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d2b30cd4b7
When using a toolchain with gold as the default linker, the VDSO build fails: VDSO arch/arm/vdso/vdso.so.raw HOSTCC arch/arm/vdso/vdsomunge MUNGE arch/arm/vdso/vdso.so.dbg OBJCOPY arch/arm/vdso/vdso.so BFD: arch/arm/vdso/vdso.so: Not enough room for program headers, try linking with -N For whatever reason, ld.gold is omitting an exidx program header that ld.bfd emits, and even when I work around that, I don't get a working VDSO. For now, instead of supporting gold (which will fail to link the kernel anyway since it does not implement --pic-veneer), direct the compiler to use the traditional bfd linker. This is accomplished by using -fuse-ld, which is implemented in GCC 4.8 and later. Note: one limitation of this is that if the toolchain is configured to use gold by default, and the bfd linker is not in $PATH, the VDSO build will fail: VDSO arch/arm/vdso/vdso.so.raw collect2: fatal error: cannot find 'ld' This will happen if CROSS_COMPILE begins with a path such as /opt/bin/arm-linux-gnu- but /opt/bin is not in $PATH. This is considered an acceptable corner-case limitation and is easily worked around. Additonal note: we use cc-option instead of cc-ldoption so that -fuse-ld=bfd is placed in the command line if the compiler recognizes the option. Using cc-ldoption results in an attempt to link, which fails in the situation just described, causing -fuse-ld=bfd to be omitted and gold to be used for the VDSO link, which is what we're trying to prevent. Reported-by: Stefan Agner <stefan@agner.ch> Signed-off-by: Nathan Lynch <nathan_lynch@mentor.com> Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
79 lines
2.3 KiB
Makefile
79 lines
2.3 KiB
Makefile
hostprogs-y := vdsomunge
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obj-vdso := vgettimeofday.o datapage.o
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# Build rules
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targets := $(obj-vdso) vdso.so vdso.so.dbg vdso.so.raw vdso.lds
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obj-vdso := $(addprefix $(obj)/, $(obj-vdso))
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ccflags-y := -fPIC -fno-common -fno-builtin -fno-stack-protector
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ccflags-y += -DDISABLE_BRANCH_PROFILING
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VDSO_LDFLAGS := -Wl,-Bsymbolic -Wl,--no-undefined -Wl,-soname=linux-vdso.so.1
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VDSO_LDFLAGS += -Wl,-z,max-page-size=4096 -Wl,-z,common-page-size=4096
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VDSO_LDFLAGS += -nostdlib -shared
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VDSO_LDFLAGS += $(call cc-ldoption, -Wl$(comma)--hash-style=sysv)
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VDSO_LDFLAGS += $(call cc-ldoption, -Wl$(comma)--build-id)
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VDSO_LDFLAGS += $(call cc-option, -fuse-ld=bfd)
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obj-$(CONFIG_VDSO) += vdso.o
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extra-$(CONFIG_VDSO) += vdso.lds
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CPPFLAGS_vdso.lds += -P -C -U$(ARCH)
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CFLAGS_REMOVE_vdso.o = -pg
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# Force -O2 to avoid libgcc dependencies
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CFLAGS_REMOVE_vgettimeofday.o = -pg -Os
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CFLAGS_vgettimeofday.o = -O2
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# Disable gcov profiling for VDSO code
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GCOV_PROFILE := n
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# Force dependency
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$(obj)/vdso.o : $(obj)/vdso.so
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# Link rule for the .so file
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$(obj)/vdso.so.raw: $(src)/vdso.lds $(obj-vdso) FORCE
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$(call if_changed,vdsold)
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$(obj)/vdso.so.dbg: $(obj)/vdso.so.raw $(obj)/vdsomunge FORCE
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$(call if_changed,vdsomunge)
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# Strip rule for the .so file
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$(obj)/%.so: OBJCOPYFLAGS := -S
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$(obj)/%.so: $(obj)/%.so.dbg FORCE
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$(call if_changed,objcopy)
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# Actual build commands
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quiet_cmd_vdsold = VDSO $@
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cmd_vdsold = $(CC) $(c_flags) $(VDSO_LDFLAGS) \
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-Wl,-T $(filter %.lds,$^) $(filter %.o,$^) -o $@
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quiet_cmd_vdsomunge = MUNGE $@
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cmd_vdsomunge = $(objtree)/$(obj)/vdsomunge $< $@
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#
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# Install the unstripped copy of vdso.so.dbg. If our toolchain
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# supports build-id, install .build-id links as well.
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#
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# Cribbed from arch/x86/vdso/Makefile.
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#
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quiet_cmd_vdso_install = INSTALL $<
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define cmd_vdso_install
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cp $< "$(MODLIB)/vdso/vdso.so"; \
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if readelf -n $< | grep -q 'Build ID'; then \
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buildid=`readelf -n $< |grep 'Build ID' |sed -e 's/^.*Build ID: \(.*\)$$/\1/'`; \
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first=`echo $$buildid | cut -b-2`; \
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last=`echo $$buildid | cut -b3-`; \
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mkdir -p "$(MODLIB)/vdso/.build-id/$$first"; \
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ln -sf "../../vdso.so" "$(MODLIB)/vdso/.build-id/$$first/$$last.debug"; \
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fi
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endef
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$(MODLIB)/vdso: FORCE
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@mkdir -p $(MODLIB)/vdso
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PHONY += vdso_install
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vdso_install: $(obj)/vdso.so.dbg $(MODLIB)/vdso FORCE
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$(call cmd,vdso_install)
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