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
  21 #include <asm/apic.h>
  22
  23 DEFINE_PER_CPU_SHARED_ALIGNED(irq_cpustat_t, irq_stat);
  24 EXPORT_PER_CPU_SYMBOL(irq_stat);
  25
  26 DEFINE_PER_CPU(struct pt_regs *, irq_regs);
  27 EXPORT_PER_CPU_SYMBOL(irq_regs);
  28
  29 #ifdef CONFIG_DEBUG_STACKOVERFLOW
  30 /* Debugging check for stack overflow: is there less than 1KB free? */
  31 static int check_stack_overflow(void)
  32 {
  33         long sp;
  34
  35         __asm__ __volatile__("andl %%esp,%0" :
  36                              "=r" (sp) : "0" (THREAD_SIZE - 1));
  37
  38         return sp < (sizeof(struct thread_info) + STACK_WARN);
  39 }
  40
  41 static void print_stack_overflow(void)
  42 {
  43         printk(KERN_WARNING "low stack detected by irq handler\n");
  44         dump_stack();
  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 /*
  53  * per-CPU IRQ handling contexts (thread information and stack)
  54  */
  55 union irq_ctx {
  56         struct thread_info      tinfo;
  57         u32                     stack[THREAD_SIZE/sizeof(u32)];
  58 } __attribute__((aligned(THREAD_SIZE)));
  59
  60 static DEFINE_PER_CPU(union irq_ctx *, hardirq_ctx);
  61 static DEFINE_PER_CPU(union irq_ctx *, softirq_ctx);
  62
  63 static DEFINE_PER_CPU_PAGE_ALIGNED(union irq_ctx, hardirq_stack);
  64 static DEFINE_PER_CPU_PAGE_ALIGNED(union irq_ctx, softirq_stack);
  65
  66 static void call_on_stack(void *func, void *stack)
  67 {
  68         asm volatile("xchgl     %%ebx,%%esp     \n"
  69                      "call      *%%edi          \n"
  70                      "movl      %%ebx,%%esp     \n"
  71                      : "=b" (stack)
  72                      : "0" (stack),
  73                        "D"(func)
  74                      : "memory", "cc", "edx", "ecx", "eax");
  75 }
  76
  77 static inline int
  78 execute_on_irq_stack(int overflow, struct irq_desc *desc, int irq)
  79 {
  80         union irq_ctx *curctx, *irqctx;
  81         u32 *isp, arg1, arg2;
  82
  83         curctx = (union irq_ctx *) current_thread_info();
  84         irqctx = __get_cpu_var(hardirq_ctx);
  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(curctx == irqctx))
  93                 return 0;
  94
  95         /* build the stack frame on the IRQ stack */
  96         isp = (u32 *) ((char *)irqctx + sizeof(*irqctx));
  97         irqctx->tinfo.task = curctx->tinfo.task;
  98         irqctx->tinfo.previous_esp = current_stack_pointer;
  99
 100         /*
 101          * Copy the softirq bits in preempt_count so that the
 102          * softirq checks work in the hardirq context.
 103          */
 104         irqctx->tinfo.preempt_count =
 105                 (irqctx->tinfo.preempt_count & ~SOFTIRQ_MASK) |
 106                 (curctx->tinfo.preempt_count & SOFTIRQ_MASK);
 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 __cpuinit irq_ctx_init(int cpu)
 125 {
 126         union irq_ctx *irqctx;
 127
 128         if (per_cpu(hardirq_ctx, cpu))
 129                 return;
 130
 131         irqctx = &per_cpu(hardirq_stack, cpu);
 132         irqctx->tinfo.task              = NULL;
 133         irqctx->tinfo.exec_domain       = NULL;
 134         irqctx->tinfo.cpu               = cpu;
 135         irqctx->tinfo.preempt_count     = HARDIRQ_OFFSET;
 136         irqctx->tinfo.addr_limit        = MAKE_MM_SEG(0);
 137
 138         per_cpu(hardirq_ctx, cpu) = irqctx;
 139
 140         irqctx = &per_cpu(softirq_stack, cpu);
 141         irqctx->tinfo.task              = NULL;
 142         irqctx->tinfo.exec_domain       = NULL;
 143         irqctx->tinfo.cpu               = cpu;
 144         irqctx->tinfo.preempt_count     = 0;
 145         irqctx->tinfo.addr_limit        = MAKE_MM_SEG(0);
 146
 147         per_cpu(softirq_ctx, cpu) = irqctx;
 148
 149         printk(KERN_DEBUG "CPU %u irqstacks, hard=%p soft=%p\n",
 150                cpu, per_cpu(hardirq_ctx, cpu),  per_cpu(softirq_ctx, cpu));
 151 }
 152
 153 void irq_ctx_exit(int cpu)
 154 {
 155         per_cpu(hardirq_ctx, cpu) = NULL;
 156 }
 157
 158 asmlinkage void do_softirq(void)
 159 {
 160         unsigned long flags;
 161         struct thread_info *curctx;
 162         union irq_ctx *irqctx;
 163         u32 *isp;
 164
 165         if (in_interrupt())
 166                 return;
 167
 168         local_irq_save(flags);
 169
 170         if (local_softirq_pending()) {
 171                 curctx = current_thread_info();
 172                 irqctx = __get_cpu_var(softirq_ctx);
 173                 irqctx->tinfo.task = curctx->task;
 174                 irqctx->tinfo.previous_esp = current_stack_pointer;
 175
 176                 /* build the stack frame on the softirq stack */
 177                 isp = (u32 *) ((char *)irqctx + sizeof(*irqctx));
 178
 179                 call_on_stack(__do_softirq, isp);
 180                 /*
 181                  * Shouldnt happen, we returned above if in_interrupt():
 182                  */
 183                 WARN_ON_ONCE(softirq_count());
 184         }
 185
 186         local_irq_restore(flags);
 187 }
 188
 189 bool handle_irq(unsigned irq, struct pt_regs *regs)
 190 {
 191         struct irq_desc *desc;
 192         int overflow;
 193
 194         overflow = check_stack_overflow();
 195
 196         desc = irq_to_desc(irq);
 197         if (unlikely(!desc))
 198                 return false;
 199
 200         if (!execute_on_irq_stack(overflow, desc, irq)) {
 201                 if (unlikely(overflow))
 202                         print_stack_overflow();
 203                 desc->handle_irq(irq, desc);
 204         }
 205
 206         return true;
 207 }