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  1. #include <stdio.h>
  2. #include <unistd.h>
  3. #include <stdint.h>
  4. #include <fcntl.h>
  5. #include <sys/types.h>
  6. #include <sys/stat.h>
  7.  
  8. unsigned long virt_to_phys(void *virt_addr) {
  9.     int fd = open("/proc/self/pagemap", O_RDONLY);
  10.     if (fd < 0) {
  11.         perror("open");
  12.         return 0;
  13.     }
  14.  
  15.     unsigned long virt_pfn;
  16.     unsigned long offset = ((unsigned long)virt_addr / getpagesize()) * sizeof(unsigned long);
  17.     if (lseek(fd, offset, SEEK_SET) == (off_t)-1) {
  18.         perror("lseek");
  19.         close(fd);
  20.         return 0;
  21.     }
  22.  
  23.     if (read(fd, &virt_pfn, sizeof(virt_pfn)) != sizeof(virt_pfn)) {
  24.         perror("read");
  25.         close(fd);
  26.         return 0;
  27.     }
  28.  
  29.     close(fd);
  30.  
  31.     if (!(virt_pfn & (1ULL << 63))) {
  32.         return 0; // page not present
  33.     }
  34.  
  35.     unsigned long phys_pfn = virt_pfn & ((1ULL << 55) - 1);
  36.     return (phys_pfn * getpagesize()) + ((unsigned long)virt_addr % getpagesize());
  37. }
  38.  
  39. int main() {
  40.     int a = 5;
  41.     if (fork() == 0) {
  42.         a = a + 5;
  43.         printf("Child: value=%d, virt=%p, phys=%lx\n", a, &a, virt_to_phys(&a));
  44.     } else {
  45.         a = a - 5;
  46.         printf("Parent: value=%d, virt=%p, phys=%lx\n", a, &a, virt_to_phys(&a));
  47.     }
  48.     return 0;
  49. }
Success #stdin #stdout 0s 5320KB
comments (?)
stdin 
Standard input is empty
stdout 
Parent: value=0, virt=0x7ffcb07e5e44, phys=e44
Child: value=10, virt=0x7ffcb07e5e44, phys=e44
https://ideone.com/s64pMd
language:
C (gcc 8.3)
created:
7 days ago
visibility:
public

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