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Shadow stack instructions are taken from the Zimop ISA extension, which is mandated on RVA23. Any userspace with shadow stack instructions in it will fault on hardware that doesn't have support for Zimop. Thus, a shadow stack-enabled userspace can't be run on hardware that doesn't support Zimop. It's not known how Linux userspace providers will respond to this kind of binary fragmentation. In order to keep kernel portable across different hardware, 'arch/riscv/kernel/vdso_cfi' is created which has Makefile logic to compile 'arch/riscv/kernel/vdso' sources with CFI flags, and 'arch/riscv/kernel/vdso.c' is modified to select the appropriate vdso depending on whether the underlying CPU implements the Zimop extension. Since the offset of vdso symbols will change due to having two different vdso binaries, there is added logic to include a new generated vdso offset header and dynamically select the offset (like for rt_sigreturn). Signed-off-by: Deepak Gupta <debug@rivosinc.com> Acked-by: Charles Mirabile <cmirabil@redhat.com> Tested-by: Andreas Korb <andreas.korb@aisec.fraunhofer.de> # QEMU, custom CVA6 Tested-by: Valentin Haudiquet <valentin.haudiquet@canonical.com> Link: https://patch.msgid.link/20251112-v5_user_cfi_series-v23-24-b55691eacf4f@rivosinc.com [pjw@kernel.org: cleaned up patch description] Signed-off-by: Paul Walmsley <pjw@kernel.org>
106 lines
3.1 KiB
Makefile
106 lines
3.1 KiB
Makefile
# SPDX-License-Identifier: GPL-2.0-only
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# Copied from arch/tile/kernel/vdso/Makefile
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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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# Symbols present in the vdso
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vdso-syms = rt_sigreturn
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ifdef CONFIG_64BIT
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vdso-syms += vgettimeofday
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endif
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vdso-syms += getcpu
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vdso-syms += flush_icache
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vdso-syms += hwprobe
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vdso-syms += sys_hwprobe
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ifdef CONFIG_VDSO_GETRANDOM
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vdso-syms += getrandom
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endif
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ifdef VDSO_CFI_BUILD
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CFI_MARCH = _zicfilp_zicfiss
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CFI_FULL = -fcf-protection=full
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CFI_SUFFIX = -cfi
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OFFSET_SUFFIX = _cfi
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ccflags-y += -DVDSO_CFI=1
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asflags-y += -DVDSO_CFI=1
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endif
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# Files to link into the vdso
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obj-vdso = $(patsubst %, %.o, $(vdso-syms)) note.o
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ifdef CONFIG_VDSO_GETRANDOM
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obj-vdso += vgetrandom-chacha.o
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endif
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ccflags-y := -fno-stack-protector
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ccflags-y += -DDISABLE_BRANCH_PROFILING
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ccflags-y += -fno-builtin
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ccflags-y += $(KBUILD_BASE_ISA)$(CFI_MARCH)
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ccflags-y += $(CFI_FULL)
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asflags-y += $(KBUILD_BASE_ISA)$(CFI_MARCH)
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asflags-y += $(CFI_FULL)
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ifneq ($(c-gettimeofday-y),)
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CFLAGS_vgettimeofday.o += -fPIC -include $(c-gettimeofday-y)
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endif
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ifneq ($(c-getrandom-y),)
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CFLAGS_getrandom.o += -fPIC -include $(c-getrandom-y)
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endif
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CFLAGS_hwprobe.o += -fPIC
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# Build rules
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vdso_offsets := vdso$(if $(VDSO_CFI_BUILD),$(CFI_SUFFIX),)-offsets.h
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vdso_o := vdso$(if $(VDSO_CFI_BUILD),$(CFI_SUFFIX),).o
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vdso_so := vdso$(if $(VDSO_CFI_BUILD),$(CFI_SUFFIX),).so
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vdso_so_dbg := vdso$(if $(VDSO_CFI_BUILD),$(CFI_SUFFIX),).so.dbg
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vdso_lds := vdso.lds
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targets := $(obj-vdso) $(vdso_so) $(vdso_so_dbg) $(vdso_lds)
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obj-vdso := $(addprefix $(obj)/, $(obj-vdso))
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obj-y += vdso$(if $(VDSO_CFI_BUILD),$(CFI_SUFFIX),).o
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CPPFLAGS_$(vdso_lds) += -P -C -U$(ARCH)
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ifneq ($(filter vgettimeofday, $(vdso-syms)),)
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CPPFLAGS_$(vdso_lds) += -DHAS_VGETTIMEOFDAY
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endif
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# Disable -pg to prevent insert call site
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CFLAGS_REMOVE_vgettimeofday.o = $(CC_FLAGS_FTRACE) $(CC_FLAGS_SCS)
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CFLAGS_REMOVE_getrandom.o = $(CC_FLAGS_FTRACE) $(CC_FLAGS_SCS)
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CFLAGS_REMOVE_hwprobe.o = $(CC_FLAGS_FTRACE) $(CC_FLAGS_SCS)
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# Force dependency
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$(obj)/$(vdso_o): $(obj)/$(vdso_so)
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# link rule for the .so file, .lds has to be first
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$(obj)/$(vdso_so_dbg): $(obj)/$(vdso_lds) $(obj-vdso) FORCE
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$(call if_changed,vdsold_and_check)
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LDFLAGS_$(vdso_so_dbg) = -shared -soname=linux-vdso.so.1 \
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--build-id=sha1 --eh-frame-hdr
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# strip rule for the .so file
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$(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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# 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) $(OFFSET_SUFFIX) | LC_ALL=C sort > $@
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include/generated/$(vdso_offsets): $(obj)/$(vdso_so_dbg) FORCE
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$(call if_changed,vdsosym)
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# actual build commands
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# The DSO images are built using a special linker script
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# Make sure only to export the intended __vdso_xxx symbol offsets.
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quiet_cmd_vdsold_and_check = VDSOLD $@
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cmd_vdsold_and_check = $(LD) $(CFI_FULL) $(ld_flags) -T $(filter-out FORCE,$^) -o $@.tmp && \
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$(OBJCOPY) $(patsubst %, -G __vdso_%, $(vdso-syms)) $@.tmp $@ && \
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rm $@.tmp && \
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$(cmd_vdso_check)
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