141 lines
3.2 KiB
C
141 lines
3.2 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 "cpu/halt.h"
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#include "vga_err.h"
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#include <grub/multiboot2.h>
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#include <stdint.h>
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#include <stdlib.h>
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#define BMAP_LEN (NUM_FRAMES/8) //!< The size of the physical memory manager's bitmap
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static char bmap[BMAP_LEN]; //!< Bitmap of allocated/non-present page frames
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/**
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* Get a bit in the 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(int index) {
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int byte=index/8;
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int bit=index%8;
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char entry=bmap[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(int index) {
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int byte=index/8;
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int bit=index%8;
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bmap[byte]=bmap[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(int index) {
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int byte=index/8;
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int bit=index%8;
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bmap[byte]=bmap[byte]&(~(1<<bit));
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}
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void pmem_init(struct multiboot_boot_header_tag* tags) {
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for (int i=0;i<BMAP_LEN;i++) {
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bmap[i]=0xFF;
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}
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char found_mmap=0;
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struct multiboot_tag* tag=(struct multiboot_tag*)(tags+1);
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while (tag->type!=0) {
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switch (tag->type) {
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case MULTIBOOT_TAG_TYPE_MMAP: {
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found_mmap=1;
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struct multiboot_mmap_entry* orig_ptr=(struct multiboot_mmap_entry*)(((char*)tag)+16);
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for (struct multiboot_mmap_entry* ptr=orig_ptr;(char*)ptr<((char*)orig_ptr)+tag->size;ptr++) {
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if (ptr->type!=MULTIBOOT_MEMORY_AVAILABLE) continue;
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size_t start=ptr->addr;
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if (start<0x100000) continue;
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size_t end=start+ptr->len-1;
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if (start&(FRAME_SZ-1)) {
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start+=FRAME_SZ;
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}
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start=start>>FRAME_NO_OFFSET;
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end=end>>FRAME_NO_OFFSET;
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for (size_t i=start;i<end;i++) {
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clear_bmap_bit(i);
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}
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}
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break;
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}
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}
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tag=(struct multiboot_tag*)((char*)tag+((tag->size+7)&0xFFFFFFF8));
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}
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if (!found_mmap) {
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vga_write_string("[PANIC] No memory map supplied by bootloader!");
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halt();
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}
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for (size_t i=0;i<NUM_KERN_FRAMES;i++) {
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set_bmap_bit(i);
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}
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}
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void* pmem_alloc(int num_pages) {
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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<131072;i++) {
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char got_0=0;
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remaining_blks=num_pages;
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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 (int i=0;i<num_pages;i++) {
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set_bmap_bit(bmap_index+i);
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}
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void* addr=(void*)(bmap_index<<12);
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return addr;
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}
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void pmem_free(void* start,int num_pages) {
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int start_page=(size_t)start>>FRAME_NO_OFFSET;
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for (int i=start_page;i<num_pages;i++) {
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set_bmap_bit(i);
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}
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}
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