18 ` Nick Desaulniers
2020-11-10 4:48 ` Sami Tolvanen
2020-11-10 16:11 ` Josh Poimboeuf
2020-11-10 17:46 ` Josh Poimboeuf
2020-11-10 18:59 ` Sami Tolvanen
2020-11-13 19:54 ` Josh Poimboeuf
2020-11-13 20:24 ` Sami Tolvanen
2020-11-13 20:52 ` Josh Poimboeuf
2020-11-13 22:34 ` Josh Poimboeuf
2020-11-13 22:54 ` Sami Tolvanen
2020-11-13 22:56 ` Josh Poimboeuf
2020-11-13 23:31 ` Sami Tolvanen
2020-11-14 0:49 ` Josh Poimboeuf
2020-10-21 9:51 ` Peter Zijlstra
2020-10-21 18:30 ` Josh Poimboeuf
2020-10-13 0:32 ` [PATCH v6 23/25] x86, vdso: disable LTO only for vDSO Sami Tolvanen
2020-10-13 0:32 ` [PATCH v6 24/25] x86, cpu: disable LTO for cpu.c Sami Tolvanen
2020-10-13 0:32 ` [PATCH v6 25/25] x86, build: allow LTO_CLANG and THINLTO to be selected Sami Tolvanen
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