8 #define SYSCALL_INT 0x80
10 /* IDT gate descriptor bits */
11 #define GATE_TASK (5 << 8)
12 #define GATE_INTR (6 << 8)
13 #define GATE_TRAP (7 << 8)
14 #define GATE_DEFAULT (1 << 11)
15 #define GATE_PRESENT (1 << 15)
17 /* PIC command and data ports */
19 #define PIC1_DATA 0x21
21 #define PIC2_DATA 0xa1
23 /* PIC initialization command word 1 bits */
24 #define ICW1_ICW4_NEEDED (1 << 0)
25 #define ICW1_SINGLE (1 << 1)
26 #define ICW1_INTERVAL4 (1 << 2)
27 #define ICW1_LEVEL (1 << 3)
28 #define ICW1_INIT (1 << 4)
29 /* PIC initialization command word 4 bits */
30 #define ICW4_8086 (1 << 0)
31 #define ICW4_AUTO_EOI (1 << 1)
32 #define ICW4_BUF_SLAVE (1 << 3) /* 1000 */
33 #define ICW4_BUF_MASTER (3 << 2) /* 1100 */
34 #define ICW4_SPECIAL (1 << 4)
36 /* PIC operation command word 2 bits */
37 #define OCW2_EOI (1 << 5)
40 static void init_pic(int offset);
41 static void gate_desc(desc_t *desc, uint16_t sel, uint32_t addr, int dpl, int type);
43 /* defined in intr_asm.S */
44 void set_idt(uint32_t addr, uint16_t limit);
45 void intr_entry_default(void);
47 /* the IDT (interrupt descriptor table) */
48 static desc_t idt[256] __attribute__((aligned(8)));
50 /* table of handler functions for all interrupts */
51 static intr_func_t intr_func[256];
53 static struct intr_frame *cur_intr_frame;
54 static int eoi_pending;
61 set_idt((uint32_t)idt, sizeof idt - 1);
63 /* initialize all entry points and interrupt handlers */
64 for(i=0; i<256; i++) {
65 set_intr_entry(i, intr_entry_default);
69 /* by including intrtab.h here (without ASM being defined)
70 * the series of INTR_ENTRY_* macros will be expanded to a series
71 * of function prototypes for all interrupt entry points and the
72 * corresponding calls to set_intr_entry to set up the IDT slots
76 /* initialize the programmable interrupt controller
77 * setting up the maping of IRQs [0, 15] to interrupts [32, 47]
83 /* retrieve the current interrupt frame.
84 * returns 0 when called during init.
86 struct intr_frame *get_intr_frame(void)
88 return cur_intr_frame;
91 /* set an interrupt handler function for a particular interrupt */
92 void interrupt(int intr_num, intr_func_t func)
94 intr_func[intr_num] = func;
97 /* this function is called from all interrupt entry points
98 * it calls the appropriate interrupt handlers if available and handles
99 * sending an end-of-interrupt command to the PICs when finished.
101 void dispatch_intr(struct intr_frame frm)
103 cur_intr_frame = &frm;
105 if(IS_IRQ(frm.inum)) {
106 eoi_pending = frm.inum;
109 if(intr_func[frm.inum]) {
110 intr_func[frm.inum](frm.inum);
113 panic("unhandled exception %d, error code: %d\n", frm.inum, frm.err);
115 printf("unhandled interrupt %d\n", frm.inum);
120 end_of_irq(INTR_TO_IRQ(eoi_pending));
124 static void init_pic(int offset)
126 /* send ICW1 saying we'll follow with ICW4 later on */
127 outb(ICW1_INIT | ICW1_ICW4_NEEDED, PIC1_CMD);
128 outb(ICW1_INIT | ICW1_ICW4_NEEDED, PIC2_CMD);
129 /* send ICW2 with IRQ remapping */
130 outb(offset, PIC1_DATA);
131 outb(offset + 8, PIC2_DATA);
132 /* send ICW3 to setup the master/slave relationship */
133 /* ... set bit3 = 3rd interrupt input has a slave */
135 /* ... set slave ID to 2 */
137 /* send ICW4 to set 8086 mode (no calls generated) */
138 outb(ICW4_8086, PIC1_DATA);
139 outb(ICW4_8086, PIC2_DATA);
140 /* done, just reset the data port to 0 */
145 static void gate_desc(desc_t *desc, uint16_t sel, uint32_t addr, int dpl, int type)
147 /* first 16bit part is the low 16bits of the entry address */
148 desc->d[0] = addr & 0xffff;
149 /* second 16bit part is the segment selector for the entry code */
151 /* third 16bit part has the privilege level, type, and present bit */
152 desc->d[2] = ((dpl & 3) << 13) | type | GATE_DEFAULT | GATE_PRESENT;
153 /* last 16bit part is the high 16bits of the entry address */
154 desc->d[3] = (addr & 0xffff0000) >> 16;
157 #define IS_TRAP(n) ((n) >= 32 && !IS_IRQ(n))
158 void set_intr_entry(int num, void (*handler)(void))
160 int type = IS_TRAP(num) ? GATE_TRAP : GATE_INTR;
162 /* the syscall interrupt has to have a dpl of 3 otherwise calling it from
163 * user space will raise a general protection exception. All the rest should
164 * have a dpl of 0 to disallow user programs to execute critical interrupt
165 * handlers and possibly crashing the system.
167 int dpl = (num == SYSCALL_INT) ? 3 : 0;
169 gate_desc(idt + num, selector(SEGM_KCODE, 0), (uint32_t)handler, dpl, type);
172 void end_of_irq(int irq)
174 int intr_state = get_intr_flag();
183 outb(OCW2_EOI, PIC2_CMD);
185 outb(OCW2_EOI, PIC1_CMD);
187 set_intr_flag(intr_state);