84 lines
2.3 KiB
C
84 lines
2.3 KiB
C
#include <paging.h>
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#include <stdio.h>
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#include <string.h>
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uint32_t page_dir[1024] __attribute__((aligned(4096)));
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uint32_t page_table[1024] __attribute__((aligned(4096)));
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static uint32_t bitmap[NPAGES/ENTRY_WIDTH] __attribute__((aligned(4096)));
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void page_fault(registers_t regs) {
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uint32_t faulting_address;
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__asm__ volatile("mov %%cr2, %0" : "=r" (faulting_address));
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// The error code gives us details of what happened.
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int present = !(regs.err_code & 0x1); // Page not present
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int rw = regs.err_code & 0x2; // Write operation?
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int us = regs.err_code & 0x4; // Processor was in user-mode?
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int reserved = regs.err_code & 0x8; // Overwritten CPU-reserved bits of page entry?
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//int id = regs.err_code & 0x10; // Caused by an instruction fetch?
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kprintf("Page fault: ( ");
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if (present) {kprintf("present ");}
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if (rw) {kprintf("read-only ");}
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if (us) {kprintf("user-mode ");}
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if (reserved) {kprintf("reserved ");}
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kprintf(") at 0x%x\n", faulting_address);
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kprintf("PAGE FAULT\n");
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}
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void load_directory(uint32_t *dir) {
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__asm__ volatile("mov %0, %%cr3":: "r"(dir));
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}
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void enable_paging() {
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uint32_t cr0;
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__asm__ volatile("mov %%cr0, %0": "=r"(cr0));
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cr0 |= 0x80000001; // Enable paging!
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__asm__ volatile("mov %0, %%cr0":: "r"(cr0));
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}
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page_addr_t kalloc_frame() {
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uint32_t bitmap_index;
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uint32_t element_index;
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uint32_t page_frame_number;
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for (bitmap_index = 0; bitmap_index < NPAGES/ENTRY_WIDTH; bitmap_index++)
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if (bitmap[bitmap_index] != 0) break; // FIXME
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if (bitmap_index >= NPAGES/ENTRY_WIDTH)
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return -1;
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for (element_index = 0; element_index < ENTRY_WIDTH; element_index++)
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if ((bitmap[bitmap_index] & (1U << element_index)) != 0) break; // FIXME
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if ((bitmap[bitmap_index] & (1U << element_index)) == 0)
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return -1;
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bitmap[bitmap_index] &= ~(1U << element_index);
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page_frame_number = bitmap_index * ENTRY_WIDTH + element_index;
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return page_frame_number * PAGE_SIZE;
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}
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void paging_init() {
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unsigned int i;
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for(i = 0; i < 1024; i++) {
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page_dir[i] = 0x00000002;
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}
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for(i = 0; i < NPAGES/ENTRY_WIDTH; i++) {
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bitmap[i] = ~0;
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}
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for(i = 0; i < 1024; i++) {
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page_table[i] = (i * 0x1000) | 3;
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}
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page_dir[0] = ((unsigned int)page_table) | 3;
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register_interrupt_handler(14, &page_fault);
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load_directory(page_dir);
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enable_paging();
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}
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