[PATCH 0/3] properly account for stack randomization and guard gap

[riel]

When RLIMIT_STACK is larger than the minimum gap enforced by
mmap_base(), it is possible for the kernel to place the mmap
area where the stack wants to grow, resulting in the stack
not being able to use the space that should have been allocated
to it through RLIMIT_STACK.

This series ensures that x86, ARM64, and PPC have at least
RLIMIT_STACK + stack randomization + the stack guard gap
space available for the stack.

s390 seems to be ok. I have not checked other architectures.