shm.cc

cygwin, 著名的在win32下模拟unix操作系统的东东

/* shm.cc: Single unix specification IPC interface for Cygwin.

   Copyright 2002 Red Hat, Inc.

   Written by Conrad Scott <[e-mail]>.
   Based on code by Robert Collins <[e-mail]>.

This file is part of Cygwin.

This software is a copyrighted work licensed under the terms of the
Cygwin license.  Please consult the file "CYGWIN_LICENSE" for
details. */

#include "winsup.h"

#include <sys/types.h>

#include <assert.h>
#include <errno.h>
#include <stdio.h>
#include <unistd.h>

#include "cygerrno.h"
#include "safe_memory.h"
#include "sigproc.h"

#include "cygserver_ipc.h"
#include "cygserver_shm.h"

/*---------------------------------------------------------------------------*
 * class client_shmmgr
 *
 * A singleton class.
 *---------------------------------------------------------------------------*/

#define shmmgr (client_shmmgr::instance ())

class client_shmmgr
{
private:
  class segment_t
  {
  public:
    const int shmid;
    const void *const shmaddr;
    const int shmflg;
    HANDLE hFileMap;		// Updated by fixup_shms_after_fork ().

    segment_t *next;

    segment_t (const int shmid, const void *const shmaddr, const int shmflg,
	       const HANDLE hFileMap)
      : shmid (shmid), shmaddr (shmaddr), shmflg (shmflg), hFileMap (hFileMap),
	next (NULL)
    {}
  };

public:
  static client_shmmgr & instance ();

  void *shmat (int shmid, const void *, int shmflg);
  int shmctl (int shmid, int cmd, struct shmid_ds *);
  int shmdt (const void *);
  int shmget (key_t, size_t, int shmflg);

  int fixup_shms_after_fork ();

private:
  static NO_COPY client_shmmgr *_instance;

  CRITICAL_SECTION _segments_lock;
  static segment_t *_segments_head; // List of attached segs by shmaddr.

  static long _shmat_cnt;	// No. of attached segs; for info. only.

  client_shmmgr ();
  ~client_shmmgr ();

  // Undefined (as this class is a singleton):
  client_shmmgr (const client_shmmgr &);
  client_shmmgr & operator= (const client_shmmgr &);

  segment_t *find (const void *, segment_t **previous = NULL);

  void *attach (int shmid, const void *, int shmflg, HANDLE & hFileMap);

  segment_t *new_segment (int shmid, const void *, int shmflg, HANDLE);
};

/* static */ NO_COPY client_shmmgr *client_shmmgr::_instance;

/* The following two variables must be inherited by child processes
 * since they are used by fixup_shms_after_fork () to re-attach to the
 * parent's shm segments.
 */
/* static */ client_shmmgr::segment_t *client_shmmgr::_segments_head;
/* static */ long client_shmmgr::_shmat_cnt;

/*---------------------------------------------------------------------------*
 * client_shmmgr::instance ()
 *---------------------------------------------------------------------------*/

client_shmmgr &
client_shmmgr::instance ()
{
  if (!_instance)
    _instance = safe_new0 (client_shmmgr);

  assert (_instance);

  return *_instance;
}

/*---------------------------------------------------------------------------*
 * client_shmmgr::shmat ()
 *---------------------------------------------------------------------------*/

void *
client_shmmgr::shmat (const int shmid,
		      const void *const shmaddr,
		      const int shmflg)
{
  syscall_printf ("shmat (shmid = %d, shmaddr = %p, shmflg = 0%o)",
		  shmid, shmaddr, shmflg);

  EnterCriticalSection (&_segments_lock);

  HANDLE hFileMap = NULL;

  void *const ptr = attach (shmid, shmaddr, shmflg, hFileMap);

  if (ptr)
    new_segment (shmid, ptr, shmflg, hFileMap);

  LeaveCriticalSection (&_segments_lock);

  if (ptr)
    syscall_printf ("%p = shmat (shmid = %d, shmaddr = %p, shmflg = 0%o)",
		    ptr, shmid, shmaddr, shmflg);
  // else
    // See the syscall_printf in client_shmmgr::attach ().

  return (ptr ? ptr : (void *) -1);
}

/*---------------------------------------------------------------------------*
 * client_shmmgr::shmctl ()
 *---------------------------------------------------------------------------*/

int
client_shmmgr::shmctl (const int shmid,
		       const int cmd,
		       struct shmid_ds *const buf)
{
  syscall_printf ("shmctl (shmid = %d, cmd = 0x%x, buf = %p)",
		  shmid, cmd, buf);

  // Check parameters and set up in parameters as required.

  const struct shmid_ds *in_buf = NULL;

  switch (cmd)
    {
    case IPC_SET:
      if (__check_invalid_read_ptr_errno (buf, sizeof (struct shmid_ds)))
	{
	  syscall_printf (("-1 [EFAULT] = "
			   "shmctl (shmid = %d, cmd = 0x%x, buf = %p)"),
			  shmid, cmd, buf);
	  set_errno (EFAULT);
	  return -1;
	}
      in_buf = buf;
      break;

    case IPC_STAT:
    case SHM_STAT:
      if (__check_null_invalid_struct_errno (buf, sizeof (struct shmid_ds)))
	{
	  syscall_printf (("-1 [EFAULT] = "
			   "shmctl (shmid = %d, cmd = 0x%x, buf = %p)"),
			  shmid, cmd, buf);
	  set_errno (EFAULT);
	  return -1;
	}
      break;

    case IPC_INFO:
      if (__check_null_invalid_struct_errno (buf, sizeof (struct shminfo)))
	{
	  syscall_printf (("-1 [EFAULT] = "
			   "shmctl (shmid = %d, cmd = 0x%x, buf = %p)"),
			  shmid, cmd, buf);
	  set_errno (EFAULT);
	  return -1;
	}
      break;

    case SHM_INFO:
      if (__check_null_invalid_struct_errno (buf, sizeof (struct shm_info)))
	{
	  syscall_printf (("-1 [EFAULT] = "
			   "shmctl (shmid = %d, cmd = 0x%x, buf = %p)"),
			  shmid, cmd, buf);
	  set_errno (EFAULT);
	  return -1;
	}
      break;
    }

  // Create and issue the command.

  client_request_shm request (shmid, cmd, in_buf);

  if (request.make_request () == -1 || request.error_code ())
    {
      syscall_printf (("-1 [%d] = "
		       "shmctl (shmid = %d, cmd = 0x%x, buf = %p)"),
		      request.error_code (), shmid, cmd, buf);
      set_errno (request.error_code ());
      return -1;
    }

  // Some commands require special processing for their out parameters.

  int result = 0;

  switch (cmd)
    {
    case IPC_STAT:
      *buf = request.ds ();
      break;

    case IPC_INFO:
      *(struct shminfo *) buf = request.shminfo ();
      break;

    case SHM_STAT:		// ipcs(8) i'face.
      result = request.shmid ();
      *buf = request.ds ();
      break;

    case SHM_INFO:		// ipcs(8) i'face.
      result = request.shmid ();
      *(struct shm_info *) buf = request.shm_info ();
      break;
    }

  syscall_printf ("%d = shmctl (shmid = %d, cmd = 0x%x, buf = %p)",
		  result, shmid, cmd, buf);

  return result;
}

/*---------------------------------------------------------------------------*
 * client_shmmgr::shmdt ()
 *
 * According to Posix, the only error condition for this system call
 * is EINVAL if shmaddr is not the address of the start of an attached
 * shared memory segment.  Given that, all other errors just generate
 * tracing noise.
 *---------------------------------------------------------------------------*/

int
client_shmmgr::shmdt (const void *const shmaddr)
{
  syscall_printf ("shmdt (shmaddr = %p)", shmaddr);

  EnterCriticalSection (&_segments_lock);

  segment_t *previous = NULL;

  segment_t *const segptr = find (shmaddr, &previous);

  if (!segptr)
    {
      LeaveCriticalSection (&_segments_lock);
      syscall_printf ("-1 [EINVAL] = shmdt (shmaddr = %p)", shmaddr);
      set_errno (EINVAL);
      return -1;
    }

  assert (previous ? previous->next == segptr : _segments_head == segptr);

  if (previous)
    previous->next = segptr->next;
  else
    _segments_head = segptr->next;

  LeaveCriticalSection (&_segments_lock);

  const long cnt = InterlockedDecrement (&_shmat_cnt);
  assert (cnt >= 0);

  if (!UnmapViewOfFile ((void *) shmaddr))
    syscall_printf (("failed to unmap view "
		     "[shmid = %d, handle = %p, shmaddr = %p]:"
		     "%E"),
		    segptr->shmid, segptr->hFileMap, shmaddr);

  assert (segptr->hFileMap);

  if (!CloseHandle (segptr->hFileMap))
    syscall_printf (("failed to close file map handle "
		     "[shmid = %d, handle = %p]: %E"),
		    segptr->shmid, segptr->hFileMap);

  client_request_shm request (segptr->shmid);

  if (request.make_request () == -1 || request.error_code ())
    syscall_printf ("shmdt request failed [shmid = %d, handle = %p]: %s",
		    segptr->shmid, segptr->hFileMap,
		    strerror (request.error_code ()));

  safe_delete (segptr);

  syscall_printf ("0 = shmdt (shmaddr = %p)", shmaddr);

  return 0;
}

/*---------------------------------------------------------------------------*
 * client_shmmgr::shmget ()
 *---------------------------------------------------------------------------*/

int
client_shmmgr::shmget (const key_t key, const size_t size, const int shmflg)
{
  syscall_printf ("shmget (key = 0x%016X, size = %u, shmflg = 0%o)",
		  key, size, shmflg);

  client_request_shm request (key, size, shmflg);

  if (request.make_request () == -1 || request.error_code ())
    {
      syscall_printf (("-1 [%d] = "
		       "shmget (key = 0x%016X, size = %u, shmflg = 0%o)"),
		      request.error_code (),
		      key, size, shmflg);
      set_errno (request.error_code ());
      return -1;
    }

  syscall_printf (("%d = shmget (key = 0x%016X, size = %u, shmflg = 0%o)"),
		  request.shmid (),
		  key, size, shmflg);