| Message ID | 20191031164637.48901-18-samitolvanen@google.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | add support for Clang's Shadow Call Stack | expand |
On Thu, Oct 31, 2019 at 09:46:37AM -0700, samitolvanen@google.com wrote: > This change implements shadow stack switching, initial SCS set-up, > and interrupt shadow stacks for arm64. > > Signed-off-by: Sami Tolvanen <samitolvanen@google.com> The only suggestion would be calling attention the clearing step (both in comments below and in the commit log), just to record the earlier discussion about it. Reviewed-by: Kees Cook <keescook@chromium.org> -Kees > --- > arch/arm64/Kconfig | 5 ++++ > arch/arm64/include/asm/scs.h | 37 ++++++++++++++++++++++++++ > 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/entry.S | 28 ++++++++++++++++++++ > arch/arm64/kernel/head.S | 9 +++++++ > arch/arm64/kernel/irq.c | 2 ++ > arch/arm64/kernel/process.c | 2 ++ > arch/arm64/kernel/scs.c | 39 ++++++++++++++++++++++++++++ > arch/arm64/kernel/smp.c | 4 +++ > 12 files changed, 137 insertions(+) > 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 42867174920f..f4c94c5e8012 100644 > --- a/arch/arm64/Kconfig > +++ b/arch/arm64/Kconfig > @@ -66,6 +66,7 @@ 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 GCC_VERSION >= 50000 || CC_IS_CLANG > select ARCH_SUPPORTS_NUMA_BALANCING > @@ -948,6 +949,10 @@ 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..c50d2b0c6c5f > --- /dev/null > +++ b/arch/arm64/include/asm/scs.h > @@ -0,0 +1,37 @@ > +/* SPDX-License-Identifier: GPL-2.0 */ > +#ifndef _ASM_SCS_H > +#define _ASM_SCS_H > + > +#ifndef __ASSEMBLY__ > + > +#include <linux/scs.h> > + > +#ifdef CONFIG_SHADOW_CALL_STACK > + > +extern void scs_init_irq(void); > + > +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_init_irq(void) {} > +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/stacktrace.h b/arch/arm64/include/asm/stacktrace.h > index 4d9b1f48dc39..b6cf32fb4efe 100644 > --- a/arch/arm64/include/asm/stacktrace.h > +++ b/arch/arm64/include/asm/stacktrace.h > @@ -68,6 +68,10 @@ extern void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk); > > DECLARE_PER_CPU(unsigned long *, irq_stack_ptr); > > +#ifdef CONFIG_SHADOW_CALL_STACK > +DECLARE_PER_CPU(unsigned long *, irq_shadow_call_stack_ptr); > +#endif > + > static inline bool on_irq_stack(unsigned long sp, > struct stack_info *info) > { > diff --git a/arch/arm64/include/asm/thread_info.h b/arch/arm64/include/asm/thread_info.h > index f0cec4160136..8c73764b9ed2 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 478491f07b4f..b3995329d9e5 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 214685760e1c..f6762b9ae1e1 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 cf3bd2976e57..12a5bc209280 100644 > --- a/arch/arm64/kernel/entry.S > +++ b/arch/arm64/kernel/entry.S > @@ -172,6 +172,10 @@ alternative_cb_end > > apply_ssbd 1, x22, x23 > > +#ifdef CONFIG_SHADOW_CALL_STACK > + ldr x18, [tsk, #TSK_TI_SCS] // Restore shadow call stack > + str xzr, [tsk, #TSK_TI_SCS] > +#endif > .else > add x21, sp, #S_FRAME_SIZE > get_current_task tsk > @@ -278,6 +282,12 @@ 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 > @@ -383,6 +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 x20, x18 // preserve the original shadow stack > +#endif > > /* > * Compare sp with the base of the task stack. > @@ -400,6 +413,12 @@ 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 */ > + ldr_this_cpu x18, irq_shadow_call_stack_ptr, x26 > +#endif > + > 9998: > .endm > > @@ -409,6 +428,10 @@ alternative_insn eret, nop, ARM64_UNMAP_KERNEL_AT_EL0 > */ > .macro irq_stack_exit > mov sp, x19 > +#ifdef CONFIG_SHADOW_CALL_STACK > + /* x20 is also preserved */ > + mov x18, x20 > +#endif > .endm > > /* GPRs used by entry code */ > @@ -1155,6 +1178,11 @@ ENTRY(cpu_switch_to) > ldr lr, [x8] > mov sp, x9 > msr sp_el0, x1 > +#ifdef CONFIG_SHADOW_CALL_STACK > + str x18, [x0, #TSK_TI_SCS] > + ldr x18, [x1, #TSK_TI_SCS] > + str xzr, [x1, #TSK_TI_SCS] For example here. > +#endif > ret > ENDPROC(cpu_switch_to) > NOKPROBE(cpu_switch_to) > diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S > index 989b1944cb71..2be977c6496f 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 @@ __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 > @@ -731,6 +736,10 @@ __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] And here. Maybe something like "// Limit visibility of saved SCS" -Kees > +#endif > mov x29, #0 > mov x30, #0 > b secondary_start_kernel > diff --git a/arch/arm64/kernel/irq.c b/arch/arm64/kernel/irq.c > index 04a327ccf84d..fe0ca522ff60 100644 > --- a/arch/arm64/kernel/irq.c > +++ b/arch/arm64/kernel/irq.c > @@ -21,6 +21,7 @@ > #include <linux/vmalloc.h> > #include <asm/daifflags.h> > #include <asm/vmap_stack.h> > +#include <asm/scs.h> > > unsigned long irq_err_count; > > @@ -63,6 +64,7 @@ static void init_irq_stacks(void) > void __init init_IRQ(void) > { > init_irq_stacks(); > + scs_init_irq(); > irqchip_init(); > if (!handle_arch_irq) > panic("No interrupt controller found."); > diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c > index 71f788cd2b18..5f0aec285848 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) > @@ -507,6 +508,7 @@ __notrace_funcgraph struct task_struct *__switch_to(struct task_struct *prev, > uao_thread_switch(next); > ptrauth_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..6f255072c9a9 > --- /dev/null > +++ b/arch/arm64/kernel/scs.c > @@ -0,0 +1,39 @@ > +// SPDX-License-Identifier: GPL-2.0 > +/* > + * Shadow Call Stack support. > + * > + * Copyright (C) 2019 Google LLC > + */ > + > +#include <linux/percpu.h> > +#include <linux/vmalloc.h> > +#include <asm/scs.h> > + > +DEFINE_PER_CPU(unsigned long *, irq_shadow_call_stack_ptr); > + > +#ifndef CONFIG_SHADOW_CALL_STACK_VMAP > +DEFINE_PER_CPU(unsigned long [SCS_SIZE/sizeof(long)], irq_shadow_call_stack) > + __aligned(SCS_SIZE); > +#endif > + > +void scs_init_irq(void) > +{ > + int cpu; > + > + for_each_possible_cpu(cpu) { > +#ifdef CONFIG_SHADOW_CALL_STACK_VMAP > + unsigned long *p; > + > + p = __vmalloc_node_range(SCS_SIZE, SCS_SIZE, > + VMALLOC_START, VMALLOC_END, > + SCS_GFP, PAGE_KERNEL, > + 0, cpu_to_node(cpu), > + __builtin_return_address(0)); > + > + per_cpu(irq_shadow_call_stack_ptr, cpu) = p; > +#else > + per_cpu(irq_shadow_call_stack_ptr, cpu) = > + per_cpu(irq_shadow_call_stack, cpu); > +#endif /* CONFIG_SHADOW_CALL_STACK_VMAP */ > + } > +} > diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c > index dc9fe879c279..cc1938a585d2 100644 > --- a/arch/arm64/kernel/smp.c > +++ b/arch/arm64/kernel/smp.c > @@ -44,6 +44,7 @@ > #include <asm/pgtable.h> > #include <asm/pgalloc.h> > #include <asm/processor.h> > +#include <asm/scs.h> > #include <asm/smp_plat.h> > #include <asm/sections.h> > #include <asm/tlbflush.h> > @@ -357,6 +358,9 @@ void cpu_die(void) > { > unsigned int cpu = smp_processor_id(); > > + /* Save the shadow stack pointer before exiting the idle task */ > + scs_save(current); > + > idle_task_exit(); > > local_daif_mask(); > -- > 2.24.0.rc0.303.g954a862665-goog >
On Thu, Oct 31, 2019 at 8:45 PM Kees Cook <keescook@chromium.org> wrote: > The only suggestion would be calling attention the clearing step (both in > comments below and in the commit log), just to record the earlier > discussion about it. Sure, makes sense. I'll add comments about this in v4. Sami
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig index 42867174920f..f4c94c5e8012 100644 --- a/arch/arm64/Kconfig +++ b/arch/arm64/Kconfig @@ -66,6 +66,7 @@ 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 GCC_VERSION >= 50000 || CC_IS_CLANG select ARCH_SUPPORTS_NUMA_BALANCING @@ -948,6 +949,10 @@ 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..c50d2b0c6c5f --- /dev/null +++ b/arch/arm64/include/asm/scs.h @@ -0,0 +1,37 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef _ASM_SCS_H +#define _ASM_SCS_H + +#ifndef __ASSEMBLY__ + +#include <linux/scs.h> + +#ifdef CONFIG_SHADOW_CALL_STACK + +extern void scs_init_irq(void); + +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_init_irq(void) {} +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/stacktrace.h b/arch/arm64/include/asm/stacktrace.h index 4d9b1f48dc39..b6cf32fb4efe 100644 --- a/arch/arm64/include/asm/stacktrace.h +++ b/arch/arm64/include/asm/stacktrace.h @@ -68,6 +68,10 @@ extern void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk); DECLARE_PER_CPU(unsigned long *, irq_stack_ptr); +#ifdef CONFIG_SHADOW_CALL_STACK +DECLARE_PER_CPU(unsigned long *, irq_shadow_call_stack_ptr); +#endif + static inline bool on_irq_stack(unsigned long sp, struct stack_info *info) { diff --git a/arch/arm64/include/asm/thread_info.h b/arch/arm64/include/asm/thread_info.h index f0cec4160136..8c73764b9ed2 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 478491f07b4f..b3995329d9e5 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 214685760e1c..f6762b9ae1e1 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 cf3bd2976e57..12a5bc209280 100644 --- a/arch/arm64/kernel/entry.S +++ b/arch/arm64/kernel/entry.S @@ -172,6 +172,10 @@ alternative_cb_end apply_ssbd 1, x22, x23 +#ifdef CONFIG_SHADOW_CALL_STACK + ldr x18, [tsk, #TSK_TI_SCS] // Restore shadow call stack + str xzr, [tsk, #TSK_TI_SCS] +#endif .else add x21, sp, #S_FRAME_SIZE get_current_task tsk @@ -278,6 +282,12 @@ 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 @@ -383,6 +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 x20, x18 // preserve the original shadow stack +#endif /* * Compare sp with the base of the task stack. @@ -400,6 +413,12 @@ 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 */ + ldr_this_cpu x18, irq_shadow_call_stack_ptr, x26 +#endif + 9998: .endm @@ -409,6 +428,10 @@ alternative_insn eret, nop, ARM64_UNMAP_KERNEL_AT_EL0 */ .macro irq_stack_exit mov sp, x19 +#ifdef CONFIG_SHADOW_CALL_STACK + /* x20 is also preserved */ + mov x18, x20 +#endif .endm /* GPRs used by entry code */ @@ -1155,6 +1178,11 @@ ENTRY(cpu_switch_to) ldr lr, [x8] mov sp, x9 msr sp_el0, x1 +#ifdef CONFIG_SHADOW_CALL_STACK + str x18, [x0, #TSK_TI_SCS] + ldr x18, [x1, #TSK_TI_SCS] + str xzr, [x1, #TSK_TI_SCS] +#endif ret ENDPROC(cpu_switch_to) NOKPROBE(cpu_switch_to) diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S index 989b1944cb71..2be977c6496f 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 @@ __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 @@ -731,6 +736,10 @@ __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] +#endif mov x29, #0 mov x30, #0 b secondary_start_kernel diff --git a/arch/arm64/kernel/irq.c b/arch/arm64/kernel/irq.c index 04a327ccf84d..fe0ca522ff60 100644 --- a/arch/arm64/kernel/irq.c +++ b/arch/arm64/kernel/irq.c @@ -21,6 +21,7 @@ #include <linux/vmalloc.h> #include <asm/daifflags.h> #include <asm/vmap_stack.h> +#include <asm/scs.h> unsigned long irq_err_count; @@ -63,6 +64,7 @@ static void init_irq_stacks(void) void __init init_IRQ(void) { init_irq_stacks(); + scs_init_irq(); irqchip_init(); if (!handle_arch_irq) panic("No interrupt controller found."); diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c index 71f788cd2b18..5f0aec285848 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) @@ -507,6 +508,7 @@ __notrace_funcgraph struct task_struct *__switch_to(struct task_struct *prev, uao_thread_switch(next); ptrauth_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..6f255072c9a9 --- /dev/null +++ b/arch/arm64/kernel/scs.c @@ -0,0 +1,39 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Shadow Call Stack support. + * + * Copyright (C) 2019 Google LLC + */ + +#include <linux/percpu.h> +#include <linux/vmalloc.h> +#include <asm/scs.h> + +DEFINE_PER_CPU(unsigned long *, irq_shadow_call_stack_ptr); + +#ifndef CONFIG_SHADOW_CALL_STACK_VMAP +DEFINE_PER_CPU(unsigned long [SCS_SIZE/sizeof(long)], irq_shadow_call_stack) + __aligned(SCS_SIZE); +#endif + +void scs_init_irq(void) +{ + int cpu; + + for_each_possible_cpu(cpu) { +#ifdef CONFIG_SHADOW_CALL_STACK_VMAP + unsigned long *p; + + p = __vmalloc_node_range(SCS_SIZE, SCS_SIZE, + VMALLOC_START, VMALLOC_END, + SCS_GFP, PAGE_KERNEL, + 0, cpu_to_node(cpu), + __builtin_return_address(0)); + + per_cpu(irq_shadow_call_stack_ptr, cpu) = p; +#else + per_cpu(irq_shadow_call_stack_ptr, cpu) = + per_cpu(irq_shadow_call_stack, cpu); +#endif /* CONFIG_SHADOW_CALL_STACK_VMAP */ + } +} diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c index dc9fe879c279..cc1938a585d2 100644 --- a/arch/arm64/kernel/smp.c +++ b/arch/arm64/kernel/smp.c @@ -44,6 +44,7 @@ #include <asm/pgtable.h> #include <asm/pgalloc.h> #include <asm/processor.h> +#include <asm/scs.h> #include <asm/smp_plat.h> #include <asm/sections.h> #include <asm/tlbflush.h> @@ -357,6 +358,9 @@ void cpu_die(void) { unsigned int cpu = smp_processor_id(); + /* Save the shadow stack pointer before exiting the idle task */ + scs_save(current); + idle_task_exit(); local_daif_mask();
This change implements shadow stack switching, initial SCS set-up, and interrupt shadow stacks for arm64. Signed-off-by: Sami Tolvanen <samitolvanen@google.com> --- arch/arm64/Kconfig | 5 ++++ arch/arm64/include/asm/scs.h | 37 ++++++++++++++++++++++++++ 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/entry.S | 28 ++++++++++++++++++++ arch/arm64/kernel/head.S | 9 +++++++ arch/arm64/kernel/irq.c | 2 ++ arch/arm64/kernel/process.c | 2 ++ arch/arm64/kernel/scs.c | 39 ++++++++++++++++++++++++++++ arch/arm64/kernel/smp.c | 4 +++ 12 files changed, 137 insertions(+) create mode 100644 arch/arm64/include/asm/scs.h create mode 100644 arch/arm64/kernel/scs.c