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Fully stripping the vDSO has other unfortunate side effects: - binutils is unable to find ELF notes without a SHT_NOTE section. - Even elfutils has trouble: it can find ELF notes without a section table at all, but if a section table is present, it won't look for PT_NOTE. - gdb wants section names to match between stripped DSOs and their symbols; otherwise it will corrupt symbol addresses. We're also breaking the rules: section 0 is supposed to be SHT_NULL. Fix these problems by building a better fake section table. While we're at it, we might as well let buggy Go versions keep working well by giving the SHT_DYNSYM entry the correct size. This is a bit unfortunate: it adds quite a bit of size to the vdso image. If/when binutils improves and the improved versions become widespread, it would be worth considering dropping most of this. Signed-off-by: Andy Lutomirski <luto@amacapital.net> Link: http://lkml.kernel.org/r/0e546a5eeaafdf1840e6ee654a55c1e727c26663.1403129369.git.luto@amacapital.net Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
193 lines
5.7 KiB
Makefile
193 lines
5.7 KiB
Makefile
#
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# Building vDSO images for x86.
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#
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KBUILD_CFLAGS += $(DISABLE_LTO)
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VDSO64-$(CONFIG_X86_64) := y
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VDSOX32-$(CONFIG_X86_X32_ABI) := y
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VDSO32-$(CONFIG_X86_32) := y
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VDSO32-$(CONFIG_COMPAT) := y
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# files to link into the vdso
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vobjs-y := vdso-note.o vclock_gettime.o vgetcpu.o vdso-fakesections.o
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# files to link into kernel
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obj-y += vma.o
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# vDSO images to build
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vdso_img-$(VDSO64-y) += 64
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vdso_img-$(VDSOX32-y) += x32
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vdso_img-$(VDSO32-y) += 32-int80
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vdso_img-$(CONFIG_COMPAT) += 32-syscall
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vdso_img-$(VDSO32-y) += 32-sysenter
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obj-$(VDSO32-y) += vdso32-setup.o
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vobjs := $(foreach F,$(vobjs-y),$(obj)/$F)
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$(obj)/vdso.o: $(obj)/vdso.so
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targets += vdso.lds $(vobjs-y)
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# Build the vDSO image C files and link them in.
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vdso_img_objs := $(vdso_img-y:%=vdso-image-%.o)
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vdso_img_cfiles := $(vdso_img-y:%=vdso-image-%.c)
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vdso_img_sodbg := $(vdso_img-y:%=vdso%.so.dbg)
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obj-y += $(vdso_img_objs)
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targets += $(vdso_img_cfiles)
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targets += $(vdso_img_sodbg)
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.SECONDARY: $(vdso_img-y:%=$(obj)/vdso-image-%.c)
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export CPPFLAGS_vdso.lds += -P -C
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VDSO_LDFLAGS_vdso.lds = -m64 -Wl,-soname=linux-vdso.so.1 \
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-Wl,--no-undefined \
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-Wl,-z,max-page-size=4096 -Wl,-z,common-page-size=4096 \
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$(DISABLE_LTO)
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$(obj)/vdso64.so.dbg: $(src)/vdso.lds $(vobjs) FORCE
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$(call if_changed,vdso)
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HOST_EXTRACFLAGS += -I$(srctree)/tools/include
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hostprogs-y += vdso2c
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quiet_cmd_vdso2c = VDSO2C $@
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define cmd_vdso2c
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$(obj)/vdso2c $< $@
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endef
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$(obj)/vdso-image-%.c: $(obj)/vdso%.so.dbg $(obj)/vdso2c FORCE
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$(call if_changed,vdso2c)
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#
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# Don't omit frame pointers for ease of userspace debugging, but do
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# optimize sibling calls.
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#
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CFL := $(PROFILING) -mcmodel=small -fPIC -O2 -fasynchronous-unwind-tables -m64 \
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$(filter -g%,$(KBUILD_CFLAGS)) $(call cc-option, -fno-stack-protector) \
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-fno-omit-frame-pointer -foptimize-sibling-calls
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$(vobjs): KBUILD_CFLAGS += $(CFL)
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#
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# vDSO code runs in userspace and -pg doesn't help with profiling anyway.
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#
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CFLAGS_REMOVE_vdso-note.o = -pg
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CFLAGS_REMOVE_vclock_gettime.o = -pg
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CFLAGS_REMOVE_vgetcpu.o = -pg
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CFLAGS_REMOVE_vvar.o = -pg
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#
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# X32 processes use x32 vDSO to access 64bit kernel data.
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#
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# Build x32 vDSO image:
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# 1. Compile x32 vDSO as 64bit.
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# 2. Convert object files to x32.
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# 3. Build x32 VDSO image with x32 objects, which contains 64bit codes
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# so that it can reach 64bit address space with 64bit pointers.
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#
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CPPFLAGS_vdsox32.lds = $(CPPFLAGS_vdso.lds)
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VDSO_LDFLAGS_vdsox32.lds = -Wl,-m,elf32_x86_64 \
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-Wl,-soname=linux-vdso.so.1 \
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-Wl,-z,max-page-size=4096 \
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-Wl,-z,common-page-size=4096
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# 64-bit objects to re-brand as x32
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vobjs64-for-x32 := $(filter-out $(vobjs-nox32),$(vobjs-y))
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# x32-rebranded versions
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vobjx32s-y := $(vobjs64-for-x32:.o=-x32.o)
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# same thing, but in the output directory
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vobjx32s := $(foreach F,$(vobjx32s-y),$(obj)/$F)
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# Convert 64bit object file to x32 for x32 vDSO.
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quiet_cmd_x32 = X32 $@
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cmd_x32 = $(OBJCOPY) -O elf32-x86-64 $< $@
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$(obj)/%-x32.o: $(obj)/%.o FORCE
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$(call if_changed,x32)
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targets += vdsox32.lds $(vobjx32s-y)
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$(obj)/vdsox32.so.dbg: $(src)/vdsox32.lds $(vobjx32s) FORCE
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$(call if_changed,vdso)
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#
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# Build multiple 32-bit vDSO images to choose from at boot time.
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#
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vdso32.so-$(VDSO32-y) += int80
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vdso32.so-$(CONFIG_COMPAT) += syscall
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vdso32.so-$(VDSO32-y) += sysenter
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vdso32-images = $(vdso32.so-y:%=vdso32-%.so)
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CPPFLAGS_vdso32.lds = $(CPPFLAGS_vdso.lds)
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VDSO_LDFLAGS_vdso32.lds = -m32 -Wl,-m,elf_i386 -Wl,-soname=linux-gate.so.1
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# This makes sure the $(obj) subdirectory exists even though vdso32/
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# is not a kbuild sub-make subdirectory.
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override obj-dirs = $(dir $(obj)) $(obj)/vdso32/
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targets += vdso32/vdso32.lds
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targets += vdso32/note.o vdso32/vclock_gettime.o $(vdso32.so-y:%=vdso32/%.o)
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targets += vdso32/vclock_gettime.o vdso32/vdso-fakesections.o
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$(obj)/vdso32.o: $(vdso32-images:%=$(obj)/%)
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KBUILD_AFLAGS_32 := $(filter-out -m64,$(KBUILD_AFLAGS))
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$(vdso32-images:%=$(obj)/%.dbg): KBUILD_AFLAGS = $(KBUILD_AFLAGS_32)
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$(vdso32-images:%=$(obj)/%.dbg): asflags-$(CONFIG_X86_64) += -m32
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KBUILD_CFLAGS_32 := $(filter-out -m64,$(KBUILD_CFLAGS))
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KBUILD_CFLAGS_32 := $(filter-out -mcmodel=kernel,$(KBUILD_CFLAGS_32))
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KBUILD_CFLAGS_32 := $(filter-out -fno-pic,$(KBUILD_CFLAGS_32))
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KBUILD_CFLAGS_32 := $(filter-out -mfentry,$(KBUILD_CFLAGS_32))
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KBUILD_CFLAGS_32 += -m32 -msoft-float -mregparm=0 -fpic
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KBUILD_CFLAGS_32 += $(call cc-option, -fno-stack-protector)
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KBUILD_CFLAGS_32 += $(call cc-option, -foptimize-sibling-calls)
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KBUILD_CFLAGS_32 += -fno-omit-frame-pointer
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$(vdso32-images:%=$(obj)/%.dbg): KBUILD_CFLAGS = $(KBUILD_CFLAGS_32)
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$(vdso32-images:%=$(obj)/%.dbg): $(obj)/vdso32-%.so.dbg: FORCE \
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$(obj)/vdso32/vdso32.lds \
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$(obj)/vdso32/vclock_gettime.o \
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$(obj)/vdso32/vdso-fakesections.o \
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$(obj)/vdso32/note.o \
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$(obj)/vdso32/%.o
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$(call if_changed,vdso)
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#
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# The DSO images are built using a special linker script.
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#
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quiet_cmd_vdso = VDSO $@
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cmd_vdso = $(CC) -nostdlib -o $@ \
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$(VDSO_LDFLAGS) $(VDSO_LDFLAGS_$(filter %.lds,$(^F))) \
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-Wl,-T,$(filter %.lds,$^) $(filter %.o,$^) && \
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sh $(srctree)/$(src)/checkundef.sh '$(NM)' '$@'
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VDSO_LDFLAGS = -fPIC -shared $(call cc-ldoption, -Wl$(comma)--hash-style=sysv) \
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-Wl,-Bsymbolic $(LTO_CFLAGS)
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GCOV_PROFILE := n
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#
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# Install the unstripped copies of vdso*.so.
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#
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quiet_cmd_vdso_install = INSTALL $(@:install_%=%)
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cmd_vdso_install = cp $< $(MODLIB)/vdso/$(@:install_%=%)
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vdso_img_insttargets := $(vdso_img_sodbg:%.dbg=install_%)
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$(MODLIB)/vdso: FORCE
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@mkdir -p $(MODLIB)/vdso
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$(vdso_img_insttargets): install_%: $(obj)/%.dbg $(MODLIB)/vdso FORCE
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$(call cmd,vdso_install)
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PHONY += vdso_install $(vdso_img_insttargets)
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vdso_install: $(vdso_img_insttargets) FORCE
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clean-files := vdso32-syscall* vdso32-sysenter* vdso32-int80*
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