arch/x86/kernel/irq_32.c

   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 DEFINE_PER_CPU_SHARED_ALIGNED(irq_cpustat_t, irq_stat);
  25 EXPORT_PER_CPU_SYMBOL(irq_stat);
  26
  27 DEFINE_PER_CPU(struct pt_regs *, irq_regs);
  28 EXPORT_PER_CPU_SYMBOL(irq_regs);
  29
  30 #ifdef CONFIG_DEBUG_STACKOVERFLOW
  31
  32 int sysctl_panic_on_stackoverflow __read_mostly;
  33
  34 /* Debugging check for stack overflow: is there less than 1KB free? */
  35 static int check_stack_overflow(void)
  36 {
  37         long sp;
  38
  39         __asm__ __volatile__("andl %%esp,%0" :
  40                              "=r" (sp) : "0" (THREAD_SIZE - 1));
  41
  42         return sp < (sizeof(struct thread_info) + STACK_WARN);
  43 }
  44
  45 static void print_stack_overflow(void)
  46 {
  47         printk(KERN_WARNING "low stack detected by irq handler\n");
  48         dump_stack();
  49         if (sysctl_panic_on_stackoverflow)
  50                 panic("low stack detected by irq handler - check messages\n");
  51 }
  52
  53 #else
  54 static inline int check_stack_overflow(void) { return 0; }
  55 static inline void print_stack_overflow(void) { }
  56 #endif
  57
  58 DEFINE_PER_CPU(struct irq_stack *, hardirq_stack);
  59 DEFINE_PER_CPU(struct irq_stack *, softirq_stack);
  60
  61 static void call_on_stack(void *func, void *stack)
  62 {
  63         asm volatile("xchgl     %%ebx,%%esp     \n"
  64                      "call      *%%edi          \n"
  65                      "movl      %%ebx,%%esp     \n"
  66                      : "=b" (stack)
  67                      : "0" (stack),
  68                        "D"(func)
  69                      : "memory", "cc", "edx", "ecx", "eax");
  70 }
  71
  72 static inline void *current_stack(void)
  73 {
  74         return (void *)(current_stack_pointer() & ~(THREAD_SIZE - 1));
  75 }
  76
  77 static inline int
  78 execute_on_irq_stack(int overflow, struct irq_desc *desc, int irq)
  79 {
  80         struct irq_stack *curstk, *irqstk;
  81         u32 *isp, *prev_esp, arg1, arg2;
  82
  83         curstk = (struct irq_stack *) current_stack();
  84         irqstk = __this_cpu_read(hardirq_stack);
  85
  86         /*
  87          * this is where we switch to the IRQ stack. However, if we are
  88          * already using the IRQ stack (because we interrupted a hardirq
  89          * handler) we can't do that and just have to keep using the
  90          * current stack (which is the irq stack already after all)
  91          */
  92         if (unlikely(curstk == irqstk))
  93                 return 0;
  94
  95         isp = (u32 *) ((char *)irqstk + sizeof(*irqstk));
  96
  97         /* Save the next esp at the bottom of the stack */
  98         prev_esp = (u32 *)irqstk;
  99         *prev_esp = current_stack_pointer();
 100
 101         if (unlikely(overflow))
 102                 call_on_stack(print_stack_overflow, isp);
 103
 104         asm volatile("xchgl     %%ebx,%%esp     \n"
 105                      "call      *%%edi          \n"
 106                      "movl      %%ebx,%%esp     \n"
 107                      : "=a" (arg1), "=d" (arg2), "=b" (isp)
 108                      :  "0" (irq),   "1" (desc),  "2" (isp),
 109                         "D" (desc->handle_irq)
 110                      : "memory", "cc", "ecx");
 111         return 1;
 112 }
 113
 114 /*
 115  * allocate per-cpu stacks for hardirq and for softirq processing
 116  */
 117 void irq_ctx_init(int cpu)
 118 {
 119         struct irq_stack *irqstk;
 120
 121         if (per_cpu(hardirq_stack, cpu))
 122                 return;
 123
 124         irqstk = page_address(alloc_pages_node(cpu_to_node(cpu),
 125                                                THREADINFO_GFP,
 126                                                THREAD_SIZE_ORDER));
 127         per_cpu(hardirq_stack, cpu) = irqstk;
 128
 129         irqstk = page_address(alloc_pages_node(cpu_to_node(cpu),
 130                                                THREADINFO_GFP,
 131                                                THREAD_SIZE_ORDER));
 132         per_cpu(softirq_stack, cpu) = irqstk;
 133
 134         printk(KERN_DEBUG "CPU %u irqstacks, hard=%p soft=%p\n",
 135                cpu, per_cpu(hardirq_stack, cpu),  per_cpu(softirq_stack, cpu));
 136 }
 137
 138 void do_softirq_own_stack(void)
 139 {
 140         struct thread_info *curstk;
 141         struct irq_stack *irqstk;
 142         u32 *isp, *prev_esp;
 143
 144         curstk = current_stack();
 145         irqstk = __this_cpu_read(softirq_stack);
 146
 147         /* build the stack frame on the softirq stack */
 148         isp = (u32 *) ((char *)irqstk + sizeof(*irqstk));
 149
 150         /* Push the previous esp onto the stack */
 151         prev_esp = (u32 *)irqstk;
 152         *prev_esp = current_stack_pointer();
 153
 154         call_on_stack(__do_softirq, isp);
 155 }
 156
 157 bool handle_irq(unsigned irq, struct pt_regs *regs)
 158 {
 159         struct irq_desc *desc;
 160         int overflow;
 161
 162         overflow = check_stack_overflow();
 163
 164         desc = irq_to_desc(irq);
 165         if (unlikely(!desc))
 166                 return false;
 167
 168         if (user_mode_vm(regs) || !execute_on_irq_stack(overflow, desc, irq)) {
 169                 if (unlikely(overflow))
 170                         print_stack_overflow();
 171                 desc->handle_irq(irq, desc);
 172         }
 173
 174         return true;
 175 }