SQLite

** The safest way to deal with the problem is to always use this wrapper
** which always has the same well-defined interface.
*/
static int posixOpen(const char *zFile, int flags, int mode){
  return open(zFile, flags, mode);
}














/* Forward reference */
static int openDirectory(const char*, int*);
static int unixGetpagesize(void);

/*
** Many system calls are accessed through pointer-to-functions so that
** they may be overridden at runtime to facilitate fault injection during

  { "pwrite64",     (sqlite3_syscall_ptr)pwrite64,   0  },
#else
  { "pwrite64",     (sqlite3_syscall_ptr)0,          0  },
#endif
#define osPwrite64  ((ssize_t(*)(int,const void*,size_t,off_t))\
                    aSyscall[13].pCurrent)

  { "fchmod",       (sqlite3_syscall_ptr)fchmod,          0  },
#define osFchmod    ((int(*)(int,mode_t))aSyscall[14].pCurrent)

#if defined(HAVE_POSIX_FALLOCATE) && HAVE_POSIX_FALLOCATE
  { "fallocate",    (sqlite3_syscall_ptr)posix_fallocate,  0 },
#else
  { "fallocate",    (sqlite3_syscall_ptr)0,                0 },
#endif

  { "mkdir",        (sqlite3_syscall_ptr)mkdir,           0 },
#define osMkdir     ((int(*)(const char*,mode_t))aSyscall[18].pCurrent)

  { "rmdir",        (sqlite3_syscall_ptr)rmdir,           0 },
#define osRmdir     ((int(*)(const char*))aSyscall[19].pCurrent)

  { "fchown",       (sqlite3_syscall_ptr)fchown,          0 },
#define osFchown    ((int(*)(int,uid_t,gid_t))aSyscall[20].pCurrent)

  { "geteuid",      (sqlite3_syscall_ptr)geteuid,         0 },
#define osGeteuid   ((uid_t(*)(void))aSyscall[21].pCurrent)

#if !defined(SQLITE_OMIT_WAL) || SQLITE_MAX_MMAP_SIZE>0
  { "mmap",       (sqlite3_syscall_ptr)mmap,     0 },
#define osMmap ((void*(*)(void*,size_t,int,int,int,off_t))aSyscall[22].pCurrent)

  { "munmap",       (sqlite3_syscall_ptr)munmap,          0 },
#define osMunmap ((void*(*)(void*,size_t))aSyscall[23].pCurrent)

#if HAVE_MREMAP
  { "mremap",       (sqlite3_syscall_ptr)mremap,          0 },
#else
  { "mremap",       (sqlite3_syscall_ptr)0,               0 },
#endif
#define osMremap ((void*(*)(void*,size_t,size_t,int,...))aSyscall[24].pCurrent)

  { "getpagesize",  (sqlite3_syscall_ptr)unixGetpagesize, 0 },
#define osGetpagesize ((int(*)(void))aSyscall[25].pCurrent)

  { "readlink",     (sqlite3_syscall_ptr)readlink,        0 },
#define osReadlink ((ssize_t(*)(const char*,char*,size_t))aSyscall[26].pCurrent)

#endif

}; /* End of the overrideable system calls */


/*
** On some systems, calls to fchown() will trigger a message in a security
** log if they come from non-root processes.  So avoid calling fchown() if
** we are not running as root.
*/
static int robustFchown(int fd, uid_t uid, gid_t gid){
#if OS_VXWORKS
  return 0;
#else
  return osGeteuid() ? 0 : osFchown(fd,uid,gid);
#endif
}

/*
** This is the xSetSystemCall() method of sqlite3_vfs for all of the
** "unix" VFSes.  Return SQLITE_OK opon successfully updating the
** system call pointer, or SQLITE_NOTFOUND if there is no configurable
** system call named zName.
*/
static int unixSetSystemCall(

        goto shm_open_err;
      }

      /* If this process is running as root, make sure that the SHM file
      ** is owned by the same user that owns the original database.  Otherwise,
      ** the original owner will not be able to connect.
      */
      robustFchown(pShmNode->h, sStat.st_uid, sStat.st_gid);
  
      /* Check to see if another process is holding the dead-man switch.
      ** If not, truncate the file to zero length. 
      */
      rc = SQLITE_OK;
      if( unixShmSystemLock(pDbFd, F_WRLCK, UNIX_SHM_DMS, 1)==SQLITE_OK ){
        if( robust_ftruncate(pShmNode->h, 0) ){

    }

    /* If this process is running as root and if creating a new rollback
    ** journal or WAL file, set the ownership of the journal or WAL to be
    ** the same as the original database.
    */
    if( flags & (SQLITE_OPEN_WAL|SQLITE_OPEN_MAIN_JOURNAL) ){
      robustFchown(fd, uid, gid);
    }
  }
  assert( fd>=0 );
  if( pOutFlags ){
    *pOutFlags = flags;
  }

    UNIXVFS("unix-proxy",    proxyIoFinder ),
#endif
  };
  unsigned int i;          /* Loop counter */

  /* Double-check that the aSyscall[] array has been constructed
  ** correctly.  See ticket [bb3a86e890c8e96ab] */
  assert( ArraySize(aSyscall)==27 );

  /* Register all VFSes defined in the aVfs[] array */
  for(i=0; i<(sizeof(aVfs)/sizeof(sqlite3_vfs)); i++){
    sqlite3_vfs_register(&aVfs[i], i==0);
  }
  return SQLITE_OK; 
}

#-------------------------------------------------------------------------
# Tests for the xNextSystemCall method.
#
foreach s {
    open close access getcwd stat fstat ftruncate
    fcntl read pread write pwrite fchmod fallocate
    pread64 pwrite64 unlink openDirectory mkdir rmdir 
    statvfs fchown geteuid umask mmap munmap mremap
    getpagesize readlink
} {
  if {[test_syscall exists $s]} {lappend syscall_list $s}
}
do_test 3.1 { lsort [test_syscall list] } [lsort $syscall_list]

#-------------------------------------------------------------------------