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#include <paging.h>
#include <frame.h>
#include <idt.h>
#include <dbglog.h>
#include <region.h>
#define PAGE_OF_ADDR(x) (((size_t)x >> PAGE_SHIFT) % N_PAGES_IN_PT)
#define PT_OF_ADDR(x) ((size_t)x >> (PAGE_SHIFT + PT_SHIFT))
#define PTE_PRESENT (1<<0)
#define PTE_RW (1<<1)
#define PTE_USER (1<<2)
#define PTE_WRITE_THROUGH (1<<3)
#define PTE_DISABLE_CACHE (1<<4)
#define PTE_ACCESSED (1<<5)
#define PTE_DIRTY (1<<6) // only PTE
#define PTE_SIZE_4M (1<<7) // only PDE
#define PTE_GLOBAL (1<<8) // only PTE
#define PTE_FRAME_SHIFT 12
typedef struct page_table {
uint32_t page[1024];
} pagetable_t;
struct page_directory {
uint32_t phys_addr; // physical address of page directory
// to modify a page directory, we first map it
// then we can use mirroring to edit it
// (the last 4M of the address space are mapped to the PD itself)
// more info to be stored here, potentially
};
// access kernel page directory page defined in loader.s
// (this is a correct higher-half address)
extern pagetable_t kernel_pd;
// pre-allocate a page table so that we can map the first 4M of kernel memory
static pagetable_t __attribute__((aligned(PAGE_SIZE))) kernel_pt0;
extern char kernel_stack_protector;
static pagedir_t kernel_pd_d;
static pagedir_t *current_pd_d;
#define current_pt ((pagetable_t*)PD_MIRROR_ADDR)
#define current_pd ((pagetable_t*)(PD_MIRROR_ADDR + (N_PAGES_IN_PT-1)*PAGE_SIZE))
void page_fault_handler(registers_t *regs) {
void* vaddr;
asm volatile("movl %%cr2, %0":"=r"(vaddr));
if ((size_t)vaddr >= K_HIGHHALF_ADDR) {
uint32_t pt = PT_OF_ADDR(vaddr);
if (current_pd != &kernel_pd && current_pd->page[pt] != kernel_pd.page[pt]) {
current_pd->page[pt] = kernel_pd.page[pt];
invlpg(¤t_pt[pt]);
return;
}
if (vaddr >= (void*)&kernel_stack_protector && vaddr < (void*)&kernel_stack_protector + PAGE_SIZE) {
dbg_printf("Kernel stack overflow at 0x%p\n", vaddr);
PANIC("Kernel stack overflow.");
}
if ((size_t)vaddr >= PD_MIRROR_ADDR) {
dbg_printf("Fault on access to mirrorred PD at 0x%p\n", vaddr);
dbg_print_region_stats();
PANIC("Unhandled kernel space page fault");
}
region_info_t *i = find_region(vaddr);
if (i == 0) {
dbg_printf("Kernel pagefault in non-existing region at 0x%p\n", vaddr);
dbg_dump_registers(regs);
PANIC("Unhandled kernel space page fault");
}
if (i->pf == 0) {
dbg_printf("Kernel pagefault in region with no handler at 0x%p\n", vaddr);
dbg_dump_registers(regs);
PANIC("Unhandled kernel space page fault");
}
i->pf(current_pd_d, i, vaddr);
} else {
dbg_printf("Userspace page fault at 0x%p\n", vaddr);
PANIC("Unhandled userspace page fault");
// not handled yet
// TODO
}
}
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); // we use less than 4M for kernel
// setup kernel_pd_d structure
kernel_pd_d.phys_addr = (size_t)&kernel_pd - K_HIGHHALF_ADDR;
// setup kernel_pt0
ASSERT(PAGE_OF_ADDR(K_HIGHHALF_ADDR) == 0); // kernel is 4M-aligned
ASSERT(FIRST_KERNEL_PT == 768);
for (size_t i = 0; i < n_kernel_pages; i++) {
if ((i * PAGE_SIZE) + K_HIGHHALF_ADDR == (size_t)&kernel_stack_protector) {
frame_free(i, 1); // don't map kernel stack protector page
} else {
kernel_pt0.page[i] = (i << PTE_FRAME_SHIFT) | PTE_PRESENT | PTE_RW | PTE_GLOBAL;
}
}
for (size_t i = n_kernel_pages; i < 1024; i++){
kernel_pt0.page[i] = 0;
}
// replace 4M mapping by kernel_pt0
kernel_pd.page[FIRST_KERNEL_PT] =
(((size_t)&kernel_pt0 - K_HIGHHALF_ADDR) & PAGE_MASK) | PTE_PRESENT | PTE_RW;
// set up mirroring
kernel_pd.page[N_PAGES_IN_PT-1] =
(((size_t)&kernel_pd - K_HIGHHALF_ADDR) & PAGE_MASK) | PTE_PRESENT | PTE_RW;
invlpg((void*)K_HIGHHALF_ADDR);
// paging already enabled in loader, nothing to do.
switch_pagedir(&kernel_pd_d);
// 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));
idt_set_ex_handler(EX_PAGE_FAULT, page_fault_handler);
}
pagedir_t *get_current_pagedir() {
return current_pd_d;
}
pagedir_t *get_kernel_pagedir() {
return &kernel_pd_d;
}
void switch_pagedir(pagedir_t *pd) {
asm volatile("movl %0, %%cr3":: "r"(pd->phys_addr));
invlpg(current_pd);
current_pd_d = pd;
}
// ============================== //
// Mapping and unmapping of pages //
// ============================== //
uint32_t pd_get_frame(void* vaddr) {
uint32_t pt = PT_OF_ADDR(vaddr);
uint32_t page = PAGE_OF_ADDR(vaddr);
pagetable_t *pd = ((size_t)vaddr >= K_HIGHHALF_ADDR ? &kernel_pd : current_pd);
if (!pd->page[pt] & PTE_PRESENT) return 0;
if (!current_pt[pt].page[page] & PTE_PRESENT) return 0;
return current_pt[pt].page[page] >> PTE_FRAME_SHIFT;
}
int pd_map_page(void* vaddr, uint32_t frame_id, bool rw) {
uint32_t pt = PT_OF_ADDR(vaddr);
uint32_t page = PAGE_OF_ADDR(vaddr);
ASSERT((size_t)vaddr < PD_MIRROR_ADDR);
pagetable_t *pd = ((size_t)vaddr >= K_HIGHHALF_ADDR ? &kernel_pd : current_pd);
if (!pd->page[pt] & PTE_PRESENT) {
uint32_t new_pt_frame = frame_alloc(1);
if (new_pt_frame == 0) return 1; // OOM
current_pd->page[pt] = pd->page[pt] =
(new_pt_frame << PTE_FRAME_SHIFT) | PTE_PRESENT | PTE_RW;
invlpg(¤t_pt[pt]);
}
current_pt[pt].page[page] =
(frame_id << PTE_FRAME_SHIFT)
| PTE_PRESENT
| ((size_t)vaddr < K_HIGHHALF_ADDR ? PTE_USER : PTE_GLOBAL)
| (rw ? PTE_RW : 0);
invlpg(vaddr);
return 0;
}
void pd_unmap_page(void* vaddr) {
uint32_t pt = PT_OF_ADDR(vaddr);
uint32_t page = PAGE_OF_ADDR(vaddr);
pagetable_t *pd = ((size_t)vaddr >= K_HIGHHALF_ADDR ? &kernel_pd : current_pd);
if (!pd->page[pt] & PTE_PRESENT) return;
if (!current_pt[pt].page[page] & PTE_PRESENT) return;
current_pt[pt].page[page] = 0;
invlpg(vaddr);
// 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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