Consider the mappings in the virtual memory of a small test program I wrote:
0000000000400000 20K r-x-- /home/arvidj/dev/examples/testgen.c.out
0000000000604000 4K r---- /home/arvidj/dev/examples/testgen.c.out
0000000000605000 4K rw--- /home/arvidj/dev/examples/testgen.c.out
0000000000606000 16K rw--- [ anon ]
00007ffff7a12000 1780K r-x-- /lib/x86_64-linux-gnu/libc-2.17.so
00007ffff7bcf000 2048K ----- /lib/x86_64-linux-gnu/libc-2.17.so
00007ffff7dcf000 16K r---- /lib/x86_64-linux-gnu/libc-2.17.so
00007ffff7dd3000 8K rw--- /lib/x86_64-linux-gnu/libc-2.17.so
00007ffff7dd5000 20K rw--- [ anon ]
00007ffff7dda000 140K r-x-- /lib/x86_64-linux-gnu/ld-2.17.so
00007ffff7fde000 12K rw--- [ anon ]
00007ffff7ff8000 8K rw--- [ anon ]
00007ffff7ffa000 8K r-x-- [ anon ]
00007ffff7ffc000 4K r---- /lib/x86_64-linux-gnu/ld-2.17.so
00007ffff7ffd000 8K rw--- /lib/x86_64-linux-gnu/ld-2.17.so
00007ffffffde000 132K rw--- [ stack ]
ffffffffff600000 4K r-x-- [ anon ]
How flexible is this layout? Which parts can be moved (statically or dynamically), and how? If I want the stack to start at 0x0000000001000000, how can I change this? Conversely, can I move up the DATA/TEXT segments, am I at liberty to do so?
If I manage to move the stack (perhaps via makecontext, or by fiddling with sp in asm), how can I re-use that space? Can I use map over it, or can I have to unmap it using munmap? You can find my motivation in this question.
