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.
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 |
Opcode: 6
| Input | Output | |
|---|---|---|
| R0 | Opcode (0006) | Error code |
| R1 | Type |
Also have to check their current execution map
Opcode: 7
| Input | Output | |
|---|---|---|
| R0 | Opcode (0007) | Error code |
| R1 | Type | |
| R2 | Local page number for start of shared area |
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 |