QEMU脆弱性を利用したVMエスケープ攻撃の検証：概要＆テスト環境構築編：OSS脆弱性ウォッチ（12）（2/2 ページ）

Bits 0-54 : physical frame number if present.
Bit 55 : page table entry is soft-dirty.
Bit 56 : page exclusively mapped.
Bits 57-60 : zero
Bit 61 : page is file-page or shared-anon.
Bit 62 : page is swapped.
Bit 63 : page is present

#include <stdio.h>
#include <string.h>
#include <stdint.h>
#include <stdlib.h>
#include <fcntl.h>
#include <assert.h>
#include <inttypes.h>
 
#define PAGE_SHIFT  12
#define PAGE_SIZE   (1 << PAGE_SHIFT)
#define PFN_PRESENT (1ull << 63)
#define PFN_PFN     ((1ull << 55) - 1)
 
int fd;
 
uint32_t page_offset(uint32_t addr)
{
    return addr & ((1 << PAGE_SHIFT) - 1);
}
 
uint64_t gva_to_gfn(void *addr)
{
    uint64_t pme, gfn;
    size_t offset;
    offset = ((uintptr_t)addr >> 9) & ~7;
    lseek(fd, offset, SEEK_SET);
    read(fd, &pme, 8);
    if (!(pme & PFN_PRESENT))
        return -1;
    gfn = pme & PFN_PFN;
    return gfn;
}
 
uint64_t gva_to_gpa(void *addr)
{
    uint64_t gfn = gva_to_gfn(addr);
    assert(gfn != -1);
    return (gfn << PAGE_SHIFT) | page_offset((uint64_t)addr);
}
 
int main()
{
    uint8_t *ptr;
    uint64_t ptr_mem;
    
    fd = open("/proc/self/pagemap", O_RDONLY);
    if (fd < 0) {
        perror("open");
        exit(1);
    }
    
    ptr = malloc(256);
    strcpy(ptr, "Where am I?");
    printf("%s\n", ptr);
    ptr_mem = gva_to_gpa(ptr);
    printf("Your physical address is at 0x%"PRIx64"\n", ptr_mem);
 
    getchar();
    return 0;
}