---
title: "page_frame.h"
summary: "physical memory management"
---

# `PFRAME_SIZE` - macro
The size of one page (4KB).

# `page_frame_manager_T` - struct

| Name              | Type     | Description                                                                        |
|-------------------|----------|------------------------------------------------------------------------------------|
| free_memory       | uint64_t | The amount of free/usable memory in bytes                                          |
| reserved_memory   | uint64_t | The amount of reserved memory in bytes                                             |
| used_memory       | uint64_t | The amount of memory used by noxos in bytes                                        |
| page_bitmap_index | uint64_t | The index to the first free page                                                   |
| page_bitmap       | bitmap_T | A huge bitmap, that stores, which pages are claimable and which are already in use |
| blocked           | bool     | Thread safety guard                                                                |


#### `pframe_manager_init()` - function (void)
Initializes the page frame manager, needs to be called once at kernel init.

#### `pframe_reserve(address)` - function (void) [Thread Safe]
Blocks a page, so it can't be requested or anything else.
If the page is already blocked by anything else, e.g. by a request, it won't be reserved.

#### `pframe_reserve_multi(address, n)` - function (void) [Thread Safe]
Reserves the page at the given address, plus *n* pages after that page.

#### `pframe_unreserve(address)` - function (void) [Thread Safe]
Unreserves a reserved page and makes it accessible again.

#### `pframe_unreserve_multi(address, n)` - function (void) [Thread Safe]
Unreserves the page at the given address, plus *n* pages after that page.

#### `pframe_request()` - function (void*) [Thread Safe]
Returns the physical address of a page.
This is kind of the low level version of `memory_allocate`.

#### `pframe_free(address)` - function (void) [Thread Safe]
Needs a valid page address produced by [pframe_request](https://nerdcult.net/projects/noxos/docs/codebase/mm/page_frame.h/#pframe_request---function-void-thread-safe) as argument.
Invalidates the address and frees it, so it can be requested again.
This is kind of the low level version of `memory_free`.

#### `pframe_free_multi(address, n)` - function (void) [Thread Safe]
Frees the page at the given address, plus *n* pages after that page.