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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