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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/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) : "" (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                      : "" (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                      :  "" (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 }
162 

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