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#include <kernel/memory.h>
#include <stdint.h>
#include <sys/types.h>
static char __attribute__((aligned (4096))) mapped_page[4096];
static pdir_t kpdir;
ptab_t ktab;
static ptab_t flow;
static ptab_t fupp;
void *alloc_physical_page(void) {
int i;
void *ret;
for(i = 0; i < PGENT; i++) {
if(flow[i] & 1) {
ret = (void*) (flow[i] & ~1);
flow[i] = 0;
return ret;
}
if(fupp[i] & 1) {
ret = (void*) (fupp[i] & ~1);
fupp[i] = 0;
return ret;
}
}
return NULL;
}
int free_physical_page(void *page) {
int i;
page = (void*) ((uint32_t) page & ~0xFFF);
for(int i = 0; i < PGENT; i++) {
if(!(flow[i] & 1)) {
flow[i] = (uint32_t) page | 1;
return 0;
}
if(!(fupp[i] & 1)) {
fupp[i] = (uint32_t) page | 1;
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;
/*
* invalidate any cached entries for
* the mapped page window.
* TODO: skip this on i386
*/
__asm__ ("invlpg %0" :: "m" (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 free page tables */
for(i = 0; i < PGENT; i++) {
/* populate the lower table */
flow[i] = (i << 12);
/* only pages >1MB can be allocated */
if(i >= 0x100)
flow[i] |= 0x001;
/* populate the upper table */
fupp[i] = ((i << 12) + 0x400000) | 0x001;
}
/* 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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