24005d184a
Sami Tolvanen <samitolvanen@google.com> says: This series adds Shadow Call Stack (SCS) support for RISC-V. SCS uses compiler instrumentation to store return addresses in a separate shadow stack to protect them against accidental or malicious overwrites. More information about SCS can be found here: https://clang.llvm.org/docs/ShadowCallStack.html Patch 1 is from Deepak, and it simplifies VMAP_STACK overflow handling by adding support for accessing per-CPU variables directly in assembly. The patch is included in this series to make IRQ stack switching cleaner with SCS, and I've simply rebased it and fixed a couple of minor issues. Patch 2 uses this functionality to clean up the stack switching by moving duplicate code into a single function. On RISC-V, the compiler uses the gp register for storing the current shadow call stack pointer, which is incompatible with global pointer relaxation. Patch 3 moves global pointer loading into a macro that can be easily disabled with SCS. Patch 4 implements SCS register loading and switching, and allows the feature to be enabled, and patch 5 adds separate per-CPU IRQ shadow call stacks when CONFIG_IRQ_STACKS is enabled. Patch 6 fixes the backward-edge CFI test in lkdtm for RISC-V. Note that this series requires Clang 17. Earlier Clang versions support SCS on RISC-V, but use the x18 register instead of gp, which isn't ideal. gcc has SCS support for arm64, but I'm not aware of plans to support RISC-V. Once the Zicfiss extension is ratified, it's probably preferable to use hardware-backed shadow stacks instead of SCS on hardware that supports the extension, and we may want to consider implementing CONFIG_DYNAMIC_SCS to patch between the implementation at runtime (similarly to the arm64 implementation, which switches to SCS when hardware PAC support isn't available). * b4-shazam-merge: lkdtm: Fix CFI_BACKWARD on RISC-V riscv: Use separate IRQ shadow call stacks riscv: Implement Shadow Call Stack riscv: Move global pointer loading to a macro riscv: Deduplicate IRQ stack switching riscv: VMAP_STACK overflow detection thread-safe Link: https://lore.kernel.org/r/20230927224757.1154247-8-samitolvanen@google.com Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
115 lines
3.5 KiB
Makefile
115 lines
3.5 KiB
Makefile
# SPDX-License-Identifier: GPL-2.0
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OBJECT_FILES_NON_STANDARD := y
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purgatory-y := purgatory.o sha256.o entry.o string.o ctype.o memcpy.o memset.o
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purgatory-y += strcmp.o strlen.o strncmp.o
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targets += $(purgatory-y)
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PURGATORY_OBJS = $(addprefix $(obj)/,$(purgatory-y))
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$(obj)/string.o: $(srctree)/lib/string.c FORCE
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$(call if_changed_rule,cc_o_c)
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$(obj)/ctype.o: $(srctree)/lib/ctype.c FORCE
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$(call if_changed_rule,cc_o_c)
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$(obj)/memcpy.o: $(srctree)/arch/riscv/lib/memcpy.S FORCE
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$(call if_changed_rule,as_o_S)
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$(obj)/memset.o: $(srctree)/arch/riscv/lib/memset.S FORCE
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$(call if_changed_rule,as_o_S)
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$(obj)/strcmp.o: $(srctree)/arch/riscv/lib/strcmp.S FORCE
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$(call if_changed_rule,as_o_S)
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$(obj)/strlen.o: $(srctree)/arch/riscv/lib/strlen.S FORCE
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$(call if_changed_rule,as_o_S)
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$(obj)/strncmp.o: $(srctree)/arch/riscv/lib/strncmp.S FORCE
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$(call if_changed_rule,as_o_S)
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$(obj)/sha256.o: $(srctree)/lib/crypto/sha256.c FORCE
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$(call if_changed_rule,cc_o_c)
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CFLAGS_sha256.o := -D__DISABLE_EXPORTS -D__NO_FORTIFY
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CFLAGS_string.o := -D__DISABLE_EXPORTS
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CFLAGS_ctype.o := -D__DISABLE_EXPORTS
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# When profile-guided optimization is enabled, llvm emits two different
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# overlapping text sections, which is not supported by kexec. Remove profile
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# optimization flags.
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KBUILD_CFLAGS := $(filter-out -fprofile-sample-use=% -fprofile-use=%,$(KBUILD_CFLAGS))
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# When linking purgatory.ro with -r unresolved symbols are not checked,
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# also link a purgatory.chk binary without -r to check for unresolved symbols.
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PURGATORY_LDFLAGS := -e purgatory_start -z nodefaultlib
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LDFLAGS_purgatory.ro := -r $(PURGATORY_LDFLAGS)
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LDFLAGS_purgatory.chk := $(PURGATORY_LDFLAGS)
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targets += purgatory.ro purgatory.chk
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# Sanitizer, etc. runtimes are unavailable and cannot be linked here.
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GCOV_PROFILE := n
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KASAN_SANITIZE := n
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UBSAN_SANITIZE := n
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KCSAN_SANITIZE := n
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KCOV_INSTRUMENT := n
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# These are adjustments to the compiler flags used for objects that
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# make up the standalone purgatory.ro
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PURGATORY_CFLAGS_REMOVE := -mcmodel=kernel
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PURGATORY_CFLAGS := -mcmodel=medany -ffreestanding -fno-zero-initialized-in-bss
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PURGATORY_CFLAGS += $(DISABLE_STACKLEAK_PLUGIN) -DDISABLE_BRANCH_PROFILING
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PURGATORY_CFLAGS += -fno-stack-protector -g0
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# Default KBUILD_CFLAGS can have -pg option set when FTRACE is enabled. That
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# in turn leaves some undefined symbols like __fentry__ in purgatory and not
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# sure how to relocate those.
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ifdef CONFIG_FUNCTION_TRACER
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PURGATORY_CFLAGS_REMOVE += $(CC_FLAGS_FTRACE)
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endif
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ifdef CONFIG_STACKPROTECTOR
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PURGATORY_CFLAGS_REMOVE += -fstack-protector
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endif
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ifdef CONFIG_STACKPROTECTOR_STRONG
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PURGATORY_CFLAGS_REMOVE += -fstack-protector-strong
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endif
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ifdef CONFIG_CFI_CLANG
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PURGATORY_CFLAGS_REMOVE += $(CC_FLAGS_CFI)
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endif
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ifdef CONFIG_RELOCATABLE
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PURGATORY_CFLAGS_REMOVE += -fPIE
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endif
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ifdef CONFIG_SHADOW_CALL_STACK
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PURGATORY_CFLAGS_REMOVE += $(CC_FLAGS_SCS)
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endif
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CFLAGS_REMOVE_purgatory.o += $(PURGATORY_CFLAGS_REMOVE)
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CFLAGS_purgatory.o += $(PURGATORY_CFLAGS)
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CFLAGS_REMOVE_sha256.o += $(PURGATORY_CFLAGS_REMOVE)
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CFLAGS_sha256.o += $(PURGATORY_CFLAGS)
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CFLAGS_REMOVE_string.o += $(PURGATORY_CFLAGS_REMOVE)
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CFLAGS_string.o += $(PURGATORY_CFLAGS)
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CFLAGS_REMOVE_ctype.o += $(PURGATORY_CFLAGS_REMOVE)
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CFLAGS_ctype.o += $(PURGATORY_CFLAGS)
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asflags-remove-y += $(foreach x, -g -gdwarf-4 -gdwarf-5, $(x) -Wa,$(x))
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$(obj)/purgatory.ro: $(PURGATORY_OBJS) FORCE
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$(call if_changed,ld)
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$(obj)/purgatory.chk: $(obj)/purgatory.ro FORCE
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$(call if_changed,ld)
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$(obj)/kexec-purgatory.o: $(obj)/purgatory.ro $(obj)/purgatory.chk
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obj-y += kexec-purgatory.o
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