GeneveOS Memory Management Functions

Memory management in MDOS is available via XOP 7. In the MDOS sources the relevant files are manage2s and manage2t.

General purpose XOPs

Return number of free pages in system

Opcode: 0

	Input	Output
R0	Opcode (0000)	Error code (always 0)
R1		Number of free pages
R2		Number of fast free pages
R3		Total number of pages in system

Claim pages into local map from free pages

Opcode: 1

	Input	Output
R0	Opcode (0001)	Error code (0, 1, 7, 8)
R1	Number of pages	Number of pages actually fetched to complete map as required
R2	Local page address	Number of fast pages fetched
R3	Speed flag (if not 0, only fast)

Return pages into free pool from local map

Opcode: 2

	Input	Output
R0	Opcode (0002)	Error code (0, 2)
R1	Number of pages
R2	Local page address

Error code 2 is returned when the local page address (R2) is 0; page 0 cannot be freed in this way.

Map local page at excution page

Opcode: 3

	Input	Output
R0	Opcode (0003)	Error code (-, 2, 3)
R1	Local page number
R2	Execution page number

Error code 2 is returned when the local page number or the execution page number is 0.

Error code 3 is returned when the execution page number is higher than 7 or (TODO)

Get address map

Opcode: 4

	Input	Output
R0	Opcode (0004)	Error code
R1	Pointer to buffer	Count of pages reported
R2	Buffer size

On return of the call, the memory locations pointed to by R1 contain a sequence of physical page numbers that have been allocated. R1 contains the length of this sequence.

Declare shared pages

Opcode: 5

	Input	Output
R0	Opcode (0005)	Error code
R1	Number of pages to declare as shared
R2	Local page address
R3	Type to be assigned to shared pages

Release shared pages (type)

Opcode: 6

	Input	Output
R0	Opcode (0006)	Error code
R1	Type

Also have to check their current execution map

Get shared pages

Opcode: 7

	Input	Output
R0	Opcode (0007)	Error code
R1	Type
R2	Local page number for start of shared area

Return size of shared page group

Opcode: 8

	Input	Output
R0	Opcode (0008)	Error code
R1	Type	Number of pages in shared group

Privileged XOPs (only available for operating system)

Release task

Opcode: 9

	Input	Output
R0	Opcode (0009)

Task header at >8000

Page get

Opcode: 10

	Input	Output
R0	Opcode (000A)	Error code
R1	Page number to get (if high byte not 0, get first available)	Pointer to node
R2	Speed flag (if not 0, only fast)	Page number from node

Add page to free pages in system

Opcode: 11

	Input	Output
R0	Opcode (000B)	Error code (if no free nodes available)
R1	Page number	Pointer to node

Add a node to the list of free nodes

Opcode: 12

	Input	Output
R0	Opcode (000C)	Error code (always 0000)
R1	Pointer to node

Link a node to the specified node

Opcode: 13

	Input	Output
R0	Opcode (000D)	Error code (always 0000)
R1	Pointer to node
R2	Pointer to node to link to

Get address map (system)

Opcode: 14

	Input	Output
R0	Opcode (000E)	Count of valid pages

Error codes

Code	Meaning
00	No error
01	not enough free pages
02	can't remap execution page zero
03	no page at LOCAL address
04	user area not large enough for list
05	shared type already defined
06	shared type doesn't exist
07	can't overlay shared and private memory
08	out of table space