linux-low.c

这个是LINUX下的GDB调度工具的源码

      p_sig = malloc (sizeof (*p_sig));
      p_sig->prev = process->pending_signals;
      p_sig->signal = process->resume->sig;
      process->pending_signals = p_sig;
    }

  process->resume = NULL;
}

/* Set DUMMY if this process has an interesting status pending.  */
static int
resume_status_pending_p (struct inferior_list_entry *entry, void *flag_p)
{
  struct process_info *process = (struct process_info *) entry;

  /* Processes which will not be resumed are not interesting, because
     we might not wait for them next time through linux_wait.  */
  if (process->resume->leave_stopped)
    return 0;

  /* If this thread has a removed breakpoint, we won't have any
     events to report later, so check now.  check_removed_breakpoint
     may clear status_pending_p.  We avoid calling check_removed_breakpoint
     for any thread that we are not otherwise going to resume - this
     lets us preserve stopped status when two threads hit a breakpoint.
     GDB removes the breakpoint to single-step a particular thread
     past it, then re-inserts it and resumes all threads.  We want
     to report the second thread without resuming it in the interim.  */
  if (process->status_pending_p)
    check_removed_breakpoint (process);

  if (process->status_pending_p)
    * (int *) flag_p = 1;

  return 0;
}

static void
linux_resume (struct thread_resume *resume_info)
{
  int pending_flag;

  /* Yes, the use of a global here is rather ugly.  */
  resume_ptr = resume_info;

  for_each_inferior (&all_threads, linux_set_resume_request);

  /* If there is a thread which would otherwise be resumed, which
     has a pending status, then don't resume any threads - we can just
     report the pending status.  Make sure to queue any signals
     that would otherwise be sent.  */
  pending_flag = 0;
  find_inferior (&all_processes, resume_status_pending_p, &pending_flag);

  if (debug_threads)
    {
      if (pending_flag)
	fprintf (stderr, "Not resuming, pending status\n");
      else
	fprintf (stderr, "Resuming, no pending status\n");
    }

  if (pending_flag)
    for_each_inferior (&all_threads, linux_queue_one_thread);
  else
    {
      block_async_io ();
      enable_async_io ();
      for_each_inferior (&all_threads, linux_continue_one_thread);
    }
}

#ifdef HAVE_LINUX_USRREGS

int
register_addr (int regnum)
{
  int addr;

  if (regnum < 0 || regnum >= the_low_target.num_regs)
    error ("Invalid register number %d.", regnum);

  addr = the_low_target.regmap[regnum];

  return addr;
}

/* Fetch one register.  */
static void
fetch_register (int regno)
{
  CORE_ADDR regaddr;
  register int i;
  char *buf;

  if (regno >= the_low_target.num_regs)
    return;
  if ((*the_low_target.cannot_fetch_register) (regno))
    return;

  regaddr = register_addr (regno);
  if (regaddr == -1)
    return;
  buf = alloca (register_size (regno));
  for (i = 0; i < register_size (regno); i += sizeof (PTRACE_XFER_TYPE))
    {
      errno = 0;
      *(PTRACE_XFER_TYPE *) (buf + i) =
	ptrace (PTRACE_PEEKUSER, inferior_pid, (PTRACE_ARG3_TYPE) regaddr, 0);
      regaddr += sizeof (PTRACE_XFER_TYPE);
      if (errno != 0)
	{
	  /* Warning, not error, in case we are attached; sometimes the
	     kernel doesn't let us at the registers.  */
	  char *err = strerror (errno);
	  char *msg = alloca (strlen (err) + 128);
	  sprintf (msg, "reading register %d: %s", regno, err);
	  error (msg);
	  goto error_exit;
	}
    }
  supply_register (regno, buf);

error_exit:;
}

/* Fetch all registers, or just one, from the child process.  */
static void
usr_fetch_inferior_registers (int regno)
{
  if (regno == -1 || regno == 0)
    for (regno = 0; regno < the_low_target.num_regs; regno++)
      fetch_register (regno);
  else
    fetch_register (regno);
}

/* Store our register values back into the inferior.
   If REGNO is -1, do this for all registers.
   Otherwise, REGNO specifies which register (so we can save time).  */
static void
usr_store_inferior_registers (int regno)
{
  CORE_ADDR regaddr;
  int i;
  char *buf;

  if (regno >= 0)
    {
      if (regno >= the_low_target.num_regs)
	return;

      if ((*the_low_target.cannot_store_register) (regno) == 1)
	return;

      regaddr = register_addr (regno);
      if (regaddr == -1)
	return;
      errno = 0;
      buf = alloca (register_size (regno));
      collect_register (regno, buf);
      for (i = 0; i < register_size (regno); i += sizeof (PTRACE_XFER_TYPE))
	{
	  errno = 0;
	  ptrace (PTRACE_POKEUSER, inferior_pid, (PTRACE_ARG3_TYPE) regaddr,
		  *(PTRACE_XFER_TYPE *) (buf + i));
	  if (errno != 0)
	    {
	      if ((*the_low_target.cannot_store_register) (regno) == 0)
		{
		  char *err = strerror (errno);
		  char *msg = alloca (strlen (err) + 128);
		  sprintf (msg, "writing register %d: %s",
			   regno, err);
		  error (msg);
		  return;
		}
	    }
	  regaddr += sizeof (PTRACE_XFER_TYPE);
	}
    }
  else
    for (regno = 0; regno < the_low_target.num_regs; regno++)
      usr_store_inferior_registers (regno);
}
#endif /* HAVE_LINUX_USRREGS */



#ifdef HAVE_LINUX_REGSETS

static int
regsets_fetch_inferior_registers ()
{
  struct regset_info *regset;

  regset = target_regsets;

  while (regset->size >= 0)
    {
      void *buf;
      int res;

      if (regset->size == 0)
	{
	  regset ++;
	  continue;
	}

      buf = malloc (regset->size);
      res = ptrace (regset->get_request, inferior_pid, 0, buf);
      if (res < 0)
	{
	  if (errno == EIO)
	    {
	      /* If we get EIO on the first regset, do not try regsets again.
		 If we get EIO on a later regset, disable that regset.  */
	      if (regset == target_regsets)
		{
		  use_regsets_p = 0;
		  return -1;
		}
	      else
		{
		  regset->size = 0;
		  continue;
		}
	    }
	  else
	    {
	      char s[256];
	      sprintf (s, "ptrace(regsets_fetch_inferior_registers) PID=%d",
		       inferior_pid);
	      perror (s);
	    }
	}
      regset->store_function (buf);
      regset ++;
    }
  return 0;
}

static int
regsets_store_inferior_registers ()
{
  struct regset_info *regset;

  regset = target_regsets;

  while (regset->size >= 0)
    {
      void *buf;
      int res;

      if (regset->size == 0)
	{
	  regset ++;
	  continue;
	}

      buf = malloc (regset->size);
      regset->fill_function (buf);
      res = ptrace (regset->set_request, inferior_pid, 0, buf);
      if (res < 0)
	{
	  if (errno == EIO)
	    {
	      /* If we get EIO on the first regset, do not try regsets again.
		 If we get EIO on a later regset, disable that regset.  */
	      if (regset == target_regsets)
		{
		  use_regsets_p = 0;
		  return -1;
		}
	      else
		{
		  regset->size = 0;
		  continue;
		}
	    }
	  else
	    {
	      perror ("Warning: ptrace(regsets_store_inferior_registers)");
	    }
	}
      regset ++;
      free (buf);
    }
  return 0;
}

#endif /* HAVE_LINUX_REGSETS */


void
linux_fetch_registers (int regno)
{
#ifdef HAVE_LINUX_REGSETS
  if (use_regsets_p)
    {
      if (regsets_fetch_inferior_registers () == 0)
	return;
    }
#endif
#ifdef HAVE_LINUX_USRREGS
  usr_fetch_inferior_registers (regno);
#endif
}

void
linux_store_registers (int regno)
{
#ifdef HAVE_LINUX_REGSETS
  if (use_regsets_p)
    {
      if (regsets_store_inferior_registers () == 0)
	return;
    }
#endif
#ifdef HAVE_LINUX_USRREGS
  usr_store_inferior_registers (regno);
#endif
}


/* Copy LEN bytes from inferior's memory starting at MEMADDR
   to debugger memory starting at MYADDR.  */

static int
linux_read_memory (CORE_ADDR memaddr, char *myaddr, int len)
{
  register int i;
  /* Round starting address down to longword boundary.  */
  register CORE_ADDR addr = memaddr & -(CORE_ADDR) sizeof (PTRACE_XFER_TYPE);
  /* Round ending address up; get number of longwords that makes.  */
  register int count
    = (((memaddr + len) - addr) + sizeof (PTRACE_XFER_TYPE) - 1)
      / sizeof (PTRACE_XFER_TYPE);
  /* Allocate buffer of that many longwords.  */
  register PTRACE_XFER_TYPE *buffer
    = (PTRACE_XFER_TYPE *) alloca (count * sizeof (PTRACE_XFER_TYPE));

  /* Read all the longwords */
  for (i = 0; i < count; i++, addr += sizeof (PTRACE_XFER_TYPE))
    {
      errno = 0;
      buffer[i] = ptrace (PTRACE_PEEKTEXT, inferior_pid, (PTRACE_ARG3_TYPE) addr, 0);
      if (errno)
	return errno;
    }

  /* Copy appropriate bytes out of the buffer.  */
  memcpy (myaddr, (char *) buffer + (memaddr & (sizeof (PTRACE_XFER_TYPE) - 1)), len);

  return 0;
}

/* Copy LEN bytes of data from debugger memory at MYADDR
   to inferior's memory at MEMADDR.
   On failure (cannot write the inferior)
   returns the value of errno.  */

static int
linux_write_memory (CORE_ADDR memaddr, const char *myaddr, int len)
{
  register int i;
  /* Round starting address down to longword boundary.  */
  register CORE_ADDR addr = memaddr & -(CORE_ADDR) sizeof (PTRACE_XFER_TYPE);
  /* Round ending address up; get number of longwords that makes.  */
  register int count
  = (((memaddr + len) - addr) + sizeof (PTRACE_XFER_TYPE) - 1) / sizeof (PTRACE_XFER_TYPE);
  /* Allocate buffer of that many longwords.  */
  register PTRACE_XFER_TYPE *buffer = (PTRACE_XFER_TYPE *) alloca (count * sizeof (PTRACE_XFER_TYPE));
  extern int errno;

  if (debug_threads)
    {
      fprintf (stderr, "Writing %02x to %08lx\n", (unsigned)myaddr[0], (long)memaddr);
    }

  /* Fill start and end extra bytes of buffer with existing memory data.  */

  buffer[0] = ptrace (PTRACE_PEEKTEXT, inferior_pid,
		      (PTRACE_ARG3_TYPE) addr, 0);

  if (count > 1)
    {
      buffer[count - 1]
	= ptrace (PTRACE_PEEKTEXT, inferior_pid,
		  (PTRACE_ARG3_TYPE) (addr + (count - 1)
				      * sizeof (PTRACE_XFER_TYPE)),
		  0);
    }

  /* Copy data to be written over corresponding part of buffer */

  memcpy ((char *) buffer + (memaddr & (sizeof (PTRACE_XFER_TYPE) - 1)), myaddr, len);

  /* Write the entire buffer.  */

  for (i = 0; i < count; i++, addr += sizeof (PTRACE_XFER_TYPE))
    {
      errno = 0;
      ptrace (PTRACE_POKETEXT, inferior_pid, (PTRACE_ARG3_TYPE) addr, buffer[i]);
      if (errno)
	return errno;
    }

  return 0;
}

static void
linux_look_up_symbols (void)
{
#ifdef USE_THREAD_DB
  if (using_threads)
    return;

  using_threads = thread_db_init ();
#endif
}

static void
linux_send_signal (int signum)
{
  extern int signal_pid;

  if (cont_thread > 0)
    {
      struct process_info *process;

      process = get_thread_process (current_inferior);
      kill_lwp (process->lwpid, signum);
    }
  else
    kill_lwp (signal_pid, signum);
}

/* Copy LEN bytes from inferior's auxiliary vector starting at OFFSET
   to debugger memory starting at MYADDR.  */

static int
linux_read_auxv (CORE_ADDR offset, char *myaddr, unsigned int len)
{
  char filename[PATH_MAX];
  int fd, n;

  snprintf (filename, sizeof filename, "/proc/%d/auxv", inferior_pid);

  fd = open (filename, O_RDONLY);
  if (fd < 0)
    return -1;

  if (offset != (CORE_ADDR) 0
      && lseek (fd, (off_t) offset, SEEK_SET) != (off_t) offset)
    n = -1;
  else
    n = read (fd, myaddr, len);

  close (fd);

  return n;
}


static struct target_ops linux_target_ops = {
  linux_create_inferior,
  linux_attach,
  linux_kill,
  linux_detach,
  linux_thread_alive,
  linux_resume,
  linux_wait,
  linux_fetch_registers,
  linux_store_registers,
  linux_read_memory,
  linux_write_memory,
  linux_look_up_symbols,
  linux_send_signal,
  linux_read_auxv,
};

static void
linux_init_signals ()
{
  /* FIXME drow/2002-06-09: As above, we should check with LinuxThreads
     to find what the cancel signal actually is.  */
  signal (__SIGRTMIN+1, SIG_IGN);
}

void
initialize_low (void)
{
  using_threads = 0;
  set_target_ops (&linux_target_ops);
  set_breakpoint_data (the_low_target.breakpoint,
		       the_low_target.breakpoint_len);
  init_registers ();
  linux_init_signals ();
}