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 #ifdef CONFIG_4KSTACKS
  53 /*
  54  * per-CPU IRQ handling contexts (thread information and stack)
  55  */
  56 union irq_ctx {
  57         struct thread_info      tinfo;
  58         u32                     stack[THREAD_SIZE/sizeof(u32)];
  59 } __attribute__((aligned(PAGE_SIZE)));
  60
  61 static DEFINE_PER_CPU(union irq_ctx *, hardirq_ctx);
  62 static DEFINE_PER_CPU(union irq_ctx *, softirq_ctx);
  63
  64 static DEFINE_PER_CPU_PAGE_ALIGNED(union irq_ctx, hardirq_stack);
  65 static DEFINE_PER_CPU_PAGE_ALIGNED(union irq_ctx, softirq_stack);
  66
  67 static void call_on_stack(void *func, void *stack)
  68 {
  69         asm volatile("xchgl     %%ebx,%%esp     \n"
  70                      "call      *%%edi          \n"
  71                      "movl      %%ebx,%%esp     \n"
  72                      : "=b" (stack)
  73                      : "0" (stack),
  74                        "D"(func)
  75                      : "memory", "cc", "edx", "ecx", "eax");
  76 }
  77
  78 static inline int
  79 execute_on_irq_stack(int overflow, struct irq_desc *desc, int irq)
  80 {
  81         union irq_ctx *curctx, *irqctx;
  82         u32 *isp, arg1, arg2;
  83
  84         curctx = (union irq_ctx *) current_thread_info();
  85         irqctx = __get_cpu_var(hardirq_ctx);
  86
  87         /*
  88          * this is where we switch to the IRQ stack. However, if we are
  89          * already using the IRQ stack (because we interrupted a hardirq
  90          * handler) we can't do that and just have to keep using the
  91          * current stack (which is the irq stack already after all)
  92          */
  93         if (unlikely(curctx == irqctx))
  94                 return 0;
  95
  96         /* build the stack frame on the IRQ stack */
  97         isp = (u32 *) ((char *)irqctx + sizeof(*irqctx));
  98         irqctx->tinfo.task = curctx->tinfo.task;
  99         irqctx->tinfo.previous_esp = current_stack_pointer;
 100
 101         /*
 102          * Copy the softirq bits in preempt_count so that the
 103          * softirq checks work in the hardirq context.
 104          */
 105         irqctx->tinfo.preempt_count =
 106                 (irqctx->tinfo.preempt_count & ~SOFTIRQ_MASK) |
 107                 (curctx->tinfo.preempt_count & SOFTIRQ_MASK);
 108
 109         if (unlikely(overflow))
 110                 call_on_stack(print_stack_overflow, isp);
 111
 112         asm volatile("xchgl     %%ebx,%%esp     \n"
 113                      "call      *%%edi          \n"
 114                      "movl      %%ebx,%%esp     \n"
 115                      : "=a" (arg1), "=d" (arg2), "=b" (isp)
 116                      :  "0" (irq),   "1" (desc),  "2" (isp),
 117                         "D" (desc->handle_irq)
 118                      : "memory", "cc", "ecx");
 119         return 1;
 120 }
 121
 122 /*
 123  * allocate per-cpu stacks for hardirq and for softirq processing
 124  */
 125 void __cpuinit irq_ctx_init(int cpu)
 126 {
 127         union irq_ctx *irqctx;
 128
 129         if (per_cpu(hardirq_ctx, cpu))
 130                 return;
 131
 132         irqctx = &per_cpu(hardirq_stack, cpu);
 133         irqctx->tinfo.task              = NULL;
 134         irqctx->tinfo.exec_domain       = NULL;
 135         irqctx->tinfo.cpu               = cpu;
 136         irqctx->tinfo.preempt_count     = HARDIRQ_OFFSET;
 137         irqctx->tinfo.addr_limit        = MAKE_MM_SEG(0);
 138
 139         per_cpu(hardirq_ctx, cpu) = irqctx;
 140
 141         irqctx = &per_cpu(softirq_stack, cpu);
 142         irqctx->tinfo.task              = NULL;
 143         irqctx->tinfo.exec_domain       = NULL;
 144         irqctx->tinfo.cpu               = cpu;
 145         irqctx->tinfo.preempt_count     = 0;
 146         irqctx->tinfo.addr_limit        = MAKE_MM_SEG(0);
 147
 148         per_cpu(softirq_ctx, cpu) = irqctx;
 149
 150         printk(KERN_DEBUG "CPU %u irqstacks, hard=%p soft=%p\n",
 151                cpu, per_cpu(hardirq_ctx, cpu),  per_cpu(softirq_ctx, cpu));
 152 }
 153
 154 void irq_ctx_exit(int cpu)
 155 {
 156         per_cpu(hardirq_ctx, cpu) = NULL;
 157 }
 158
 159 asmlinkage void do_softirq(void)
 160 {
 161         unsigned long flags;
 162         struct thread_info *curctx;
 163         union irq_ctx *irqctx;
 164         u32 *isp;
 165
 166         if (in_interrupt())
 167                 return;
 168
 169         local_irq_save(flags);
 170
 171         if (local_softirq_pending()) {
 172                 curctx = current_thread_info();
 173                 irqctx = __get_cpu_var(softirq_ctx);
 174                 irqctx->tinfo.task = curctx->task;
 175                 irqctx->tinfo.previous_esp = current_stack_pointer;
 176
 177                 /* build the stack frame on the softirq stack */
 178                 isp = (u32 *) ((char *)irqctx + sizeof(*irqctx));
 179
 180                 call_on_stack(__do_softirq, isp);
 181                 /*
 182                  * Shouldnt happen, we returned above if in_interrupt():
 183                  */
 184                 WARN_ON_ONCE(softirq_count());
 185         }
 186
 187         local_irq_restore(flags);
 188 }
 189
 190 #else
 191 static inline int
 192 execute_on_irq_stack(int overflow, struct irq_desc *desc, int irq) { return 0; }
 193 #endif
 194
 195 bool handle_irq(unsigned irq, struct pt_regs *regs)
 196 {
 197         struct irq_desc *desc;
 198         int overflow;
 199
 200         overflow = check_stack_overflow();
 201
 202         desc = irq_to_desc(irq);
 203         if (unlikely(!desc))
 204                 return false;
 205
 206         if (!execute_on_irq_stack(overflow, desc, irq)) {
 207                 if (unlikely(overflow))
 208                         print_stack_overflow();
 209                 desc->handle_irq(irq, desc);
 210         }
 211
 212         return true;
 213 }