From 6f0fa58e459642b16901521cc58ac474b787ec5b Mon Sep 17 00:00:00 2001 From: Masahiro Yamada Date: Fri, 19 May 2017 20:42:30 +0900 Subject: kbuild: simplify silent build (-s) detection This allows to detect -s (--silent) option without checking GNU Make version. As commit e36aaea28972 ("kbuild: Fix silent builds with make-4") pointed out, GNU Make 4.x changed the way/order it presents the command line options into MAKEFLAGS. In Make 3.8x, 's' is always the first in a group of short options. The group may be prefixed with '-' in some cases. In Make 4.x, 's' is always the last in a group of short options. As commit e6ac89fabd03 ("kbuild: Correctly deal with make options which contain an 's'") addressed, we also need to deal with long options that contain 's', like --warn-undefined-variables. Test cases: [1] command line input: make --silent -> MAKEFLAGS for Make 3.8x: s -> MAKEFLAGS for Make 4.x : s [2] command line input: make -srR -> MAKEFLAGS for Make 3.8x: sRr -> MAKEFLAGS for Make 4.x : rRs [3] command line input: make -s -rR --warn-undefined-variables -> MAKEFLAGS for Make 3.8x: --warn-undefined-variables -sRr -> MAKEFLAGS for Make 4.x : rRs --warn-undefined-variables My idea to cater to all the cases more easily is to filter out long options (--%), then search 's' with $(findstring ...). This way will be more future-proof even if future versions of Make put 's' in the middle of the group. Signed-off-by: Masahiro Yamada --- Makefile | 9 +-------- tools/build/Makefile.build | 8 +------- tools/scripts/Makefile.include | 8 +------- 3 files changed, 3 insertions(+), 22 deletions(-) diff --git a/Makefile b/Makefile index 63e10bd4f14a..57a013dc0364 100644 --- a/Makefile +++ b/Makefile @@ -84,17 +84,10 @@ endif # If the user is running make -s (silent mode), suppress echoing of # commands -ifneq ($(filter 4.%,$(MAKE_VERSION)),) # make-4 -ifneq ($(filter %s ,$(firstword x$(MAKEFLAGS))),) +ifneq ($(findstring s,$(filter-out --%,$(MAKEFLAGS))),) quiet=silent_ tools_silent=s endif -else # make-3.8x -ifneq ($(filter s% -s%,$(MAKEFLAGS)),) - quiet=silent_ - tools_silent=-s -endif -endif export quiet Q KBUILD_VERBOSE diff --git a/tools/build/Makefile.build b/tools/build/Makefile.build index e279a71c650d..c46b20e4ad87 100644 --- a/tools/build/Makefile.build +++ b/tools/build/Makefile.build @@ -19,15 +19,9 @@ else Q=@ endif -ifneq ($(filter 4.%,$(MAKE_VERSION)),) # make-4 -ifneq ($(filter %s ,$(firstword x$(MAKEFLAGS))),) +ifneq ($(findstring s,$(filter-out --%,$(MAKEFLAGS))),) quiet=silent_ endif -else # make-3.8x -ifneq ($(filter s% -s%,$(MAKEFLAGS)),) - quiet=silent_ -endif -endif build-dir := $(srctree)/tools/build diff --git a/tools/scripts/Makefile.include b/tools/scripts/Makefile.include index fc74db62fef4..ccad8ce925e4 100644 --- a/tools/scripts/Makefile.include +++ b/tools/scripts/Makefile.include @@ -58,15 +58,9 @@ else NO_SUBDIR = : endif -ifneq ($(filter 4.%,$(MAKE_VERSION)),) # make-4 -ifneq ($(filter %s ,$(firstword x$(MAKEFLAGS))),) +ifneq ($(findstring s,$(filter-out --%,$(MAKEFLAGS))),) silent=1 endif -else # make-3.8x -ifneq ($(filter s% -s%,$(MAKEFLAGS)),) - silent=1 -endif -endif # # Define a callable command for descending to a new directory -- cgit v1.2.1 From d21832e212d2613c0a0f3e5f09967cb3402c8a53 Mon Sep 17 00:00:00 2001 From: Arnd Bergmann Date: Thu, 1 Jun 2017 16:57:07 +0200 Subject: kbuild: speed up checksyscalls.sh checksyscalls.sh is run at every "make" run while building the kernel, even if no files have changed. I looked at where we spend time in a trivial empty rebuild and found checksyscalls.sh to be a source of noticeable overhead, as it spawns a lot of child processes just to call 'cat' copying from stdin to stdout, once for each of the over 400 x86 syscalls. Using a shell-builtin (echo) instead of the external command gives us a 13x speedup: Before After real 0m1.018s real 0m0.077s user 0m0.068s user 0m0.048s sys 0m0.156s sys 0m0.024s The time it took to rebuild a single file on my machine dropped from 5.5 seconds to 4.5 seconds. Signed-off-by: Arnd Bergmann Signed-off-by: Masahiro Yamada --- scripts/checksyscalls.sh | 11 ++++------- 1 file changed, 4 insertions(+), 7 deletions(-) diff --git a/scripts/checksyscalls.sh b/scripts/checksyscalls.sh index 116b7735ee9f..5a387a264201 100755 --- a/scripts/checksyscalls.sh +++ b/scripts/checksyscalls.sh @@ -202,15 +202,12 @@ EOF } syscall_list() { - grep '^[0-9]' "$1" | sort -n | ( + grep '^[0-9]' "$1" | sort -n | while read nr abi name entry ; do - cat < Date: Tue, 6 Jun 2017 16:15:28 +0900 Subject: kbuild: remove duplicated arch/*/include/generated/uapi include path Commit 90ac086bca10 ("Makefile: include arch/*/include/generated/uapi before .../generated") introduced this for bisect'ability. The commit chose to promote arch/*/include/generated/uapi in the search path rather than cleaning stale headers. After all, we found that approach was not enough, and ended up with cleaning stale headers by commit cda2c65f981d ("kbuild: Remove stale asm-generic wrappers"). So, the extra search path is no longer needed because Kbuild invokes scripts/Makefile.asm-generic and remove stale headers before it starts descending. This commit is also reverting commit dc33db7c338e ("Kbuild: avoid duplicate include path") because we have no more duplicated path. Signed-off-by: Masahiro Yamada --- Makefile | 6 ++---- 1 file changed, 2 insertions(+), 4 deletions(-) diff --git a/Makefile b/Makefile index 57a013dc0364..0afd7f3c22b2 100644 --- a/Makefile +++ b/Makefile @@ -381,12 +381,10 @@ USERINCLUDE := \ # Needed to be compatible with the O= option LINUXINCLUDE := \ -I$(srctree)/arch/$(hdr-arch)/include \ - -I$(objtree)/arch/$(hdr-arch)/include/generated/uapi \ -I$(objtree)/arch/$(hdr-arch)/include/generated \ $(if $(KBUILD_SRC), -I$(srctree)/include) \ - -I$(objtree)/include - -LINUXINCLUDE += $(filter-out $(LINUXINCLUDE),$(USERINCLUDE)) + -I$(objtree)/include \ + $(USERINCLUDE) KBUILD_CPPFLAGS := -D__KERNEL__ -- cgit v1.2.1 From bfb38988c51e440fd7062ddf3157f7d8b1dd5d70 Mon Sep 17 00:00:00 2001 From: Matthias Kaehlcke Date: Fri, 21 Apr 2017 14:39:30 -0700 Subject: kbuild: clang: Disable 'address-of-packed-member' warning clang generates plenty of these warnings in different parts of the code, to an extent that the warnings are little more than noise. Disable the 'address-of-packed-member' warning. Signed-off-by: Matthias Kaehlcke Reviewed-by: Douglas Anderson Signed-off-by: Masahiro Yamada --- Makefile | 1 + 1 file changed, 1 insertion(+) diff --git a/Makefile b/Makefile index 0afd7f3c22b2..58d7f9cc73ca 100644 --- a/Makefile +++ b/Makefile @@ -698,6 +698,7 @@ KBUILD_CPPFLAGS += $(call cc-option,-Qunused-arguments,) KBUILD_CFLAGS += $(call cc-disable-warning, unused-variable) KBUILD_CFLAGS += $(call cc-disable-warning, format-invalid-specifier) KBUILD_CFLAGS += $(call cc-disable-warning, gnu) +KBUILD_CFLAGS += $(call cc-disable-warning, address-of-packed-member) # Quiet clang warning: comparison of unsigned expression < 0 is always false KBUILD_CFLAGS += $(call cc-disable-warning, tautological-compare) # CLANG uses a _MergedGlobals as optimization, but this breaks modpost, as the -- cgit v1.2.1 From ae3f4151737d2aad271e5b1f2553c5d56e52850c Mon Sep 17 00:00:00 2001 From: Masahiro Yamada Date: Fri, 9 Jun 2017 17:29:52 +0900 Subject: kbuild: replace genhdr-y with generated-y Originally, generated-y and genhdr-y had different meaning, like follows: - generated-y: generated headers (other than asm-generic wrappers) - header-y : headers to be exported - genhdr-y : generated headers to be exported (generated-y + header-y) Since commit fcc8487d477a ("uapi: export all headers under uapi directories"), headers under UAPI directories are all exported. So, there is no more difference between generated-y and genhdr-y. We see two users of genhdr-y, arch/{arm,x86}/include/uapi/asm/Kbuild. They generate some headers in arch/{arm,x86}/include/generated/uapi/asm directories, which are obviously exported. Replace them with generated-y, and abolish genhdr-y. Signed-off-by: Masahiro Yamada Acked-by: Nicolas Dichtel --- Documentation/kbuild/makefiles.txt | 25 ++++++------------------- arch/arm/include/uapi/asm/Kbuild | 6 +++--- arch/x86/include/uapi/asm/Kbuild | 6 +++--- scripts/Makefile.asm-generic | 2 +- 4 files changed, 13 insertions(+), 26 deletions(-) diff --git a/Documentation/kbuild/makefiles.txt b/Documentation/kbuild/makefiles.txt index e18daca65ccd..1c49e87cea4f 100644 --- a/Documentation/kbuild/makefiles.txt +++ b/Documentation/kbuild/makefiles.txt @@ -45,10 +45,9 @@ This document describes the Linux kernel Makefiles. === 7 Kbuild syntax for exported headers --- 7.1 no-export-headers - --- 7.2 genhdr-y - --- 7.3 generic-y - --- 7.4 generated-y - --- 7.5 mandatory-y + --- 7.2 generic-y + --- 7.3 generated-y + --- 7.4 mandatory-y === 8 Kbuild Variables === 9 Makefile language @@ -1277,18 +1276,7 @@ See subsequent chapter for the syntax of the Kbuild file. avoid exporting specific headers (e.g. kvm.h) on architectures that do not support it. It should be avoided as much as possible. - --- 7.2 genhdr-y - - genhdr-y specifies asm files to be generated. - - Example: - #arch/x86/include/uapi/asm/Kbuild - genhdr-y += unistd_32.h - genhdr-y += unistd_64.h - genhdr-y += unistd_x32.h - - - --- 7.3 generic-y + --- 7.2 generic-y If an architecture uses a verbatim copy of a header from include/asm-generic then this is listed in the file @@ -1315,11 +1303,10 @@ See subsequent chapter for the syntax of the Kbuild file. Example: termios.h #include - --- 7.4 generated-y + --- 7.3 generated-y If an architecture generates other header files alongside generic-y - wrappers, and not included in genhdr-y, then generated-y specifies - them. + wrappers, generated-y specifies them. This prevents them being treated as stale asm-generic wrappers and removed. diff --git a/arch/arm/include/uapi/asm/Kbuild b/arch/arm/include/uapi/asm/Kbuild index 607f702c2d62..424935e4515d 100644 --- a/arch/arm/include/uapi/asm/Kbuild +++ b/arch/arm/include/uapi/asm/Kbuild @@ -1,6 +1,6 @@ # UAPI Header export list include include/uapi/asm-generic/Kbuild.asm -genhdr-y += unistd-common.h -genhdr-y += unistd-oabi.h -genhdr-y += unistd-eabi.h +generated-y += unistd-common.h +generated-y += unistd-oabi.h +generated-y += unistd-eabi.h diff --git a/arch/x86/include/uapi/asm/Kbuild b/arch/x86/include/uapi/asm/Kbuild index 83b6e9a0dce4..da1489cb64dc 100644 --- a/arch/x86/include/uapi/asm/Kbuild +++ b/arch/x86/include/uapi/asm/Kbuild @@ -1,6 +1,6 @@ # UAPI Header export list include include/uapi/asm-generic/Kbuild.asm -genhdr-y += unistd_32.h -genhdr-y += unistd_64.h -genhdr-y += unistd_x32.h +generated-y += unistd_32.h +generated-y += unistd_64.h +generated-y += unistd_x32.h diff --git a/scripts/Makefile.asm-generic b/scripts/Makefile.asm-generic index e4d017d53819..95f7d8090152 100644 --- a/scripts/Makefile.asm-generic +++ b/scripts/Makefile.asm-generic @@ -15,7 +15,7 @@ _dummy := $(shell [ -d $(obj) ] || mkdir -p $(obj)) # Stale wrappers when the corresponding files are removed from generic-y # need removing. -generated-y := $(generic-y) $(genhdr-y) $(generated-y) +generated-y := $(generic-y) $(generated-y) all-files := $(patsubst %, $(obj)/%, $(generated-y)) old-headers := $(wildcard $(obj)/*.h) unwanted := $(filter-out $(all-files),$(old-headers)) -- cgit v1.2.1 From 39a33ff80a259b2bddebb236549baee55f9b4f41 Mon Sep 17 00:00:00 2001 From: Masahiro Yamada Date: Mon, 19 Jun 2017 16:28:22 +0900 Subject: kbuild: remove cc-option-align Documentation/kbuild/makefiles.txt says the change for align options occurred at GCC 3.0, and Documentation/process/changes.rst says the minimal supported GCC version is 3.2, so it should be safe to hard-code -falign* options. Fix the only user arch/x86/Makefile_32.cpu and remove cc-option-align. Signed-off-by: Masahiro Yamada Acked-by: Ingo Molnar --- Documentation/kbuild/makefiles.txt | 16 ---------------- arch/x86/Makefile_32.cpu | 7 +++---- scripts/Kbuild.include | 5 ----- 3 files changed, 3 insertions(+), 25 deletions(-) diff --git a/Documentation/kbuild/makefiles.txt b/Documentation/kbuild/makefiles.txt index 1c49e87cea4f..247fb331c4b2 100644 --- a/Documentation/kbuild/makefiles.txt +++ b/Documentation/kbuild/makefiles.txt @@ -486,22 +486,6 @@ more details, with real examples. respectively. Note: cc-option-yn uses KBUILD_CFLAGS for $(CC) options - cc-option-align - gcc versions >= 3.0 changed the type of options used to specify - alignment of functions, loops etc. $(cc-option-align), when used - as prefix to the align options, will select the right prefix: - gcc < 3.00 - cc-option-align = -malign - gcc >= 3.00 - cc-option-align = -falign - - Example: - KBUILD_CFLAGS += $(cc-option-align)-functions=4 - - In the above example, the option -falign-functions=4 is used for - gcc >= 3.00. For gcc < 3.00, -malign-functions=4 is used. - Note: cc-option-align uses KBUILD_CFLAGS for $(CC) options - cc-disable-warning cc-disable-warning checks if gcc supports a given warning and returns the commandline switch to disable it. This special function is needed, diff --git a/arch/x86/Makefile_32.cpu b/arch/x86/Makefile_32.cpu index a45eb15b7cf2..f3717d36718a 100644 --- a/arch/x86/Makefile_32.cpu +++ b/arch/x86/Makefile_32.cpu @@ -9,7 +9,6 @@ else tune = $(call cc-option,-mcpu=$(1),$(2)) endif -align := $(cc-option-align) cflags-$(CONFIG_M486) += -march=i486 cflags-$(CONFIG_M586) += -march=i586 cflags-$(CONFIG_M586TSC) += -march=i586 @@ -24,11 +23,11 @@ cflags-$(CONFIG_MK6) += -march=k6 # They make zero difference whatsosever to performance at this time. cflags-$(CONFIG_MK7) += -march=athlon cflags-$(CONFIG_MK8) += $(call cc-option,-march=k8,-march=athlon) -cflags-$(CONFIG_MCRUSOE) += -march=i686 $(align)-functions=0 $(align)-jumps=0 $(align)-loops=0 -cflags-$(CONFIG_MEFFICEON) += -march=i686 $(call tune,pentium3) $(align)-functions=0 $(align)-jumps=0 $(align)-loops=0 +cflags-$(CONFIG_MCRUSOE) += -march=i686 -falign-functions=0 -falign-jumps=0 -falign-loops=0 +cflags-$(CONFIG_MEFFICEON) += -march=i686 $(call tune,pentium3) -falign-functions=0 -falign-jumps=0 -falign-loops=0 cflags-$(CONFIG_MWINCHIPC6) += $(call cc-option,-march=winchip-c6,-march=i586) cflags-$(CONFIG_MWINCHIP3D) += $(call cc-option,-march=winchip2,-march=i586) -cflags-$(CONFIG_MCYRIXIII) += $(call cc-option,-march=c3,-march=i486) $(align)-functions=0 $(align)-jumps=0 $(align)-loops=0 +cflags-$(CONFIG_MCYRIXIII) += $(call cc-option,-march=c3,-march=i486) -falign-functions=0 -falign-jumps=0 -falign-loops=0 cflags-$(CONFIG_MVIAC3_2) += $(call cc-option,-march=c3-2,-march=i686) cflags-$(CONFIG_MVIAC7) += -march=i686 cflags-$(CONFIG_MCORE2) += -march=i686 $(call tune,core2) diff --git a/scripts/Kbuild.include b/scripts/Kbuild.include index 61f87a99bf0a..53b7d47ce43a 100644 --- a/scripts/Kbuild.include +++ b/scripts/Kbuild.include @@ -123,11 +123,6 @@ cc-option = $(call try-run,\ cc-option-yn = $(call try-run,\ $(CC) -Werror $(KBUILD_CPPFLAGS) $(CC_OPTION_CFLAGS) $(1) -c -x c /dev/null -o "$$TMP",y,n) -# cc-option-align -# Prefix align with either -falign or -malign -cc-option-align = $(subst -functions=0,,\ - $(call cc-option,-falign-functions=0,-malign-functions=0)) - # cc-disable-warning # Usage: cflags-y += $(call cc-disable-warning,unused-but-set-variable) cc-disable-warning = $(call try-run,\ -- cgit v1.2.1 From 9f3f1fd299768782465cb32cdf0dd4528d11f26b Mon Sep 17 00:00:00 2001 From: Matthias Kaehlcke Date: Wed, 21 Jun 2017 16:28:03 -0700 Subject: kbuild: Add __cc-option macro cc-option uses KBUILD_CFLAGS and KBUILD_CPPFLAGS when it determines whether an option is supported or not. This is fine for options used to build the kernel itself, however some components like the x86 boot code use a different set of flags. Add the new macro __cc-option which is a more generic version of cc-option with additional parameters. One parameter is the compiler with which the check should be performed, the other the compiler options to be used instead KBUILD_C*FLAGS. Refactor cc-option and hostcc-option to use __cc-option and move hostcc-option to scripts/Kbuild.include. Suggested-by: Arnd Bergmann Suggested-by: Masahiro Yamada Signed-off-by: Matthias Kaehlcke Acked-by: Arnd Bergmann Acked-by: Michal Marek Signed-off-by: Masahiro Yamada --- Makefile | 2 +- scripts/Kbuild.include | 14 ++++++++++++-- scripts/Makefile.host | 6 ------ 3 files changed, 13 insertions(+), 9 deletions(-) diff --git a/Makefile b/Makefile index 58d7f9cc73ca..4d50f0546637 100644 --- a/Makefile +++ b/Makefile @@ -296,7 +296,7 @@ CONFIG_SHELL := $(shell if [ -x "$$BASH" ]; then echo $$BASH; \ HOSTCC = gcc HOSTCXX = g++ -HOSTCFLAGS = -Wall -Wmissing-prototypes -Wstrict-prototypes -O2 -fomit-frame-pointer -std=gnu89 +HOSTCFLAGS := -Wall -Wmissing-prototypes -Wstrict-prototypes -O2 -fomit-frame-pointer -std=gnu89 HOSTCXXFLAGS = -O2 ifeq ($(shell $(HOSTCC) -v 2>&1 | grep -c "clang version"), 1) diff --git a/scripts/Kbuild.include b/scripts/Kbuild.include index 53b7d47ce43a..dd8e2dde0b34 100644 --- a/scripts/Kbuild.include +++ b/scripts/Kbuild.include @@ -108,6 +108,11 @@ as-option = $(call try-run,\ as-instr = $(call try-run,\ printf "%b\n" "$(1)" | $(CC) $(KBUILD_AFLAGS) -c -x assembler -o "$$TMP" -,$(2),$(3)) +# __cc-option +# Usage: MY_CFLAGS += $(call __cc-option,$(CC),$(MY_CFLAGS),-march=winchip-c6,-march=i586) +__cc-option = $(call try-run,\ + $(1) -Werror $(2) $(3) -c -x c /dev/null -o "$$TMP",$(3),$(4)) + # Do not attempt to build with gcc plugins during cc-option tests. # (And this uses delayed resolution so the flags will be up to date.) CC_OPTION_CFLAGS = $(filter-out $(GCC_PLUGINS_CFLAGS),$(KBUILD_CFLAGS)) @@ -115,8 +120,13 @@ CC_OPTION_CFLAGS = $(filter-out $(GCC_PLUGINS_CFLAGS),$(KBUILD_CFLAGS)) # cc-option # Usage: cflags-y += $(call cc-option,-march=winchip-c6,-march=i586) -cc-option = $(call try-run,\ - $(CC) -Werror $(KBUILD_CPPFLAGS) $(CC_OPTION_CFLAGS) $(1) -c -x c /dev/null -o "$$TMP",$(1),$(2)) +cc-option = $(call __cc-option, $(CC),\ + $(KBUILD_CPPFLAGS) $(CC_OPTION_CFLAGS),$(1),$(2)) + +# hostcc-option +# Usage: cflags-y += $(call hostcc-option,-march=winchip-c6,-march=i586) +hostcc-option = $(call __cc-option, $(HOSTCC),\ + $(HOSTCFLAGS) $(HOST_EXTRACFLAGS),$(1),$(2)) # cc-option-yn # Usage: flag := $(call cc-option-yn,-march=winchip-c6) diff --git a/scripts/Makefile.host b/scripts/Makefile.host index 45b5b1aaedbd..9cfd5c84d76f 100644 --- a/scripts/Makefile.host +++ b/scripts/Makefile.host @@ -20,12 +20,6 @@ # Will compile qconf as a C++ program, and menu as a C program. # They are linked as C++ code to the executable qconf -# hostcc-option -# Usage: cflags-y += $(call hostcc-option,-march=winchip-c6,-march=i586) - -hostcc-option = $(call try-run,\ - $(HOSTCC) $(HOSTCFLAGS) $(HOST_EXTRACFLAGS) $(1) -c -x c /dev/null -o "$$TMP",$(1),$(2)) - __hostprogs := $(sort $(hostprogs-y) $(hostprogs-m)) host-cshlib := $(sort $(hostlibs-y) $(hostlibs-m)) host-cxxshlib := $(sort $(hostcxxlibs-y) $(hostcxxlibs-m)) -- cgit v1.2.1 From 032a2c4f65a2f81c93e161a11197ba19bc14a909 Mon Sep 17 00:00:00 2001 From: Matthias Kaehlcke Date: Wed, 21 Jun 2017 16:28:04 -0700 Subject: x86/build: Use __cc-option for boot code compiler options cc-option is used to enable compiler options for the boot code if they are available. The macro uses KBUILD_CFLAGS and KBUILD_CPPFLAGS for the check, however these flags aren't used to build the boot code, in consequence cc-option can yield wrong results. For example -mpreferred-stack-boundary=2 is never set with a 64-bit compiler, since the setting is only valid for 16 and 32-bit binaries. This is also the case for 32-bit kernel builds, because the option -m32 is added to KBUILD_CFLAGS after the assignment of REALMODE_CFLAGS. Use __cc-option instead of cc-option for the boot mode options. The macro receives the compiler options as parameter instead of using KBUILD_C*FLAGS, for the boot code we pass REALMODE_CFLAGS. Also use separate statements for the __cc-option checks instead of performing them in the initial assignment of REALMODE_CFLAGS since the variable is an input of the macro. Signed-off-by: Matthias Kaehlcke Acked-by: Ingo Molnar Signed-off-by: Masahiro Yamada --- arch/x86/Makefile | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-) diff --git a/arch/x86/Makefile b/arch/x86/Makefile index 5851411e60fb..f1791addf7fc 100644 --- a/arch/x86/Makefile +++ b/arch/x86/Makefile @@ -24,10 +24,11 @@ REALMODE_CFLAGS := $(M16_CFLAGS) -g -Os -D__KERNEL__ \ -DDISABLE_BRANCH_PROFILING \ -Wall -Wstrict-prototypes -march=i386 -mregparm=3 \ -fno-strict-aliasing -fomit-frame-pointer -fno-pic \ - -mno-mmx -mno-sse \ - $(call cc-option, -ffreestanding) \ - $(call cc-option, -fno-stack-protector) \ - $(call cc-option, -mpreferred-stack-boundary=2) + -mno-mmx -mno-sse + +REALMODE_CFLAGS += $(call __cc-option, $(CC), $(REALMODE_CFLAGS), -ffreestanding) +REALMODE_CFLAGS += $(call __cc-option, $(CC), $(REALMODE_CFLAGS), -fno-stack-protector) +REALMODE_CFLAGS += $(call __cc-option, $(CC), $(REALMODE_CFLAGS), -mpreferred-stack-boundary=2) export REALMODE_CFLAGS # BITS is used as extension for files which are available in a 32 bit -- cgit v1.2.1 From d77698df39a512911586834d303275ea5fda74d0 Mon Sep 17 00:00:00 2001 From: Matthias Kaehlcke Date: Wed, 21 Jun 2017 16:28:05 -0700 Subject: x86/build: Specify stack alignment for clang For gcc stack alignment is configured with -mpreferred-stack-boundary=N, clang has the option -mstack-alignment=N for that purpose. Use the same alignment as with gcc. If the alignment is not specified clang assumes an alignment of 16 bytes, as required by the standard ABI. However as mentioned in d9b0cde91c60 ("x86-64, gcc: Use -mpreferred-stack-boundary=3 if supported") the standard kernel entry on x86-64 leaves the stack on an 8-byte boundary, as a consequence clang will keep the stack misaligned. Signed-off-by: Matthias Kaehlcke Acked-by: Ingo Molnar Signed-off-by: Masahiro Yamada --- arch/x86/Makefile | 26 +++++++++++++++++++++----- 1 file changed, 21 insertions(+), 5 deletions(-) diff --git a/arch/x86/Makefile b/arch/x86/Makefile index f1791addf7fc..d56318ba7ca5 100644 --- a/arch/x86/Makefile +++ b/arch/x86/Makefile @@ -11,6 +11,14 @@ else KBUILD_DEFCONFIG := $(ARCH)_defconfig endif +# For gcc stack alignment is specified with -mpreferred-stack-boundary, +# clang has the option -mstack-alignment for that purpose. +ifneq ($(call cc-option, -mpreferred-stack-boundary=4),) + cc_stack_align_opt := -mpreferred-stack-boundary +else ifneq ($(call cc-option, -mstack-alignment=4),) + cc_stack_align_opt := -mstack-alignment +endif + # How to compile the 16-bit code. Note we always compile for -march=i386; # that way we can complain to the user if the CPU is insufficient. # @@ -28,7 +36,7 @@ REALMODE_CFLAGS := $(M16_CFLAGS) -g -Os -D__KERNEL__ \ REALMODE_CFLAGS += $(call __cc-option, $(CC), $(REALMODE_CFLAGS), -ffreestanding) REALMODE_CFLAGS += $(call __cc-option, $(CC), $(REALMODE_CFLAGS), -fno-stack-protector) -REALMODE_CFLAGS += $(call __cc-option, $(CC), $(REALMODE_CFLAGS), -mpreferred-stack-boundary=2) +REALMODE_CFLAGS += $(call __cc-option, $(CC), $(REALMODE_CFLAGS), $(cc_stack_align_opt)=2) export REALMODE_CFLAGS # BITS is used as extension for files which are available in a 32 bit @@ -65,8 +73,10 @@ ifeq ($(CONFIG_X86_32),y) # with nonstandard options KBUILD_CFLAGS += -fno-pic - # prevent gcc from keeping the stack 16 byte aligned - KBUILD_CFLAGS += $(call cc-option,-mpreferred-stack-boundary=2) + # Align the stack to the register width instead of using the default + # alignment of 16 bytes. This reduces stack usage and the number of + # alignment instructions. + KBUILD_CFLAGS += $(call cc-option,$(cc_stack_align_opt)=2) # Disable unit-at-a-time mode on pre-gcc-4.0 compilers, it makes gcc use # a lot more stack due to the lack of sharing of stacklots: @@ -98,8 +108,14 @@ else KBUILD_CFLAGS += $(call cc-option,-mno-80387) KBUILD_CFLAGS += $(call cc-option,-mno-fp-ret-in-387) - # Use -mpreferred-stack-boundary=3 if supported. - KBUILD_CFLAGS += $(call cc-option,-mpreferred-stack-boundary=3) + # By default gcc and clang use a stack alignment of 16 bytes for x86. + # However the standard kernel entry on x86-64 leaves the stack on an + # 8-byte boundary. If the compiler isn't informed about the actual + # alignment it will generate extra alignment instructions for the + # default alignment which keep the stack *mis*aligned. + # Furthermore an alignment to the register width reduces stack usage + # and the number of alignment instructions. + KBUILD_CFLAGS += $(call cc-option,$(cc_stack_align_opt)=3) # Use -mskip-rax-setup if supported. KBUILD_CFLAGS += $(call cc-option,-mskip-rax-setup) -- cgit v1.2.1 From c4e6fff1ae5729c2af159008b13fca39fbbac70e Mon Sep 17 00:00:00 2001 From: Cao jin Date: Fri, 30 Jun 2017 10:45:43 +0800 Subject: kbuild: improve comments on KBUILD_SRC Original comments is confusing on "OBJ directory", make it clear. Bonus: move comments close to what it wants to comment. Signed-off-by: Cao jin Signed-off-by: Masahiro Yamada --- Makefile | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/Makefile b/Makefile index 4d50f0546637..41ed3062337b 100644 --- a/Makefile +++ b/Makefile @@ -106,8 +106,8 @@ export quiet Q KBUILD_VERBOSE # The O= assignment takes precedence over the KBUILD_OUTPUT environment # variable. -# KBUILD_SRC is set on invocation of make in OBJ directory -# KBUILD_SRC is not intended to be used by the regular user (for now) +# KBUILD_SRC is not intended to be used by the regular user (for now), +# it is set on invocation of make with KBUILD_OUTPUT or O= specified. ifeq ($(KBUILD_SRC),) # OK, Make called in directory where kernel src resides @@ -128,7 +128,6 @@ ifneq ($(words $(subst :, ,$(CURDIR))), 1) endif ifneq ($(KBUILD_OUTPUT),) -# Invoke a second make in the output directory, passing relevant variables # check that the output directory actually exists saved-output := $(KBUILD_OUTPUT) KBUILD_OUTPUT := $(shell mkdir -p $(KBUILD_OUTPUT) && cd $(KBUILD_OUTPUT) \ @@ -141,6 +140,7 @@ PHONY += $(MAKECMDGOALS) sub-make $(filter-out _all sub-make $(CURDIR)/Makefile, $(MAKECMDGOALS)) _all: sub-make @: +# Invoke a second make in the output directory, passing relevant variables sub-make: $(Q)$(MAKE) -C $(KBUILD_OUTPUT) KBUILD_SRC=$(CURDIR) \ -f $(CURDIR)/Makefile $(filter-out _all sub-make,$(MAKECMDGOALS)) -- cgit v1.2.1