From 9abcee5156e441679298a03a5af29675c6161802 Mon Sep 17 00:00:00 2001 From: Sami Tolvanen Date: Fri, 16 Jun 2017 12:52:57 -0700 Subject: [PATCH] FROMLIST: kbuild: fix dynamic ftrace with clang LTO 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. Bug: 62093296 Bug: 67506682 Change-Id: Iba2c053968206acf533fadab1eb34a743b5088ee (am from https://patchwork.kernel.org/patch/10060327/) 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 e59db803807f..534589f07e7b 100644 --- a/arch/Kconfig +++ b/arch/Kconfig @@ -628,7 +628,7 @@ config LTO_NONE config LTO_CLANG bool "Use clang Link Time Optimization (LTO) (EXPERIMENTAL)" depends on ARCH_SUPPORTS_LTO_CLANG - depends on !FTRACE_MCOUNT_RECORD + depends on !FTRACE_MCOUNT_RECORD || HAVE_C_RECORDMCOUNT select LTO select THIN_ARCHIVES select LD_DEAD_CODE_DATA_ELIMINATION diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h index f4a6799cfbc5..d60eaf87e8d9 100644 --- a/include/asm-generic/vmlinux.lds.h +++ b/include/asm-generic/vmlinux.lds.h @@ -460,6 +460,7 @@ ALIGN_FUNCTION(); \ *(.text.hot TEXT_MAIN .text.fixup .text.unlikely) \ *(.text..refcount) \ + *(.text..ftrace) \ *(.ref.text) \ MEM_KEEP(init.text) \ MEM_KEEP(exit.text) \ diff --git a/include/linux/compiler-clang.h b/include/linux/compiler-clang.h index 070f85d92c15..9f9ab1461367 100644 --- a/include/linux/compiler-clang.h +++ b/include/linux/compiler-clang.h @@ -21,3 +21,10 @@ #ifdef __noretpoline #undef __noretpoline #endif + +#ifdef CONFIG_LTO_CLANG +#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 7379bcf3baa0..c52b8e4e173a 100644 --- a/kernel/trace/ftrace.c +++ b/kernel/trace/ftrace.c @@ -5572,9 +5572,9 @@ 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 bda756f438f1..b5b05f115775 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 @@ -254,22 +260,28 @@ 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 \ $(sub_cmd_record_mcount) \ fi; +endif endif # CONFIG_FTRACE_MCOUNT_RECORD ifdef CONFIG_STACK_VALIDATION diff --git a/scripts/Makefile.modpost b/scripts/Makefile.modpost index c86c99b4a1cf..acd7ea0b5f26 100644 --- a/scripts/Makefile.modpost +++ b/scripts/Makefile.modpost @@ -143,6 +143,10 @@ ifdef CONFIG_LTO_CLANG echo -T $(@:.ko=.o.symversions)) \ -o $@ --whole-archive \ $(filter-out FORCE,$(^:$(modpost-ext).o=.o)) + + 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 ece268ceaaa1..cfa44718cef7 100755 --- a/scripts/link-vmlinux.sh +++ b/scripts/link-vmlinux.sh @@ -127,6 +127,19 @@ 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 # ${2} - output file @@ -311,6 +324,9 @@ if [ -n "${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 */ -- 2.20.1