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