os/kernel/pmem.c
2020-07-23 11:50:23 -05:00

124 lines
2.8 KiB
C

#include "cpu/arch_consts.h"
#include "cpu/halt.h"
#include "vga_err.h"
#include <grub/multiboot2.h>
#include <klog.h>
#include <stdint.h>
#include <stdlib.h>
#define BMAP_LEN (NUM_FRAMES/8)
static char bmap[BMAP_LEN];
static char get_bmap_bit(int index) {
int byte=index/8;
int bit=index%8;
char entry=bmap[byte];
return (entry&(1<<bit))>0;
}
static void set_bmap_bit(int index) {
int byte=index/8;
int bit=index%8;
bmap[byte]=bmap[byte]|(1<<bit);
}
static void clear_bmap_bit(int index) {
int byte=index/8;
int bit=index%8;
bmap[byte]=bmap[byte]&(~(1<<bit));
}
void pmem_init(struct multiboot_boot_header_tag* tags) {
for (int i=0;i<BMAP_LEN;i++) {
bmap[i]=0xFF;
}
char found_mmap=0;
struct multiboot_tag* tag=(struct multiboot_tag*)(tags+1);
while (tag->type!=0) {
switch (tag->type) {
case MULTIBOOT_TAG_TYPE_MMAP: {
found_mmap=1;
struct multiboot_mmap_entry* orig_ptr=(struct multiboot_mmap_entry*)(((char*)tag)+16);
for (struct multiboot_mmap_entry* ptr=orig_ptr;(char*)ptr<((char*)orig_ptr)+tag->size;ptr++) {
if (ptr->type!=MULTIBOOT_MEMORY_AVAILABLE) continue;
size_t start=ptr->addr;
if (start<0x100000) continue;
size_t end=start+ptr->len-1;
if (start&(FRAME_SZ-1)) {
start+=FRAME_SZ;
}
start=start>>FRAME_NO_OFFSET;
end=end>>FRAME_NO_OFFSET;
for (size_t i=start;i<end;i++) {
clear_bmap_bit(i);
}
}
break;
}
}
tag=(struct multiboot_tag*)((char*)tag+((tag->size+7)&0xFFFFFFF8));
}
if (!found_mmap) {
vga_write_string("[PANIC] No memory map supplied by bootloader!");
halt();
}
for (size_t i=0;i<NUM_KERN_FRAMES;i++) {
set_bmap_bit(i);
}
}
void* pmem_alloc(int num_pages) {
size_t bmap_index;
size_t remaining_blks;
for(size_t i=0;i<131072;i++) {
char got_0=0;
remaining_blks=num_pages;
size_t old_j;
for (size_t j=i*8;;j++) {
char bit=get_bmap_bit(j);
if (got_0) {
if (bit) {
if (remaining_blks==0) {
bmap_index=old_j;
break;
} else {
i+=j/8;
i--;
break;
}
} else {
remaining_blks--;
}
} else {
if (!bit) {
got_0=1;
old_j=j;
remaining_blks--;
}
}
if (remaining_blks==0) {
bmap_index=old_j;
break;
}
}
if (remaining_blks==0) {
break;
}
}
if (remaining_blks!=0) {
return NULL;
}
for (int i=0;i<num_pages;i++) {
set_bmap_bit(bmap_index+i);
}
void* addr=(void*)(bmap_index<<12);
return addr;
}
void pmem_free(int start_page,int num_pages) {
for (int i=start_page;i<num_pages;i++) {
set_bmap_bit(i);
}
}