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After a recent change in LLVM [1], builds with the random vDSO implementation, such as PowerPC and RISC-V, fail when checking the vDSO: arch/powerpc/kernel/vdso/vdso32.so.dbg: dynamic relocations are not supported arch/riscv/kernel/vdso/vdso.so.dbg: dynamic relocations are not supported memset() is now generated when zeroing params->reserved for some builds because LLVM has an optimization (now run in more instances) that can recognize at compile time when it is assigning a static value to a contiguous area of memory and turn that into a call to memset(). Both clang and GCC assume memset() is always available [2]. Clang has an internal fiddly hook, -max-store-memset, which we can set to a high number, to disable generating out of line memset calls [3]. Similarly, GCC has -finline-stringops=memset to do the same [4], should this issue ever hit future version of GCC. While these options wouldn't make sense for normal kernel code, it is fine for the extremely limited and intentionally compact vDSO code. Link:90cebef141[1] Link: https://gcc.gnu.org/onlinedocs/gcc-16.2.0/gcc/Standards.html#index-ffreestanding [2] Link:b28eeb28be[3] Link: https://gcc.gnu.org/onlinedocs/gcc/Optimize-Options.html#index-finline-stringops [4] Closes: https://github.com/ClangBuiltLinux/linux/issues/2183 Cc: stable@vger.kernel.org # v6.12+ Signed-off-by: Nathan Chancellor <nathan@kernel.org> Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
93 lines
2.6 KiB
Makefile
93 lines
2.6 KiB
Makefile
# SPDX-License-Identifier: GPL-2.0
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# Objects to go into the VDSO.
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# Include the generic Makefile to check the built vdso.
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include $(srctree)/lib/vdso/Makefile.include
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obj-vdso-y := elf.o vgetcpu.o vgetrandom.o \
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vgetrandom-chacha.o sigreturn.o
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obj-vdso-$(CONFIG_GENERIC_GETTIMEOFDAY) += vgettimeofday.o
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# Common compiler flags between ABIs.
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ccflags-vdso := \
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$(filter -I%,$(KBUILD_CFLAGS)) \
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$(filter -E%,$(KBUILD_CFLAGS)) \
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$(filter -m32,$(KBUILD_CFLAGS)) \
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$(filter -m64,$(KBUILD_CFLAGS)) \
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$(filter -march=%,$(KBUILD_CFLAGS)) \
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$(filter -m%-float,$(KBUILD_CFLAGS)) \
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$(CONFIG_CC_OPT_INLINE_MEMSET) \
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$(CLANG_FLAGS) \
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-D__VDSO__
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ifdef CONFIG_32BIT
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ccflags-vdso += -DBUILD_VDSO32
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endif
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cflags-vdso := $(ccflags-vdso) \
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-isystem $(shell $(CC) -print-file-name=include) \
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$(filter -W%,$(filter-out -Wa$(comma)%,$(KBUILD_CFLAGS))) \
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$(CC_FLAGS_DIALECT) -O2 -g -fno-strict-aliasing -fno-common -fno-builtin \
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-fno-stack-protector -fno-jump-tables -DDISABLE_BRANCH_PROFILING \
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$(call cc-option, -fasynchronous-unwind-tables) \
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$(call cc-option, -fno-stack-protector)
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aflags-vdso := $(ccflags-vdso) \
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-D__ASSEMBLY__ -Wa,-gdwarf-2
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ifneq ($(c-gettimeofday-y),)
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CFLAGS_vgettimeofday.o += -include $(c-gettimeofday-y)
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endif
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ifneq ($(c-getrandom-y),)
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CFLAGS_vgetrandom.o += -include $(c-getrandom-y)
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endif
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# VDSO linker flags.
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ldflags-y := -Bsymbolic --no-undefined -soname=linux-vdso.so.1 \
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$(filter -E%,$(KBUILD_CFLAGS)) -shared --build-id --eh-frame-hdr -T
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#
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# Shared build commands.
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#
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quiet_cmd_vdsold_and_vdso_check = LD $@
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cmd_vdsold_and_vdso_check = $(cmd_ld); $(cmd_vdso_check)
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quiet_cmd_vdsoas_o_S = AS $@
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cmd_vdsoas_o_S = $(CC) $(a_flags) -c -o $@ $<
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# Generate VDSO offsets using helper script
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gen-vdsosym := $(src)/gen_vdso_offsets.sh
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quiet_cmd_vdsosym = VDSOSYM $@
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cmd_vdsosym = $(NM) $< | $(gen-vdsosym) | LC_ALL=C sort > $@
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include/generated/vdso-offsets.h: $(obj)/vdso.so.dbg FORCE
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$(call if_changed,vdsosym)
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#
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# Build native VDSO.
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#
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native-abi := $(filter -mabi=%,$(KBUILD_CFLAGS))
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targets += $(obj-vdso-y)
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targets += vdso.lds vdso.so.dbg vdso.so
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obj-vdso := $(obj-vdso-y:%.o=$(obj)/%.o)
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$(obj-vdso): KBUILD_CFLAGS := $(cflags-vdso) $(native-abi)
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$(obj-vdso): KBUILD_AFLAGS := $(aflags-vdso) $(native-abi)
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$(obj)/vdso.lds: KBUILD_CPPFLAGS := $(ccflags-vdso) $(native-abi)
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$(obj)/vdso.so.dbg: $(obj)/vdso.lds $(obj-vdso) FORCE
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$(call if_changed,vdsold_and_vdso_check)
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$(obj)/vdso.so: OBJCOPYFLAGS := -S
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$(obj)/vdso.so: $(obj)/vdso.so.dbg FORCE
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$(call if_changed,objcopy)
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obj-y += vdso.o
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$(obj)/vdso.o : $(obj)/vdso.so
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