memcheck/tests/pointer-trace.c

   1 /*
   2    Make sure that leak-check's pointer tracing avoids traps, i.e. tricky
   3    memory areas where it could crash if not careful.
   4  */
   5
   6 #include <stdio.h>
   7 #include "memcheck/memcheck.h"
   8 #include "tests/sys_mman.h"
   9 #include <stdlib.h>
  10 #include <fcntl.h>
  11 #include <unistd.h>
  12
  13 #if !defined(MAP_NORESERVE)
  14 #  define MAP_NORESERVE 0
  15 #endif
  16
  17 int main()
  18 {
  19         char **volatile ptrs;
  20         int i;
  21         int fd;
  22         char *map;
  23
  24         /* I _think_ the point of this is to fill ptrs with a pointer
  25            to every 4th page in the entire address space, hence
  26            guaranteeing that at least one of them points into one of
  27            the below traps, and so checks that the leak checker
  28            doesn't bomb when following them.  That's fine on 32-bit
  29            platforms, but hopeless for a 64-bit system.  So the
  30            following settings do achieve that on a 32-bit target but
  31            merely make a 64-bit target give the same output without
  32            properly testing it. */
  33         int ptrbits, stepbits, stepsize, nptrs;
  34         if (sizeof(void*) == 8) {
  35            /* 64-bit machine */
  36            ptrbits = 32;   //bogus
  37            stepbits = 14+1;  //bogus
  38            stepsize = (1 << stepbits);
  39            nptrs = 1 << (ptrbits - stepbits);
  40         } else {
  41            /* 32-bit machine */
  42            ptrbits = 32;
  43            stepbits = 14;
  44            stepsize = (1 << stepbits);
  45            nptrs = 1 << (ptrbits - stepbits);
  46         }
  47
  48         ptrs = malloc(nptrs * sizeof(char *));
  49         for (i = 0; i < nptrs; i++)
  50                 ptrs[i] = (char *)((long)i << stepbits);
  51
  52         /* lay some traps */
  53         /* non-RWX memory, and MAP_NORESERVE if present */
  54         map = mmap(0, stepsize * 2, PROT_NONE, MAP_PRIVATE|MAP_NORESERVE|MAP_ANONYMOUS, -1, 0);
  55         if (map == (char *)-1)
  56                 perror("trap 1 failed");
  57
  58         /* write-only memory, and MAP_NORESERVE if supported */
  59         map = mmap(0, stepsize * 2, PROT_WRITE, MAP_PRIVATE|MAP_NORESERVE|MAP_ANONYMOUS, -1, 0);
  60         if (map == (char *)-1)
  61                 perror("trap 2 failed");
  62
  63         /* non-zero mmap of a zero-length file -> SIGBUS */
  64         fd = open("./pointer-trace-test-file", O_RDWR | O_CREAT | O_EXCL, 0600);
  65         unlink("./pointer-trace-test-file");
  66         map = mmap(0, stepsize * 2, PROT_WRITE|PROT_READ, MAP_PRIVATE, fd, 0);
  67         if (map == (char *)-1)
  68                 perror("trap 3 failed");
  69         //printf("trap 3 = %p-%p\n", map, map+stepsize*2);
  70
  71         /* unmapped memory that's marked as defined */
  72         map = mmap(0, 256*1024, PROT_NONE, MAP_PRIVATE|MAP_NORESERVE|MAP_ANONYMOUS, -1, 0);
  73         if (map == (char *)-1)
  74                 perror("trap 4 failed");
  75         else {
  76                 munmap(map, 256*1024);
  77                 (void)VALGRIND_MAKE_MEM_DEFINED(map, 256*1024); /* great big fat lie */
  78         }
  79
  80         VALGRIND_DO_LEAK_CHECK;
  81
  82         free(ptrs);
  83
  84         // We deliberately make a leak, it'll be obvious if something went
  85         // wrong because the message won't be printed.
  86         ptrs = malloc(1000);
  87
  88         return 0;
  89 }