* Resource Allocation Maps.
* Associated routines manage sub-allocation of an address space using
* an array of segment descriptors. The first element of this array
* is a map structure, describing the arrays extent and the name
* of the controlled object. Each additional structure represents
* a free segment of the address space.
* A call to rminit initializes a resource map and may also be used
* to free some address space for the map. Subsequent calls to rmalloc
* and rmfree allocate and free space in the resource map. If the resource
* map becomes too fragmented to be described in the available space,
* then some of the resource is discarded. This may lead to critical
* shortages, but is better than not checking (as the previous versions
* of these routines did) or giving up and calling panic(). The routines
* could use linked lists and call a memory allocator when they run
* out of space, but that would not solve the out of space problem when
* called at interrupt time.
* N.B.: The address 0 in the resource address space is not available
* as it is used internally by the resource map routines.
struct mapent
*m_limit
; /* address of last slot in map */
char *m_name
; /* name of resource */
/* we use m_name when the map overflows, in warning messages */
int m_size
; /* size of this segment of the map */
int m_addr
; /* resource-space addr of start of segment */