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Wed, 15 Nov 2017 13:35:03 -0800 (PST) From: Sami Tolvanen To: Alex Matveev , Andi Kleen , Ard Biesheuvel , Greg Hackmann , Kees Cook , linux-arm-kernel@lists.infradead.org, linux-kbuild@vger.kernel.org, linux-kernel@vger.kernel.org, Mark Rutland , Masahiro Yamada , Maxim Kuvyrkov , Michal Marek , Nick Desaulniers , Yury Norov , Matthias Kaehlcke Subject: [PATCH v2 13/18] kbuild: fix dynamic ftrace with clang LTO Date: Wed, 15 Nov 2017 13:34:23 -0800 Message-Id: <20171115213428.22559-14-samitolvanen@google.com> X-Mailer: git-send-email 2.15.0.448.gf294e3d99a-goog In-Reply-To: <20171115213428.22559-1-samitolvanen@google.com> References: <20171115213428.22559-1-samitolvanen@google.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20171115_133526_050806_88CF96D0 X-CRM114-Status: GOOD ( 18.38 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Sami Tolvanen MIME-Version: 1.0 Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org X-Virus-Scanned: ClamAV using ClamSMTP With CONFIG_LTO_CLANG enabled, LLVM IR won't be compiled into object files until modpost_link. This change postpones calls to recordmcount until after this step. In order to exclude ftrace_process_locs from inspection, we add a new code section .text..ftrace, which we tell recordmcount to ignore, and a __norecordmcount attribute for moving functions to this section. Signed-off-by: Sami Tolvanen --- arch/Kconfig | 2 +- include/asm-generic/vmlinux.lds.h | 1 + include/linux/compiler-clang.h | 7 +++++++ include/linux/compiler_types.h | 4 ++++ kernel/trace/ftrace.c | 6 +++--- scripts/Makefile.build | 14 +++++++++++++- scripts/Makefile.modpost | 4 ++++ scripts/link-vmlinux.sh | 16 ++++++++++++++++ scripts/recordmcount.c | 3 ++- 9 files changed, 51 insertions(+), 6 deletions(-) diff --git a/arch/Kconfig b/arch/Kconfig index bb5296ecebdd..e0d0084308e2 100644 --- a/arch/Kconfig +++ b/arch/Kconfig @@ -620,7 +620,7 @@ config ARCH_SUPPORTS_LTO_CLANG config LTO_CLANG bool "Use clang Link Time Optimization (LTO)" depends on ARCH_SUPPORTS_LTO_CLANG - depends on !FTRACE_MCOUNT_RECORD + depends on !FTRACE_MCOUNT_RECORD || HAVE_C_RECORDMCOUNT select LTO select LD_DEAD_CODE_DATA_ELIMINATION help diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h index ce0244780988..c4c44ea73930 100644 --- a/include/asm-generic/vmlinux.lds.h +++ b/include/asm-generic/vmlinux.lds.h @@ -459,6 +459,7 @@ #define TEXT_TEXT \ ALIGN_FUNCTION(); \ *(.text.hot TEXT_MAIN .text.fixup .text.unlikely) \ + *(.text..ftrace) \ *(.text..refcount) \ *(.ref.text) \ MEM_KEEP(init.text) \ diff --git a/include/linux/compiler-clang.h b/include/linux/compiler-clang.h index a06583e41f80..62604537ea66 100644 --- a/include/linux/compiler-clang.h +++ b/include/linux/compiler-clang.h @@ -16,3 +16,10 @@ * with any version that can compile the kernel */ #define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __COUNTER__) + +#ifdef CONFIG_CLANG_LTO +#ifdef CONFIG_FTRACE_MCOUNT_RECORD +#define __norecordmcount \ + __attribute__((__section__(".text..ftrace"))) +#endif +#endif diff --git a/include/linux/compiler_types.h b/include/linux/compiler_types.h index 6b79a9bba9a7..231c413c615a 100644 --- a/include/linux/compiler_types.h +++ b/include/linux/compiler_types.h @@ -253,6 +253,10 @@ struct ftrace_likely_data { # define __nostackprotector #endif +#ifndef __norecordmcount +#define __norecordmcount +#endif + /* * Assume alignment of return value. */ diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c index 8319e09e15b9..e117b849f9dc 100644 --- a/kernel/trace/ftrace.c +++ b/kernel/trace/ftrace.c @@ -5573,9 +5573,9 @@ static int ftrace_cmp_ips(const void *a, const void *b) return 0; } -static int ftrace_process_locs(struct module *mod, - unsigned long *start, - unsigned long *end) +static int __norecordmcount ftrace_process_locs(struct module *mod, + unsigned long *start, + unsigned long *end) { struct ftrace_page *start_pg; struct ftrace_page *pg; diff --git a/scripts/Makefile.build b/scripts/Makefile.build index e8bf5c440612..4d990c7cbe34 100644 --- a/scripts/Makefile.build +++ b/scripts/Makefile.build @@ -246,6 +246,12 @@ ifdef BUILD_C_RECORDMCOUNT ifeq ("$(origin RECORDMCOUNT_WARN)", "command line") RECORDMCOUNT_FLAGS = -w endif + +ifdef CONFIG_LTO_CLANG +# With LTO, we postpone running recordmcount until after the LTO link step, so +# let's export the parameters for the link script. +export RECORDMCOUNT_FLAGS +else # Due to recursion, we must skip empty.o. # The empty.o file is created in the make process in order to determine # the target endianness and word size. It is made before all other C @@ -254,17 +260,22 @@ sub_cmd_record_mcount = \ if [ $(@) != "scripts/mod/empty.o" ]; then \ $(objtree)/scripts/recordmcount $(RECORDMCOUNT_FLAGS) "$(@)"; \ fi; +endif + recordmcount_source := $(srctree)/scripts/recordmcount.c \ $(srctree)/scripts/recordmcount.h -else +else # !BUILD_C_RECORDMCOUNT sub_cmd_record_mcount = set -e ; perl $(srctree)/scripts/recordmcount.pl "$(ARCH)" \ "$(if $(CONFIG_CPU_BIG_ENDIAN),big,little)" \ "$(if $(CONFIG_64BIT),64,32)" \ "$(OBJDUMP)" "$(OBJCOPY)" "$(CC) $(KBUILD_CFLAGS)" \ "$(LD)" "$(NM)" "$(RM)" "$(MV)" \ "$(if $(part-of-module),1,0)" "$(@)"; + recordmcount_source := $(srctree)/scripts/recordmcount.pl endif # BUILD_C_RECORDMCOUNT + +ifndef CONFIG_LTO_CLANG cmd_record_mcount = \ if [ "$(findstring $(CC_FLAGS_FTRACE),$(_c_flags))" = \ "$(CC_FLAGS_FTRACE)" ]; then \ @@ -287,6 +298,7 @@ objtool_args += --no-unreachable else objtool_args += $(call cc-ifversion, -lt, 0405, --no-unreachable) endif +endif # CONFIG_FTRACE_MCOUNT_RECORD # 'OBJECT_FILES_NON_STANDARD := y': skip objtool checking for a directory # 'OBJECT_FILES_NON_STANDARD_foo.o := 'y': skip objtool checking for a file diff --git a/scripts/Makefile.modpost b/scripts/Makefile.modpost index cb1c040a006c..5896e07c499b 100644 --- a/scripts/Makefile.modpost +++ b/scripts/Makefile.modpost @@ -164,6 +164,10 @@ lto_ko_objects = $(foreach o,$(1:$(modpost-ext).o=.o), \ $(shell [ -s $(@:.ko=.modversions) ] && \ echo -T $(@:.ko=.modversions)) \ -o $@ $(call lto_ko_objects, $(filter-out FORCE,$^)) + +ifdef CONFIG_FTRACE_MCOUNT_RECORD +cmd_ld_ko_o += ; $(objtree)/scripts/recordmcount $(RECORDMCOUNT_FLAGS) $@ +endif else cmd_ld_ko_o = \ $(LD) -r $(LDFLAGS) \ diff --git a/scripts/link-vmlinux.sh b/scripts/link-vmlinux.sh index fccc123b691f..44ec43c781e0 100755 --- a/scripts/link-vmlinux.sh +++ b/scripts/link-vmlinux.sh @@ -143,6 +143,19 @@ modpost_link() ${LD} ${LDFLAGS} -r -o ${1} $(modversions) ${objects} } +# If CONFIG_LTO_CLANG is selected, we postpone running recordmcount until +# we have compiled LLVM IR to an object file. +recordmcount() +{ + if [ -z "${CONFIG_LTO_CLANG}" ]; then + return + fi + + if [ -n "${CONFIG_FTRACE_MCOUNT_RECORD}" ]; then + scripts/recordmcount ${RECORDMCOUNT_FLAGS} $* + fi +} + # Link of vmlinux # ${1} - optional extra .o files # ${2} - output file @@ -327,6 +340,9 @@ if [ -n "${CONFIG_LTO_CLANG}" ]; then KBUILD_VMLINUX_INIT= KBUILD_VMLINUX_MAIN=vmlinux.o KBUILD_VMLINUX_LIBS= + + # Call recordmcount if needed + recordmcount vmlinux.o fi kallsymso="" diff --git a/scripts/recordmcount.c b/scripts/recordmcount.c index 16e086dcc567..69a769904da7 100644 --- a/scripts/recordmcount.c +++ b/scripts/recordmcount.c @@ -420,7 +420,8 @@ is_mcounted_section_name(char const *const txtname) strcmp(".softirqentry.text", txtname) == 0 || strcmp(".kprobes.text", txtname) == 0 || strcmp(".cpuidle.text", txtname) == 0 || - strcmp(".text.unlikely", txtname) == 0; + (strncmp(".text.", txtname, 6) == 0 && + strcmp(".text..ftrace", txtname) != 0); } /* 32 bit and 64 bit are very similar */