From: Sami Tolvanen <samitolvanen@google.com> To: Masahiro Yamada <masahiroy@kernel.org>, Will Deacon <will@kernel.org>, Steven Rostedt <rostedt@goodmis.org> Cc: 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 v5 08/29] kbuild: add support for Clang LTO Date: Fri, 9 Oct 2020 09:13:17 -0700 [thread overview] Message-ID: <20201009161338.657380-9-samitolvanen@google.com> (raw) In-Reply-To: <20201009161338.657380-1-samitolvanen@google.com> This change adds build system support for Clang's Link Time Optimization (LTO). With -flto, instead of ELF object files, Clang produces LLVM bitcode, which is compiled into native code at link time, allowing the final binary to be optimized globally. For more details, see: https://llvm.org/docs/LinkTimeOptimization.html The Kconfig option CONFIG_LTO_CLANG is implemented as a choice, which defaults to LTO being disabled. To use LTO, the architecture must select ARCH_SUPPORTS_LTO_CLANG and support: - compiling with Clang, - compiling inline assembly with Clang's integrated assembler, - and linking with LLD. While using full LTO results in the best runtime performance, the compilation is not scalable in time or memory. CONFIG_THINLTO enables ThinLTO, which allows parallel optimization and faster incremental builds. ThinLTO is used by default if the architecture also selects ARCH_SUPPORTS_THINLTO: https://clang.llvm.org/docs/ThinLTO.html To enable LTO, LLVM tools must be used to handle bitcode files. The easiest way is to pass the LLVM=1 option to make: $ make LLVM=1 defconfig $ scripts/config -e LTO_CLANG $ make LLVM=1 Alternatively, at least the following LLVM tools must be used: CC=clang LD=ld.lld AR=llvm-ar NM=llvm-nm To prepare for LTO support with other compilers, common parts are gated behind the CONFIG_LTO option, and LTO can be disabled for specific files by filtering out CC_FLAGS_LTO. Note that support for DYNAMIC_FTRACE and MODVERSIONS are added in follow-up patches. Signed-off-by: Sami Tolvanen <samitolvanen@google.com> Reviewed-by: Kees Cook <keescook@chromium.org> --- Makefile | 20 ++++++++- arch/Kconfig | 75 +++++++++++++++++++++++++++++++ include/asm-generic/vmlinux.lds.h | 11 +++-- scripts/Makefile.build | 9 +++- scripts/Makefile.modfinal | 9 +++- scripts/Makefile.modpost | 21 ++++++++- scripts/link-vmlinux.sh | 32 +++++++++---- 7 files changed, 159 insertions(+), 18 deletions(-) diff --git a/Makefile b/Makefile index fb2cf557d3ca..a3baf8388163 100644 --- a/Makefile +++ b/Makefile @@ -886,6 +886,21 @@ KBUILD_CFLAGS += $(CC_FLAGS_SCS) export CC_FLAGS_SCS endif +ifdef CONFIG_LTO_CLANG +ifdef CONFIG_THINLTO +CC_FLAGS_LTO += -flto=thin -fsplit-lto-unit +KBUILD_LDFLAGS += --thinlto-cache-dir=$(extmod-prefix).thinlto-cache +else +CC_FLAGS_LTO += -flto +endif +CC_FLAGS_LTO += -fvisibility=default +endif + +ifdef CONFIG_LTO +KBUILD_CFLAGS += $(CC_FLAGS_LTO) +export CC_FLAGS_LTO +endif + ifdef CONFIG_DEBUG_FORCE_FUNCTION_ALIGN_32B KBUILD_CFLAGS += -falign-functions=32 endif @@ -1477,7 +1492,7 @@ MRPROPER_FILES += include/config include/generated \ *.spec # Directories & files removed with 'make distclean' -DISTCLEAN_FILES += tags TAGS cscope* GPATH GTAGS GRTAGS GSYMS +DISTCLEAN_FILES += tags TAGS cscope* GPATH GTAGS GRTAGS GSYMS .thinlto-cache # clean - Delete most, but leave enough to build external modules # @@ -1714,7 +1729,8 @@ _emodinst_post: _emodinst_ $(call cmd,depmod) clean-dirs := $(KBUILD_EXTMOD) -clean: rm-files := $(KBUILD_EXTMOD)/Module.symvers $(KBUILD_EXTMOD)/modules.nsdeps +clean: rm-files := $(KBUILD_EXTMOD)/Module.symvers $(KBUILD_EXTMOD)/modules.nsdeps \ + $(KBUILD_EXTMOD)/.thinlto-cache PHONY += help help: diff --git a/arch/Kconfig b/arch/Kconfig index 76ec3395b843..4ac5dda6d873 100644 --- a/arch/Kconfig +++ b/arch/Kconfig @@ -558,6 +558,81 @@ config SHADOW_CALL_STACK reading and writing arbitrary memory may be able to locate them and hijack control flow by modifying the stacks. +config LTO + bool + +config ARCH_SUPPORTS_LTO_CLANG + bool + help + An architecture should select this option if it supports: + - compiling with Clang, + - compiling inline assembly with Clang's integrated assembler, + - and linking with LLD. + +config ARCH_SUPPORTS_THINLTO + bool + help + An architecture should select this option if it supports Clang's + ThinLTO. + +config THINLTO + bool "Clang ThinLTO" + depends on LTO_CLANG && ARCH_SUPPORTS_THINLTO + default y + help + This option enables Clang's ThinLTO, which allows for parallel + optimization and faster incremental compiles. More information + can be found from Clang's documentation: + + https://clang.llvm.org/docs/ThinLTO.html + + If you say N here, the compiler will use full LTO, which may + produce faster code, but building the kernel will be significantly + slower as the linker won't efficiently utilize multiple threads. + + If unsure, say Y. + +choice + prompt "Link Time Optimization (LTO)" + default LTO_NONE + help + This option enables Link Time Optimization (LTO), which allows the + compiler to optimize binaries globally. + + If unsure, select LTO_NONE. Note that LTO is very resource-intensive + so it's disabled by default. + +config LTO_NONE + bool "None" + +config LTO_CLANG + bool "Clang's Link Time Optimization (EXPERIMENTAL)" + # Clang >= 11: https://github.com/ClangBuiltLinux/linux/issues/510 + depends on CC_IS_CLANG && CLANG_VERSION >= 110000 && LD_IS_LLD + depends on $(success,$(NM) --help | head -n 1 | grep -qi llvm) + depends on $(success,$(AR) --help | head -n 1 | grep -qi llvm) + depends on ARCH_SUPPORTS_LTO_CLANG + depends on !FTRACE_MCOUNT_RECORD + depends on !KASAN + depends on !GCOV_KERNEL + depends on !MODVERSIONS + select LTO + help + This option enables Clang's Link Time Optimization (LTO), which + allows the compiler to optimize the kernel globally. If you enable + this option, the compiler generates LLVM bitcode instead of ELF + object files, and the actual compilation from bitcode happens at + the LTO link step, which may take several minutes depending on the + kernel configuration. More information can be found from LLVM's + documentation: + + https://llvm.org/docs/LinkTimeOptimization.html + + To select this option, you also need to use LLVM tools to handle + the bitcode by passing LLVM=1 to make. + +endchoice + config HAVE_ARCH_WITHIN_STACK_FRAMES bool help diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h index e1843976754a..77e5bd069dd4 100644 --- a/include/asm-generic/vmlinux.lds.h +++ b/include/asm-generic/vmlinux.lds.h @@ -90,15 +90,18 @@ * .data. We don't want to pull in .data..other sections, which Linux * has defined. Same for text and bss. * + * With LTO_CLANG, the linker also splits sections by default, so we need + * these macros to combine the sections during the final link. + * * RODATA_MAIN is not used because existing code already defines .rodata.x * sections to be brought in with rodata. */ -#ifdef CONFIG_LD_DEAD_CODE_DATA_ELIMINATION +#if defined(CONFIG_LD_DEAD_CODE_DATA_ELIMINATION) || defined(CONFIG_LTO_CLANG) #define TEXT_MAIN .text .text.[0-9a-zA-Z_]* -#define DATA_MAIN .data .data.[0-9a-zA-Z_]* .data..LPBX* +#define DATA_MAIN .data .data.[0-9a-zA-Z_]* .data..L* .data..compoundliteral* #define SDATA_MAIN .sdata .sdata.[0-9a-zA-Z_]* -#define RODATA_MAIN .rodata .rodata.[0-9a-zA-Z_]* -#define BSS_MAIN .bss .bss.[0-9a-zA-Z_]* +#define RODATA_MAIN .rodata .rodata.[0-9a-zA-Z_]* .rodata..L* +#define BSS_MAIN .bss .bss.[0-9a-zA-Z_]* .bss..compoundliteral* #define SBSS_MAIN .sbss .sbss.[0-9a-zA-Z_]* #else #define TEXT_MAIN .text diff --git a/scripts/Makefile.build b/scripts/Makefile.build index 2175ddb1ee0c..ed74b2f986f7 100644 --- a/scripts/Makefile.build +++ b/scripts/Makefile.build @@ -111,7 +111,7 @@ endif # --------------------------------------------------------------------------- quiet_cmd_cc_s_c = CC $(quiet_modtag) $@ - cmd_cc_s_c = $(CC) $(filter-out $(DEBUG_CFLAGS), $(c_flags)) -fverbose-asm -S -o $@ $< + cmd_cc_s_c = $(CC) $(filter-out $(DEBUG_CFLAGS) $(CC_FLAGS_LTO), $(c_flags)) -fverbose-asm -S -o $@ $< $(obj)/%.s: $(src)/%.c FORCE $(call if_changed_dep,cc_s_c) @@ -425,8 +425,15 @@ $(obj)/lib.a: $(lib-y) FORCE # Do not replace $(filter %.o,^) with $(real-prereqs). When a single object # module is turned into a multi object module, $^ will contain header file # dependencies recorded in the .*.cmd file. +ifdef CONFIG_LTO_CLANG +quiet_cmd_link_multi-m = AR [M] $@ +cmd_link_multi-m = \ + rm -f $@; \ + $(AR) cDPrsT $@ $(filter %.o,$^) +else quiet_cmd_link_multi-m = LD [M] $@ cmd_link_multi-m = $(LD) $(ld_flags) -r -o $@ $(filter %.o,$^) +endif $(multi-used-m): FORCE $(call if_changed,link_multi-m) diff --git a/scripts/Makefile.modfinal b/scripts/Makefile.modfinal index ae01baf96f4e..2cb9a1d88434 100644 --- a/scripts/Makefile.modfinal +++ b/scripts/Makefile.modfinal @@ -6,6 +6,7 @@ PHONY := __modfinal __modfinal: +include $(objtree)/include/config/auto.conf include $(srctree)/scripts/Kbuild.include # for c_flags @@ -29,6 +30,12 @@ quiet_cmd_cc_o_c = CC [M] $@ ARCH_POSTLINK := $(wildcard $(srctree)/arch/$(SRCARCH)/Makefile.postlink) +ifdef CONFIG_LTO_CLANG +# With CONFIG_LTO_CLANG, reuse the object file we compiled for modpost to +# avoid a second slow LTO link +prelink-ext := .lto +endif + quiet_cmd_ld_ko_o = LD [M] $@ cmd_ld_ko_o = \ $(LD) -r $(KBUILD_LDFLAGS) \ @@ -36,7 +43,7 @@ quiet_cmd_ld_ko_o = LD [M] $@ -T scripts/module.lds -o $@ $(filter %.o, $^); \ $(if $(ARCH_POSTLINK), $(MAKE) -f $(ARCH_POSTLINK) $@, true) -$(modules): %.ko: %.o %.mod.o scripts/module.lds FORCE +$(modules): %.ko: %$(prelink-ext).o %.mod.o scripts/module.lds FORCE +$(call if_changed,ld_ko_o) targets += $(modules) $(modules:.ko=.mod.o) diff --git a/scripts/Makefile.modpost b/scripts/Makefile.modpost index f54b6ac37ac2..9ff8bfdb574d 100644 --- a/scripts/Makefile.modpost +++ b/scripts/Makefile.modpost @@ -43,6 +43,9 @@ __modpost: include include/config/auto.conf include scripts/Kbuild.include +# for ld_flags +include scripts/Makefile.lib + MODPOST = scripts/mod/modpost \ $(if $(CONFIG_MODVERSIONS),-m) \ $(if $(CONFIG_MODULE_SRCVERSION_ALL),-a) \ @@ -102,12 +105,26 @@ $(input-symdump): @echo >&2 'WARNING: Symbol version dump "$@" is missing.' @echo >&2 ' Modules may not have dependencies or modversions.' +ifdef CONFIG_LTO_CLANG +# With CONFIG_LTO_CLANG, .o files might be LLVM bitcode, so we need to run +# LTO to compile them into native code before running modpost +prelink-ext := .lto + +quiet_cmd_cc_lto_link_modules = LTO [M] $@ +cmd_cc_lto_link_modules = $(LD) $(ld_flags) -r -o $@ --whole-archive $^ + +%.lto.o: %.o + $(call if_changed,cc_lto_link_modules) +endif + +modules := $(sort $(shell cat $(MODORDER))) + # Read out modules.order to pass in modpost. # Otherwise, allmodconfig would fail with "Argument list too long". quiet_cmd_modpost = MODPOST $@ - cmd_modpost = sed 's/ko$$/o/' $< | $(MODPOST) -T - + cmd_modpost = sed 's/\.ko$$/$(prelink-ext)\.o/' $< | $(MODPOST) -T - -$(output-symdump): $(MODORDER) $(input-symdump) FORCE +$(output-symdump): $(MODORDER) $(input-symdump) $(modules:.ko=$(prelink-ext).o) FORCE $(call if_changed,modpost) targets += $(output-symdump) diff --git a/scripts/link-vmlinux.sh b/scripts/link-vmlinux.sh index 372c3719f94c..ebb9f912aab6 100755 --- a/scripts/link-vmlinux.sh +++ b/scripts/link-vmlinux.sh @@ -56,6 +56,14 @@ modpost_link() ${KBUILD_VMLINUX_LIBS} \ --end-group" + if [ -n "${CONFIG_LTO_CLANG}" ]; then + # This might take a while, so indicate that we're doing + # an LTO link + info LTO ${1} + else + info LD ${1} + fi + ${LD} ${KBUILD_LDFLAGS} -r -o ${1} ${objects} } @@ -103,13 +111,22 @@ vmlinux_link() fi if [ "${SRCARCH}" != "um" ]; then - objects="--whole-archive \ - ${KBUILD_VMLINUX_OBJS} \ - --no-whole-archive \ - --start-group \ - ${KBUILD_VMLINUX_LIBS} \ - --end-group \ - ${@}" + if [ -n "${CONFIG_LTO_CLANG}" ]; then + # Use vmlinux.o instead of performing the slow LTO + # link again. + objects="--whole-archive \ + vmlinux.o \ + --no-whole-archive \ + ${@}" + else + objects="--whole-archive \ + ${KBUILD_VMLINUX_OBJS} \ + --no-whole-archive \ + --start-group \ + ${KBUILD_VMLINUX_LIBS} \ + --end-group \ + ${@}" + fi ${LD} ${KBUILD_LDFLAGS} ${LDFLAGS_vmlinux} \ ${strip_debug#-Wl,} \ @@ -274,7 +291,6 @@ fi; ${MAKE} -f "${srctree}/scripts/Makefile.build" obj=init need-builtin=1 #link vmlinux.o -info LD vmlinux.o modpost_link vmlinux.o objtool_link vmlinux.o -- 2.28.0.1011.ga647a8990f-goog
WARNING: multiple messages have this Message-ID (diff)
From: Sami Tolvanen <samitolvanen@google.com> To: Masahiro Yamada <masahiroy@kernel.org>, Will Deacon <will@kernel.org>, Steven Rostedt <rostedt@goodmis.org> Cc: linux-arch@vger.kernel.org, x86@kernel.org, Kees Cook <keescook@chromium.org>, "Paul E. McKenney" <paulmck@kernel.org>, kernel-hardening@lists.openwall.com, Peter Zijlstra <peterz@infradead.org>, Greg Kroah-Hartman <gregkh@linuxfoundation.org>, linux-kbuild@vger.kernel.org, Nick Desaulniers <ndesaulniers@google.com>, linux-kernel@vger.kernel.org, clang-built-linux@googlegroups.com, Sami Tolvanen <samitolvanen@google.com>, linux-pci@vger.kernel.org, linux-arm-kernel@lists.infradead.org Subject: [PATCH v5 08/29] kbuild: add support for Clang LTO Date: Fri, 9 Oct 2020 09:13:17 -0700 [thread overview] Message-ID: <20201009161338.657380-9-samitolvanen@google.com> (raw) In-Reply-To: <20201009161338.657380-1-samitolvanen@google.com> This change adds build system support for Clang's Link Time Optimization (LTO). With -flto, instead of ELF object files, Clang produces LLVM bitcode, which is compiled into native code at link time, allowing the final binary to be optimized globally. For more details, see: https://llvm.org/docs/LinkTimeOptimization.html The Kconfig option CONFIG_LTO_CLANG is implemented as a choice, which defaults to LTO being disabled. To use LTO, the architecture must select ARCH_SUPPORTS_LTO_CLANG and support: - compiling with Clang, - compiling inline assembly with Clang's integrated assembler, - and linking with LLD. While using full LTO results in the best runtime performance, the compilation is not scalable in time or memory. CONFIG_THINLTO enables ThinLTO, which allows parallel optimization and faster incremental builds. ThinLTO is used by default if the architecture also selects ARCH_SUPPORTS_THINLTO: https://clang.llvm.org/docs/ThinLTO.html To enable LTO, LLVM tools must be used to handle bitcode files. The easiest way is to pass the LLVM=1 option to make: $ make LLVM=1 defconfig $ scripts/config -e LTO_CLANG $ make LLVM=1 Alternatively, at least the following LLVM tools must be used: CC=clang LD=ld.lld AR=llvm-ar NM=llvm-nm To prepare for LTO support with other compilers, common parts are gated behind the CONFIG_LTO option, and LTO can be disabled for specific files by filtering out CC_FLAGS_LTO. Note that support for DYNAMIC_FTRACE and MODVERSIONS are added in follow-up patches. Signed-off-by: Sami Tolvanen <samitolvanen@google.com> Reviewed-by: Kees Cook <keescook@chromium.org> --- Makefile | 20 ++++++++- arch/Kconfig | 75 +++++++++++++++++++++++++++++++ include/asm-generic/vmlinux.lds.h | 11 +++-- scripts/Makefile.build | 9 +++- scripts/Makefile.modfinal | 9 +++- scripts/Makefile.modpost | 21 ++++++++- scripts/link-vmlinux.sh | 32 +++++++++---- 7 files changed, 159 insertions(+), 18 deletions(-) diff --git a/Makefile b/Makefile index fb2cf557d3ca..a3baf8388163 100644 --- a/Makefile +++ b/Makefile @@ -886,6 +886,21 @@ KBUILD_CFLAGS += $(CC_FLAGS_SCS) export CC_FLAGS_SCS endif +ifdef CONFIG_LTO_CLANG +ifdef CONFIG_THINLTO +CC_FLAGS_LTO += -flto=thin -fsplit-lto-unit +KBUILD_LDFLAGS += --thinlto-cache-dir=$(extmod-prefix).thinlto-cache +else +CC_FLAGS_LTO += -flto +endif +CC_FLAGS_LTO += -fvisibility=default +endif + +ifdef CONFIG_LTO +KBUILD_CFLAGS += $(CC_FLAGS_LTO) +export CC_FLAGS_LTO +endif + ifdef CONFIG_DEBUG_FORCE_FUNCTION_ALIGN_32B KBUILD_CFLAGS += -falign-functions=32 endif @@ -1477,7 +1492,7 @@ MRPROPER_FILES += include/config include/generated \ *.spec # Directories & files removed with 'make distclean' -DISTCLEAN_FILES += tags TAGS cscope* GPATH GTAGS GRTAGS GSYMS +DISTCLEAN_FILES += tags TAGS cscope* GPATH GTAGS GRTAGS GSYMS .thinlto-cache # clean - Delete most, but leave enough to build external modules # @@ -1714,7 +1729,8 @@ _emodinst_post: _emodinst_ $(call cmd,depmod) clean-dirs := $(KBUILD_EXTMOD) -clean: rm-files := $(KBUILD_EXTMOD)/Module.symvers $(KBUILD_EXTMOD)/modules.nsdeps +clean: rm-files := $(KBUILD_EXTMOD)/Module.symvers $(KBUILD_EXTMOD)/modules.nsdeps \ + $(KBUILD_EXTMOD)/.thinlto-cache PHONY += help help: diff --git a/arch/Kconfig b/arch/Kconfig index 76ec3395b843..4ac5dda6d873 100644 --- a/arch/Kconfig +++ b/arch/Kconfig @@ -558,6 +558,81 @@ config SHADOW_CALL_STACK reading and writing arbitrary memory may be able to locate them and hijack control flow by modifying the stacks. +config LTO + bool + +config ARCH_SUPPORTS_LTO_CLANG + bool + help + An architecture should select this option if it supports: + - compiling with Clang, + - compiling inline assembly with Clang's integrated assembler, + - and linking with LLD. + +config ARCH_SUPPORTS_THINLTO + bool + help + An architecture should select this option if it supports Clang's + ThinLTO. + +config THINLTO + bool "Clang ThinLTO" + depends on LTO_CLANG && ARCH_SUPPORTS_THINLTO + default y + help + This option enables Clang's ThinLTO, which allows for parallel + optimization and faster incremental compiles. More information + can be found from Clang's documentation: + + https://clang.llvm.org/docs/ThinLTO.html + + If you say N here, the compiler will use full LTO, which may + produce faster code, but building the kernel will be significantly + slower as the linker won't efficiently utilize multiple threads. + + If unsure, say Y. + +choice + prompt "Link Time Optimization (LTO)" + default LTO_NONE + help + This option enables Link Time Optimization (LTO), which allows the + compiler to optimize binaries globally. + + If unsure, select LTO_NONE. Note that LTO is very resource-intensive + so it's disabled by default. + +config LTO_NONE + bool "None" + +config LTO_CLANG + bool "Clang's Link Time Optimization (EXPERIMENTAL)" + # Clang >= 11: https://github.com/ClangBuiltLinux/linux/issues/510 + depends on CC_IS_CLANG && CLANG_VERSION >= 110000 && LD_IS_LLD + depends on $(success,$(NM) --help | head -n 1 | grep -qi llvm) + depends on $(success,$(AR) --help | head -n 1 | grep -qi llvm) + depends on ARCH_SUPPORTS_LTO_CLANG + depends on !FTRACE_MCOUNT_RECORD + depends on !KASAN + depends on !GCOV_KERNEL + depends on !MODVERSIONS + select LTO + help + This option enables Clang's Link Time Optimization (LTO), which + allows the compiler to optimize the kernel globally. If you enable + this option, the compiler generates LLVM bitcode instead of ELF + object files, and the actual compilation from bitcode happens at + the LTO link step, which may take several minutes depending on the + kernel configuration. More information can be found from LLVM's + documentation: + + https://llvm.org/docs/LinkTimeOptimization.html + + To select this option, you also need to use LLVM tools to handle + the bitcode by passing LLVM=1 to make. + +endchoice + config HAVE_ARCH_WITHIN_STACK_FRAMES bool help diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h index e1843976754a..77e5bd069dd4 100644 --- a/include/asm-generic/vmlinux.lds.h +++ b/include/asm-generic/vmlinux.lds.h @@ -90,15 +90,18 @@ * .data. We don't want to pull in .data..other sections, which Linux * has defined. Same for text and bss. * + * With LTO_CLANG, the linker also splits sections by default, so we need + * these macros to combine the sections during the final link. + * * RODATA_MAIN is not used because existing code already defines .rodata.x * sections to be brought in with rodata. */ -#ifdef CONFIG_LD_DEAD_CODE_DATA_ELIMINATION +#if defined(CONFIG_LD_DEAD_CODE_DATA_ELIMINATION) || defined(CONFIG_LTO_CLANG) #define TEXT_MAIN .text .text.[0-9a-zA-Z_]* -#define DATA_MAIN .data .data.[0-9a-zA-Z_]* .data..LPBX* +#define DATA_MAIN .data .data.[0-9a-zA-Z_]* .data..L* .data..compoundliteral* #define SDATA_MAIN .sdata .sdata.[0-9a-zA-Z_]* -#define RODATA_MAIN .rodata .rodata.[0-9a-zA-Z_]* -#define BSS_MAIN .bss .bss.[0-9a-zA-Z_]* +#define RODATA_MAIN .rodata .rodata.[0-9a-zA-Z_]* .rodata..L* +#define BSS_MAIN .bss .bss.[0-9a-zA-Z_]* .bss..compoundliteral* #define SBSS_MAIN .sbss .sbss.[0-9a-zA-Z_]* #else #define TEXT_MAIN .text diff --git a/scripts/Makefile.build b/scripts/Makefile.build index 2175ddb1ee0c..ed74b2f986f7 100644 --- a/scripts/Makefile.build +++ b/scripts/Makefile.build @@ -111,7 +111,7 @@ endif # --------------------------------------------------------------------------- quiet_cmd_cc_s_c = CC $(quiet_modtag) $@ - cmd_cc_s_c = $(CC) $(filter-out $(DEBUG_CFLAGS), $(c_flags)) -fverbose-asm -S -o $@ $< + cmd_cc_s_c = $(CC) $(filter-out $(DEBUG_CFLAGS) $(CC_FLAGS_LTO), $(c_flags)) -fverbose-asm -S -o $@ $< $(obj)/%.s: $(src)/%.c FORCE $(call if_changed_dep,cc_s_c) @@ -425,8 +425,15 @@ $(obj)/lib.a: $(lib-y) FORCE # Do not replace $(filter %.o,^) with $(real-prereqs). When a single object # module is turned into a multi object module, $^ will contain header file # dependencies recorded in the .*.cmd file. +ifdef CONFIG_LTO_CLANG +quiet_cmd_link_multi-m = AR [M] $@ +cmd_link_multi-m = \ + rm -f $@; \ + $(AR) cDPrsT $@ $(filter %.o,$^) +else quiet_cmd_link_multi-m = LD [M] $@ cmd_link_multi-m = $(LD) $(ld_flags) -r -o $@ $(filter %.o,$^) +endif $(multi-used-m): FORCE $(call if_changed,link_multi-m) diff --git a/scripts/Makefile.modfinal b/scripts/Makefile.modfinal index ae01baf96f4e..2cb9a1d88434 100644 --- a/scripts/Makefile.modfinal +++ b/scripts/Makefile.modfinal @@ -6,6 +6,7 @@ PHONY := __modfinal __modfinal: +include $(objtree)/include/config/auto.conf include $(srctree)/scripts/Kbuild.include # for c_flags @@ -29,6 +30,12 @@ quiet_cmd_cc_o_c = CC [M] $@ ARCH_POSTLINK := $(wildcard $(srctree)/arch/$(SRCARCH)/Makefile.postlink) +ifdef CONFIG_LTO_CLANG +# With CONFIG_LTO_CLANG, reuse the object file we compiled for modpost to +# avoid a second slow LTO link +prelink-ext := .lto +endif + quiet_cmd_ld_ko_o = LD [M] $@ cmd_ld_ko_o = \ $(LD) -r $(KBUILD_LDFLAGS) \ @@ -36,7 +43,7 @@ quiet_cmd_ld_ko_o = LD [M] $@ -T scripts/module.lds -o $@ $(filter %.o, $^); \ $(if $(ARCH_POSTLINK), $(MAKE) -f $(ARCH_POSTLINK) $@, true) -$(modules): %.ko: %.o %.mod.o scripts/module.lds FORCE +$(modules): %.ko: %$(prelink-ext).o %.mod.o scripts/module.lds FORCE +$(call if_changed,ld_ko_o) targets += $(modules) $(modules:.ko=.mod.o) diff --git a/scripts/Makefile.modpost b/scripts/Makefile.modpost index f54b6ac37ac2..9ff8bfdb574d 100644 --- a/scripts/Makefile.modpost +++ b/scripts/Makefile.modpost @@ -43,6 +43,9 @@ __modpost: include include/config/auto.conf include scripts/Kbuild.include +# for ld_flags +include scripts/Makefile.lib + MODPOST = scripts/mod/modpost \ $(if $(CONFIG_MODVERSIONS),-m) \ $(if $(CONFIG_MODULE_SRCVERSION_ALL),-a) \ @@ -102,12 +105,26 @@ $(input-symdump): @echo >&2 'WARNING: Symbol version dump "$@" is missing.' @echo >&2 ' Modules may not have dependencies or modversions.' +ifdef CONFIG_LTO_CLANG +# With CONFIG_LTO_CLANG, .o files might be LLVM bitcode, so we need to run +# LTO to compile them into native code before running modpost +prelink-ext := .lto + +quiet_cmd_cc_lto_link_modules = LTO [M] $@ +cmd_cc_lto_link_modules = $(LD) $(ld_flags) -r -o $@ --whole-archive $^ + +%.lto.o: %.o + $(call if_changed,cc_lto_link_modules) +endif + +modules := $(sort $(shell cat $(MODORDER))) + # Read out modules.order to pass in modpost. # Otherwise, allmodconfig would fail with "Argument list too long". quiet_cmd_modpost = MODPOST $@ - cmd_modpost = sed 's/ko$$/o/' $< | $(MODPOST) -T - + cmd_modpost = sed 's/\.ko$$/$(prelink-ext)\.o/' $< | $(MODPOST) -T - -$(output-symdump): $(MODORDER) $(input-symdump) FORCE +$(output-symdump): $(MODORDER) $(input-symdump) $(modules:.ko=$(prelink-ext).o) FORCE $(call if_changed,modpost) targets += $(output-symdump) diff --git a/scripts/link-vmlinux.sh b/scripts/link-vmlinux.sh index 372c3719f94c..ebb9f912aab6 100755 --- a/scripts/link-vmlinux.sh +++ b/scripts/link-vmlinux.sh @@ -56,6 +56,14 @@ modpost_link() ${KBUILD_VMLINUX_LIBS} \ --end-group" + if [ -n "${CONFIG_LTO_CLANG}" ]; then + # This might take a while, so indicate that we're doing + # an LTO link + info LTO ${1} + else + info LD ${1} + fi + ${LD} ${KBUILD_LDFLAGS} -r -o ${1} ${objects} } @@ -103,13 +111,22 @@ vmlinux_link() fi if [ "${SRCARCH}" != "um" ]; then - objects="--whole-archive \ - ${KBUILD_VMLINUX_OBJS} \ - --no-whole-archive \ - --start-group \ - ${KBUILD_VMLINUX_LIBS} \ - --end-group \ - ${@}" + if [ -n "${CONFIG_LTO_CLANG}" ]; then + # Use vmlinux.o instead of performing the slow LTO + # link again. + objects="--whole-archive \ + vmlinux.o \ + --no-whole-archive \ + ${@}" + else + objects="--whole-archive \ + ${KBUILD_VMLINUX_OBJS} \ + --no-whole-archive \ + --start-group \ + ${KBUILD_VMLINUX_LIBS} \ + --end-group \ + ${@}" + fi ${LD} ${KBUILD_LDFLAGS} ${LDFLAGS_vmlinux} \ ${strip_debug#-Wl,} \ @@ -274,7 +291,6 @@ fi; ${MAKE} -f "${srctree}/scripts/Makefile.build" obj=init need-builtin=1 #link vmlinux.o -info LD vmlinux.o modpost_link vmlinux.o objtool_link vmlinux.o -- 2.28.0.1011.ga647a8990f-goog _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next prev parent reply other threads:[~2020-10-09 16:14 UTC|newest] Thread overview: 111+ messages / expand[flat|nested] mbox.gz Atom feed top 2020-10-09 16:13 [PATCH v5 00/29] Add support for Clang LTO Sami Tolvanen 2020-10-09 16:13 ` Sami Tolvanen 2020-10-09 16:13 ` Sami Tolvanen 2020-10-09 16:13 ` [PATCH v5 01/29] kbuild: preprocess module linker script Sami Tolvanen 2020-10-09 16:13 ` Sami Tolvanen 2020-10-09 16:13 ` Sami Tolvanen 2020-10-09 16:13 ` [PATCH v5 02/29] objtool: Add a pass for generating __mcount_loc Sami Tolvanen 2020-10-09 16:13 ` Sami Tolvanen 2020-10-09 16:13 ` Sami Tolvanen 2020-10-09 16:13 ` [PATCH v5 03/29] objtool: Don't autodetect vmlinux.o Sami Tolvanen 2020-10-09 16:13 ` Sami Tolvanen 2020-10-09 16:13 ` Sami Tolvanen 2020-10-09 16:13 ` [PATCH v5 04/29] tracing: move function tracer options to Kconfig Sami Tolvanen 2020-10-09 16:13 ` Sami Tolvanen 2020-10-09 16:13 ` Sami Tolvanen 2020-10-09 16:13 ` [PATCH v5 05/29] tracing: add support for objtool mcount Sami Tolvanen 2020-10-09 16:13 ` Sami Tolvanen 2020-10-09 16:13 ` Sami Tolvanen 2020-10-09 16:13 ` [PATCH v5 06/29] x86, build: use " Sami Tolvanen 2020-10-09 16:13 ` Sami Tolvanen 2020-10-09 16:13 ` Sami Tolvanen 2020-10-09 16:13 ` [PATCH v5 07/29] treewide: remove DISABLE_LTO Sami Tolvanen 2020-10-09 16:13 ` Sami Tolvanen 2020-10-09 16:13 ` Sami Tolvanen 2020-10-09 16:13 ` Sami Tolvanen [this message] 2020-10-09 16:13 ` [PATCH v5 08/29] kbuild: add support for Clang LTO Sami Tolvanen 2020-10-09 16:13 ` Sami Tolvanen 2020-10-09 16:13 ` [PATCH v5 09/29] kbuild: lto: fix module versioning Sami Tolvanen 2020-10-09 16:13 ` Sami Tolvanen 2020-10-09 16:13 ` Sami Tolvanen 2020-10-09 16:13 ` [PATCH v5 10/29] objtool: Split noinstr validation from --vmlinux Sami Tolvanen 2020-10-09 16:13 ` Sami Tolvanen 2020-10-09 16:13 ` Sami Tolvanen 2020-10-09 16:13 ` [PATCH v5 11/29] kbuild: lto: postpone objtool Sami Tolvanen 2020-10-09 16:13 ` Sami Tolvanen 2020-10-09 16:13 ` Sami Tolvanen 2020-10-09 16:13 ` [PATCH v5 12/29] kbuild: lto: limit inlining Sami Tolvanen 2020-10-09 16:13 ` Sami Tolvanen 2020-10-09 16:13 ` Sami Tolvanen 2020-10-09 16:13 ` [PATCH v5 13/29] kbuild: lto: merge module sections Sami Tolvanen 2020-10-09 16:13 ` Sami Tolvanen 2020-10-09 16:13 ` Sami Tolvanen 2020-10-09 16:13 ` [PATCH v5 14/29] kbuild: lto: remove duplicate dependencies from .mod files Sami Tolvanen 2020-10-09 16:13 ` Sami Tolvanen 2020-10-09 16:13 ` Sami Tolvanen 2020-10-09 16:13 ` [PATCH v5 15/29] init: lto: ensure initcall ordering Sami Tolvanen 2020-10-09 16:13 ` Sami Tolvanen 2020-10-09 16:13 ` Sami Tolvanen 2020-10-09 16:13 ` [PATCH v5 16/29] init: lto: fix PREL32 relocations Sami Tolvanen 2020-10-09 16:13 ` Sami Tolvanen 2020-10-09 16:13 ` Sami Tolvanen 2020-10-09 16:13 ` [PATCH v5 17/29] PCI: Fix PREL32 relocations for LTO Sami Tolvanen 2020-10-09 16:13 ` Sami Tolvanen 2020-10-09 16:13 ` Sami Tolvanen 2020-10-09 16:13 ` [PATCH v5 18/29] modpost: lto: strip .lto from module names Sami Tolvanen 2020-10-09 16:13 ` Sami Tolvanen 2020-10-09 16:13 ` Sami Tolvanen 2020-10-09 16:13 ` [PATCH v5 19/29] scripts/mod: disable LTO for empty.c Sami Tolvanen 2020-10-09 16:13 ` Sami Tolvanen 2020-10-09 16:13 ` Sami Tolvanen 2020-10-09 16:13 ` [PATCH v5 20/29] efi/libstub: disable LTO Sami Tolvanen 2020-10-09 16:13 ` Sami Tolvanen 2020-10-09 16:13 ` Sami Tolvanen 2020-10-09 16:13 ` [PATCH v5 21/29] drivers/misc/lkdtm: disable LTO for rodata.o Sami Tolvanen 2020-10-09 16:13 ` Sami Tolvanen 2020-10-09 16:13 ` Sami Tolvanen 2020-10-09 16:13 ` [PATCH v5 22/29] arm64: vdso: disable LTO Sami Tolvanen 2020-10-09 16:13 ` Sami Tolvanen 2020-10-09 16:13 ` Sami Tolvanen 2020-10-09 16:13 ` [PATCH v5 23/29] KVM: arm64: disable LTO for the nVHE directory Sami Tolvanen 2020-10-09 16:13 ` Sami Tolvanen 2020-10-09 16:13 ` Sami Tolvanen 2020-10-09 16:13 ` [PATCH v5 24/29] arm64: disable recordmcount with DYNAMIC_FTRACE_WITH_REGS Sami Tolvanen 2020-10-09 16:13 ` Sami Tolvanen 2020-10-09 16:13 ` Sami Tolvanen 2020-10-09 16:13 ` [PATCH v5 25/29] arm64: allow LTO_CLANG and THINLTO to be selected Sami Tolvanen 2020-10-09 16:13 ` Sami Tolvanen 2020-10-09 16:13 ` Sami Tolvanen 2020-10-12 8:31 ` Will Deacon 2020-10-12 8:31 ` Will Deacon 2020-10-12 20:44 ` Kees Cook 2020-10-12 20:44 ` Kees Cook 2020-10-12 20:51 ` Will Deacon 2020-10-12 20:51 ` Will Deacon 2020-10-12 21:02 ` Kees Cook 2020-10-12 21:02 ` Kees Cook 2020-10-09 16:13 ` [PATCH v5 26/29] x86/asm: annotate indirect jumps Sami Tolvanen 2020-10-09 16:13 ` Sami Tolvanen 2020-10-09 16:13 ` Sami Tolvanen 2020-10-09 16:13 ` [PATCH v5 27/29] x86, vdso: disable LTO only for vDSO Sami Tolvanen 2020-10-09 16:13 ` Sami Tolvanen 2020-10-09 16:13 ` Sami Tolvanen 2020-10-09 16:13 ` [PATCH v5 28/29] x86, cpu: disable LTO for cpu.c Sami Tolvanen 2020-10-09 16:13 ` Sami Tolvanen 2020-10-09 16:13 ` Sami Tolvanen 2020-10-09 16:13 ` [PATCH v5 29/29] x86, build: allow LTO_CLANG and THINLTO to be selected Sami Tolvanen 2020-10-09 16:13 ` Sami Tolvanen 2020-10-09 16:13 ` Sami Tolvanen 2020-10-09 16:30 ` [PATCH v5 00/29] Add support for Clang LTO Sedat Dilek 2020-10-09 16:30 ` Sedat Dilek 2020-10-09 16:30 ` Sedat Dilek 2020-10-09 20:50 ` Sami Tolvanen 2020-10-09 20:50 ` Sami Tolvanen 2020-10-09 19:35 ` Steven Rostedt 2020-10-09 21:05 ` Sami Tolvanen 2020-10-09 21:05 ` Sami Tolvanen 2020-10-09 23:38 ` Steven Rostedt 2020-10-09 23:38 ` Steven Rostedt 2020-10-10 0:00 ` Sami Tolvanen 2020-10-10 0:00 ` Sami Tolvanen 2020-10-10 0:00 ` Sami Tolvanen
Reply instructions: You may reply publicly to this message via plain-text email using any one of the following methods: * Save the following mbox file, import it into your mail client, and reply-to-all from there: mbox Avoid top-posting and favor interleaved quoting: https://en.wikipedia.org/wiki/Posting_style#Interleaved_style * Reply using the --to, --cc, and --in-reply-to switches of git-send-email(1): git send-email \ --in-reply-to=20201009161338.657380-9-samitolvanen@google.com \ --to=samitolvanen@google.com \ --cc=clang-built-linux@googlegroups.com \ --cc=gregkh@linuxfoundation.org \ --cc=keescook@chromium.org \ --cc=kernel-hardening@lists.openwall.com \ --cc=linux-arch@vger.kernel.org \ --cc=linux-arm-kernel@lists.infradead.org \ --cc=linux-kbuild@vger.kernel.org \ --cc=linux-kernel@vger.kernel.org \ --cc=linux-pci@vger.kernel.org \ --cc=masahiroy@kernel.org \ --cc=ndesaulniers@google.com \ --cc=paulmck@kernel.org \ --cc=peterz@infradead.org \ --cc=rostedt@goodmis.org \ --cc=will@kernel.org \ --cc=x86@kernel.org \ /path/to/YOUR_REPLY https://kernel.org/pub/software/scm/git/docs/git-send-email.html * If your mail client supports setting the In-Reply-To header via mailto: links, try the mailto: linkBe sure your reply has a Subject: header at the top and a blank line before the message body.
This is an external index of several public inboxes, see mirroring instructions on how to clone and mirror all data and code used by this external index.