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linux内核中断、异常 2................. [复制链接]

so_brave

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发表于 2011-12-28 16:27 |只看该作者 |倒序浏览

linux内核中断、异常 2.................

异常返回

当执行异常处理的C函数终止时，程序执行一条jmp指令以跳转到ret_from_exception函数（上面的error_code汇编函数）

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01.ret_from_exception:
02. preempt_stop(CLBR_ANY)
03.ret_from_intr:
04. GET_THREAD_INFO(%ebp)
05.check_userspace:
06. movl PT_EFLAGS(%esp), %eax # mix EFLAGS and CS
07. movb PT_CS(%esp), %al
08. andl $(X86_EFLAGS_VM | SEGMENT_RPL_MASK), %eax
09. cmpl $USER_RPL, %eax
10. /*当被中断的程序在中断发生运行时在内核态*/
11. jb resume_kernel # not returning to v8086 or userspace
12. /*在用户空间时*/
13.ENTRY(resume_userspace)
14. LOCKDEP_SYS_EXIT
15. DISABLE_INTERRUPTS(CLBR_ANY) # make sure we don't miss an interrupt
16. # setting need_resched or sigpending
17. # between sampling and the iret
18. TRACE_IRQS_OFF
19. movl TI_flags(%ebp), %ecx
20. andl $_TIF_WORK_MASK, %ecx # is there any work to be done on
21. # int/exception return?
22. jne work_pending
23. jmp restore_all
24.END(ret_from_exception)
25.
26.#ifdef CONFIG_PREEMPT
27.ENTRY(resume_kernel)
28. DISABLE_INTERRUPTS(CLBR_ANY)
29. /*允许内核抢占时，执行need_resched*/
30. cmpl $0,TI_preempt_count(%ebp) # non-zero preempt_count ?
31. /*不等于0，被中断的程序重新开始执行*/
32. jnz restore_all
33.need_resched:
34. movl TI_flags(%ebp), %ecx # need_resched set ?
35. testb $_TIF_NEED_RESCHED, %cl
36. jz restore_all
37. testl $X86_EFLAGS_IF,PT_EFLAGS(%esp) # interrupts off (exception path) ?
38. jz restore_all
39. call preempt_schedule_irq
40. jmp need_resched
41.END(resume_kernel)
42.#endif
43. CFI_ENDPROC
ret_from_exception:
preempt_stop(CLBR_ANY)
ret_from_intr:
GET_THREAD_INFO(%ebp)
check_userspace:
movl PT_EFLAGS(%esp), %eax # mix EFLAGS and CS
movb PT_CS(%esp), %al
andl $(X86_EFLAGS_VM | SEGMENT_RPL_MASK), %eax
cmpl $USER_RPL, %eax
/*当被中断的程序在中断发生运行时在内核态*/
jb resume_kernel # not returning to v8086 or userspace
/*在用户空间时*/
ENTRY(resume_userspace)
LOCKDEP_SYS_EXIT
DISABLE_INTERRUPTS(CLBR_ANY) # make sure we don't miss an interrupt
# setting need_resched or sigpending
# between sampling and the iret
TRACE_IRQS_OFF
movl TI_flags(%ebp), %ecx
andl $_TIF_WORK_MASK, %ecx # is there any work to be done on
# int/exception return?
jne work_pending
jmp restore_all
END(ret_from_exception)
#ifdef CONFIG_PREEMPT
ENTRY(resume_kernel)
DISABLE_INTERRUPTS(CLBR_ANY)
/*允许内核抢占时，执行need_resched*/
cmpl $0,TI_preempt_count(%ebp) # non-zero preempt_count ?
/*不等于0，被中断的程序重新开始执行*/
jnz restore_all
need_resched:
movl TI_flags(%ebp), %ecx # need_resched set ?
testb $_TIF_NEED_RESCHED, %cl
jz restore_all
testl $X86_EFLAGS_IF,PT_EFLAGS(%esp) # interrupts off (exception path) ?
jz restore_all
call preempt_schedule_irq
jmp need_resched
END(resume_kernel)
#endif
CFI_ENDPROC

复制代码

中断请求初始化

对于每一个外设，要么以静态（声明为 static 类型的全局变量）或动态（调用request_irq 函数）的方式向 Linux 内核注册中断处理程序。不管以何种方式注册，都会声明或分配一块irqaction 结构（其中handler 指向中断服务程序），然后调用setup_irq() 函数，将irq_desc_t 和irqaction 联系起来。irq_desc[]数组中每一项对应一个中断向量，每一个中断向量为一个irq_desc类型的变量，该变量中有个action指针，指向irqaction链表的首地址。也就是说多个中断服务（irqaction）可以共享一个中断向量，这些中断服务以链表的方式依次链入，当中断到来时，同一中断向量中的所有中断服务函数都会依次执行一遍。request_irq函数主要是实例化一个irqaction结构，这里直接看setup_irq函数。

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01./*
02. * Internal function to register an irqaction - typically used to
03. * allocate special interrupts that are part of the architecture.
04. */
05. /*将中断服务链入irq_desc[irq]->action中*/
06.static int
07.__setup_irq(unsigned int irq, struct irq_desc *desc, struct irqaction *new)
08.{
09. struct irqaction *old, **old_ptr;
10. const char *old_name = NULL;
11. unsigned long flags;
12. int nested, shared = 0;
13. int ret;
14.
15. if (!desc)
16. return -EINVAL;
17.
18. if (desc->chip == &no_irq_chip)
19. return -ENOSYS;
20. /*
21. * Some drivers like serial.c use request_irq() heavily,
22. * so we have to be careful not to interfere with a
23. * running system.
24. */
25. if (new->flags & IRQF_SAMPLE_RANDOM) {
26. /*
27. * This function might sleep, we want to call it first,
28. * outside of the atomic block.
29. * Yes, this might clear the entropy pool if the wrong
30. * driver is attempted to be loaded, without actually
31. * installing a new handler, but is this really a problem,
32. * only the sysadmin is able to do this.
33. */
34. rand_initialize_irq(irq);
35. }
36.
37. /* Oneshot interrupts are not allowed with shared */
38. if ((new->flags & IRQF_ONESHOT) && (new->flags & IRQF_SHARED))
39. return -EINVAL;
40.
41. /*
42. * Check whether the interrupt nests into another interrupt
43. * thread.
44. */
45. /*如果嵌套在另一个中断线程中*/
46. nested = desc->status & IRQ_NESTED_THREAD;
47. if (nested) {
48. if (!new->thread_fn)
49. return -EINVAL;
50. /*
51. * Replace the primary handler which was provided from
52. * the driver for non nested interrupt handling by the
53. * dummy function which warns when called.
54. */
55. new->handler = irq_nested_primary_handler;
56. }
57.
58. /*
59. * Create a handler thread when a thread function is supplied
60. * and the interrupt does not nest into another interrupt
61. * thread.
62. *//*如果提供了中断线程*/
63. if (new->thread_fn && !nested) {
64. struct task_struct *t;
65. /*创建内核中断线程*/
66. t = kthread_create(irq_thread, new, "irq/%d-%s", irq,
67. new->name);
68. if (IS_ERR(t))
69. return PTR_ERR(t);
70. /*
71. * We keep the reference to the task struct even if
72. * the thread dies to avoid that the interrupt code
73. * references an already freed task_struct.
74. *//*增加使用计数*/
75. get_task_struct(t);
76. new->thread = t;
77. }
78.
79. /*
80. * The following block of code has to be executed atomically
81. */
82. spin_lock_irqsave(&desc->lock, flags);
83. old_ptr = &desc->action;/*保存action链表头*/
84. old = *old_ptr;
85. if (old) {/*如果链表不为空,也就是说该中断号对应的有中断服务函数*/
86. /*
87. * Can't share interrupts unless both agree to and are
88. * the same type (level, edge, polarity). So both flag
89. * fields must have IRQF_SHARED set and the bits which
90. * set the trigger type must match.
91. */
92. if (!((old->flags & new->flags) & IRQF_SHARED) ||
93. ((old->flags ^ new->flags) & IRQF_TRIGGER_MASK)) {
94. old_name = old->name;
95. goto mismatch;
96. }
97.
98.#if defined(CONFIG_IRQ_PER_CPU)
99. /* All handlers must agree on per-cpuness */
100. if ((old->flags & IRQF_PERCPU) !=
101. (new->flags & IRQF_PERCPU))
102. goto mismatch;
103.#endif
104.
105. /* add new interrupt at end of irq queue */
106. do {/*这一步是遍历到链表的最后一个
107. old->next=NULL为止*/
108. old_ptr = &old->next;
109. old = *old_ptr;
110. } while (old);
111. shared = 1;/*共享*/
112. }
113.
114. if (!shared) {
115. /*设置irq_desc[irq]结构中chip成员的还没设置的指针
116. ，让它们指向一些默认函数*/
117. irq_chip_set_defaults(desc->chip);
118.
119. init_waitqueue_head(&desc->wait_for_threads);
120.
121. /* Setup the type (level, edge polarity) if configured: */
122. /*设置触发方式*/
123. if (new->flags & IRQF_TRIGGER_MASK) {
124. ret = __irq_set_trigger(desc, irq,
125. new->flags & IRQF_TRIGGER_MASK);
126.
127. if (ret)
128. goto out_thread;
129. } else
130. compat_irq_chip_set_default_handler(desc);
131.#if defined(CONFIG_IRQ_PER_CPU)
132. if (new->flags & IRQF_PERCPU)
133. desc->status |= IRQ_PER_CPU;
134.#endif
135.
136. desc->status &= ~(IRQ_AUTODETECT | IRQ_WAITING | IRQ_ONESHOT |
137. IRQ_INPROGRESS | IRQ_SPURIOUS_DISABLED);
138.
139. if (new->flags & IRQF_ONESHOT)
140. desc->status |= IRQ_ONESHOT;
141.
142. if (!(desc->status & IRQ_NOAUTOEN)) {
143. desc->depth = 0;
144. desc->status &= ~IRQ_DISABLED;
145. desc->chip->startup(irq);
146. } else
147. /* Undo nested disables: */
148. desc->depth = 1;
149.
150. /* Exclude IRQ from balancing if requested */
151. if (new->flags & IRQF_NOBALANCING)
152. desc->status |= IRQ_NO_BALANCING;
153.
154. /* Set default affinity mask once everything is setup */
155. setup_affinity(irq, desc);
156.
157. } else if ((new->flags & IRQF_TRIGGER_MASK)
158. && (new->flags & IRQF_TRIGGER_MASK)
159. != (desc->status & IRQ_TYPE_SENSE_MASK)) {
160. /* hope the handler works with the actual trigger mode... */
161. pr_warning("IRQ %d uses trigger mode %d; requested %d\n",
162. irq, (int)(desc->status & IRQ_TYPE_SENSE_MASK),
163. (int)(new->flags & IRQF_TRIGGER_MASK));
164. }
165.
166. new->irq = irq;/*将new的irq设置为irq*/
167. *old_ptr = new;/*将new链入链表中，这个从上面可以看到*/
168.
169. /* Reset broken irq detection when installing new handler */
170. desc->irq_count = 0;
171. desc->irqs_unhandled = 0;
172.
173. /*
174. * Check whether we disabled the irq via the spurious handler
175. * before. Reenable it and give it another chance.
176. */
177. if (shared && (desc->status & IRQ_SPURIOUS_DISABLED)) {
178. desc->status &= ~IRQ_SPURIOUS_DISABLED;
179. __enable_irq(desc, irq, false);/*启用中断*/
180. }
181.
182. spin_unlock_irqrestore(&desc->lock, flags);
183.
184. /*
185. * Strictly no need to wake it up, but hung_task complains
186. * when no hard interrupt wakes the thread up.
187. */
188. if (new->thread)
189. wake_up_process(new->thread);
190. /*下面为注册proc文件系统对应的项*/
191. register_irq_proc(irq, desc);
192. new->dir = NULL;
193. register_handler_proc(irq, new);
194.
195. return 0;
196.
197.mismatch:
198.#ifdef CONFIG_DEBUG_SHIRQ
199. if (!(new->flags & IRQF_PROBE_SHARED)) {
200. printk(KERN_ERR "IRQ handler type mismatch for IRQ %d\n", irq);
201. if (old_name)
202. printk(KERN_ERR "current handler: %s\n", old_name);
203. dump_stack();
204. }
205.#endif
206. ret = -EBUSY;
207.
208.out_thread:
209. spin_unlock_irqrestore(&desc->lock, flags);
210. if (new->thread) {
211. struct task_struct *t = new->thread;
212.
213. new->thread = NULL;
214. if (likely(!test_bit(IRQTF_DIED, &new->thread_flags)))
215. kthread_stop(t);
216. put_task_struct(t);
217. }
218. return ret;
219.}
/*
* Internal function to register an irqaction - typically used to
* allocate special interrupts that are part of the architecture.
*/
/*将中断服务链入irq_desc[irq]->action中*/
static int
__setup_irq(unsigned int irq, struct irq_desc *desc, struct irqaction *new)
{
struct irqaction *old, **old_ptr;
const char *old_name = NULL;
unsigned long flags;
int nested, shared = 0;
int ret;
if (!desc)
return -EINVAL;
if (desc->chip == &no_irq_chip)
return -ENOSYS;
/*
* Some drivers like serial.c use request_irq() heavily,
* so we have to be careful not to interfere with a
* running system.
*/
if (new->flags & IRQF_SAMPLE_RANDOM) {
/*
* This function might sleep, we want to call it first,
* outside of the atomic block.
* Yes, this might clear the entropy pool if the wrong
* driver is attempted to be loaded, without actually
* installing a new handler, but is this really a problem,
* only the sysadmin is able to do this.
*/
rand_initialize_irq(irq);
}
/* Oneshot interrupts are not allowed with shared */
if ((new->flags & IRQF_ONESHOT) && (new->flags & IRQF_SHARED))
return -EINVAL;
/*
* Check whether the interrupt nests into another interrupt
* thread.
*/
/*如果嵌套在另一个中断线程中*/
nested = desc->status & IRQ_NESTED_THREAD;
if (nested) {
if (!new->thread_fn)
return -EINVAL;
/*
* Replace the primary handler which was provided from
* the driver for non nested interrupt handling by the
* dummy function which warns when called.
*/
new->handler = irq_nested_primary_handler;
}
/*
* Create a handler thread when a thread function is supplied
* and the interrupt does not nest into another interrupt
* thread.
*//*如果提供了中断线程*/
if (new->thread_fn && !nested) {
struct task_struct *t;
/*创建内核中断线程*/
t = kthread_create(irq_thread, new, "irq/%d-%s", irq,
new->name);
if (IS_ERR(t))
return PTR_ERR(t);
/*
* We keep the reference to the task struct even if
* the thread dies to avoid that the interrupt code
* references an already freed task_struct.
*//*增加使用计数*/
get_task_struct(t);
new->thread = t;
}
/*
* The following block of code has to be executed atomically
*/
spin_lock_irqsave(&desc->lock, flags);
old_ptr = &desc->action;/*保存action链表头*/
old = *old_ptr;
if (old) {/*如果链表不为空,也就是说该中断号对应的有中断服务函数*/
/*
* Can't share interrupts unless both agree to and are
* the same type (level, edge, polarity). So both flag
* fields must have IRQF_SHARED set and the bits which
* set the trigger type must match.
*/
if (!((old->flags & new->flags) & IRQF_SHARED) ||
((old->flags ^ new->flags) & IRQF_TRIGGER_MASK)) {
old_name = old->name;
goto mismatch;
}
#if defined(CONFIG_IRQ_PER_CPU)
/* All handlers must agree on per-cpuness */
if ((old->flags & IRQF_PERCPU) !=
(new->flags & IRQF_PERCPU))
goto mismatch;
#endif
/* add new interrupt at end of irq queue */
do {/*这一步是遍历到链表的最后一个
old->next=NULL为止*/
old_ptr = &old->next;
old = *old_ptr;
} while (old);
shared = 1;/*共享*/
}
if (!shared) {
/*设置irq_desc[irq]结构中chip成员的还没设置的指针
，让它们指向一些默认函数*/
irq_chip_set_defaults(desc->chip);
init_waitqueue_head(&desc->wait_for_threads);
/* Setup the type (level, edge polarity) if configured: */
/*设置触发方式*/
if (new->flags & IRQF_TRIGGER_MASK) {
ret = __irq_set_trigger(desc, irq,
new->flags & IRQF_TRIGGER_MASK);
if (ret)
goto out_thread;
} else
compat_irq_chip_set_default_handler(desc);
#if defined(CONFIG_IRQ_PER_CPU)
if (new->flags & IRQF_PERCPU)
desc->status |= IRQ_PER_CPU;
#endif
desc->status &= ~(IRQ_AUTODETECT | IRQ_WAITING | IRQ_ONESHOT |
IRQ_INPROGRESS | IRQ_SPURIOUS_DISABLED);
if (new->flags & IRQF_ONESHOT)
desc->status |= IRQ_ONESHOT;
if (!(desc->status & IRQ_NOAUTOEN)) {
desc->depth = 0;
desc->status &= ~IRQ_DISABLED;
desc->chip->startup(irq);
} else
/* Undo nested disables: */
desc->depth = 1;
/* Exclude IRQ from balancing if requested */
if (new->flags & IRQF_NOBALANCING)
desc->status |= IRQ_NO_BALANCING;
/* Set default affinity mask once everything is setup */
setup_affinity(irq, desc);
} else if ((new->flags & IRQF_TRIGGER_MASK)
&& (new->flags & IRQF_TRIGGER_MASK)
!= (desc->status & IRQ_TYPE_SENSE_MASK)) {
/* hope the handler works with the actual trigger mode... */
pr_warning("IRQ %d uses trigger mode %d; requested %d\n",
irq, (int)(desc->status & IRQ_TYPE_SENSE_MASK),
(int)(new->flags & IRQF_TRIGGER_MASK));
}
new->irq = irq;/*将new的irq设置为irq*/
*old_ptr = new;/*将new链入链表中，这个从上面可以看到*/
/* Reset broken irq detection when installing new handler */
desc->irq_count = 0;
desc->irqs_unhandled = 0;
/*
* Check whether we disabled the irq via the spurious handler
* before. Reenable it and give it another chance.
*/
if (shared && (desc->status & IRQ_SPURIOUS_DISABLED)) {
desc->status &= ~IRQ_SPURIOUS_DISABLED;
__enable_irq(desc, irq, false);/*启用中断*/
}
spin_unlock_irqrestore(&desc->lock, flags);
/*
* Strictly no need to wake it up, but hung_task complains
* when no hard interrupt wakes the thread up.
*/
if (new->thread)
wake_up_process(new->thread);
/*下面为注册proc文件系统对应的项*/
register_irq_proc(irq, desc);
new->dir = NULL;
register_handler_proc(irq, new);
return 0;
mismatch:
#ifdef CONFIG_DEBUG_SHIRQ
if (!(new->flags & IRQF_PROBE_SHARED)) {
printk(KERN_ERR "IRQ handler type mismatch for IRQ %d\n", irq);
if (old_name)
printk(KERN_ERR "current handler: %s\n", old_name);
dump_stack();
}
#endif
ret = -EBUSY;
out_thread:
spin_unlock_irqrestore(&desc->lock, flags);
if (new->thread) {
struct task_struct *t = new->thread;
new->thread = NULL;
if (likely(!test_bit(IRQTF_DIED, &new->thread_flags)))
kthread_stop(t);
put_task_struct(t);
}
return ret;
}

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