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Date: Fri, 13 May 2022 13:21:38 -0700 From: Sami Tolvanen <samitolvanen@...gle.com> To: linux-kernel@...r.kernel.org Cc: Kees Cook <keescook@...omium.org>, Josh Poimboeuf <jpoimboe@...hat.com>, Peter Zijlstra <peterz@...radead.org>, x86@...nel.org, Catalin Marinas <catalin.marinas@....com>, Will Deacon <will@...nel.org>, Mark Rutland <mark.rutland@....com>, Nathan Chancellor <nathan@...nel.org>, Nick Desaulniers <ndesaulniers@...gle.com>, Joao Moreira <joao@...rdrivepizza.com>, Sedat Dilek <sedat.dilek@...il.com>, Steven Rostedt <rostedt@...dmis.org>, linux-hardening@...r.kernel.org, linux-arm-kernel@...ts.infradead.org, llvm@...ts.linux.dev, Sami Tolvanen <samitolvanen@...gle.com> Subject: [RFC PATCH v2 00/21] KCFI support KCFI is a proposed forward-edge control-flow integrity scheme for Clang, which is more suitable for kernel use than the existing CFI scheme used by CONFIG_CFI_CLANG. KCFI doesn't require LTO, doesn't alter function references to point to a jump table, and won't break function address equality. The latest LLVM patch is here: https://reviews.llvm.org/D119296 This RFC series replaces the current arm64 CFI implementation with KCFI and adds support for x86_64. KCFI requires assembly functions that are indirectly called from C code to be annotated with type identifiers. As type information is only available in C, the compiler emits expected type identifiers into the symbol table, so they can be referenced from assembly without having to hardcode type hashes. Patch 7 adds helper macros for annotating functions, and patches 9 and 17 add annotations. In case of a type mismatch, KCFI always traps. To support error handling, the compiler generates a .kcfi_traps section for x86_64, which contains the locations of each trap, and for arm64, encodes the necessary register information to the ESR. Patches 10 and 20 add arch-specific error handlers. To test this series, you'll need to compile your own Clang toolchain with the patches linked above. You can also find the complete source tree here: https://github.com/samitolvanen/llvm-project/commits/kcfi-rfc-v2 This series is also available in GitHub: https://github.com/samitolvanen/linux/commits/kcfi-rfc-v2 Sami Tolvanen (21): efi/libstub: Filter out CC_FLAGS_CFI arm64/vdso: Filter out CC_FLAGS_CFI kallsyms: Ignore __kcfi_typeid_ cfi: Remove CONFIG_CFI_CLANG_SHADOW cfi: Drop __CFI_ADDRESSABLE cfi: Switch to -fsanitize=kcfi cfi: Add type helper macros psci: Fix the function type for psci_initcall_t arm64: Add types to indirect called assembly functions arm64: Add CFI error handling arm64: Drop unneeded __nocfi attributes treewide: Drop function_nocfi treewide: Drop WARN_ON_FUNCTION_MISMATCH treewide: Drop __cficanonical objtool: Don't warn about __cfi_ preambles falling through x86/tools/relocs: Ignore __kcfi_typeid_ relocations x86: Add types to indirectly called assembly functions x86/purgatory: Disable CFI x86/vdso: Disable CFI x86: Add support for CONFIG_CFI_CLANG init: Drop __nocfi from __init Makefile | 13 +- arch/Kconfig | 21 +- arch/arm64/crypto/ghash-ce-core.S | 5 +- arch/arm64/crypto/sm3-ce-core.S | 3 +- arch/arm64/include/asm/brk-imm.h | 6 + arch/arm64/include/asm/compiler.h | 16 - arch/arm64/include/asm/ftrace.h | 2 +- arch/arm64/include/asm/mmu_context.h | 4 +- arch/arm64/kernel/acpi_parking_protocol.c | 2 +- arch/arm64/kernel/alternative.c | 2 +- arch/arm64/kernel/cpu-reset.S | 5 +- arch/arm64/kernel/cpufeature.c | 4 +- arch/arm64/kernel/ftrace.c | 2 +- arch/arm64/kernel/machine_kexec.c | 2 +- arch/arm64/kernel/psci.c | 2 +- arch/arm64/kernel/smp_spin_table.c | 2 +- arch/arm64/kernel/traps.c | 46 ++- arch/arm64/kernel/vdso/Makefile | 3 +- arch/arm64/mm/proc.S | 5 +- arch/x86/Kconfig | 2 + arch/x86/crypto/blowfish-x86_64-asm_64.S | 5 +- arch/x86/entry/vdso/Makefile | 3 +- arch/x86/include/asm/linkage.h | 12 + arch/x86/kernel/traps.c | 60 +++- arch/x86/lib/memcpy_64.S | 3 +- arch/x86/purgatory/Makefile | 4 + arch/x86/tools/relocs.c | 1 + drivers/firmware/efi/libstub/Makefile | 2 + drivers/firmware/psci/psci.c | 6 +- drivers/misc/lkdtm/usercopy.c | 2 +- include/asm-generic/bug.h | 16 - include/asm-generic/vmlinux.lds.h | 37 +-- include/linux/cfi.h | 65 ++-- include/linux/cfi_types.h | 57 ++++ include/linux/compiler-clang.h | 6 +- include/linux/compiler.h | 16 +- include/linux/compiler_types.h | 4 - include/linux/init.h | 6 +- include/linux/module.h | 10 +- include/linux/pci.h | 4 +- kernel/cfi.c | 343 ++++------------------ kernel/kthread.c | 3 +- kernel/module.c | 49 +--- kernel/workqueue.c | 2 +- scripts/kallsyms.c | 1 + scripts/module.lds.S | 23 +- tools/objtool/check.c | 4 + 47 files changed, 357 insertions(+), 534 deletions(-) create mode 100644 include/linux/cfi_types.h -- 2.36.0.550.gb090851708-goog
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