The /proc/self/maps file on Linux contains information about the current location of virtual memory, about what each segment is, and about the memory protection of that segment. Changes made using mprotect will cause the file to be updated accordingly.
By developing /proc/self/maps , before you start modifying it with mprotect , you will need to have enough information to restore the previous layout.
The following example shows the contents of /proc/self/maps in three scenarios:
- Before performing any operation;
- After
mmap (which shows one additional entry in the file); and finally - After
mprotect (which shows that the permission bits are changing in the file).
(Tested with 32-bit Linux 2.6).
#include <sys/mman.h> #include <stdio.h> #include <errno.h> #define PAGE_SIZE 4096 void show_mappings(void) { int a; FILE *f = fopen("/proc/self/maps", "r"); while ((a = fgetc(f)) >= 0) putchar(a); fclose(f); printf("-----------------------------------------------\n"); } int main(void) { void *mapping; /* Show initial mappings. */ show_mappings(); /* Map in some pages. */ mapping = mmap(NULL, 16 * PAGE_SIZE, PROT_READ, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0); printf("*** Returned mapping: %p\n", mapping); show_mappings(); /* Change the mapping. */ mprotect(mapping, PAGE_SIZE, PROT_READ | PROT_WRITE); show_mappings(); return 0; }
As far as I know, there is no mechanism other than the /proc/ interface that Linux provides so that you can determine the location of your virtual memory. So parsing this file is the best you can do.