272 lines
6.3 KiB
C
272 lines
6.3 KiB
C
// 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_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/uaccess.h>
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#include <asm/alternative.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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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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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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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 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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if (!low)
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return false;
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if (sp < low || sp >= high)
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return false;
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if (info) {
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info->low = low;
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info->high = high;
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info->type = STACK_TYPE_SDEI_NORMAL;
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}
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return true;
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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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if (!low)
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return false;
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if (sp < low || sp >= high)
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return false;
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if (info) {
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info->low = low;
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info->high = high;
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info->type = STACK_TYPE_SDEI_CRITICAL;
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}
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return true;
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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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return 0;
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}
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if (IS_ENABLED(CONFIG_VMAP_STACK)) {
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if (init_sdei_stacks())
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return 0;
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}
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sdei_exit_mode = (conduit == 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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}
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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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/*
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* We didn't take an exception to get here, set PAN. UAO will be cleared
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* by sdei_event_handler()s set_fs(USER_DS) call.
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*/
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__uaccess_enable_hw_pan();
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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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asmlinkage __kprobes notrace 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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bool do_nmi_exit = false;
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/*
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* nmi_enter() deals with printk() re-entrance and use of RCU when
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* RCU believed this CPU was idle. Because critical events can
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* interrupt normal events, we may already be in_nmi().
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*/
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if (!in_nmi()) {
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nmi_enter();
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do_nmi_exit = true;
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}
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ret = _sdei_handler(regs, arg);
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if (do_nmi_exit)
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nmi_exit();
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return ret;
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}
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