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#include <paging.h>
#include <frame.h>
typedef union page {
struct {
uint32_t present : 1;
uint32_t rw : 1;
uint32_t user : 1;
uint32_t write_through : 1;
uint32_t disable_cache : 1;
uint32_t accessed : 1;
uint32_t dirty : 1; // only PTE
uint32_t size_4m : 1; // only PDE
uint32_t global : 1; // only PTE
uint32_t rsvd : 3;
uint32_t frame : 20;
};
uint32_t as_int32;
} page_t;
typedef struct page_table {
page_t page[1024];
} pagetable_t;
struct page_directory {
pagetable_t *pt[1024]; // virtual addresses of each page table
pagetable_t *dir; // virtual address of page directory
size_t phys_addr; // physical address of page directory
};
// access kernel page directory page defined in loader.s
// (this is a correct higher-half address)
extern pagetable_t kernel_pagedir;
static pagetable_t __attribute__((aligned(PAGE_SIZE))) kernel_pt768;
static pagedir_t kernel_pd;
static pagedir_t *current_pd;
void paging_setup(void* kernel_data_end) {
size_t n_kernel_pages =
PAGE_ALIGN_UP((size_t)kernel_data_end - K_HIGHHALF_ADDR)/PAGE_SIZE;
ASSERT(n_kernel_pages <= 1024);
// setup kernel_pd structure
kernel_pd.dir = &kernel_pagedir;
kernel_pd.phys_addr = (size_t)kernel_pd.dir - K_HIGHHALF_ADDR;
for (size_t i = 0; i < 1024; i++) kernel_pd.pt[i] = 0;
// setup kernel_pt768
for (size_t i = 0; i < n_kernel_pages; i++) {
kernel_pt768.page[i].as_int32 = 0; // clear any junk
kernel_pt768.page[i].present = 1;
kernel_pt768.page[i].user = 0;
kernel_pt768.page[i].rw = 1;
kernel_pt768.page[i].frame = i;
}
for (size_t i = n_kernel_pages; i < 1024; i++){
kernel_pt768.page[i].as_int32 = 0;
}
// replace 4M mapping by kernel_pt768
kernel_pd.pt[768] = &kernel_pt768;
kernel_pd.dir->page[768].as_int32 =
(((size_t)&kernel_pt768 - K_HIGHHALF_ADDR) & PAGE_MASK) | 0x07;
current_pd = &kernel_pd;
// paging already enabled in loader, nothing to do.
// disable 4M pages (remove PSE bit in CR4)
uint32_t cr4;
asm volatile("movl %%cr4, %0": "=r"(cr4));
cr4 &= ~0x00000010;
asm volatile("movl %0, %%cr4":: "r"(cr4));
// TODO : setup page fault handler
}
pagedir_t *get_current_pagedir() {
return current_pd;
}
pagedir_t *get_kernel_pagedir() {
return &kernel_pd;
}
void switch_pagedir(pagedir_t *pd) {
asm volatile("movl %0, %%cr3":: "r"(pd->phys_addr));
}
// ============================== //
// Mapping and unmapping of pages //
// ============================== //
uint32_t pd_get_frame(pagedir_t *pd, size_t vaddr) {
uint32_t page = vaddr / PAGE_SIZE;
uint32_t pt = page / PAGE_SIZE;
uint32_t pt_page = page % PAGE_SIZE;
if (pd == 0) return 0;
if (pd->pt[pt] == 0) return 0;
if (!pd->pt[pt]->page[pt_page].present) return 0;
return pd->pt[pt]->page[pt_page].frame;
}
int pd_map_page(pagedir_t *pd, size_t vaddr, uint32_t frame_id, uint32_t rw) {
return 1; // TODO
}
void pd_unmap_page(pagedir_t *pd, size_t vaddr) {
uint32_t page = vaddr / PAGE_SIZE;
uint32_t pt = page / PAGE_SIZE;
uint32_t pt_page = page % PAGE_SIZE;
if (pd == 0) return;
if (pd->pt[pt] == 0) return;
if (!pd->pt[pt]->page[pt_page].present) return;
pd->pt[pt]->page[pt_page].as_int32 = 0;
// TODO (?) : if pagetable is completely empty, free it
}
// Creation and deletion of page directories
pagedir_t *create_pagedir() {
return 0; // TODO
}
void delete_pagedir(pagedir_t *pd) {
return; // TODO
}
/* vim: set ts=4 sw=4 tw=0 noet :*/
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