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