os_kernel_lab/labcodes_answer/lab1_result/kern/trap/trap.c

#include <defs.h>
#include <mmu.h>
#include <memlayout.h>
#include <clock.h>
#include <trap.h>
#include <x86.h>
#include <stdio.h>
#include <assert.h>
#include <console.h>
#include <kdebug.h>
#include <string.h>
#define TICK_NUM 1

static void print_ticks() {
    cprintf("%d ticks\n",TICK_NUM);
#ifdef DEBUG_GRADE
    cprintf("End of Test.\n");
    panic("EOT: kernel seems ok.");
#endif
}

/* *
 * Interrupt descriptor table:
 *
 * Must be built at run time because shifted function addresses can't
 * be represented in relocation records.
 * */
static struct gatedesc idt[256] = {{0}};

static struct pseudodesc idt_pd = {
    sizeof(idt) - 1, (uintptr_t)idt
};

/* idt_init - initialize IDT to each of the entry points in kern/trap/vectors.S */
void
idt_init(void) {
     /* LAB1 YOUR CODE : STEP 2 */
     /* (1) Where are the entry addrs of each Interrupt Service Routine (ISR)?
      *     All ISR's entry addrs are stored in __vectors. where is uintptr_t __vectors[] ?
      *     __vectors[] is in kern/trap/vector.S which is produced by tools/vector.c
      *     (try "make" command in lab1, then you will find vector.S in kern/trap DIR)
      *     You can use  "extern uintptr_t __vectors[];" to define this extern variable which will be used later.
      * (2) Now you should setup the entries of ISR in Interrupt Description Table (IDT).
      *     Can you see idt[256] in this file? Yes, it's IDT! you can use SETGATE macro to setup each item of IDT
      * (3) After setup the contents of IDT, you will let CPU know where is the IDT by using 'lidt' instruction.
      *     You don't know the meaning of this instruction? just google it! and check the libs/x86.h to know more.
      *     Notice: the argument of lidt is idt_pd. try to find it!
      */
    extern uintptr_t __vectors[];
    int i;
    for (i = 0; i < sizeof(idt) / sizeof(struct gatedesc); i ++) {
        SETGATE(idt[i], 0, GD_KTEXT, __vectors[i], DPL_KERNEL);
    }
	// set for switch from user to kernel
    SETGATE(idt[T_SWITCH_TOK], 0, GD_KTEXT, __vectors[T_SWITCH_TOK], DPL_USER);
	// load the IDT
    lidt(&idt_pd);
}

static const char *
trapname(int trapno) {
    static const char * const excnames[] = {
        "Divide error",
        "Debug",
        "Non-Maskable Interrupt",
        "Breakpoint",
        "Overflow",
        "BOUND Range Exceeded",
        "Invalid Opcode",
        "Device Not Available",
        "Double Fault",
        "Coprocessor Segment Overrun",
        "Invalid TSS",
        "Segment Not Present",
        "Stack Fault",
        "General Protection",
        "Page Fault",
        "(unknown trap)",
        "x87 FPU Floating-Point Error",
        "Alignment Check",
        "Machine-Check",
        "SIMD Floating-Point Exception"
    };

    if (trapno < sizeof(excnames)/sizeof(const char * const)) {
        return excnames[trapno];
    }
    if (trapno >= IRQ_OFFSET && trapno < IRQ_OFFSET + 16) {
        return "Hardware Interrupt";
    }
    return "(unknown trap)";
}

/* trap_in_kernel - test if trap happened in kernel */
bool
trap_in_kernel(struct trapframe *tf) {
    return (tf->tf_cs == (uint16_t)KERNEL_CS);
}

static const char *IA32flags[] = {
    "CF", NULL, "PF", NULL, "AF", NULL, "ZF", "SF",
    "TF", "IF", "DF", "OF", NULL, NULL, "NT", NULL,
    "RF", "VM", "AC", "VIF", "VIP", "ID", NULL, NULL,
};

void
print_trapframe(struct trapframe *tf) {
    cprintf("trapframe at %p\n", tf);
    print_regs(&tf->tf_regs);
    cprintf("  ds   0x----%04x\n", tf->tf_ds);
    cprintf("  es   0x----%04x\n", tf->tf_es);
    cprintf("  fs   0x----%04x\n", tf->tf_fs);
    cprintf("  gs   0x----%04x\n", tf->tf_gs);
    cprintf("  trap 0x%08x %s\n", tf->tf_trapno, trapname(tf->tf_trapno));
    cprintf("  err  0x%08x\n", tf->tf_err);
    cprintf("  eip  0x%08x\n", tf->tf_eip);
    cprintf("  cs   0x----%04x\n", tf->tf_cs);
    cprintf("  flag 0x%08x ", tf->tf_eflags);

    int i, j;
    for (i = 0, j = 1; i < sizeof(IA32flags) / sizeof(IA32flags[0]); i ++, j <<= 1) {
        if ((tf->tf_eflags & j) && IA32flags[i] != NULL) {
            cprintf("%s,", IA32flags[i]);
        }
    }
    cprintf("IOPL=%d\n", (tf->tf_eflags & FL_IOPL_MASK) >> 12);

    if (!trap_in_kernel(tf)) {
        cprintf("  esp  0x%08x\n", tf->tf_esp);
        cprintf("  ss   0x----%04x\n", tf->tf_ss);
    }
}

void
print_regs(struct pushregs *regs) {
    cprintf("  edi  0x%08x\n", regs->reg_edi);
    cprintf("  esi  0x%08x\n", regs->reg_esi);
    cprintf("  ebp  0x%08x\n", regs->reg_ebp);
    cprintf("  oesp 0x%08x\n", regs->reg_oesp);
    cprintf("  ebx  0x%08x\n", regs->reg_ebx);
    cprintf("  edx  0x%08x\n", regs->reg_edx);
    cprintf("  ecx  0x%08x\n", regs->reg_ecx);
    cprintf("  eax  0x%08x\n", regs->reg_eax);
}

/* temporary trapframe or pointer to trapframe */
struct trapframe switchk2u, *switchu2k;

/* trap_dispatch - dispatch based on what type of trap occurred */
static void
trap_dispatch(struct trapframe *tf) {
    volatile char c;
    // 有限状态机？
    static enum {STARTED=0, STOPPED=1, WAITING_FOR_INPUT, READY_TO_OUTPUT} state = STOPPED;
    // 唉不能long long，看来很有可能会溢出啊
    static long milliseconds = 0;
    static enum {COUNTDOWN=-1, COUNTUP=1} mode = COUNTUP;

    switch (tf->tf_trapno) {
    case IRQ_OFFSET + IRQ_TIMER:
        /* LAB1 YOUR CODE : STEP 3 */
        /* handle the timer interrupt */
        /* (1) After a timer interrupt, you should record this event using a global variable (increase it), such as ticks in kern/driver/clock.c
         * (2) Every TICK_NUM cycle, you can print some info using a funciton, such as print_ticks().
         * (3) Too Simple? Yes, I think so!
         */
        switch (state) {
        case STARTED:
            if (ticks % TICK_NUM == 0) {
                // 10毫秒触发一次时钟中断，TICK_NUM次中断触发一次更新，所以毫秒数应该乘TICK_NUM * 10
                milliseconds += mode * TICK_NUM * 10;
                // 当时间倒计时到0时转成停止状态
                // 而正计时加了mode之后至少为1所以不会转换状态
                // 使用小于等于0而不是等于0是为了防止万一出现异常导致小于0的情况
                state = READY_TO_OUTPUT * (milliseconds <= 0); // 为了减少分支才写成这样
                // print_ticks();
                cprintf("\r%d.%03d\t", milliseconds / 1000, milliseconds % 1000);
            }
            break;
        case READY_TO_OUTPUT:
            state = STOPPED;
            mode = COUNTUP;
            if (milliseconds < 0) milliseconds = 0; // 防止出现异常小于0
            cprintf(MSG_COUNTDOWN_STOP);
            break;
        default:
            break;
        }
        ticks ++;
        break;
    case IRQ_OFFSET + IRQ_COM1:
        c = cons_getc();
        cprintf("serial [%03d] %c\n", c, c);
        break;
    case IRQ_OFFSET + IRQ_KBD:
        c = cons_getc();
        if (state == WAITING_FOR_INPUT) {
            long seconds = milliseconds / 1000;
            // if (c != '\0') cprintf("%c", c);
             // 如果是正在输入状态，此时不能键入字母或其他各种字符
            //  在这里不能直接break不然就直接跳出中断处理程序了
            // 所以用c=0来防止执行后面的转换状态
            if (c == '\b' || c == '\n' || ('0' <= c && c <= '9')) {
                cprintf("%c", c);
            } else {
                c = '\0';
            }
            if (c == '\b') {
                seconds /= 10;
            }
            if ('0' <= c && c <= '9') {
                seconds *= 10;
                seconds += c - '0';
            }
            milliseconds = seconds * 1000;
            if (c == '\n') {
                state = STARTED;
            }
            c = '\0'; // 如果是正在输入状态，此时不能根据字母转换状态
        }
        switch (c) {
        case 'a':
            mode = COUNTUP;
            cprintf(MSG_COUNTUP_START);
            break;
        case 'b':
            mode = COUNTDOWN;
            cprintf(MSG_COUNTDOWN_START);
            state = WAITING_FOR_INPUT;
            milliseconds = 0;
            break;
        case 's':
        case 'c':
            state = STARTED;
            cprintf(MSG_START);
            break;
        case 'p':
            state = STOPPED;
            cprintf(MSG_PAUSE, milliseconds / 1000, milliseconds % 1000);
            break;
        case 'e':
            state = STOPPED;
            mode = COUNTUP;
            cprintf(MSG_STOP, milliseconds / 1000, milliseconds % 1000);
            milliseconds = 0;
            break;
        default:
            break;
        }
        // cprintf("kbd [%03d] %c\n", c, c);
        break;
    //LAB1 CHALLENGE 1 : YOUR CODE you should modify below codes.
    case T_SWITCH_TOU:
        if (tf->tf_cs != USER_CS) {
            switchk2u = *tf;
            switchk2u.tf_cs = USER_CS;
            switchk2u.tf_ds = switchk2u.tf_es = switchk2u.tf_ss = USER_DS;
            switchk2u.tf_esp = (uint32_t)tf + sizeof(struct trapframe) - 8;
		
            // set eflags, make sure ucore can use io under user mode.
            // if CPL > IOPL, then cpu will generate a general protection.
            switchk2u.tf_eflags |= FL_IOPL_MASK;
		
            // set temporary stack
            // then iret will jump to the right stack
            *((uint32_t *)tf - 1) = (uint32_t)&switchk2u;
        }
        break;
    case T_SWITCH_TOK:
        if (tf->tf_cs != KERNEL_CS) {
            tf->tf_cs = KERNEL_CS;
            tf->tf_ds = tf->tf_es = KERNEL_DS;
            tf->tf_eflags &= ~FL_IOPL_MASK;
            switchu2k = (struct trapframe *)(tf->tf_esp - (sizeof(struct trapframe) - 8));
            memmove(switchu2k, tf, sizeof(struct trapframe) - 8);
            *((uint32_t *)tf - 1) = (uint32_t)switchu2k;
        }
        break;
    case IRQ_OFFSET + IRQ_IDE1:
    case IRQ_OFFSET + IRQ_IDE2:
        /* do nothing */
        break;
    default:
        // in kernel, it must be a mistake
        if ((tf->tf_cs & 3) == 0) {
            print_trapframe(tf);
            panic("unexpected trap in kernel.\n");
        }
    }
}

/* *
 * trap - handles or dispatches an exception/interrupt. if and when trap() returns,
 * the code in kern/trap/trapentry.S restores the old CPU state saved in the
 * trapframe and then uses the iret instruction to return from the exception.
 * */
void
trap(struct trapframe *tf) {
    // dispatch based on what type of trap occurred
    trap_dispatch(tf);
}