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 /*
  59  * per-CPU IRQ handling contexts (thread information and stack)
  60  */
  61 union irq_ctx {
  62         struct thread_info      tinfo;
  63         u32                     stack[THREAD_SIZE/sizeof(u32)];
  64 } __attribute__((aligned(THREAD_SIZE)));
  65
  66 static DEFINE_PER_CPU(union irq_ctx *, hardirq_ctx);
  67 static DEFINE_PER_CPU(union irq_ctx *, softirq_ctx);
  68
  69 static void call_on_stack(void *func, void *stack)
  70 {
  71         asm volatile("xchgl     %%ebx,%%esp     \n"
  72                      "call      *%%edi          \n"
  73                      "movl      %%ebx,%%esp     \n"
  74                      : "=b" (stack)
  75                      : "0" (stack),
  76                        "D"(func)
  77                      : "memory", "cc", "edx", "ecx", "eax");
  78 }
  79
  80 static inline int
  81 execute_on_irq_stack(int overflow, struct irq_desc *desc, int irq)
  82 {
  83         union irq_ctx *curctx, *irqctx;
  84         u32 *isp, arg1, arg2;
  85
  86         curctx = (union irq_ctx *) current_thread_info();
  87         irqctx = __this_cpu_read(hardirq_ctx);
  88
  89         /*
  90          * this is where we switch to the IRQ stack. However, if we are
  91          * already using the IRQ stack (because we interrupted a hardirq
  92          * handler) we can't do that and just have to keep using the
  93          * current stack (which is the irq stack already after all)
  94          */
  95         if (unlikely(curctx == irqctx))
  96                 return 0;
  97
  98         /* build the stack frame on the IRQ stack */
  99         isp = (u32 *) ((char *)irqctx + sizeof(*irqctx));
 100         irqctx->tinfo.task = curctx->tinfo.task;
 101         irqctx->tinfo.previous_esp = current_stack_pointer;
 102
 103         if (unlikely(overflow))
 104                 call_on_stack(print_stack_overflow, isp);
 105
 106         asm volatile("xchgl     %%ebx,%%esp     \n"
 107                      "call      *%%edi          \n"
 108                      "movl      %%ebx,%%esp     \n"
 109                      : "=a" (arg1), "=d" (arg2), "=b" (isp)
 110                      :  "0" (irq),   "1" (desc),  "2" (isp),
 111                         "D" (desc->handle_irq)
 112                      : "memory", "cc", "ecx");
 113         return 1;
 114 }
 115
 116 /*
 117  * allocate per-cpu stacks for hardirq and for softirq processing
 118  */
 119 void irq_ctx_init(int cpu)
 120 {
 121         union irq_ctx *irqctx;
 122
 123         if (per_cpu(hardirq_ctx, cpu))
 124                 return;
 125
 126         irqctx = page_address(alloc_pages_node(cpu_to_node(cpu),
 127                                                THREADINFO_GFP,
 128                                                THREAD_SIZE_ORDER));
 129         memset(&irqctx->tinfo, 0, sizeof(struct thread_info));
 130         irqctx->tinfo.cpu               = cpu;
 131         irqctx->tinfo.addr_limit        = MAKE_MM_SEG(0);
 132
 133         per_cpu(hardirq_ctx, cpu) = irqctx;
 134
 135         irqctx = page_address(alloc_pages_node(cpu_to_node(cpu),
 136                                                THREADINFO_GFP,
 137                                                THREAD_SIZE_ORDER));
 138         memset(&irqctx->tinfo, 0, sizeof(struct thread_info));
 139         irqctx->tinfo.cpu               = cpu;
 140         irqctx->tinfo.addr_limit        = MAKE_MM_SEG(0);
 141
 142         per_cpu(softirq_ctx, cpu) = irqctx;
 143
 144         printk(KERN_DEBUG "CPU %u irqstacks, hard=%p soft=%p\n",
 145                cpu, per_cpu(hardirq_ctx, cpu),  per_cpu(softirq_ctx, cpu));
 146 }
 147
 148 void do_softirq_own_stack(void)
 149 {
 150         struct thread_info *curctx;
 151         union irq_ctx *irqctx;
 152         u32 *isp;
 153
 154         curctx = current_thread_info();
 155         irqctx = __this_cpu_read(softirq_ctx);
 156         irqctx->tinfo.task = curctx->task;
 157         irqctx->tinfo.previous_esp = current_stack_pointer;
 158
 159         /* build the stack frame on the softirq stack */
 160         isp = (u32 *) ((char *)irqctx + sizeof(*irqctx));
 161
 162         call_on_stack(__do_softirq, isp);
 163 }
 164
 165 bool handle_irq(unsigned irq, struct pt_regs *regs)
 166 {
 167         struct irq_desc *desc;
 168         int overflow;
 169
 170         overflow = check_stack_overflow();
 171
 172         desc = irq_to_desc(irq);
 173         if (unlikely(!desc))
 174                 return false;
 175
 176         if (user_mode_vm(regs) || !execute_on_irq_stack(overflow, desc, irq)) {
 177                 if (unlikely(overflow))
 178                         print_stack_overflow();
 179                 desc->handle_irq(irq, desc);
 180         }
 181
 182         return true;
 183 }