diff options
author | Sami Tolvanen <samitolvanen@google.com> | 2020-04-27 18:00:16 +0200 |
---|---|---|
committer | Will Deacon <will@kernel.org> | 2020-05-15 17:35:50 +0200 |
commit | 5287569a790d2546a06db07e391bf84b8bd6cf51 (patch) | |
tree | 137dc42c9e15afc1b7880798d2ea1ed146301211 | |
parent | arm64: Disable SCS for hypervisor code (diff) | |
download | linux-5287569a790d2546a06db07e391bf84b8bd6cf51.tar.xz linux-5287569a790d2546a06db07e391bf84b8bd6cf51.zip |
arm64: Implement Shadow Call Stack
This change implements shadow stack switching, initial SCS set-up,
and interrupt shadow stacks for arm64.
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Will Deacon <will@kernel.org>
-rw-r--r-- | arch/arm64/Kconfig | 5 | ||||
-rw-r--r-- | arch/arm64/include/asm/scs.h | 46 | ||||
-rw-r--r-- | arch/arm64/include/asm/thread_info.h | 13 | ||||
-rw-r--r-- | arch/arm64/kernel/Makefile | 1 | ||||
-rw-r--r-- | arch/arm64/kernel/asm-offsets.c | 4 | ||||
-rw-r--r-- | arch/arm64/kernel/entry.S | 24 | ||||
-rw-r--r-- | arch/arm64/kernel/head.S | 6 | ||||
-rw-r--r-- | arch/arm64/kernel/process.c | 2 | ||||
-rw-r--r-- | arch/arm64/kernel/scs.c | 15 |
9 files changed, 114 insertions, 2 deletions
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig index 40fb05d96c60..c380a16533f6 100644 --- a/arch/arm64/Kconfig +++ b/arch/arm64/Kconfig @@ -64,6 +64,7 @@ config ARM64 select ARCH_USE_QUEUED_RWLOCKS select ARCH_USE_QUEUED_SPINLOCKS select ARCH_SUPPORTS_MEMORY_FAILURE + select ARCH_SUPPORTS_SHADOW_CALL_STACK if CC_HAVE_SHADOW_CALL_STACK select ARCH_SUPPORTS_ATOMIC_RMW select ARCH_SUPPORTS_INT128 if CC_HAS_INT128 && (GCC_VERSION >= 50000 || CC_IS_CLANG) select ARCH_SUPPORTS_NUMA_BALANCING @@ -1025,6 +1026,10 @@ config ARCH_HAS_CACHE_LINE_SIZE config ARCH_ENABLE_SPLIT_PMD_PTLOCK def_bool y if PGTABLE_LEVELS > 2 +# Supported by clang >= 7.0 +config CC_HAVE_SHADOW_CALL_STACK + def_bool $(cc-option, -fsanitize=shadow-call-stack -ffixed-x18) + config SECCOMP bool "Enable seccomp to safely compute untrusted bytecode" ---help--- diff --git a/arch/arm64/include/asm/scs.h b/arch/arm64/include/asm/scs.h new file mode 100644 index 000000000000..96549353b0cb --- /dev/null +++ b/arch/arm64/include/asm/scs.h @@ -0,0 +1,46 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef _ASM_SCS_H +#define _ASM_SCS_H + +#ifdef __ASSEMBLY__ + +#ifdef CONFIG_SHADOW_CALL_STACK + .macro scs_load tsk, tmp + ldp x18, \tmp, [\tsk, #TSK_TI_SCS_BASE] + add x18, x18, \tmp + .endm + + .macro scs_save tsk, tmp + ldr \tmp, [\tsk, #TSK_TI_SCS_BASE] + sub \tmp, x18, \tmp + str \tmp, [\tsk, #TSK_TI_SCS_OFFSET] + .endm +#else + .macro scs_load tsk, tmp + .endm + + .macro scs_save tsk, tmp + .endm +#endif /* CONFIG_SHADOW_CALL_STACK */ + +#else /* __ASSEMBLY__ */ + +#include <linux/scs.h> + +#ifdef CONFIG_SHADOW_CALL_STACK + +static inline void scs_overflow_check(struct task_struct *tsk) +{ + if (unlikely(scs_corrupted(tsk))) + panic("corrupted shadow stack detected inside scheduler\n"); +} + +#else /* CONFIG_SHADOW_CALL_STACK */ + +static inline void scs_overflow_check(struct task_struct *tsk) {} + +#endif /* CONFIG_SHADOW_CALL_STACK */ + +#endif /* __ASSEMBLY __ */ + +#endif /* _ASM_SCS_H */ diff --git a/arch/arm64/include/asm/thread_info.h b/arch/arm64/include/asm/thread_info.h index 512174a8e789..9df79c0a4c43 100644 --- a/arch/arm64/include/asm/thread_info.h +++ b/arch/arm64/include/asm/thread_info.h @@ -41,6 +41,10 @@ struct thread_info { #endif } preempt; }; +#ifdef CONFIG_SHADOW_CALL_STACK + void *scs_base; + unsigned long scs_offset; +#endif }; #define thread_saved_pc(tsk) \ @@ -100,11 +104,20 @@ void arch_release_task_struct(struct task_struct *tsk); _TIF_SYSCALL_TRACEPOINT | _TIF_SECCOMP | \ _TIF_SYSCALL_EMU) +#ifdef CONFIG_SHADOW_CALL_STACK +#define INIT_SCS \ + .scs_base = init_shadow_call_stack, \ + .scs_offset = 0, +#else +#define INIT_SCS +#endif + #define INIT_THREAD_INFO(tsk) \ { \ .flags = _TIF_FOREIGN_FPSTATE, \ .preempt_count = INIT_PREEMPT_COUNT, \ .addr_limit = KERNEL_DS, \ + INIT_SCS \ } #endif /* __ASM_THREAD_INFO_H */ diff --git a/arch/arm64/kernel/Makefile b/arch/arm64/kernel/Makefile index 4e5b8ee31442..151f28521f1e 100644 --- a/arch/arm64/kernel/Makefile +++ b/arch/arm64/kernel/Makefile @@ -63,6 +63,7 @@ obj-$(CONFIG_CRASH_CORE) += crash_core.o obj-$(CONFIG_ARM_SDE_INTERFACE) += sdei.o obj-$(CONFIG_ARM64_SSBD) += ssbd.o obj-$(CONFIG_ARM64_PTR_AUTH) += pointer_auth.o +obj-$(CONFIG_SHADOW_CALL_STACK) += scs.o obj-y += vdso/ probes/ obj-$(CONFIG_COMPAT_VDSO) += vdso32/ diff --git a/arch/arm64/kernel/asm-offsets.c b/arch/arm64/kernel/asm-offsets.c index 9981a0a5a87f..d7934250b68c 100644 --- a/arch/arm64/kernel/asm-offsets.c +++ b/arch/arm64/kernel/asm-offsets.c @@ -34,6 +34,10 @@ int main(void) #ifdef CONFIG_ARM64_SW_TTBR0_PAN DEFINE(TSK_TI_TTBR0, offsetof(struct task_struct, thread_info.ttbr0)); #endif +#ifdef CONFIG_SHADOW_CALL_STACK + DEFINE(TSK_TI_SCS_BASE, offsetof(struct task_struct, thread_info.scs_base)); + DEFINE(TSK_TI_SCS_OFFSET, offsetof(struct task_struct, thread_info.scs_offset)); +#endif DEFINE(TSK_STACK, offsetof(struct task_struct, stack)); #ifdef CONFIG_STACKPROTECTOR DEFINE(TSK_STACK_CANARY, offsetof(struct task_struct, stack_canary)); diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S index ddcde093c433..244268d5ae47 100644 --- a/arch/arm64/kernel/entry.S +++ b/arch/arm64/kernel/entry.S @@ -23,6 +23,7 @@ #include <asm/mmu.h> #include <asm/processor.h> #include <asm/ptrace.h> +#include <asm/scs.h> #include <asm/thread_info.h> #include <asm/asm-uaccess.h> #include <asm/unistd.h> @@ -179,6 +180,8 @@ alternative_cb_end apply_ssbd 1, x22, x23 ptrauth_keys_install_kernel tsk, 1, x20, x22, x23 + + scs_load tsk, x20 .else add x21, sp, #S_FRAME_SIZE get_current_task tsk @@ -343,6 +346,8 @@ alternative_else_nop_endif msr cntkctl_el1, x1 4: #endif + scs_save tsk, x0 + /* No kernel C function calls after this as user keys are set. */ ptrauth_keys_install_user tsk, x0, x1, x2 @@ -388,6 +393,9 @@ alternative_insn eret, nop, ARM64_UNMAP_KERNEL_AT_EL0 .macro irq_stack_entry mov x19, sp // preserve the original sp +#ifdef CONFIG_SHADOW_CALL_STACK + mov x24, x18 // preserve the original shadow stack +#endif /* * Compare sp with the base of the task stack. @@ -405,15 +413,25 @@ alternative_insn eret, nop, ARM64_UNMAP_KERNEL_AT_EL0 /* switch to the irq stack */ mov sp, x26 + +#ifdef CONFIG_SHADOW_CALL_STACK + /* also switch to the irq shadow stack */ + adr_this_cpu x18, irq_shadow_call_stack, x26 +#endif + 9998: .endm /* - * x19 should be preserved between irq_stack_entry and - * irq_stack_exit. + * The callee-saved regs (x19-x29) should be preserved between + * irq_stack_entry and irq_stack_exit, but note that kernel_entry + * uses x20-x23 to store data for later use. */ .macro irq_stack_exit mov sp, x19 +#ifdef CONFIG_SHADOW_CALL_STACK + mov x18, x24 +#endif .endm /* GPRs used by entry code */ @@ -901,6 +919,8 @@ SYM_FUNC_START(cpu_switch_to) mov sp, x9 msr sp_el0, x1 ptrauth_keys_install_kernel x1, 1, x8, x9, x10 + scs_save x0, x8 + scs_load x1, x8 ret SYM_FUNC_END(cpu_switch_to) NOKPROBE(cpu_switch_to) diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S index 57a91032b4c2..2b01c19c5483 100644 --- a/arch/arm64/kernel/head.S +++ b/arch/arm64/kernel/head.S @@ -27,6 +27,7 @@ #include <asm/pgtable-hwdef.h> #include <asm/pgtable.h> #include <asm/page.h> +#include <asm/scs.h> #include <asm/smp.h> #include <asm/sysreg.h> #include <asm/thread_info.h> @@ -424,6 +425,10 @@ SYM_FUNC_START_LOCAL(__primary_switched) stp xzr, x30, [sp, #-16]! mov x29, sp +#ifdef CONFIG_SHADOW_CALL_STACK + adr_l x18, init_shadow_call_stack // Set shadow call stack +#endif + str_l x21, __fdt_pointer, x5 // Save FDT pointer ldr_l x4, kimage_vaddr // Save the offset between @@ -737,6 +742,7 @@ SYM_FUNC_START_LOCAL(__secondary_switched) ldr x2, [x0, #CPU_BOOT_TASK] cbz x2, __secondary_too_slow msr sp_el0, x2 + scs_load x2, x3 mov x29, #0 mov x30, #0 b secondary_start_kernel diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c index 56be4cbf771f..a35d3318492c 100644 --- a/arch/arm64/kernel/process.c +++ b/arch/arm64/kernel/process.c @@ -52,6 +52,7 @@ #include <asm/mmu_context.h> #include <asm/processor.h> #include <asm/pointer_auth.h> +#include <asm/scs.h> #include <asm/stacktrace.h> #if defined(CONFIG_STACKPROTECTOR) && !defined(CONFIG_STACKPROTECTOR_PER_TASK) @@ -515,6 +516,7 @@ __notrace_funcgraph struct task_struct *__switch_to(struct task_struct *prev, entry_task_switch(next); uao_thread_switch(next); ssbs_thread_switch(next); + scs_overflow_check(next); /* * Complete any pending TLB or cache maintenance on this CPU in case diff --git a/arch/arm64/kernel/scs.c b/arch/arm64/kernel/scs.c new file mode 100644 index 000000000000..acc6741d1a40 --- /dev/null +++ b/arch/arm64/kernel/scs.c @@ -0,0 +1,15 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Shadow Call Stack support. + * + * Copyright (C) 2019 Google LLC + */ + +#include <linux/percpu.h> +#include <asm/scs.h> + +/* Allocate a static per-CPU shadow stack */ +#define DEFINE_SCS(name) \ + DEFINE_PER_CPU(unsigned long [SCS_SIZE/sizeof(long)], name) \ + +DEFINE_SCS(irq_shadow_call_stack); |