There is a major difference between slices and maps: Slices are backed by a backing array and maps are not. If a map grows or shrinks a potential pointer to a map element may become a dangling pointer pointing into nowhere (uninitialised memory). The problem here is not “confusion of the user” but that it … Read more
This answer is by no means exhaustive but it may explain it enough to make things click. In virtual memory systems, there is a disconnect between logical and physical addresses. An application can be given a virtual address space of (let’s say) 4G. This is its usable memory and it’s free to use it as … Read more
On Ubuntu , it can be disabled with… echo 0 > /proc/sys/kernel/randomize_va_space On Windows, this post might be of some help… Quickpost: Another Funny Vista Trick with ASLR
When t is used on its own in the expression, an array-to-pointer conversion takes place, this produces a pointer to the first element of the array. When t is used as the argument of the & operator, no such conversion takes place. The & then explicitly takes the address of t (the array). &t is … Read more
Have a look at ctypes.string_at. Here’s an example. It dumps the raw data structure of a CPython integer. from ctypes import string_at from sys import getsizeof a = 0x7fff print(string_at(id(a),getsizeof(a)).hex()) Output: 0200000000000000d00fbeaafe7f00000100000000000000ff7f0000 Note that this works with the CPython implementation because id() happens to return the virtual memory address of a Python object, but this … Read more
Python reuses string literals fairly aggressively. The rules by which it does so are implementation-dependent, but CPython uses two that I’m aware of: Strings that contain only characters valid in Python identifiers are interned, which means they are stored in a big table and reused wherever they occur. So, no matter where you use “cat”, … Read more
busybox devmem busybox devmem is a tiny CLI utility that mmaps /dev/mem. You can get it in Ubuntu with: sudo apt-get install busybox Usage: read 4 bytes from the physical address 0x12345678: sudo busybox devmem 0x12345678 Write 0x9abcdef0 to that address: sudo busybox devmem 0x12345678 w 0x9abcdef0 Source: https://github.com/mirror/busybox/blob/1_27_2/miscutils/devmem.c#L85 mmap MAP_SHARED When mmapping /dev/mem, you … Read more
You want to use %p to print a pointer. From the spec: p The argument shall be a pointer to void. The value of the pointer is converted to a sequence of printing characters, in an implementation-defined manner. And don’t forget the cast, e.g. printf(“%p\n”,(void*)&a);
Here’s how process memory is laid out on Linux (from http://www.thegeekstuff.com/2012/03/linux-processes-memory-layout/): The .rodata section is a write-protected subsection of the Initialized Global Data block. (A section which ELF executables designate .data is its writable counterpart for writable globals initialized to nonzero values. Writable globals initialized to zeros go to the .bss block. By globals here … Read more
Use the format specifier %p: printf(“variable A is at address: %p\n”, (void*)&A); The standard requires that the argument is of type void* for %p specifier. Since, printf is a variadic function, there’s no implicit conversion to void * from T * which would happen implicitly for any non-variadic functions in C. Hence, the cast is … Read more