37 lines
958 B
ArmAsm
37 lines
958 B
ArmAsm
/* https://github.com/cirosantilli/x86-bare-metal-examples#paging.S */
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#include "common.h"
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BEGIN
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CLEAR
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STAGE2
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PROTECTED_MODE
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SETUP_PAGING_4M
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/* Setup a test canary value. */
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movl $0x1234, 0x1000
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/* Print the canary to make sure it is really there. */
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VGA_PRINT_HEX_4 0x1000
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/* Make page 0 point to 4KiB. */
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orb $0x10, page_table + 1
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PAGING_ON
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/* THIS is what we've been working for!!!
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* Even though we mov to 0, the paging circuit reads that as physical address 0x1000,
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* so the canary value 0x1234 should be modified to 0x5678.
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**/
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movl $0x5678, 0
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/* Turn paging back off to prevent it from messing with us.
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* Remember that VGA does memory accesses, so if paging is still on,
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* we must identity map up to it, which we have, so this is not mandatory.
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* */
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PAGING_OFF
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/* Print the (hopefully) modified value 0x5678. */
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VGA_PRINT_HEX_4 0x1000
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jmp .
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