Date: Fri, 18 Oct 2019 09:10:15 -0700 From: Sami Tolvanen <samitolvanen@...gle.com> To: Will Deacon <will@...nel.org>, Catalin Marinas <catalin.marinas@....com>, Steven Rostedt <rostedt@...dmis.org>, Ard Biesheuvel <ard.biesheuvel@...aro.org> Cc: Dave Martin <Dave.Martin@....com>, Kees Cook <keescook@...omium.org>, Laura Abbott <labbott@...hat.com>, Mark Rutland <mark.rutland@....com>, Nick Desaulniers <ndesaulniers@...gle.com>, clang-built-linux@...glegroups.com, kernel-hardening@...ts.openwall.com, linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org, Sami Tolvanen <samitolvanen@...gle.com> Subject: [PATCH 00/18] add support for Clang's Shadow Call Stack This patch series adds support for Clang's Shadow Call Stack (SCS) mitigation, which uses a separately allocated shadow stack to protect against return address overwrites. More information can be found here: https://clang.llvm.org/docs/ShadowCallStack.html SCS is currently supported only on arm64, where the compiler requires the x18 register to be reserved for holding the current task's shadow stack pointer. Because of this, the series includes four patches from Ard to remove x18 usage from assembly code and to reserve the register from general allocation. With -fsanitize=shadow-call-stack, the compiler injects instructions to all non-leaf C functions to store the return address to the shadow stack and unconditionally load it again before returning. As a result, SCS is incompatible with features that rely on modifying function return addresses to alter control flow, such as function graph tracing and kretprobes. A copy of the return address is still kept in the kernel stack for compatibility with stack unwinding, for example. SCS has a minimal performance overhead, but allocating shadow stacks increases kernel memory usage. The feature is therefore mostly useful on hardware that lacks support for PAC instructions. This series adds a ROP protection choice to the kernel configuration, where other return address protection options can be selected as they are added to the kernel. Ard Biesheuvel (4): arm64/lib: copy_page: avoid x18 register in assembler code arm64: kvm: stop treating register x18 as caller save arm64: kernel: avoid x18 as an arbitrary temp register arm64: kbuild: reserve reg x18 from general allocation by the compiler Sami Tolvanen (14): arm64: mm: don't use x18 in idmap_kpti_install_ng_mappings add support for Clang's Shadow Call Stack (SCS) scs: add accounting scs: add support for stack usage debugging trace: disable function graph tracing with SCS kprobes: fix compilation without CONFIG_KRETPROBES kprobes: disable kretprobes with SCS arm64: reserve x18 only with Shadow Call Stack arm64: preserve x18 when CPU is suspended arm64: efi: restore x18 if it was corrupted arm64: vdso: disable Shadow Call Stack arm64: kprobes: fix kprobes without CONFIG_KRETPROBES arm64: disable SCS for hypervisor code arm64: implement Shadow Call Stack Makefile | 6 + arch/Kconfig | 41 ++++- arch/arm64/Kconfig | 1 + arch/arm64/Makefile | 4 + arch/arm64/include/asm/scs.h | 60 ++++++++ arch/arm64/include/asm/stacktrace.h | 4 + arch/arm64/include/asm/thread_info.h | 3 + arch/arm64/kernel/Makefile | 1 + arch/arm64/kernel/asm-offsets.c | 3 + arch/arm64/kernel/cpu-reset.S | 4 +- arch/arm64/kernel/efi-rt-wrapper.S | 7 +- arch/arm64/kernel/entry.S | 23 +++ arch/arm64/kernel/head.S | 9 ++ arch/arm64/kernel/irq.c | 2 + arch/arm64/kernel/probes/kprobes.c | 2 + arch/arm64/kernel/process.c | 3 + arch/arm64/kernel/scs.c | 39 +++++ arch/arm64/kernel/smp.c | 4 + arch/arm64/kernel/vdso/Makefile | 2 +- arch/arm64/kvm/hyp/Makefile | 3 +- arch/arm64/kvm/hyp/entry.S | 12 +- arch/arm64/lib/copy_page.S | 38 ++--- arch/arm64/mm/proc.S | 69 +++++---- drivers/base/node.c | 6 + fs/proc/meminfo.c | 4 + include/linux/compiler-clang.h | 2 + include/linux/compiler_types.h | 4 + include/linux/mmzone.h | 3 + include/linux/scs.h | 88 +++++++++++ init/init_task.c | 6 + init/main.c | 3 + kernel/Makefile | 1 + kernel/fork.c | 9 ++ kernel/kprobes.c | 38 ++--- kernel/sched/core.c | 2 + kernel/sched/sched.h | 1 + kernel/scs.c | 221 +++++++++++++++++++++++++++ kernel/trace/Kconfig | 1 + mm/page_alloc.c | 6 + mm/vmstat.c | 3 + 40 files changed, 656 insertions(+), 82 deletions(-) create mode 100644 arch/arm64/include/asm/scs.h create mode 100644 arch/arm64/kernel/scs.c create mode 100644 include/linux/scs.h create mode 100644 kernel/scs.c -- 220.127.116.116.gb869b98d4c-goog
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