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