Language: C C++ D Haskell Lua OCaml PHP Perl Plain Text Python Ruby Scheme Tcl #include <sys/mman.h> #include <fcntl.h> #include <stdio.h> #include <unistd.h> /** ** A quasi-implementation of malloc(), which allocates 2 additional words, one ** before the memory segment of the requested size, one after. It protects ** those words against reading/writing, so accessing them raises a SIGSEGV. ** \param size length of the memory segment to be allocated for reading/writing ** \returns a pointer to the allocated memory, NULL on failure ** \warning Needs to be freed by free_bounded(), not the regular free() **/ static void* malloc_bounded(size_t size) { int fd = open("/dev/zero", O_RDWR); size_t *stp = NULL; if (fd != -1) { size += 2 * sizeof(size_t); //+boundry words stp = mmap(NULL, size, PROT_READ|PROT_WRITE, MAP_PRIVATE, fd, 0); if (stp != MAP_FAILED) { *stp = size; //write metadata to the first word //seal both ends: mprotect(stp, sizeof(size_t), PROT_NONE); mprotect((((char*)stp)+size)-sizeof(size_t), sizeof(size_t), PROT_NONE); ++stp; } else stp = NULL; close(fd); } return (void *)stp; } int main() { char *s = malloc_bounded(100); s[98] = '\0'; return 0; } Private [?] Run code Submit