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 void call_on_stack(void *func, void *stack)
  64 {
  65         asm volatile("xchgl     %%ebx,%%esp     \n"
  66                      "call      *%%edi          \n"
  67                      "movl      %%ebx,%%esp     \n"
  68                      : "=b" (stack)
  69                      : "0" (stack),
  70                        "D"(func)
  71                      : "memory", "cc", "edx", "ecx", "eax");
  72 }
  73
  74 static inline int
  75 execute_on_irq_stack(int overflow, struct irq_desc *desc, int irq)
  76 {
  77         union irq_ctx *curctx, *irqctx;
  78         u32 *isp, arg1, arg2;
  79
  80         curctx = (union irq_ctx *) current_thread_info();
  81         irqctx = __get_cpu_var(hardirq_ctx);
  82
  83         /*
  84          * this is where we switch to the IRQ stack. However, if we are
  85          * already using the IRQ stack (because we interrupted a hardirq
  86          * handler) we can't do that and just have to keep using the
  87          * current stack (which is the irq stack already after all)
  88          */
  89         if (unlikely(curctx == irqctx))
  90                 return 0;
  91
  92         /* build the stack frame on the IRQ stack */
  93         isp = (u32 *) ((char *)irqctx + sizeof(*irqctx));
  94         irqctx->tinfo.task = curctx->tinfo.task;
  95         irqctx->tinfo.previous_esp = current_stack_pointer;
  96
  97         /*
  98          * Copy the softirq bits in preempt_count so that the
  99          * softirq checks work in the hardirq context.
 100          */
 101         irqctx->tinfo.preempt_count =
 102                 (irqctx->tinfo.preempt_count & ~SOFTIRQ_MASK) |
 103                 (curctx->tinfo.preempt_count & SOFTIRQ_MASK);
 104
 105         if (unlikely(overflow))
 106                 call_on_stack(print_stack_overflow, isp);
 107
 108         asm volatile("xchgl     %%ebx,%%esp     \n"
 109                      "call      *%%edi          \n"
 110                      "movl      %%ebx,%%esp     \n"
 111                      : "=a" (arg1), "=d" (arg2), "=b" (isp)
 112                      :  "0" (irq),   "1" (desc),  "2" (isp),
 113                         "D" (desc->handle_irq)
 114                      : "memory", "cc", "ecx");
 115         return 1;
 116 }
 117
 118 /*
 119  * allocate per-cpu stacks for hardirq and for softirq processing
 120  */
 121 void __cpuinit irq_ctx_init(int cpu)
 122 {
 123         union irq_ctx *irqctx;
 124
 125         if (per_cpu(hardirq_ctx, cpu))
 126                 return;
 127
 128         irqctx = (union irq_ctx *)__get_free_pages(THREAD_FLAGS, THREAD_ORDER);
 129         irqctx->tinfo.task              = NULL;
 130         irqctx->tinfo.exec_domain       = NULL;
 131         irqctx->tinfo.cpu               = cpu;
 132         irqctx->tinfo.preempt_count     = HARDIRQ_OFFSET;
 133         irqctx->tinfo.addr_limit        = MAKE_MM_SEG(0);
 134
 135         per_cpu(hardirq_ctx, cpu) = irqctx;
 136
 137         irqctx = (union irq_ctx *)__get_free_pages(THREAD_FLAGS, THREAD_ORDER);
 138         irqctx->tinfo.task              = NULL;
 139         irqctx->tinfo.exec_domain       = NULL;
 140         irqctx->tinfo.cpu               = cpu;
 141         irqctx->tinfo.preempt_count     = 0;
 142         irqctx->tinfo.addr_limit        = MAKE_MM_SEG(0);
 143
 144         per_cpu(softirq_ctx, cpu) = irqctx;
 145
 146         printk(KERN_DEBUG "CPU %u irqstacks, hard=%p soft=%p\n",
 147                cpu, per_cpu(hardirq_ctx, cpu),  per_cpu(softirq_ctx, cpu));
 148 }
 149
 150 asmlinkage void do_softirq(void)
 151 {
 152         unsigned long flags;
 153         struct thread_info *curctx;
 154         union irq_ctx *irqctx;
 155         u32 *isp;
 156
 157         if (in_interrupt())
 158                 return;
 159
 160         local_irq_save(flags);
 161
 162         if (local_softirq_pending()) {
 163                 curctx = current_thread_info();
 164                 irqctx = __get_cpu_var(softirq_ctx);
 165                 irqctx->tinfo.task = curctx->task;
 166                 irqctx->tinfo.previous_esp = current_stack_pointer;
 167
 168                 /* build the stack frame on the softirq stack */
 169                 isp = (u32 *) ((char *)irqctx + sizeof(*irqctx));
 170
 171                 call_on_stack(__do_softirq, isp);
 172                 /*
 173                  * Shouldnt happen, we returned above if in_interrupt():
 174                  */
 175                 WARN_ON_ONCE(softirq_count());
 176         }
 177
 178         local_irq_restore(flags);
 179 }
 180
 181 bool handle_irq(unsigned irq, struct pt_regs *regs)
 182 {
 183         struct irq_desc *desc;
 184         int overflow;
 185
 186         overflow = check_stack_overflow();
 187
 188         desc = irq_to_desc(irq);
 189         if (unlikely(!desc))
 190                 return false;
 191
 192         if (!execute_on_irq_stack(overflow, desc, irq)) {
 193                 if (unlikely(overflow))
 194                         print_stack_overflow();
 195                 desc->handle_irq(irq, desc);
 196         }
 197
 198         return true;
 199 }