summaryrefslogtreecommitdiff
path: root/main.c
blob: c2b9b3fbb9ae3e5427329d301317da43a4c729fc (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
#include "types.h"
#include "param.h"
#include "mmu.h"
#include "proc.h"
#include "defs.h"
#include "x86.h"
#include "traps.h"
#include "syscall.h"
#include "elf.h"
#include "param.h"
#include "spinlock.h"

extern char edata[], end[];
extern uchar _binary_init_start[], _binary_init_size[];

void process0();

// CPU 0 starts running C code here.
// This is called main0 not main so that it can have
// a void return type.  Gcc can't handle functions named
// main that don't return int.  Really.
void
main0(void)
{
  int i;
  struct proc *p;

  // clear BSS
  memset(edata, 0, end - edata);

  // switch to cpu0's cpu stack
  asm volatile("movl %0, %%esp" : : "r" (cpus[0].mpstack + MPSTACK - 32));
  asm volatile("movl %0, %%ebp" : : "r" (cpus[0].mpstack + MPSTACK));

  // Prevent release() from enabling interrupts.
  for(i=0; i<NCPU; i++)
    cpus[i].nlock = 1;

  mp_init(); // collect info about this machine

  lapic_init(mp_bcpu());

  cprintf("\ncpu%d: starting xv6\n\n", cpu());

  pinit(); // process table
  binit(); // buffer cache
  pic_init();
  ioapic_init();
  kinit(); // physical memory allocator
  tvinit(); // trap vectors
  idtinit(); // this CPU's interrupt descriptor table
  fd_init();
  iinit(); // i-node table

  // initialize process 0
  p = &proc[0];
  p->state = RUNNABLE;
  p->kstack = kalloc(KSTACKSIZE);

  // cause proc[0] to start in kernel at process0
  p->jmpbuf.eip = (uint) process0;
  p->jmpbuf.esp = (uint) (p->kstack + KSTACKSIZE - 4);

  // make sure there's a TSS
  setupsegs(0);

  // initialize I/O devices, let them enable interrupts
  console_init();
  ide_init(); 

  // start other CPUs
  mp_startthem();

  // turn on timer and enable interrupts on the local APIC
  lapic_timerinit();
  lapic_enableintr();

  // Enable interrupts on this processor.
  cpus[cpu()].nlock--;
  sti();

  scheduler();
}

// Additional processors start here.
void
mpmain(void)
{
  cprintf("cpu%d: starting\n", cpu());
  idtinit(); // CPU's idt
  if(cpu() == 0)
    panic("mpmain on cpu 0");
  lapic_init(cpu());
  lapic_timerinit();
  lapic_enableintr();

  // make sure there's a TSS
  setupsegs(0);

  cpuid(0, 0, 0, 0, 0);	// memory barrier
  cpus[cpu()].booted = 1;

  // Enable interrupts on this processor.
  cpus[cpu()].nlock--;
  sti();

  scheduler();
}

// proc[0] starts here, called by scheduler() in the ordinary way.
void
process0()
{
  struct proc *p0 = &proc[0];
  struct proc *p1;
  extern struct spinlock proc_table_lock;
  struct trapframe tf;

  release(&proc_table_lock);

  p0->cwd = iget(rootdev, 1);
  iunlock(p0->cwd);

  // dummy user memory to make copyproc() happy
  p0->sz = 4 * PAGE;
  p0->mem = kalloc(p0->sz);

  // fake a trap frame as if a user process had made a system
  // call, so that copyproc will have a place for the new
  // process to return to.
  p0->tf = &tf;
  memset(p0->tf, 0, sizeof(struct trapframe));
  p0->tf->es = p0->tf->ds = p0->tf->ss = (SEG_UDATA << 3) | 3;
  p0->tf->cs = (SEG_UCODE << 3) | 3;
  p0->tf->eflags = FL_IF;
  p0->tf->esp = p0->sz;

  p1 = copyproc(p0);
  
  load_icode(p1, _binary_init_start, (uint) _binary_init_size);
  p1->state = RUNNABLE;

  proc_wait();
  panic("init exited");
}

void
load_icode(struct proc *p, uchar *binary, uint size)
{
  int i;
  struct elfhdr *elf;
  struct proghdr *ph;

  elf = (struct elfhdr*) binary;
  if (elf->magic != ELF_MAGIC)
    panic("load_icode: not an ELF binary");

  p->tf->eip = elf->entry;

  // Map and load segments as directed.
  ph = (struct proghdr*) (binary + elf->phoff);
  for (i = 0; i < elf->phnum; i++, ph++) {
    if (ph->type != ELF_PROG_LOAD)
      continue;
    if (ph->va + ph->memsz < ph->va)
      panic("load_icode: overflow in elf header segment");
    if (ph->va + ph->memsz >= p->sz)
      panic("load_icode: icode wants to be above UTOP");

    // Load/clear the segment
    memmove(p->mem + ph->va, binary + ph->offset, ph->filesz);
    memset(p->mem + ph->va + ph->filesz, 0, ph->memsz - ph->filesz);
  }
}