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Message-Id: <20160407231143.0482c1a67c1d98cc3ccdfad8@gmail.com> Date: Thu, 7 Apr 2016 23:11:43 +0200 From: Emese Revfy <re.emese@...il.com> To: linux-kbuild@...r.kernel.org Cc: pageexec@...email.hu, spender@...ecurity.net, kernel-hardening@...ts.openwall.com, mmarek@...e.com, keescook@...omium.org, linux@...musvillemoes.dk, fengguang.wu@...el.com, dvyukov@...gle.com, linux-kernel@...r.kernel.org, david.brown@...aro.org, yamada.masahiro@...ionext.com Subject: [PATCH v6 1/6] Shared library support Infrastructure for building independent shared library targets. This effectively also reverts commit 62e2210798ed38928ab24841e8b4878a (Masahiro Yamada, kbuild: drop shared library support from Makefile.host). Signed-off-by: Emese Revfy <re.emese@...il.com> --- Documentation/kbuild/makefiles.txt | 39 ++++++++++++++++----- scripts/Makefile.build | 2 +- scripts/Makefile.clean | 3 +- scripts/Makefile.host | 70 +++++++++++++++++++++++++++++++++++++- 4 files changed, 103 insertions(+), 11 deletions(-) diff --git a/Documentation/kbuild/makefiles.txt b/Documentation/kbuild/makefiles.txt index 13f888a..250729b 100644 --- a/Documentation/kbuild/makefiles.txt +++ b/Documentation/kbuild/makefiles.txt @@ -23,10 +23,11 @@ This document describes the Linux kernel Makefiles. === 4 Host Program support --- 4.1 Simple Host Program --- 4.2 Composite Host Programs - --- 4.3 Using C++ for host programs - --- 4.4 Controlling compiler options for host programs - --- 4.5 When host programs are actually built - --- 4.6 Using hostprogs-$(CONFIG_FOO) + --- 4.3 Defining shared libraries + --- 4.4 Using C++ for host programs + --- 4.5 Controlling compiler options for host programs + --- 4.6 When host programs are actually built + --- 4.7 Using hostprogs-$(CONFIG_FOO) === 5 Kbuild clean infrastructure @@ -643,7 +644,29 @@ Both possibilities are described in the following. Finally, the two .o files are linked to the executable, lxdialog. Note: The syntax <executable>-y is not permitted for host-programs. ---- 4.3 Using C++ for host programs +--- 4.3 Defining shared libraries + + Objects with extension .so are considered shared libraries, and + will be compiled as position independent objects. + Kbuild provides support for shared libraries, but the usage + shall be restricted. + In the following example the libkconfig.so shared library is used + to link the executable conf. + + Example: + #scripts/kconfig/Makefile + hostprogs-y := conf + conf-objs := conf.o libkconfig.so + libkconfig-objs := expr.o type.o + + Shared libraries always require a corresponding -objs line, and + in the example above the shared library libkconfig is composed by + the two objects expr.o and type.o. + expr.o and type.o will be built as position independent code and + linked as a shared library libkconfig.so. C++ is not supported for + shared libraries. + +--- 4.4 Using C++ for host programs kbuild offers support for host programs written in C++. This was introduced solely to support kconfig, and is not recommended @@ -666,7 +689,7 @@ Both possibilities are described in the following. qconf-cxxobjs := qconf.o qconf-objs := check.o ---- 4.4 Controlling compiler options for host programs +--- 4.5 Controlling compiler options for host programs When compiling host programs, it is possible to set specific flags. The programs will always be compiled utilising $(HOSTCC) passed @@ -694,7 +717,7 @@ Both possibilities are described in the following. When linking qconf, it will be passed the extra option "-L$(QTDIR)/lib". ---- 4.5 When host programs are actually built +--- 4.6 When host programs are actually built Kbuild will only build host-programs when they are referenced as a prerequisite. @@ -725,7 +748,7 @@ Both possibilities are described in the following. This will tell kbuild to build lxdialog even if not referenced in any rule. ---- 4.6 Using hostprogs-$(CONFIG_FOO) +--- 4.7 Using hostprogs-$(CONFIG_FOO) A typical pattern in a Kbuild file looks like this: diff --git a/scripts/Makefile.build b/scripts/Makefile.build index e1bc190..b2ce235 100644 --- a/scripts/Makefile.build +++ b/scripts/Makefile.build @@ -60,7 +60,7 @@ endif endif # Do not include host rules unless needed -ifneq ($(hostprogs-y)$(hostprogs-m),) +ifneq ($(hostprogs-y)$(hostprogs-m)$(hostlibs-y)$(hostlibs-m)$(hostcxxlibs-y)$(hostcxxlibs-m),) include scripts/Makefile.host endif diff --git a/scripts/Makefile.clean b/scripts/Makefile.clean index 55c96cb..e4e88ab 100644 --- a/scripts/Makefile.clean +++ b/scripts/Makefile.clean @@ -38,7 +38,8 @@ subdir-ymn := $(addprefix $(obj)/,$(subdir-ymn)) __clean-files := $(extra-y) $(extra-m) $(extra-) \ $(always) $(targets) $(clean-files) \ $(host-progs) \ - $(hostprogs-y) $(hostprogs-m) $(hostprogs-) + $(hostprogs-y) $(hostprogs-m) $(hostprogs-) \ + $(hostlibs-y) $(hostlibs-m) $(hostlibs-) __clean-files := $(filter-out $(no-clean-files), $(__clean-files)) diff --git a/scripts/Makefile.host b/scripts/Makefile.host index 133edfa..3439bd8 100644 --- a/scripts/Makefile.host +++ b/scripts/Makefile.host @@ -20,7 +20,25 @@ # Will compile qconf as a C++ program, and menu as a C program. # They are linked as C++ code to the executable qconf +# hostprogs-y := conf +# conf-objs := conf.o libkconfig.so +# libkconfig-objs := expr.o type.o +# Will create a shared library named libkconfig.so that consists of +# expr.o and type.o (they are both compiled as C code and the object files +# are made as position independent code). +# conf.c is compiled as a C program, and conf.o is linked together with +# libkconfig.so as the executable conf. +# Note: Shared libraries consisting of C++ files are not supported + +# 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)) +__hostlibs := $(sort $(hostlibs-y) $(hostlibs-m)) +__hostcxxlibs := $(sort $(hostcxxlibs-y) $(hostcxxlibs-m)) # C code # Executables compiled from a single .c file @@ -42,6 +60,18 @@ host-cxxmulti := $(foreach m,$(__hostprogs),$(if $($(m)-cxxobjs),$(m))) # C++ Object (.o) files compiled from .cc files host-cxxobjs := $(sort $(foreach m,$(host-cxxmulti),$($(m)-cxxobjs))) +# Shared libaries (only .c supported) +# Shared libraries (.so) - all .so files referenced in "xxx-objs" +host-cshlib := $(sort $(filter %.so, $(__hostlibs))) +host-cxxshlib := $(sort $(filter %.so, $(__hostcxxlibs))) +# Remove .so files from "xxx-objs" +host-cobjs := $(filter-out %.so,$(host-cobjs)) +host-cxxobjs := $(filter-out %.so,$(host-cxxobjs)) + +# Object (.o) files used by the shared libaries +host-cshobjs := $(sort $(foreach m,$(host-cshlib),$($(m:.so=-objs)))) +host-cxxshobjs := $(sort $(foreach m,$(host-cxxshlib),$($(m:.so=-objs)))) + # output directory for programs/.o files # hostprogs-y := tools/build may have been specified. # Retrieve also directory of .o files from prog-objs or prog-cxxobjs notation @@ -56,6 +86,10 @@ host-cmulti := $(addprefix $(obj)/,$(host-cmulti)) host-cobjs := $(addprefix $(obj)/,$(host-cobjs)) host-cxxmulti := $(addprefix $(obj)/,$(host-cxxmulti)) host-cxxobjs := $(addprefix $(obj)/,$(host-cxxobjs)) +host-cshlib := $(addprefix $(obj)/,$(host-cshlib)) +host-cxxshlib := $(addprefix $(obj)/,$(host-cxxshlib)) +host-cshobjs := $(addprefix $(obj)/,$(host-cshobjs)) +host-cxxshobjs := $(addprefix $(obj)/,$(host-cxxshobjs)) host-objdirs := $(addprefix $(obj)/,$(host-objdirs)) obj-dirs += $(host-objdirs) @@ -124,5 +158,39 @@ quiet_cmd_host-cxxobjs = HOSTCXX $@ $(host-cxxobjs): $(obj)/%.o: $(src)/%.cc FORCE $(call if_changed_dep,host-cxxobjs) +# Compile .c file, create position independent .o file +# host-cshobjs -> .o +quiet_cmd_host-cshobjs = HOSTCC -fPIC $@ + cmd_host-cshobjs = $(HOSTCC) $(hostc_flags) -fPIC -c -o $@ $< +$(host-cshobjs): $(obj)/%.o: $(src)/%.c FORCE + $(call if_changed_dep,host-cshobjs) + +# Compile .c file, create position independent .o file +# host-cxxshobjs -> .o +quiet_cmd_host-cxxshobjs = HOSTCXX -fPIC $@ + cmd_host-cxxshobjs = $(HOSTCXX) $(hostcxx_flags) -fPIC -c -o $@ $< +$(host-cxxshobjs): $(obj)/%.o: $(src)/%.c FORCE + $(call if_changed_dep,host-cxxshobjs) + +# Link a shared library, based on position independent .o files +# *.o -> .so shared library (host-cshlib) +quiet_cmd_host-cshlib = HOSTLLD -shared $@ + cmd_host-cshlib = $(HOSTCC) $(HOSTLDFLAGS) -shared -o $@ \ + $(addprefix $(obj)/,$($(@F:.so=-objs))) \ + $(HOST_LOADLIBES) $(HOSTLOADLIBES_$(@F)) +$(host-cshlib): FORCE + $(call if_changed,host-cshlib) +$(call multi_depend, $(host-cshlib), .so, -objs -cshobjs) + +# Link a shared library, based on position independent .o files +# *.o -> .so shared library (host-cxxshlib) +quiet_cmd_host-cxxshlib = HOSTLLD -shared $@ + cmd_host-cxxshlib = $(HOSTCXX) $(HOSTLDFLAGS) -shared -o $@ \ + $(addprefix $(obj)/,$($(@F:.so=-objs))) \ + $(HOST_LOADLIBES) $(HOSTLOADLIBES_$(@F)) +$(host-cxxshlib): FORCE + $(call if_changed,host-cxxshlib) +$(call multi_depend, $(host-cxxshlib), .so, -objs -cxxshobjs) + targets += $(host-csingle) $(host-cmulti) $(host-cobjs)\ - $(host-cxxmulti) $(host-cxxobjs) + $(host-cxxmulti) $(host-cxxobjs) $(host-cshlib) $(host-cshobjs) $(host-cxxshlib) $(host-cxxshobjs) -- 2.4.1
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