109 lines
2.3 KiB
C
109 lines
2.3 KiB
C
/**
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* \file
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*/
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#include "cpu/arch_consts.h"
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#include <math.h>
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#include <stdlib.h>
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#include <string.h>
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#define KMALLOC_BMAP_SZ (((KMALLOC_SZ*1024)/4)/8) //!< The size of the kmalloc bitmap
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static char bitmap[KMALLOC_BMAP_SZ]; //!< Bitmap of used areas of the heap
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static void* data=(void*)KMALLOC_START; //!< Start of the kmalloc heap
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/**
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* Get a bit in the heap bitmap
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* \param index The bit to get
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* \return the bit
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*/
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static char get_bmap_bit(size_t index) {
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size_t byte=index/8;
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size_t bit=index%8;
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char entry=bitmap[byte];
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return (entry&(1<<bit))>0;
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}
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/**
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* Set a bit in the heap bitmap
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* \param index The bit to set
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*/
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static void set_bmap_bit(size_t index) {
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size_t byte=index/8;
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size_t bit=index%8;
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bitmap[byte]=bitmap[byte]|(1<<bit);
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}
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/**
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* Clear a bit in the heap bitmap
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* \param index The bit to clear
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*/
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static void clear_bmap_bit(size_t index) {
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size_t byte=index/8;
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size_t bit=index%8;
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bitmap[byte]=bitmap[byte]&(~(1<<bit));
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}
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void* kmalloc(size_t size) {
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size_t num_4b_grps=(size_t)ceilf((float)size/4);
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num_4b_grps+=2;
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size_t bmap_index;
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size_t remaining_blks;
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for(size_t i=0;i<KMALLOC_BMAP_SZ;i++) {
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char got_0=0;
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remaining_blks=num_4b_grps;
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size_t old_j;
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for (size_t j=i*8;;j++) {
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char bit=get_bmap_bit(j);
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if (got_0) {
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if (bit) {
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if (remaining_blks==0) {
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bmap_index=old_j;
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break;
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} else {
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i+=j/8;
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i--;
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break;
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}
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} else {
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remaining_blks--;
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}
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} else {
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if (!bit) {
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got_0=1;
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old_j=j;
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remaining_blks--;
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}
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}
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if (remaining_blks==0) {
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bmap_index=old_j;
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break;
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}
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}
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if (remaining_blks==0) {
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break;
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}
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}
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if (remaining_blks!=0) {
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return NULL;
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}
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for (size_t i=0;i<num_4b_grps;i++) {
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set_bmap_bit(bmap_index+i);
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}
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size_t data_offset=(bmap_index*8)+8;
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size_t* info=(void*)(((char*)data)+data_offset-8);
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info[0]=num_4b_grps;
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info[1]=bmap_index;
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return (void*)(((char*)data)+data_offset);
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}
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void kfree(void* mem) {
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size_t* info=(size_t*)((size_t)mem-8);
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size_t num_4b_grps=info[0];
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size_t bmap_index=info[1];
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for (size_t i=0;i<num_4b_grps;i++) {
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clear_bmap_bit(bmap_index+i);
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}
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}
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