1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * Copyright (C) 1992, 1998 Linus Torvalds, Ingo Molnar 4 * 5 * This file contains the lowest level x86-specific interrupt 6 * entry, irq-stacks and irq statistics code. All the remaining 7 * irq logic is done by the generic kernel/irq/ code and 8 * by the x86-specific irq controller code. (e.g. i8259.c and 9 * io_apic.c.) 10 */ 11 12 #include <linux/seq_file.h> 13 #include <linux/interrupt.h> 14 #include <linux/irq.h> 15 #include <linux/kernel_stat.h> 16 #include <linux/notifier.h> 17 #include <linux/cpu.h> 18 #include <linux/delay.h> 19 #include <linux/uaccess.h> 20 #include <linux/percpu.h> 21 #include <linux/mm.h> 22 23 #include <asm/apic.h> 24 #include <asm/nospec-branch.h> 25 26 #ifdef CONFIG_DEBUG_STACKOVERFLOW 27 28 int sysctl_panic_on_stackoverflow __read_mostly; 29 30 /* Debugging check for stack overflow: is there less than 1KB free? */ 31 static int check_stack_overflow(void) 32 { 33 long sp; 34 35 __asm__ __volatile__("andl %%esp,%0" : 36 "=r" (sp) : "0" (THREAD_SIZE - 1)); 37 38 return sp < (sizeof(struct thread_info) + STACK_WARN); 39 } 40 41 static void print_stack_overflow(void) 42 { 43 printk(KERN_WARNING "low stack detected by irq handler\n"); 44 dump_stack(); 45 if (sysctl_panic_on_stackoverflow) 46 panic("low stack detected by irq handler - check messages\n"); 47 } 48 49 #else 50 static inline int check_stack_overflow(void) { return 0; } 51 static inline void print_stack_overflow(void) { } 52 #endif 53 54 DEFINE_PER_CPU(struct irq_stack *, hardirq_stack); 55 DEFINE_PER_CPU(struct irq_stack *, softirq_stack); 56 57 static void call_on_stack(void *func, void *stack) 58 { 59 asm volatile("xchgl %%ebx,%%esp \n" 60 CALL_NOSPEC 61 "movl %%ebx,%%esp \n" 62 : "=b" (stack) 63 : "0" (stack), 64 [thunk_target] "D"(func) 65 : "memory", "cc", "edx", "ecx", "eax"); 66 } 67 68 static inline void *current_stack(void) 69 { 70 return (void *)(current_stack_pointer & ~(THREAD_SIZE - 1)); 71 } 72 73 static inline int execute_on_irq_stack(int overflow, struct irq_desc *desc) 74 { 75 struct irq_stack *curstk, *irqstk; 76 u32 *isp, *prev_esp, arg1; 77 78 curstk = (struct irq_stack *) current_stack(); 79 irqstk = __this_cpu_read(hardirq_stack); 80 81 /* 82 * this is where we switch to the IRQ stack. However, if we are 83 * already using the IRQ stack (because we interrupted a hardirq 84 * handler) we can't do that and just have to keep using the 85 * current stack (which is the irq stack already after all) 86 */ 87 if (unlikely(curstk == irqstk)) 88 return 0; 89 90 isp = (u32 *) ((char *)irqstk + sizeof(*irqstk)); 91 92 /* Save the next esp at the bottom of the stack */ 93 prev_esp = (u32 *)irqstk; 94 *prev_esp = current_stack_pointer; 95 96 if (unlikely(overflow)) 97 call_on_stack(print_stack_overflow, isp); 98 99 asm volatile("xchgl %%ebx,%%esp \n" 100 CALL_NOSPEC 101 "movl %%ebx,%%esp \n" 102 : "=a" (arg1), "=b" (isp) 103 : "0" (desc), "1" (isp), 104 [thunk_target] "D" (desc->handle_irq) 105 : "memory", "cc", "ecx"); 106 return 1; 107 } 108 109 /* 110 * allocate per-cpu stacks for hardirq and for softirq processing 111 */ 112 void irq_ctx_init(int cpu) 113 { 114 struct irq_stack *irqstk; 115 116 if (per_cpu(hardirq_stack, cpu)) 117 return; 118 119 irqstk = page_address(alloc_pages_node(cpu_to_node(cpu), 120 THREADINFO_GFP, 121 THREAD_SIZE_ORDER)); 122 per_cpu(hardirq_stack, cpu) = irqstk; 123 124 irqstk = page_address(alloc_pages_node(cpu_to_node(cpu), 125 THREADINFO_GFP, 126 THREAD_SIZE_ORDER)); 127 per_cpu(softirq_stack, cpu) = irqstk; 128 129 printk(KERN_DEBUG "CPU %u irqstacks, hard=%p soft=%p\n", 130 cpu, per_cpu(hardirq_stack, cpu), per_cpu(softirq_stack, cpu)); 131 } 132 133 void do_softirq_own_stack(void) 134 { 135 struct irq_stack *irqstk; 136 u32 *isp, *prev_esp; 137 138 irqstk = __this_cpu_read(softirq_stack); 139 140 /* build the stack frame on the softirq stack */ 141 isp = (u32 *) ((char *)irqstk + sizeof(*irqstk)); 142 143 /* Push the previous esp onto the stack */ 144 prev_esp = (u32 *)irqstk; 145 *prev_esp = current_stack_pointer; 146 147 call_on_stack(__do_softirq, isp); 148 } 149 150 bool handle_irq(struct irq_desc *desc, struct pt_regs *regs) 151 { 152 int overflow = check_stack_overflow(); 153 154 if (IS_ERR_OR_NULL(desc)) 155 return false; 156 157 if (user_mode(regs) || !execute_on_irq_stack(overflow, desc)) { 158 if (unlikely(overflow)) 159 print_stack_overflow(); 160 generic_handle_irq_desc(desc); 161 } 162 163 return true; 164 } 165