在ARM中，事件发生将会触发中断，然而，中断并不会直接触发CPU，而是在由一个GIC，中断控制器来管理：
其中，中断分为?
Supports three interrupt types:
Private Peripheral Interrupt (PPI）一个中断源对应一个CPU
Software Generated Interrupt (SGI) CPU对应CPU
Shared Peripheral Interrupt (SPI) 一个中断源对应多个CPU
今天的例子是用SGI中断来实现的，在处理中断的时候，主要分三步：
//step 1: cpu cpsr
CPU允许中断
20 __asm__ __volatile__(
21 "mrs r0, cpsr\n"
22 "bic r0, r0, #0x80\n"//设置CPSR的I位，将IRQ位打开
23 "msr cpsr, r0\n"
24 ::: "r0"
25 );
26
27 //step 2: GIC
GIC
28 ICCICR_CPU0 = 1;//CPU接口控制寄存器
29 ICCPMR_CPU0 = 0xff;//中断优先标志寄存器
30 ICDDCR = 1;//设置本中断的开关
31 ICDIPR0_CPU0 = (0x00 << 0);//本中断的优先级
32 ICDIPTR0_CPU0 = 1;//选择指定的CPU
33 ICDISER0_CPU0 = (1 << 0);//设置本中断开启
34 各个寄存器描述如下：详细见4412 782页
35 //step 3: interrupt source
中断源
36 ICDSGIR = 0 | (1 << 16) | (0 << 24);//SGI控制寄存器CPUTargetList.TargetListFi lte
37 printf("welcome back! \n");
下面是代码：
1 #include"regs.h"
2
3 int (*printf)(char *, ...) = 0xc3e114d8;
4
5 void init_ttb(unsigned long *addr);
6 void enable_mmu(void);
7 unsigned long data_abort_init();
8 void memcopy(unsigned long* dest,unsigned long* source,int len);
9 void do_irq();
10
11 int main()
12 {
13 *(unsigned long *)0x66000000 = do_irq;
14 unsigned long source_addr=data_abort_init();
15 printf("swi_souce addr is %x\n",source_addr);
16 memcopy(0x60000000,source_addr,0x1000);
17 enable_mmu();
18
19 //step 1: cpu cpsr
20 __asm__ __volatile__(
21 "mrs r0, cpsr\n"
22 "bic r0, r0, #0x80\n"//设置CPSR的I位，将IRQ位打开
23 "msr cpsr, r0\n"
24 ::: "r0"
25 );
26
27 //step 2: GIC
28 ICCICR_CPU0 = 1;//CPU接口控制寄存器
29 ICCPMR_CPU0 = 0xff;//中断优先标志寄存器
30 ICDDCR = 1;//设置本中断的开关
31 ICDIPR0_CPU0 = (0x00 << 0);//本中断的优先级
32 ICDIPTR0_CPU0 = 1;//选择指定的CPU
33 ICDISER0_CPU0 = (1 << 0);//设置本中断开启
34
35 //step 3: interrupt source
36 ICDSGIR = 0 | (1 << 16) | (0 << 24);//SGI控制寄存器CPUTargetList.TargetListFi lte
37 printf("welcome back! \n");
38 }
39
40 void do_irq()
41 {
42 unsigned long data = ICCIAR_CPU0;
43 unsigned long irq_id = data & 0x3ff;
44 unsigned long cpu_id = (data >> 10) & 0x7;
45 ICCEOIR_CPU0 = irq_id | (cpu_id << 10);
46 printf("irq is %d, cpu is %d\n", irq_id, cpu_id);
47 }
48
49 void memcopy(unsigned long* dest, unsigned long* source,int len)
50 {
51 int i=0;;
52 for(i=0;i<len;i++)
53 dest[i]=source[i];
54 }
55
56 unsigned long data_abort_init()
57 {
58 unsigned long source;
59 __asm__ __volatile__(
60 "ldr %0, =voliate_start\n"
61 : "=r" (source)
62 );
63 return source;
64 }
65
66 __asm__(
67 "voliate_start:\n"
68 //跳转目录
69 " b reset\n"
70 " b undefined\n"
71 " b swi\n"
72 " b pre_abt\n"
73 " b data_abt\n"
74 " .word 0\n"//占位符号，一个位占4个字节
75 " b irq\n"
76 " b fiq\n"
77 "\n"
78 //跳转要分三部:
79 //1:将PC保存到新模式下的lr中；
80 //2:将CPSR保存在SPSR中
81 //3:初始化SP
82 //前两步由硬件完成，而第三部需要手动完成
83 "reset:\n"
84
85 "undefined:\n"
86 "mov sp, #0x66000000\n"//初始化SP
87 "stmfd sp!, {r0-r12, lr}\n"//初始化sp，入栈保护寄存器
88 //打印一句话
89 "ldr r0, =und_string\n"
90 "ldr r2, show\n"
91 "blx r2\n"
92 //跳回来分两部
93 //1:将CPSR保存在SPSR中
84
85 "undefined:\n"
86 "mov sp, #0x66000000\n"//初始化SP
87 "stmfd sp!, {r0-r12, lr}\n"//初始化sp，入栈保护寄存器
88 //打印一句话
89 "ldr r0, =und_string\n"
90 "ldr r2, show\n"
91 "blx r2\n"
92 //跳回来分两部
93 //1:将CPSR保存在SPSR中
94 //2:将PC保存到新模式下的lr中；
95 "mov sp, #0x66000000\n"//
96 "ldmea sp, {r0-r12, pc}^\n"//
97
98 "swi:\n"
99
100 "pre_abt:\n"
101 "data_abt:\n"
102 "sub lr, lr, #4\n"
103 "mov sp, #0x66000000\n"//初始化SP
104 "stmfd sp!, {r0-r12, lr}\n"//初始化sp，入栈保护寄存器
105 //打印一句话
106 "ldr r0, =data_string\n"
107 "ldr r2, show\n"
108 "blx r2\n"
109 //跳回来分两部
110 //1:将CPSR保存在SPSR中
111 //2:将PC保存到新模式下的lr中；
112 "mov sp, #0x66000000\n"//
113 "ldmea sp, {r0-r12, pc}^\n"//
114
115 "irq:\n"
116 "sub lr, lr, #4\n"
117 "mov sp, #0x66000000\n"//初始化SP
118 "stmfd sp!, {r0-r12, lr}\n"//初始化sp，入栈保护寄存器
119 //打印一句话
120 "mov r2, #0x66000000\n"
121 "ldr r1, [r2]\n"
122 "blx r1\n"
123
124 // "ldr r0, =irq_string\n"
125 // "ldr r2, show\n"
126 // "blx r2\n"
127 //跳回来分两部
128 //1:将CPSR保存在SPSR中
129 //2:将PC保存到新模式下的lr中；
130 "mov sp, #0x66000000\n"//
131 "ldmea sp, {r0-r12, pc}^\n"//
132 "fiq:\n"
133 "show:\n"
134 ".word 0xc3e114d8\n"
135
136 "und_string:\n"
137 ".asciz \"This is UND!\\n\" \n"
138 "data_string:\n"
139 ".asciz \"This DATA_ABORT!\\n\" \n"
140 "irq_string:\n"
141 ".asciz \"This IRQ!\\n\" \n"
142
143 );
144
145 void init_ttb(unsigned long *addr)
146 {
147 unsigned long va = 0;//定义虚拟地址
148 unsigned long pa = 0;//定义物理地址
149
150 //40000000-------80000000 ==== 40000000------80000000
151 for(va=0x40000000; va<=0x80000000; va+=0x100000){
152 pa = va;
153 addr[va >> 20] = pa | 2;
154 //|2的目的是将0-2位置为10此时将是小页模式4K
155 }
156
157 //00000000-------10000000 ==== 60000000------70000000
158 for(va=0x00000000; va<=0x10000000; va+=0x100000){
159 pa = va+0x60000000;
160 addr[va >> 20] = pa | 2;
161 }
162
163 //10000000-------14000000 ==== 10000000------14000000
164 for(va=0x10000000; va<=0x14000000; va+=0x100000){
165 pa = va;
166 addr[va >> 20] = pa | 2;
167 }
168
169 //30000000-------40000000 ==== 50000000------60000000
170 for(va=0x30000000; va<0x40000000; va+=0x100000){
171 pa = va + 0x20000000;
172 addr[va >> 20] = pa | 2;
173 }
174 }
175
176 void enable_mmu(void)
177
178 {
179 unsigned long addr = 0x70000000;
180 init_ttb(addr);
181 //step:初始化页表
182
183 unsigned long mmu = 1 | (1 << 1) | (1 << 8);
184 //将MMU的第0,1,8位置1
185 __asm__ __volatile__(
186 "mov r0, #3\n"
187 "MCR p15, 0, r0, c3, c0, 0\n"//manager
188 "MCR p15, 0, %0, c2, c0, 0\n"//addr
189 "MCR p15, 0, %1, c1, c0, 0\n"// enable mmu
190 :
191 : "r" (addr), "r" (mmu)
192 : "r0"
193 );
194 printf("MMU is enable!\n");
195 }
196
在代码中，主函数其他的部分在前面都已经说了，已不再说。主要是在VICTOR函数中，将处理中断的部分，做成了一个函数，以后更容易修改处理的部分。
void do_irq()
41 {
42 unsigned long data = ICCIAR_CPU0;//取出IRQ ID 和CPU ID
43 unsigned long irq_id = data & 0x3ff;
44 unsigned long cpu_id = (data >> 10) & 0x7;
45 ICCEOIR_CPU0 = irq_id | (cpu_id << 10);//清除CPU
46 printf("irq is %d, cpu is %d\n", irq_id, cpu_id);
47 }
//总的来说，在以前的基础上面，今天主要认识了GIC的配置，更重要的是，中断分为四步：
1，CPU开
2，GIC配置
3，中断源
4，处理中断，清中断