int kernel_start()
{
int i;
// point to low address (0GB ~ ...)
pgd_tmp[PGD_INDEX(0)] =
(uint32_t)pte_low | PAGE_PRESENT | PAGE_WRITE;
// point to high address (3GB ~ 4GB)
pgd_tmp[PGD_INDEX(PAGE_OFFSET)] =
(uint32_t)pte_hig | PAGE_PRESENT | PAGE_WRITE;
for (i = 0; i < 1024; i++) {
pte_low[i] = (i << 12) | PAGE_PRESENT | PAGE_WRITE;
}
for (i = 0; i < 1024; i++) {
pte_hig[i] = (i << 12) | PAGE_PRESENT | PAGE_WRITE;
}
// set page directory
set_cr3(pgd_tmp);
page_on();
kernel_stack_top = ((uint32_t)kernel_stack + STACK_SIZE) & 0xFFFFFFF0;
set_esp(kernel_stack_top);
global_mboot_ptr =
(multiboot_t *)((uint32_t)global_mboot_tmp + PAGE_OFFSET);
kernel_init();
return 0;
}
void map(pgd_t *pgd_now, uint32_t va, uint32_t pa, uint32_t flags)
{
uint32_t pgd_idx = PGD_INDEX(va);
uint32_t pte_idx = PTE_INDEX(va);
pte_t *pte = (pte_t *)(pgd_now[pgd_idx] & PAGE_MASK);
if (!pte) {
pte = (pte_t *)alloc_pages(1);
pgd_now[pgd_idx] = (uint32_t)pte | PAGE_PRESENT | PAGE_WRITE;
pte = (pte_t *)pa_to_ka(pte);
} else {
pte = (pte_t *)pa_to_ka(pte);
}
pte[pte_idx] = (pa & PAGE_MASK) | flags;
tlb_reload_page(va);
}
void unmap(pgd_t *pgd_now, uint32_t va)
{
uint32_t pgd_idx = PGD_INDEX(va);
uint32_t pte_idx = PTE_INDEX(va);
pte_t *pte = (pte_t *)(pgd_now[pgd_idx] & PAGE_MASK);
if (!pte) {
return;
}
// 转换到内核线性地址
pte = (pte_t *)(pa_to_ka(pte));
pte[pte_idx] = 0;
tlb_reload_page(va);
}
uint32_t get_mapping(pgd_t *pgd_now, uint32_t va, uint32_t *pa)
{
uint32_t pgd_idx = PGD_INDEX(va);
uint32_t pte_idx = PTE_INDEX(va);
pte_t *pte = (pte_t *)(pgd_now[pgd_idx] & PAGE_MASK);
if (!pte) {
return 0;
}
// 转换到内核线性地址
pte = (pte_t *)(pa_to_ka(pte));
// 如果地址有效而且指针不为NULL，则返回地址
if (pte[pte_idx] != 0 && pa) {
*pa = pte[pte_idx] & PAGE_MASK;
return 1;
}
return 0;
}
void vmm_init(void)
{
// 注册页错误中断的处理函数
register_interrupt_handler(INT_PAGE_FAULT, &do_page_fault);
// 页表数组指针
pte_t (*pte_kern)[PTE_SIZE] = (pte_t (*)[PTE_SIZE])pte_addr;
// 构造页目录(MMU需要的是物理地址，此处需要减去偏移)
uint32_t pgd_idx = PGD_INDEX(PAGE_OFFSET);
for (uint32_t i = pgd_idx; i < pgd_idx + PTE_COUNT; ++i) {
pgd_kern[i] = ((uint32_t)ka_to_pa(pte_kern[i])) | PAGE_PRESENT | PAGE_WRITE;
}
// 构造页表映射，内核 0xC0000000～0xF8000000 映射到 物理 0x00000000～0x38000000 (物理内存前896MB)
uint32_t *pte_start = (uint32_t *)(pte_addr + PTE_SIZE * pgd_idx);
for (uint32_t i = 0; i < PTE_SIZE * PTE_COUNT; ++i) {
pte_start[i] = (i << 12) | PAGE_PRESENT | PAGE_WRITE;
}
switch_pgd((uint32_t)ka_to_pa(pgd_kern));
}