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336 lines
8.0 KiB
336 lines
8.0 KiB
// SPDX-License-Identifier: GPL-2.0 |
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// Copyright (C) 2017 Arm Ltd. |
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#define pr_fmt(fmt) "sdei: " fmt |
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#include <linux/arm-smccc.h> |
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#include <linux/arm_sdei.h> |
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#include <linux/hardirq.h> |
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#include <linux/irqflags.h> |
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#include <linux/sched/task_stack.h> |
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#include <linux/scs.h> |
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#include <linux/uaccess.h> |
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#include <asm/alternative.h> |
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#include <asm/exception.h> |
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#include <asm/kprobes.h> |
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#include <asm/mmu.h> |
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#include <asm/ptrace.h> |
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#include <asm/sections.h> |
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#include <asm/stacktrace.h> |
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#include <asm/sysreg.h> |
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#include <asm/vmap_stack.h> |
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unsigned long sdei_exit_mode; |
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/* |
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* VMAP'd stacks checking for stack overflow on exception using sp as a scratch |
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* register, meaning SDEI has to switch to its own stack. We need two stacks as |
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* a critical event may interrupt a normal event that has just taken a |
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* synchronous exception, and is using sp as scratch register. For a critical |
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* event interrupting a normal event, we can't reliably tell if we were on the |
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* sdei stack. |
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* For now, we allocate stacks when the driver is probed. |
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*/ |
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DECLARE_PER_CPU(unsigned long *, sdei_stack_normal_ptr); |
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DECLARE_PER_CPU(unsigned long *, sdei_stack_critical_ptr); |
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#ifdef CONFIG_VMAP_STACK |
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DEFINE_PER_CPU(unsigned long *, sdei_stack_normal_ptr); |
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DEFINE_PER_CPU(unsigned long *, sdei_stack_critical_ptr); |
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#endif |
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DECLARE_PER_CPU(unsigned long *, sdei_shadow_call_stack_normal_ptr); |
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DECLARE_PER_CPU(unsigned long *, sdei_shadow_call_stack_critical_ptr); |
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#ifdef CONFIG_SHADOW_CALL_STACK |
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DEFINE_PER_CPU(unsigned long *, sdei_shadow_call_stack_normal_ptr); |
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DEFINE_PER_CPU(unsigned long *, sdei_shadow_call_stack_critical_ptr); |
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#endif |
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static void _free_sdei_stack(unsigned long * __percpu *ptr, int cpu) |
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{ |
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unsigned long *p; |
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p = per_cpu(*ptr, cpu); |
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if (p) { |
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per_cpu(*ptr, cpu) = NULL; |
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vfree(p); |
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} |
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} |
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static void free_sdei_stacks(void) |
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{ |
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int cpu; |
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if (!IS_ENABLED(CONFIG_VMAP_STACK)) |
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return; |
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for_each_possible_cpu(cpu) { |
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_free_sdei_stack(&sdei_stack_normal_ptr, cpu); |
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_free_sdei_stack(&sdei_stack_critical_ptr, cpu); |
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} |
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} |
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static int _init_sdei_stack(unsigned long * __percpu *ptr, int cpu) |
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{ |
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unsigned long *p; |
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p = arch_alloc_vmap_stack(SDEI_STACK_SIZE, cpu_to_node(cpu)); |
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if (!p) |
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return -ENOMEM; |
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per_cpu(*ptr, cpu) = p; |
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return 0; |
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} |
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static int init_sdei_stacks(void) |
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{ |
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int cpu; |
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int err = 0; |
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if (!IS_ENABLED(CONFIG_VMAP_STACK)) |
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return 0; |
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for_each_possible_cpu(cpu) { |
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err = _init_sdei_stack(&sdei_stack_normal_ptr, cpu); |
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if (err) |
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break; |
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err = _init_sdei_stack(&sdei_stack_critical_ptr, cpu); |
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if (err) |
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break; |
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} |
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if (err) |
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free_sdei_stacks(); |
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return err; |
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} |
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static void _free_sdei_scs(unsigned long * __percpu *ptr, int cpu) |
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{ |
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void *s; |
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s = per_cpu(*ptr, cpu); |
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if (s) { |
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per_cpu(*ptr, cpu) = NULL; |
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scs_free(s); |
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} |
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} |
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static void free_sdei_scs(void) |
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{ |
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int cpu; |
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for_each_possible_cpu(cpu) { |
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_free_sdei_scs(&sdei_shadow_call_stack_normal_ptr, cpu); |
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_free_sdei_scs(&sdei_shadow_call_stack_critical_ptr, cpu); |
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} |
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} |
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static int _init_sdei_scs(unsigned long * __percpu *ptr, int cpu) |
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{ |
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void *s; |
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s = scs_alloc(cpu_to_node(cpu)); |
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if (!s) |
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return -ENOMEM; |
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per_cpu(*ptr, cpu) = s; |
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return 0; |
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} |
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static int init_sdei_scs(void) |
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{ |
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int cpu; |
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int err = 0; |
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if (!IS_ENABLED(CONFIG_SHADOW_CALL_STACK)) |
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return 0; |
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for_each_possible_cpu(cpu) { |
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err = _init_sdei_scs(&sdei_shadow_call_stack_normal_ptr, cpu); |
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if (err) |
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break; |
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err = _init_sdei_scs(&sdei_shadow_call_stack_critical_ptr, cpu); |
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if (err) |
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break; |
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} |
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if (err) |
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free_sdei_scs(); |
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return err; |
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} |
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static bool on_sdei_normal_stack(unsigned long sp, struct stack_info *info) |
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{ |
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unsigned long low = (unsigned long)raw_cpu_read(sdei_stack_normal_ptr); |
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unsigned long high = low + SDEI_STACK_SIZE; |
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return on_stack(sp, low, high, STACK_TYPE_SDEI_NORMAL, info); |
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} |
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static bool on_sdei_critical_stack(unsigned long sp, struct stack_info *info) |
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{ |
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unsigned long low = (unsigned long)raw_cpu_read(sdei_stack_critical_ptr); |
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unsigned long high = low + SDEI_STACK_SIZE; |
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return on_stack(sp, low, high, STACK_TYPE_SDEI_CRITICAL, info); |
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} |
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bool _on_sdei_stack(unsigned long sp, struct stack_info *info) |
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{ |
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if (!IS_ENABLED(CONFIG_VMAP_STACK)) |
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return false; |
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if (on_sdei_critical_stack(sp, info)) |
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return true; |
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if (on_sdei_normal_stack(sp, info)) |
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return true; |
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return false; |
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} |
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unsigned long sdei_arch_get_entry_point(int conduit) |
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{ |
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/* |
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* SDEI works between adjacent exception levels. If we booted at EL1 we |
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* assume a hypervisor is marshalling events. If we booted at EL2 and |
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* dropped to EL1 because we don't support VHE, then we can't support |
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* SDEI. |
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*/ |
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if (is_hyp_mode_available() && !is_kernel_in_hyp_mode()) { |
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pr_err("Not supported on this hardware/boot configuration\n"); |
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goto out_err; |
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} |
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if (init_sdei_stacks()) |
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goto out_err; |
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if (init_sdei_scs()) |
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goto out_err_free_stacks; |
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sdei_exit_mode = (conduit == SMCCC_CONDUIT_HVC) ? SDEI_EXIT_HVC : SDEI_EXIT_SMC; |
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#ifdef CONFIG_UNMAP_KERNEL_AT_EL0 |
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if (arm64_kernel_unmapped_at_el0()) { |
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unsigned long offset; |
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offset = (unsigned long)__sdei_asm_entry_trampoline - |
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(unsigned long)__entry_tramp_text_start; |
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return TRAMP_VALIAS + offset; |
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} else |
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#endif /* CONFIG_UNMAP_KERNEL_AT_EL0 */ |
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return (unsigned long)__sdei_asm_handler; |
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out_err_free_stacks: |
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free_sdei_stacks(); |
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out_err: |
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return 0; |
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} |
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/* |
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* __sdei_handler() returns one of: |
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* SDEI_EV_HANDLED - success, return to the interrupted context. |
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* SDEI_EV_FAILED - failure, return this error code to firmare. |
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* virtual-address - success, return to this address. |
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*/ |
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static __kprobes unsigned long _sdei_handler(struct pt_regs *regs, |
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struct sdei_registered_event *arg) |
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{ |
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u32 mode; |
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int i, err = 0; |
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int clobbered_registers = 4; |
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u64 elr = read_sysreg(elr_el1); |
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u32 kernel_mode = read_sysreg(CurrentEL) | 1; /* +SPSel */ |
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unsigned long vbar = read_sysreg(vbar_el1); |
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if (arm64_kernel_unmapped_at_el0()) |
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clobbered_registers++; |
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/* Retrieve the missing registers values */ |
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for (i = 0; i < clobbered_registers; i++) { |
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/* from within the handler, this call always succeeds */ |
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sdei_api_event_context(i, ®s->regs[i]); |
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} |
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err = sdei_event_handler(regs, arg); |
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if (err) |
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return SDEI_EV_FAILED; |
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if (elr != read_sysreg(elr_el1)) { |
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/* |
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* We took a synchronous exception from the SDEI handler. |
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* This could deadlock, and if you interrupt KVM it will |
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* hyp-panic instead. |
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*/ |
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pr_warn("unsafe: exception during handler\n"); |
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} |
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mode = regs->pstate & (PSR_MODE32_BIT | PSR_MODE_MASK); |
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/* |
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* If we interrupted the kernel with interrupts masked, we always go |
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* back to wherever we came from. |
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*/ |
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if (mode == kernel_mode && !interrupts_enabled(regs)) |
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return SDEI_EV_HANDLED; |
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/* |
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* Otherwise, we pretend this was an IRQ. This lets user space tasks |
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* receive signals before we return to them, and KVM to invoke it's |
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* world switch to do the same. |
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* |
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* See DDI0487B.a Table D1-7 'Vector offsets from vector table base |
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* address'. |
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*/ |
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if (mode == kernel_mode) |
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return vbar + 0x280; |
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else if (mode & PSR_MODE32_BIT) |
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return vbar + 0x680; |
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return vbar + 0x480; |
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} |
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static void __kprobes notrace __sdei_pstate_entry(void) |
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{ |
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/* |
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* The original SDEI spec (ARM DEN 0054A) can be read ambiguously as to |
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* whether PSTATE bits are inherited unchanged or generated from |
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* scratch, and the TF-A implementation always clears PAN and always |
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* clears UAO. There are no other known implementations. |
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* |
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* Subsequent revisions (ARM DEN 0054B) follow the usual rules for how |
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* PSTATE is modified upon architectural exceptions, and so PAN is |
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* either inherited or set per SCTLR_ELx.SPAN, and UAO is always |
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* cleared. |
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* |
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* We must explicitly reset PAN to the expected state, including |
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* clearing it when the host isn't using it, in case a VM had it set. |
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*/ |
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if (system_uses_hw_pan()) |
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set_pstate_pan(1); |
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else if (cpu_has_pan()) |
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set_pstate_pan(0); |
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} |
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asmlinkage noinstr unsigned long |
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__sdei_handler(struct pt_regs *regs, struct sdei_registered_event *arg) |
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{ |
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unsigned long ret; |
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/* |
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* We didn't take an exception to get here, so the HW hasn't |
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* set/cleared bits in PSTATE that we may rely on. Initialize PAN. |
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*/ |
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__sdei_pstate_entry(); |
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arm64_enter_nmi(regs); |
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ret = _sdei_handler(regs, arg); |
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arm64_exit_nmi(regs); |
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return ret; |
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}
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