112 lines
2.3 KiB
C
112 lines
2.3 KiB
C
#include <memory.h>
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#define FLAGS_MASK (PAGE_SIZE-1)
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#define MASK_FLAGS(addr) ((uint64_t)addr & ~FLAGS_MASK)
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union PTE {
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uint64_t value;
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struct {
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uint64_t present:1;
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uint64_t write:1;
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uint64_t user:1;
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uint64_t write_through:1;
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uint64_t nocache:1;
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uint64_t accessed:1;
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uint64_t dirty:1;
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uint64_t huge:1;
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uint64_t global:1;
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uint64_t flags:3;
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};
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};
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#define PT(ptr) ((union PTE *)P2V(MASK_FLAGS(ptr)))
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// Get the entry correspoding to address addr in page dir P4
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// for P4 table (P4E), P3 table (P3E) and so on.
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// Note: Those macros requires variables to be named
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#define P4E (PT(P4)[P4_OFFSET(addr)])
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#define P3E PT(P4E.value)[P3_OFFSET(addr)]
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#define P2E PT(P3E.value)[P2_OFFSET(addr)]
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#define P1E PT(P2E.value)[P1_OFFSET(addr)]
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static int page_exists(uint64_t P4, uint64_t addr)
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{
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if(P4 && P4E.present && P3E.present && P2E.present)
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return 1;
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return 0;
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}
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uint64_t vmm_get_page(uint64_t P4, uint64_t addr)
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{
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if(page_exists(P4, addr))
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{
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return P1E.value;
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}
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return -1;
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}
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int vmm_set_page(uint64_t P4, uint64_t addr, uint64_t page, uint16_t flags, int touch)
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{
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if(!page_exists(P4, addr))
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{
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if(!touch)
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return -1;
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touch_page(P4, addr, flags);
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}
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P1E.value = page | flags;
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return 0;
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}
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int touch_page(uint64_t P4, uint64_t addr, uint16_t flags)
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{
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if(!P4) return -1;
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if((!P4E.present) && (!(P4E.value = pmm_calloc())))
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return -1;
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P4E.value |= flags | PAGE_PRESENT;
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if((!P3E.present) && (!(P3E.value = pmm_calloc())))
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return -1;
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P3E.value |= flags | PAGE_PRESENT;
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if((!P2E.present) && (!(P2E.value = pmm_calloc())))
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return -1;
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P2E.value |= flags | PAGE_PRESENT;
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return 0;
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}
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void free_page(uint64_t P4, uint64_t addr, int free)
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{
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if(!page_exists(P4, addr))
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return;
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union PTE *pt;
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P1E.value = 0;
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if(!free)
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return;
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pt = PT(P2E.value);
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for(int i = 0; i < ENTRIES_PER_PT; i++)
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if(pt[i].value)
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return;
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pmm_free(MASK_FLAGS(P2E.value));
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P2E.value = 0;
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pt = PT(P3E.value);
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for(int i = 0; i < ENTRIES_PER_PT; i++)
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if(pt[i].value)
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return;
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pmm_free(MASK_FLAGS(P3E.value));
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P3E.value = 0;
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pt = PT(P4E.value);
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for(int i = 0; i < ENTRIES_PER_PT; i++)
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if(pt[i].value)
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return;
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pmm_free(MASK_FLAGS(P4E.value));
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P4E.value = 0;
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}
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