xv6-riscv/kernel/console.c

// Console input and output.
// Input is from the keyboard or serial port.
// Output is written to the screen and serial port.

#include <stdarg.h>

#include "types.h"
#include "param.h"
#include "spinlock.h"
#include "sleeplock.h"
#include "fs.h"
#include "file.h"
#include "memlayout.h"
#include "riscv.h"
#include "defs.h"
#include "proc.h"

static void consputc(int);

static volatile int panicked = 0;

static struct {
  struct spinlock lock;
  int locking;
} cons;

static char digits[] = "0123456789abcdef";

static void
printint(int xx, int base, int sign)
{
  char buf[16];
  int i;
  uint x;

  if(sign && (sign = xx < 0))
    x = -xx;
  else
    x = xx;

  i = 0;
  do{
    buf[i++] = digits[x % base];
  }while((x /= base) != 0);

  if(sign)
    buf[i++] = '-';

  while(--i >= 0)
    consputc(buf[i]);
}

static void
printptr(uint64 x) {
  int i;
  consputc('0');
  consputc('x');
  for (i = 0; i < (sizeof(uint64) * 2); i++, x <<= 4)
    consputc(digits[x >> (sizeof(uint64) * 8 - 4)]);
}

// Print to the console. only understands %d, %x, %p, %s.
void
printf(char *fmt, ...)
{
  va_list ap;
  int i, c, locking;
  char *s;

  locking = cons.locking;
  if(locking)
    acquire(&cons.lock);

  if (fmt == 0)
    panic("null fmt");

  va_start(ap, fmt);
  for(i = 0; (c = fmt[i] & 0xff) != 0; i++){
    if(c != '%'){
      consputc(c);
      continue;
    }
    c = fmt[++i] & 0xff;
    if(c == 0)
      break;
    switch(c){
    case 'd':
      printint(va_arg(ap, int), 10, 1);
      break;
    case 'x':
      printint(va_arg(ap, int), 16, 1);
      break;
    case 'p':
      printptr(va_arg(ap, uint64));
      break;
    case 's':
      if((s = va_arg(ap, char*)) == 0)
        s = "(null)";
      for(; *s; s++)
        consputc(*s);
      break;
    case '%':
      consputc('%');
      break;
    default:
      // Print unknown % sequence to draw attention.
      consputc('%');
      consputc(c);
      break;
    }
  }

  if(locking)
    release(&cons.lock);
}

void
panic(char *s)
{
  cons.locking = 0;
  printf("panic: ");
  printf(s);
  printf("\n");
  panicked = 1; // freeze other CPU
  for(;;)
    ;
}

#define BACKSPACE 0x100

void
consputc(int c)
{
  if(panicked){
    for(;;)
      ;
  }

  if(c == BACKSPACE){
    uartputc('\b'); uartputc(' '); uartputc('\b');
  } else
    uartputc(c);
}

#define INPUT_BUF 128
struct {
  char buf[INPUT_BUF];
  uint r;  // Read index
  uint w;  // Write index
  uint e;  // Edit index
} input;

#define C(x)  ((x)-'@')  // Contro

int
consoleread(int user_dst, uint64 dst, int n)
{
  uint target;
  int c;
  char buf[1];

  target = n;
  acquire(&cons.lock);
  while(n > 0){
    while(input.r == input.w){
      if(myproc()->killed){
        release(&cons.lock);
        return -1;
      }
      sleep(&input.r, &cons.lock);
    }
    c = input.buf[input.r++ % INPUT_BUF];
    if(c == C('D')){  // EOF
      if(n < target){
        // Save ^D for next time, to make sure
        // caller gets a 0-byte result.
        input.r--;
      }
      break;
    }
    buf[0] = c;
    if(either_copyout(user_dst, dst, &buf[0], 1) == -1)
      break;
    dst++;
    --n;
    if(c == '\n')
      break;
  }
  release(&cons.lock);

  return target - n;
}

int
consolewrite(int user_src, uint64 src, int n)
{
  int i;

  acquire(&cons.lock);
  for(i = 0; i < n; i++){
    char c;
    if(either_copyin(&c, user_src, src+i, 1) == -1)
      break;
    consputc(c);
  }
  release(&cons.lock);

  return n;
}

void
consoleintr(int c)
{
  int doprocdump = 0;
  
  acquire(&cons.lock);

  switch(c){
  case C('P'):  // Process list.
    // procdump() locks cons.lock indirectly; invoke later
    doprocdump = 1;
    break;
  case C('U'):  // Kill line.
    while(input.e != input.w &&
          input.buf[(input.e-1) % INPUT_BUF] != '\n'){
      input.e--;
      consputc(BACKSPACE);
    }
    break;
  case C('H'): case '\x7f':  // Backspace
    if(input.e != input.w){
      input.e--;
      consputc(BACKSPACE);
    }
    break;
  default:
    if(c != 0 && input.e-input.r < INPUT_BUF){
      c = (c == '\r') ? '\n' : c;
      input.buf[input.e++ % INPUT_BUF] = c;
      consputc(c);
      if(c == '\n' || c == C('D') || input.e == input.r+INPUT_BUF){
        input.w = input.e;
        wakeup(&input.r);
      }
    }
    break;
  }
  
  release(&cons.lock);

  if(doprocdump)
    procdump();
}

void
consoleinit(void)
{
  initlock(&cons.lock, "console");

  devsw[CONSOLE].write = consolewrite;
  devsw[CONSOLE].read = consoleread;
  cons.locking = 1;
}