51 lines
1.5 KiB
C
51 lines
1.5 KiB
C
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#include "paging.h"
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uint32_t page_directory[1024] __attribute__((aligned(4096)));
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uint32_t first_page_table[1024] __attribute__((aligned(4096))); // 0x00000000 - 0x00400000
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uint32_t second_page_table[1024] __attribute__((aligned(4096))); // 0x00400000 - 0x00800000
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void enable_paging() {
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asm(
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"mov %%eax, %%cr3\n"
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"mov %%cr0, %%eax\n"
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"or $0x80000001, %%eax\n"
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"mov %%eax, %%cr0\n"
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::"a"(page_directory));
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}
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void init_paging() {
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for (int i = 0; i < 1024; i++)
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// Supervisor, R/W, Not Present
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page_directory[i] = 2;
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// First Page Table
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// First MB: Real Mode
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{
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int i;
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// Up to 0xC0000
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// TODO make some areas here Read Only
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for (i = 0;i < 16*0xC; i++)
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// User, R/W, Present
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first_page_table[i] = (i * 0x1000) |4|2|1;
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// Remainder of first MB BIOS Area (writable?)
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for (;i < 256; i++)
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// User, R/W, Present
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first_page_table[i] = (i * 0x1000) |4|2|1;
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}
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// Next 3MB: Kernel
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for (int i = 256; i < 1024; i++)
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// Supervisor, R/W, Present
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first_page_table[i] = (i * 0x1000) |2|1;
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// Usermode Page Table
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for (int i = 0; i < 1024; i++)
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// User, R/W, Present
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second_page_table[i] = (i * 0x1000 + 0x400000) |4|2|1;
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// User, R/W, Present
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page_directory[0] = ((uintptr_t)first_page_table)|4|2|1;
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page_directory[1] = ((uintptr_t)second_page_table)|4|2|1;
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enable_paging();
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}
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