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a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:in-reply-to:message-id:mime-version :references:subject:from:to:cc; bh=6eRw7Y3w5tFwzaDk4cwrjvOp2ujNvhfVr2XLQsgcDIc=; b=KCLSF/tknvLkPPaCfnZtwweiKtVb9b6EYAK+aBg/hwHrmO4FaFSrZmHb4UFKEPbDG2 NqGBAhlrqIjHj1Y0fuP6m96VdNSOMkYmNi0ZVs+S1knsIPFHcPSPBYIl6Iol7OX3630/ Z0CoDSnlQq8JQ9d1W+XM4yjWUJ32z1JWY4tL7V2k8L8zUjU0dEPRpFN07nxvmtLoDKiV uv9BXzD/Rp2Fvu2WTpCm8AzYRJWWaE+PTm1aP1m29n2vaoTrjLPh4ZDVbve8Qn0ybj97 T91jHDmR++5NRMugr21+TdfmjlvhZL+ClFoMCHW3vJDBca26oQXDEpulEzW/O+dcnK1E LYgA== X-Gm-Message-State: AGi0Pubtk2hC9Ij9SpF2mSTsOozaHSXsIaY3P20fLn+7RYlWZVIPIesr z+VExt9Z9mNlG6hBaIB8SfFxyQhMshO/jGyF2u0= X-Google-Smtp-Source: APiQypLqITkQwYFBJL5fmJ4Scj4591QC2iEfv7D5vdvy8OQNehbWaINW1Ho/mISESA0m1HZ1h0ChyaTi2ZpBK+1Kir8= X-Received: by 2002:a17:90a:2645:: with SMTP id l63mr2922202pje.54.1587435321715; Mon, 20 Apr 2020 19:15:21 -0700 (PDT) Date: Mon, 20 Apr 2020 19:14:51 -0700 In-Reply-To: <20200421021453.198187-1-samitolvanen@google.com> Message-Id: <20200421021453.198187-11-samitolvanen@google.com> Mime-Version: 1.0 References: <20191018161033.261971-1-samitolvanen@google.com> <20200421021453.198187-1-samitolvanen@google.com> X-Mailer: git-send-email 2.26.1.301.g55bc3eb7cb9-goog Subject: [PATCH v12 10/12] arm64: implement Shadow Call Stack From: Sami Tolvanen To: Will Deacon , Catalin Marinas , James Morse , Steven Rostedt , Ard Biesheuvel , Mark Rutland , Masahiro Yamada , Michal Marek , Ingo Molnar , Peter Zijlstra , Juri Lelli , Vincent Guittot X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200420_191523_667359_D08C0C8C X-CRM114-Status: GOOD ( 18.17 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Kees Cook , Jann Horn , Marc Zyngier , kernel-hardening@lists.openwall.com, Nick Desaulniers , linux-kernel@vger.kernel.org, Miguel Ojeda , Masami Hiramatsu , Sami Tolvanen , clang-built-linux@googlegroups.com, Laura Abbott , Dave Martin , linux-arm-kernel@lists.infradead.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org This change implements shadow stack switching, initial SCS set-up, and interrupt shadow stacks for arm64. Signed-off-by: Sami Tolvanen Reviewed-by: Kees Cook --- arch/arm64/Kconfig | 5 ++++ arch/arm64/include/asm/scs.h | 34 ++++++++++++++++++++++++++++ arch/arm64/include/asm/thread_info.h | 3 +++ arch/arm64/kernel/Makefile | 1 + arch/arm64/kernel/asm-offsets.c | 3 +++ arch/arm64/kernel/entry.S | 33 +++++++++++++++++++++++++-- arch/arm64/kernel/head.S | 8 +++++++ arch/arm64/kernel/process.c | 2 ++ arch/arm64/kernel/scs.c | 16 +++++++++++++ arch/arm64/kernel/smp.c | 4 ++++ 10 files changed, 107 insertions(+), 2 deletions(-) create mode 100644 arch/arm64/include/asm/scs.h create mode 100644 arch/arm64/kernel/scs.c 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 $(cc-option, -fsanitize=shadow-call-stack -ffixed-x18) + config SECCOMP bool "Enable seccomp to safely compute untrusted bytecode" ---help--- diff --git a/arch/arm64/include/asm/scs.h b/arch/arm64/include/asm/scs.h new file mode 100644 index 000000000000..27dced9cbaf7 --- /dev/null +++ b/arch/arm64/include/asm/scs.h @@ -0,0 +1,34 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef _ASM_SCS_H +#define _ASM_SCS_H + +#ifndef __ASSEMBLY__ + +#include + +#ifdef CONFIG_SHADOW_CALL_STACK + +static __always_inline void scs_save(struct task_struct *tsk) +{ + void *s; + + asm volatile("mov %0, x18" : "=r" (s)); + task_set_scs(tsk, s); +} + +static inline void scs_overflow_check(struct task_struct *tsk) +{ + if (unlikely(scs_corrupted(tsk))) + panic("corrupted shadow stack detected inside scheduler\n"); +} + +#else /* CONFIG_SHADOW_CALL_STACK */ + +static inline void scs_save(struct task_struct *tsk) {} +static inline void scs_overflow_check(struct task_struct *tsk) {} + +#endif /* CONFIG_SHADOW_CALL_STACK */ + +#endif /* __ASSEMBLY __ */ + +#endif /* _ASM_SCS_H */ diff --git a/arch/arm64/include/asm/thread_info.h b/arch/arm64/include/asm/thread_info.h index 512174a8e789..1fb651f73da3 100644 --- a/arch/arm64/include/asm/thread_info.h +++ b/arch/arm64/include/asm/thread_info.h @@ -41,6 +41,9 @@ struct thread_info { #endif } preempt; }; +#ifdef CONFIG_SHADOW_CALL_STACK + void *shadow_call_stack; +#endif }; #define thread_saved_pc(tsk) \ diff --git a/arch/arm64/kernel/Makefile b/arch/arm64/kernel/Makefile index 4e5b8ee31442..151f28521f1e 100644 --- a/arch/arm64/kernel/Makefile +++ b/arch/arm64/kernel/Makefile @@ -63,6 +63,7 @@ obj-$(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..777a662888ec 100644 --- a/arch/arm64/kernel/asm-offsets.c +++ b/arch/arm64/kernel/asm-offsets.c @@ -33,6 +33,9 @@ int main(void) DEFINE(TSK_TI_ADDR_LIMIT, offsetof(struct task_struct, thread_info.addr_limit)); #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, offsetof(struct task_struct, thread_info.shadow_call_stack)); #endif DEFINE(TSK_STACK, offsetof(struct task_struct, stack)); #ifdef CONFIG_STACKPROTECTOR diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S index ddcde093c433..14f0ff763b39 100644 --- a/arch/arm64/kernel/entry.S +++ b/arch/arm64/kernel/entry.S @@ -179,6 +179,11 @@ alternative_cb_end apply_ssbd 1, x22, x23 ptrauth_keys_install_kernel tsk, 1, x20, x22, x23 + +#ifdef CONFIG_SHADOW_CALL_STACK + ldr x18, [tsk, #TSK_TI_SCS] // Restore shadow call stack + str xzr, [tsk, #TSK_TI_SCS] // Limit visibility of saved SCS +#endif .else add x21, sp, #S_FRAME_SIZE get_current_task tsk @@ -280,6 +285,12 @@ alternative_else_nop_endif ct_user_enter .endif +#ifdef CONFIG_SHADOW_CALL_STACK + .if \el == 0 + str x18, [tsk, #TSK_TI_SCS] // Save shadow call stack + .endif +#endif + #ifdef CONFIG_ARM64_SW_TTBR0_PAN /* * Restore access to TTBR0_EL1. If returning to EL0, no need for SPSR @@ -388,6 +399,9 @@ 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 +419,25 @@ 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 +925,11 @@ SYM_FUNC_START(cpu_switch_to) mov sp, x9 msr sp_el0, x1 ptrauth_keys_install_kernel x1, 1, x8, x9, x10 +#ifdef CONFIG_SHADOW_CALL_STACK + str x18, [x0, #TSK_TI_SCS] + ldr x18, [x1, #TSK_TI_SCS] + str xzr, [x1, #TSK_TI_SCS] // limit visibility of saved SCS +#endif 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..1514445bbccb 100644 --- a/arch/arm64/kernel/head.S +++ b/arch/arm64/kernel/head.S @@ -424,6 +424,10 @@ 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 +741,10 @@ SYM_FUNC_START_LOCAL(__secondary_switched) ldr x2, [x0, #CPU_BOOT_TASK] cbz x2, __secondary_too_slow msr sp_el0, x2 +#ifdef CONFIG_SHADOW_CALL_STACK + ldr x18, [x2, #TSK_TI_SCS] // set shadow call stack + str xzr, [x2, #TSK_TI_SCS] // limit visibility of saved SCS +#endif 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 #include #include +#include #include #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..086ad97bba86 --- /dev/null +++ b/arch/arm64/kernel/scs.c @@ -0,0 +1,16 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Shadow Call Stack support. + * + * Copyright (C) 2019 Google LLC + */ + +#include +#include + +/* Allocate a static per-CPU shadow stack */ +#define DEFINE_SCS(name) \ + DEFINE_PER_CPU(unsigned long [SCS_SIZE/sizeof(long)], name) \ + __aligned(SCS_SIZE) + +DEFINE_SCS(irq_shadow_call_stack); diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c index 061f60fe452f..1d112e34a636 100644 --- a/arch/arm64/kernel/smp.c +++ b/arch/arm64/kernel/smp.c @@ -46,6 +46,7 @@ #include #include #include +#include #include #include #include @@ -370,6 +371,9 @@ void cpu_die(void) unsigned int cpu = smp_processor_id(); const struct cpu_operations *ops = get_cpu_ops(cpu); + /* Save the shadow stack pointer before exiting the idle task */ + scs_save(current); + idle_task_exit(); local_daif_mask(); -- 2.26.1.301.g55bc3eb7cb9-goog _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel