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 /* how to get the current stack pointer from C */
  73 #define current_stack_pointer ({                \
  74         unsigned long sp;                       \
  75         asm("mov %%esp,%0" : "=g" (sp));        \
  76         sp;                                     \
  77 })
  78
  79 static inline void *current_stack(void)
  80 {
  81         return (void *)(current_stack_pointer & ~(THREAD_SIZE - 1));
  82 }
  83
  84 static inline int
  85 execute_on_irq_stack(int overflow, struct irq_desc *desc, int irq)
  86 {
  87         struct irq_stack *curstk, *irqstk;
  88         u32 *isp, *prev_esp, arg1, arg2;
  89
  90         curstk = (struct irq_stack *) current_stack();
  91         irqstk = __this_cpu_read(hardirq_stack);
  92
  93         /*
  94          * this is where we switch to the IRQ stack. However, if we are
  95          * already using the IRQ stack (because we interrupted a hardirq
  96          * handler) we can't do that and just have to keep using the
  97          * current stack (which is the irq stack already after all)
  98          */
  99         if (unlikely(curstk == irqstk))
 100                 return 0;
 101
 102         isp = (u32 *) ((char *)irqstk + sizeof(*irqstk));
 103
 104         /* Save the next esp at the bottom of the stack */
 105         prev_esp = (u32 *)irqstk;
 106         *prev_esp = current_stack_pointer;
 107
 108         if (unlikely(overflow))
 109                 call_on_stack(print_stack_overflow, isp);
 110
 111         asm volatile("xchgl     %%ebx,%%esp     \n"
 112                      "call      *%%edi          \n"
 113                      "movl      %%ebx,%%esp     \n"
 114                      : "=a" (arg1), "=d" (arg2), "=b" (isp)
 115                      :  "0" (irq),   "1" (desc),  "2" (isp),
 116                         "D" (desc->handle_irq)
 117                      : "memory", "cc", "ecx");
 118         return 1;
 119 }
 120
 121 /*
 122  * allocate per-cpu stacks for hardirq and for softirq processing
 123  */
 124 void irq_ctx_init(int cpu)
 125 {
 126         struct irq_stack *irqstk;
 127
 128         if (per_cpu(hardirq_stack, cpu))
 129                 return;
 130
 131         irqstk = page_address(alloc_pages_node(cpu_to_node(cpu),
 132                                                THREADINFO_GFP,
 133                                                THREAD_SIZE_ORDER));
 134         per_cpu(hardirq_stack, cpu) = irqstk;
 135
 136         irqstk = page_address(alloc_pages_node(cpu_to_node(cpu),
 137                                                THREADINFO_GFP,
 138                                                THREAD_SIZE_ORDER));
 139         per_cpu(softirq_stack, cpu) = irqstk;
 140
 141         printk(KERN_DEBUG "CPU %u irqstacks, hard=%p soft=%p\n",
 142                cpu, per_cpu(hardirq_stack, cpu),  per_cpu(softirq_stack, cpu));
 143 }
 144
 145 void do_softirq_own_stack(void)
 146 {
 147         struct thread_info *curstk;
 148         struct irq_stack *irqstk;
 149         u32 *isp, *prev_esp;
 150
 151         curstk = current_stack();
 152         irqstk = __this_cpu_read(softirq_stack);
 153
 154         /* build the stack frame on the softirq stack */
 155         isp = (u32 *) ((char *)irqstk + sizeof(*irqstk));
 156
 157         /* Push the previous esp onto the stack */
 158         prev_esp = (u32 *)irqstk;
 159         *prev_esp = current_stack_pointer;
 160
 161         call_on_stack(__do_softirq, isp);
 162 }
 163
 164 bool handle_irq(unsigned irq, struct pt_regs *regs)
 165 {
 166         struct irq_desc *desc;
 167         int overflow;
 168
 169         overflow = check_stack_overflow();
 170
 171         desc = irq_to_desc(irq);
 172         if (unlikely(!desc))
 173                 return false;
 174
 175         if (user_mode_vm(regs) || !execute_on_irq_stack(overflow, desc, irq)) {
 176                 if (unlikely(overflow))
 177                         print_stack_overflow();
 178                 desc->handle_irq(irq, desc);
 179         }
 180
 181         return true;
 182 }