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/seq_file.h>
  12 #include <linux/interrupt.h>
  13 #include <linux/kernel_stat.h>
  14 #include <linux/notifier.h>
  15 #include <linux/cpu.h>
  16 #include <linux/delay.h>
  17 #include <linux/uaccess.h>
  18 #include <linux/percpu.h>
  19 #include <linux/mm.h>
  20
  21 #include <asm/apic.h>
  22
  23 #ifdef CONFIG_DEBUG_STACKOVERFLOW
  24
  25 int sysctl_panic_on_stackoverflow __read_mostly;
  26
  27 /* Debugging check for stack overflow: is there less than 1KB free? */
  28 static int check_stack_overflow(void)
  29 {
  30         long sp;
  31
  32         __asm__ __volatile__("andl %%esp,%0" :
  33                              "=r" (sp) : "0" (THREAD_SIZE - 1));
  34
  35         return sp < (sizeof(struct thread_info) + STACK_WARN);
  36 }
  37
  38 static void print_stack_overflow(void)
  39 {
  40         printk(KERN_WARNING "low stack detected by irq handler\n");
  41         dump_stack();
  42         if (sysctl_panic_on_stackoverflow)
  43                 panic("low stack detected by irq handler - check messages\n");
  44 }
  45
  46 #else
  47 static inline int check_stack_overflow(void) { return 0; }
  48 static inline void print_stack_overflow(void) { }
  49 #endif
  50
  51 DEFINE_PER_CPU(struct irq_stack *, hardirq_stack);
  52 DEFINE_PER_CPU(struct irq_stack *, softirq_stack);
  53
  54 static void call_on_stack(void *func, void *stack)
  55 {
  56         asm volatile("xchgl     %%ebx,%%esp     \n"
  57                      "call      *%%edi          \n"
  58                      "movl      %%ebx,%%esp     \n"
  59                      : "=b" (stack)
  60                      : "0" (stack),
  61                        "D"(func)
  62                      : "memory", "cc", "edx", "ecx", "eax");
  63 }
  64
  65 static inline void *current_stack(void)
  66 {
  67         return (void *)(current_stack_pointer() & ~(THREAD_SIZE - 1));
  68 }
  69
  70 static inline int execute_on_irq_stack(int overflow, struct irq_desc *desc)
  71 {
  72         struct irq_stack *curstk, *irqstk;
  73         u32 *isp, *prev_esp, arg1;
  74
  75         curstk = (struct irq_stack *) current_stack();
  76         irqstk = __this_cpu_read(hardirq_stack);
  77
  78         /*
  79          * this is where we switch to the IRQ stack. However, if we are
  80          * already using the IRQ stack (because we interrupted a hardirq
  81          * handler) we can't do that and just have to keep using the
  82          * current stack (which is the irq stack already after all)
  83          */
  84         if (unlikely(curstk == irqstk))
  85                 return 0;
  86
  87         isp = (u32 *) ((char *)irqstk + sizeof(*irqstk));
  88
  89         /* Save the next esp at the bottom of the stack */
  90         prev_esp = (u32 *)irqstk;
  91         *prev_esp = current_stack_pointer();
  92
  93         if (unlikely(overflow))
  94                 call_on_stack(print_stack_overflow, isp);
  95
  96         asm volatile("xchgl     %%ebx,%%esp     \n"
  97                      "call      *%%edi          \n"
  98                      "movl      %%ebx,%%esp     \n"
  99                      : "=a" (arg1), "=b" (isp)
 100                      :  "0" (desc),   "1" (isp),
 101                         "D" (desc->handle_irq)
 102                      : "memory", "cc", "ecx");
 103         return 1;
 104 }
 105
 106 /*
 107  * allocate per-cpu stacks for hardirq and for softirq processing
 108  */
 109 void irq_ctx_init(int cpu)
 110 {
 111         struct irq_stack *irqstk;
 112
 113         if (per_cpu(hardirq_stack, cpu))
 114                 return;
 115
 116         irqstk = page_address(alloc_pages_node(cpu_to_node(cpu),
 117                                                THREADINFO_GFP,
 118                                                THREAD_SIZE_ORDER));
 119         per_cpu(hardirq_stack, cpu) = irqstk;
 120
 121         irqstk = page_address(alloc_pages_node(cpu_to_node(cpu),
 122                                                THREADINFO_GFP,
 123                                                THREAD_SIZE_ORDER));
 124         per_cpu(softirq_stack, cpu) = irqstk;
 125
 126         printk(KERN_DEBUG "CPU %u irqstacks, hard=%p soft=%p\n",
 127                cpu, per_cpu(hardirq_stack, cpu),  per_cpu(softirq_stack, cpu));
 128 }
 129
 130 void do_softirq_own_stack(void)
 131 {
 132         struct irq_stack *irqstk;
 133         u32 *isp, *prev_esp;
 134
 135         irqstk = __this_cpu_read(softirq_stack);
 136
 137         /* build the stack frame on the softirq stack */
 138         isp = (u32 *) ((char *)irqstk + sizeof(*irqstk));
 139
 140         /* Push the previous esp onto the stack */
 141         prev_esp = (u32 *)irqstk;
 142         *prev_esp = current_stack_pointer();
 143
 144         call_on_stack(__do_softirq, isp);
 145 }
 146
 147 bool handle_irq(struct irq_desc *desc, struct pt_regs *regs)
 148 {
 149         int overflow = check_stack_overflow();
 150
 151         if (IS_ERR_OR_NULL(desc))
 152                 return false;
 153
 154         if (user_mode(regs) || !execute_on_irq_stack(overflow, desc)) {
 155                 if (unlikely(overflow))
 156                         print_stack_overflow();
 157                 generic_handle_irq_desc(desc);
 158         }
 159
 160         return true;
 161 }