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#include <asm/system.h>
#include <kernel/memory.h>
#include <stdint.h>
#include <sys/types.h>
static char __attribute__((aligned (4096))) mapped_page[4096];
static char map[NPAGES / 8];
static pdir_t kpdir;
ptab_t ktab;
void *alloc_physical_page(void) {
int i, j;
for(i = 32; i < sizeof(map); i++) {
if(map[i] == -1)
continue;
for(j = 0; j < 8; j++) {
if(!((map[i] >> j) & 1))
break;
}
map[i] |= 1 << j;
return (void*) (((i << 3) + j) << 12);
}
return NULL;
}
int free_physical_page(void *page) {
char tmp;
uint32_t p = (uint32_t) page >> 12;
if(p > NPAGES)
return -1;
tmp = map[p >> 3];
map[p >> 3] &= ~(1 << (p & 7));
if((tmp & (1 << (p & 7))))
return 0;
return -1;
}
void *alloc_physical_pages(unsigned int n) {
void *p = NULL;
void *last = NULL;
void **page;
while(n--) {
p = alloc_physical_page();
if(p == NULL) {
page = &last;
while(*page) {
free_physical_page(*page);
page = *page;
}
return NULL;
}
map_page(p);
*((void**) mapped_page) = last;
last = p;
}
return p;
}
void *map_page(void *page) {
uint32_t p = (uint32_t) mapped_page;
/* enforce 4KB page alignment */
page = (void*) ((uint32_t) page & ~0xFFF);
ktab[(p >> 12) & 0x3FF] = (uint32_t) page | 0x003;
invlpg(mapped_page);
return mapped_page;
}
void paging_init(void) {
int i;
/* empty the page directory */
for(i = 0; i < PGENT; i++)
kpdir[i] = 0;
/* populate the kernel's page table */
for(i = 0; i < PGENT; i++) {
ktab[i] = 0;
if(i < 256)
ktab[i] = (i << 12) | 0x003;
}
/* populate the kernel's page directory */
kpdir[0] = ((pde_t) ktab) | 0x007;
__asm__ (
"mov %%eax, %%cr3\n"
"mov %%cr0, %%eax\n"
"or $0x80000000, %%eax\n"
"mov %%eax, %%cr0\n"
:: "a" (&kpdir)
);
}
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