i386/ucla/src/lab2/kern/trap.c

   1 #include <inc/mmu.h>
   2 #include <inc/x86.h>
   3 #include <inc/assert.h>
   4
   5 #include <kern/pmap.h>
   6 #include <kern/trap.h>
   7 #include <kern/console.h>
   8 #include <kern/monitor.h>
   9
  10 static struct Taskstate ts;
  11
  12 /* Interrupt descriptor table.  (Must be built at run time because
  13  * shifted function addresses can't be represented in relocation records.)
  14  */
  15 struct Gatedesc idt[256] = { { 0 } };
  16 struct Pseudodesc idt_pd = {
  17         sizeof(idt) - 1, (uint32_t) idt
  18 };
  19
  20
  21 static const char *trapname(int trapno)
  22 {
  23         static const char * const excnames[] = {
  24                 "Divide error",
  25                 "Debug",
  26                 "Non-Maskable Interrupt",
  27                 "Breakpoint",
  28                 "Overflow",
  29                 "BOUND Range Exceeded",
  30                 "Invalid Opcode",
  31                 "Device Not Available",
  32                 "Double Fault",
  33                 "Coprocessor Segment Overrun",
  34                 "Invalid TSS",
  35                 "Segment Not Present",
  36                 "Stack Fault",
  37                 "General Protection",
  38                 "Page Fault",
  39                 "(unknown trap)",
  40                 "x87 FPU Floating-Point Error",
  41                 "Alignment Check",
  42                 "Machine-Check",
  43                 "SIMD Floating-Point Exception"
  44         };
  45
  46         if (trapno < (int) (sizeof(excnames)/sizeof(excnames[0])))
  47                 return excnames[trapno];
  48         if (trapno == T_SYSCALL)
  49                 return "System call";
  50         return "(unknown trap)";
  51 }
  52
  53
  54 void
  55 idt_init(void)
  56 {
  57         extern struct Segdesc gdt[];
  58
  59         // LAB 2: Your code here.
  60
  61         // Setup a TSS so that we get the right stack
  62         // when we trap to the kernel.
  63         ts.ts_esp0 = KSTACKTOP;
  64         ts.ts_ss0 = GD_KD;
  65
  66         // Initialize the TSS field of the gdt.
  67         gdt[GD_TSS >> 3] = SEG16(STS_T32A, (uint32_t) (&ts),
  68                                         sizeof(struct Taskstate), 0);
  69         gdt[GD_TSS >> 3].sd_s = 0;
  70
  71         // Load the TSS
  72         ltr(GD_TSS);
  73
  74         // Load the IDT
  75         asm volatile("lidt idt_pd");
  76 }
  77
  78
  79 void
  80 print_trapframe(struct Trapframe *tf)
  81 {
  82         cprintf("TRAP frame at %p\n", tf);
  83         print_regs(&tf->tf_regs);
  84         cprintf("  es   0x----%04x\n", tf->tf_es);
  85         cprintf("  ds   0x----%04x\n", tf->tf_ds);
  86         cprintf("  trap 0x%08x %s\n", tf->tf_trapno, trapname(tf->tf_trapno));
  87         cprintf("  err  0x%08x\n", tf->tf_err);
  88         cprintf("  eip  0x%08x\n", tf->tf_eip);
  89         cprintf("  cs   0x----%04x\n", tf->tf_cs);
  90         cprintf("  flag 0x%08x\n", tf->tf_eflags);
  91         cprintf("  esp  0x%08x\n", tf->tf_esp);
  92         cprintf("  ss   0x----%04x\n", tf->tf_ss);
  93 }
  94
  95 void
  96 print_regs(struct PushRegs *regs)
  97 {
  98         cprintf("  edi  0x%08x\n", regs->reg_edi);
  99         cprintf("  esi  0x%08x\n", regs->reg_esi);
 100         cprintf("  ebp  0x%08x\n", regs->reg_ebp);
 101         cprintf("  oesp 0x%08x\n", regs->reg_oesp);
 102         cprintf("  ebx  0x%08x\n", regs->reg_ebx);
 103         cprintf("  edx  0x%08x\n", regs->reg_edx);
 104         cprintf("  ecx  0x%08x\n", regs->reg_ecx);
 105         cprintf("  eax  0x%08x\n", regs->reg_eax);
 106 }
 107
 108 static void
 109 trap_dispatch(struct Trapframe *tf)
 110 {
 111         // Handle the breakpoint exception.
 112         // LAB 2: Your code here.
 113
 114
 115         // Unexpected trap: The user process or the kernel has a bug.
 116         print_trapframe(tf);
 117         if (tf->tf_cs == GD_KT)
 118                 panic("unhandled trap in kernel");
 119         else
 120                 panic("unhandled trap in user mode");
 121 }
 122
 123 asmlinkage void
 124 trap(struct Trapframe *tf)
 125 {
 126         // The environment may have set DF and some versions
 127         // of GCC rely on DF being clear
 128         asm volatile("cld" : : : "cc");
 129
 130         // Check that interrupts are disabled.  If this assertion
 131         // fails, DO NOT be tempted to fix it by inserting a "cli" in
 132         // the interrupt path.
 133         assert(!(read_eflags() & FL_IF));
 134
 135         // Dispatch based on what type of trap occurred
 136         trap_dispatch(tf);
 137 }