The stack test incorrectly assumed the page immediately
following the stack pointer could never be changed. This doesn't work,
because this page can be a part of another mapping.
This commit introduces a dedicated "stack redzone," a small guard region
directly after the stack. The stack test is modified to specifically
check for corruption within this redzone.
Signed-off-by: Andrei Vagin <avagin@gmail.com>
Some ABIs allow functions to store data in caller frame, which
means that we have to allocate an initial stack frame before
executing code on the parasite stack.
This test saves the contents of writable memory that follows the stack
after the victim has been infected but before we start using the
parasite stack. It later checks that the saved data matches the
current contents of the two memory areas. This is done while the
victim is halted so we expect a match unless executing parasite code
caused memory corruption. The test doesn't detect cases where we
corrupted memory by writing the same value.
Signed-off-by: Younes Manton <ymanton@ca.ibm.com>
