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glibc  2.9
Functions
readonly-area.c File Reference
#include <errno.h>
#include <stdint.h>
#include <stdio.h>
#include <stdio_ext.h>
#include <stdlib.h>
#include <string.h>
#include "libio/libioP.h"

Go to the source code of this file.

Functions

int __readonly_area (const char *ptr, size_t size)

Function Documentation

int __readonly_area ( const char *  ptr,
size_t  size 
)

Definition at line 31 of file readonly-area.c.

{
  const void *ptr_end = ptr + size;

  FILE *fp = fopen ("/proc/self/maps", "rc");
  if (fp == NULL)
    {
      /* It is the system administrator's choice to not have /proc
        available to this process (e.g., because it runs in a chroot
        environment.  Don't fail in this case.  */
      if (errno == ENOENT
         /* The kernel has a bug in that a process is denied access
            to the /proc filesystem if it is set[ug]id.  There has
            been no willingness to change this in the kernel so
            far.  */
         || errno == EACCES)
       return 1;
      return -1;
    }

  /* We need no locking.  */
  __fsetlocking (fp, FSETLOCKING_BYCALLER);

  char *line = NULL;
  size_t linelen = 0;

  while (! feof_unlocked (fp))
    {
      if (_IO_getdelim (&line, &linelen, '\n', fp) <= 0)
       break;

      char *p;
      uintptr_t from = strtoul (line, &p, 16);

      if (p == line || *p++ != '-')
       break;

      char *q;
      uintptr_t to = strtoul (p, &q, 16);

      if (q == p || *q++ != ' ')
       break;

      if (from < (uintptr_t) ptr_end && to > (uintptr_t) ptr)
       {
         /* Found an entry that at least partially covers the area.  */
         if (*q++ != 'r' || *q++ != '-')
           break;

         if (from <= (uintptr_t) ptr && to >= (uintptr_t) ptr_end)
           {
             size = 0;
             break;
           }
         else if (from <= (uintptr_t) ptr)
           size -= to - (uintptr_t) ptr;
         else if (to >= (uintptr_t) ptr_end)
           size -= (uintptr_t) ptr_end - from;
         else
           size -= to - from;

         if (!size)
           break;
       }
    }

  fclose (fp);
  free (line);

  /* If the whole area between ptr and ptr_end is covered by read-only
     VMAs, return 1.  Otherwise return -1.  */
  return size == 0 ? 1 : -1;
}

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