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The actual intention is that no dynamic relocation exists in the VDSO. For this the VDSO build validates that the resulting .so file does not have any relocations which are specified via $(ARCH_REL_TYPE_ABS) per architecture, which is fragile as e.g. ARM64 lacks an entry for R_AARCH64_RELATIVE. Aside of that ARCH_REL_TYPE_ABS is a misnomer as it checks for relative relocations too. However, some GNU ld ports produce unneeded R_*_NONE relocation entries. If a port fails to determine the exact .rel[a].dyn size, the trailing zeros become R_*_NONE relocations. E.g. ld's powerpc port recently fixed https://sourceware.org/bugzilla/show_bug.cgi?id=29540). R_*_NONE are generally a no-op in the dynamic loaders. So just ignore them. Remove the ARCH_REL_TYPE_ABS defines and just validate that the resulting .so file does not contain any R_* relocation entries except R_*_NONE. Signed-off-by: Fangrui Song <maskray@google.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Tested-by: Vincenzo Frascino <vincenzo.frascino@arm.com> # for aarch64 Reviewed-by: Christophe Leroy <christophe.leroy@csgroup.eu> Reviewed-by: Vincenzo Frascino <vincenzo.frascino@arm.com> # for vDSO, aarch64 Acked-by: Michael Ellerman <mpe@ellerman.id.au> (powerpc) Link: https://lore.kernel.org/r/20230310190750.3323802-1-maskray@google.com
117 lines
4.8 KiB
Makefile
117 lines
4.8 KiB
Makefile
# SPDX-License-Identifier: GPL-2.0
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# List of files in the vdso, has to be asm only for now
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# Include the generic Makefile to check the built vdso.
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include $(srctree)/lib/vdso/Makefile
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obj-vdso32 = sigtramp32-32.o gettimeofday-32.o datapage-32.o cacheflush-32.o note-32.o getcpu-32.o
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obj-vdso64 = sigtramp64-64.o gettimeofday-64.o datapage-64.o cacheflush-64.o note-64.o getcpu-64.o
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ifneq ($(c-gettimeofday-y),)
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CFLAGS_vgettimeofday-32.o += -include $(c-gettimeofday-y)
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CFLAGS_vgettimeofday-32.o += $(DISABLE_LATENT_ENTROPY_PLUGIN)
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CFLAGS_vgettimeofday-32.o += $(call cc-option, -fno-stack-protector)
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CFLAGS_vgettimeofday-32.o += -DDISABLE_BRANCH_PROFILING
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CFLAGS_vgettimeofday-32.o += -ffreestanding -fasynchronous-unwind-tables
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CFLAGS_REMOVE_vgettimeofday-32.o = $(CC_FLAGS_FTRACE)
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CFLAGS_REMOVE_vgettimeofday-32.o += -mcmodel=medium -mabi=elfv1 -mabi=elfv2 -mcall-aixdesc
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# This flag is supported by clang for 64-bit but not 32-bit so it will cause
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# an unused command line flag warning for this file.
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ifdef CONFIG_CC_IS_CLANG
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CFLAGS_REMOVE_vgettimeofday-32.o += -fno-stack-clash-protection
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endif
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CFLAGS_vgettimeofday-64.o += -include $(c-gettimeofday-y)
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CFLAGS_vgettimeofday-64.o += $(DISABLE_LATENT_ENTROPY_PLUGIN)
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CFLAGS_vgettimeofday-64.o += $(call cc-option, -fno-stack-protector)
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CFLAGS_vgettimeofday-64.o += -DDISABLE_BRANCH_PROFILING
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CFLAGS_vgettimeofday-64.o += -ffreestanding -fasynchronous-unwind-tables
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CFLAGS_REMOVE_vgettimeofday-64.o = $(CC_FLAGS_FTRACE)
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# Go prior to 1.16.x assumes r30 is not clobbered by any VDSO code. That used to be true
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# by accident when the VDSO was hand-written asm code, but may not be now that the VDSO is
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# compiler generated. To avoid breaking Go tell GCC not to use r30. Impact on code
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# generation is minimal, it will just use r29 instead.
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CFLAGS_vgettimeofday-64.o += $(call cc-option, -ffixed-r30)
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endif
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# Build rules
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ifdef CROSS32_COMPILE
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VDSOCC := $(CROSS32_COMPILE)gcc
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else
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VDSOCC := $(CC)
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endif
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targets := $(obj-vdso32) vdso32.so.dbg vgettimeofday-32.o
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obj-vdso32 := $(addprefix $(obj)/, $(obj-vdso32))
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targets += $(obj-vdso64) vdso64.so.dbg vgettimeofday-64.o
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obj-vdso64 := $(addprefix $(obj)/, $(obj-vdso64))
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GCOV_PROFILE := n
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KCOV_INSTRUMENT := n
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UBSAN_SANITIZE := n
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KASAN_SANITIZE := n
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KCSAN_SANITIZE := n
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ccflags-y := -fno-common -fno-builtin
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ldflags-y := -Wl,--hash-style=both -nostdlib -shared -z noexecstack
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ldflags-$(CONFIG_LD_IS_LLD) += $(call cc-option,--ld-path=$(LD),-fuse-ld=lld)
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# Filter flags that clang will warn are unused for linking
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ldflags-y += $(filter-out $(CC_AUTO_VAR_INIT_ZERO_ENABLER) $(CC_FLAGS_FTRACE) -Wa$(comma)%, $(KBUILD_CFLAGS))
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CC32FLAGS := -m32
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LD32FLAGS := -Wl,-soname=linux-vdso32.so.1
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AS32FLAGS := -D__VDSO32__
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LD64FLAGS := -Wl,-soname=linux-vdso64.so.1
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AS64FLAGS := -D__VDSO64__
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targets += vdso32.lds
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CPPFLAGS_vdso32.lds += -P -C -Upowerpc
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targets += vdso64.lds
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CPPFLAGS_vdso64.lds += -P -C -U$(ARCH)
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# link rule for the .so file, .lds has to be first
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$(obj)/vdso32.so.dbg: $(src)/vdso32.lds $(obj-vdso32) $(obj)/vgettimeofday-32.o FORCE
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$(call if_changed,vdso32ld_and_check)
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$(obj)/vdso64.so.dbg: $(src)/vdso64.lds $(obj-vdso64) $(obj)/vgettimeofday-64.o FORCE
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$(call if_changed,vdso64ld_and_check)
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# assembly rules for the .S files
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$(obj-vdso32): %-32.o: %.S FORCE
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$(call if_changed_dep,vdso32as)
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$(obj)/vgettimeofday-32.o: %-32.o: %.c FORCE
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$(call if_changed_dep,vdso32cc)
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$(obj-vdso64): %-64.o: %.S FORCE
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$(call if_changed_dep,vdso64as)
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$(obj)/vgettimeofday-64.o: %-64.o: %.c FORCE
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$(call if_changed_dep,cc_o_c)
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# Generate VDSO offsets using helper script
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gen-vdso32sym := $(srctree)/$(src)/gen_vdso32_offsets.sh
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quiet_cmd_vdso32sym = VDSO32SYM $@
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cmd_vdso32sym = $(NM) $< | $(gen-vdso32sym) | LC_ALL=C sort > $@
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gen-vdso64sym := $(srctree)/$(src)/gen_vdso64_offsets.sh
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quiet_cmd_vdso64sym = VDSO64SYM $@
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cmd_vdso64sym = $(NM) $< | $(gen-vdso64sym) | LC_ALL=C sort > $@
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include/generated/vdso32-offsets.h: $(obj)/vdso32.so.dbg FORCE
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$(call if_changed,vdso32sym)
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include/generated/vdso64-offsets.h: $(obj)/vdso64.so.dbg FORCE
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$(call if_changed,vdso64sym)
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# actual build commands
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quiet_cmd_vdso32ld_and_check = VDSO32L $@
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cmd_vdso32ld_and_check = $(VDSOCC) $(ldflags-y) $(CC32FLAGS) $(LD32FLAGS) -o $@ -Wl,-T$(filter %.lds,$^) $(filter %.o,$^); $(cmd_vdso_check)
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quiet_cmd_vdso32as = VDSO32A $@
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cmd_vdso32as = $(VDSOCC) $(a_flags) $(CC32FLAGS) $(AS32FLAGS) -c -o $@ $<
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quiet_cmd_vdso32cc = VDSO32C $@
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cmd_vdso32cc = $(VDSOCC) $(c_flags) $(CC32FLAGS) -c -o $@ $<
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quiet_cmd_vdso64ld_and_check = VDSO64L $@
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cmd_vdso64ld_and_check = $(VDSOCC) $(ldflags-y) $(LD64FLAGS) -o $@ -Wl,-T$(filter %.lds,$^) $(filter %.o,$^); $(cmd_vdso_check)
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quiet_cmd_vdso64as = VDSO64A $@
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cmd_vdso64as = $(VDSOCC) $(a_flags) $(AS64FLAGS) -c -o $@ $<
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OBJECT_FILES_NON_STANDARD := y
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