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Linux/arch/x86/kernel/irq_32.c

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  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) : "" (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                      : "" (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         /* Copy the preempt_count so that the [soft]irq checks work. */
104         irqctx->tinfo.preempt_count = curctx->tinfo.preempt_count;
105 
106         if (unlikely(overflow))
107                 call_on_stack(print_stack_overflow, isp);
108 
109         asm volatile("xchgl     %%ebx,%%esp     \n"
110                      "call      *%%edi          \n"
111                      "movl      %%ebx,%%esp     \n"
112                      : "=a" (arg1), "=d" (arg2), "=b" (isp)
113                      :  "" (irq),   "1" (desc),  "2" (isp),
114                         "D" (desc->handle_irq)
115                      : "memory", "cc", "ecx");
116         return 1;
117 }
118 
119 /*
120  * allocate per-cpu stacks for hardirq and for softirq processing
121  */
122 void __cpuinit irq_ctx_init(int cpu)
123 {
124         union irq_ctx *irqctx;
125 
126         if (per_cpu(hardirq_ctx, cpu))
127                 return;
128 
129         irqctx = page_address(alloc_pages_node(cpu_to_node(cpu),
130                                                THREADINFO_GFP,
131                                                THREAD_SIZE_ORDER));
132         memset(&irqctx->tinfo, 0, sizeof(struct thread_info));
133         irqctx->tinfo.cpu               = cpu;
134         irqctx->tinfo.preempt_count     = HARDIRQ_OFFSET;
135         irqctx->tinfo.addr_limit        = MAKE_MM_SEG(0);
136 
137         per_cpu(hardirq_ctx, cpu) = irqctx;
138 
139         irqctx = page_address(alloc_pages_node(cpu_to_node(cpu),
140                                                THREADINFO_GFP,
141                                                THREAD_SIZE_ORDER));
142         memset(&irqctx->tinfo, 0, sizeof(struct thread_info));
143         irqctx->tinfo.cpu               = cpu;
144         irqctx->tinfo.addr_limit        = MAKE_MM_SEG(0);
145 
146         per_cpu(softirq_ctx, cpu) = irqctx;
147 
148         printk(KERN_DEBUG "CPU %u irqstacks, hard=%p soft=%p\n",
149                cpu, per_cpu(hardirq_ctx, cpu),  per_cpu(softirq_ctx, cpu));
150 }
151 
152 asmlinkage void do_softirq(void)
153 {
154         unsigned long flags;
155         struct thread_info *curctx;
156         union irq_ctx *irqctx;
157         u32 *isp;
158 
159         if (in_interrupt())
160                 return;
161 
162         local_irq_save(flags);
163 
164         if (local_softirq_pending()) {
165                 curctx = current_thread_info();
166                 irqctx = __this_cpu_read(softirq_ctx);
167                 irqctx->tinfo.task = curctx->task;
168                 irqctx->tinfo.previous_esp = current_stack_pointer;
169 
170                 /* build the stack frame on the softirq stack */
171                 isp = (u32 *) ((char *)irqctx + sizeof(*irqctx));
172 
173                 call_on_stack(__do_softirq, isp);
174                 /*
175                  * Shouldn't happen, we returned above if in_interrupt():
176                  */
177                 WARN_ON_ONCE(softirq_count());
178         }
179 
180         local_irq_restore(flags);
181 }
182 
183 bool handle_irq(unsigned irq, struct pt_regs *regs)
184 {
185         struct irq_desc *desc;
186         int overflow;
187 
188         overflow = check_stack_overflow();
189 
190         desc = irq_to_desc(irq);
191         if (unlikely(!desc))
192                 return false;
193 
194         if (user_mode_vm(regs) || !execute_on_irq_stack(overflow, desc, irq)) {
195                 if (unlikely(overflow))
196                         print_stack_overflow();
197                 desc->handle_irq(irq, desc);
198         }
199 
200         return true;
201 }
202 

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