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70 lines
1.6 KiB
70 lines
1.6 KiB
#include "memory.h"
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#include "../drivers/vga.h"
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// https://wiki.osdev.org/Page_Frame_Allocation
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// page = block
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// MAX_BLOCK_SIZE_IN_BITS/8 bytes
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// i.e. : bit i of byte n define status of block 8n+i
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// block = 8n+i
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// in 32-bit mode, we have access to 2^32 blocks
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// which is (2^32)*BLOCK_SIZE blocks
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// and with a blocksize of 1024, we git around 4.3 trillion blocks
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// which is more than enough
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#define CHECK_BITMAP(map, idx) ((map) & (1<<(idx)))
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#define BLOCK_TO_MEMP(idx) (pointer)(PM_MEM_START + (idx*BLOCK_SIZE))
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static int bitmap = 0;
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static uint last_block;
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void mod_bitmap(uint bit, uint bflag) {
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// create a bitmask that will be applied to the bitmap
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int bitmask = 1 << bit;
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// apply the bitmask, resulting in the bit:n bit will set
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// set to bflag
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bitmap = (((bitmap & ~bitmask)) | (bflag << bit));
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}
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pointer block_alloc(uint blockidx) {
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int block_bflag;
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block_bflag = CHECK_BITMAP(bitmap, blockidx);
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if( block_bflag == BM_FREE ) { // check if block is free
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println("Alloc!", DEFAULT_COLOR);
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mod_bitmap(blockidx, 1);
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last_block = blockidx;
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return BLOCK_TO_MEMP(blockidx);
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} else {
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println("ERROR! Attemped to allocate non-free block.", 0x0c);
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return 0;
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}
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}
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void block_free(uint blockidx) {
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println("Dealloc block...", DEFAULT_COLOR);
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mod_bitmap(blockidx, BM_FREE);
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last_block = blockidx;
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}
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void pm_alloc_range(uint start, uint end, bool force) {
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uint idx_start;
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uint idx_end;
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// calculate idx_start and idx_end
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// if not force, check if avaliable
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// allocate (if permitted)
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}
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/*
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pointer pm_malloc(uint block_count) {
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}
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*/
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