## memory_object_data_request

Server Interface - Request that memory manager page-in specified data.

### SYNOPSIS

    kern_return_t   memory_object_data_request
                    (memory_object_t                  memory_object,
                     memory_object_control_t         memory_control,
                     vm_offset_t                             offset,
                     vm_size_t                               length,
                     vm_prot_t                       desired_access);

    kern_return_t   seqnos_memory_object_data_request
                    (memory_object_t                  memory_object,
                     mach_port_seqno_t                        seqno,
                     memory_object_control_t         memory_control,
                     vm_offset_t                             offset,
                     vm_size_t                               length,
                     vm_prot_t                       desired_access);

### PARAMETERS

memory_object
  [in abstract-memory-object (receive) right] The abstract memory object port that represents the memory object data.

seqno
  [in scalar] The sequence number of this message relative to the abstract memory object port.

memory_control
  [in memory-cache-control send right] The memory cache control port to be used for a response by the memory manager. If the memory object has been supplied to more than one kernel, this parameter identifies the kernel that is making the call.

offset
  [in scalar] The offset within the memory object.

length
  [in scalar] The number of bytes requested, starting at offset. The number converts to an integral number of virtual pages.

desired_access
  [in scalar] The memory access modes to be allowed for the cached data. Possible values are obtained by or'ing together the following values:

  VM_PROT_READ
    Allows read access.

  VM_PROT_WRITE
    Allows write access.

  VM_PROT_EXECUTE
    Allows execute access.

### DESCRIPTION

A memory_object_data_request function is called as the result of a kernel message requesting data from the specified memory object, for at least the access specified.

The kernel issues this call after a cache miss (that is, a page fault for which the kernel does not have the data). The kernel requests only amounts of data that are multiples of the page size included in the memory_object_init or memory_object_create call.

The memory manager is expected to use memory_object_data_supply to return at least the specified data, with as much access as it can allow. If the memory manager cannot provide the data (for example, because of a hardware error), it can use the memory_object_data_error call. The memory manager can also use memory_object_data_unavailable to tell the kernel to supply zero-filled memory for the region.

### RETURN VALUES

Only generic errors apply.

### RELATED INFORMATION

Functions: memory_object_data_error, memory_object_data_supply, memory_object_data_unavailable, memory_object_server, seqnos_memory_object_server.