Re: [RFC] User stack pointer randomisation

[Ralf Baechle <ralf@linux-mips.org>]

On Thu, Jul 19, 2007 at 09:10:23AM +0200, Franck Bui-Huu wrote:

> This patch adds a page size range randomisation to the user
> stack pointer.

Looks fine to me aside of the issue Nigel raised.

There is a constant defining the ABI-specific alignment in <asm/asm.h>:

#if (_MIPS_SIM == _MIPS_SIM_ABI32)
#define ALSZ    7
#define ALMASK  ~7
#endif
#if (_MIPS_SIM == _MIPS_SIM_NABI32) || (_MIPS_SIM == _MIPS_SIM_ABI64)
#define ALSZ    15
#define ALMASK  ~15
#endif

This will unnecessarily increase the alignment of the stack wasting a few
bytes of memory for O32 binaries running on 64-bit kernels but I'd just
ignore this artefact; the cure would be uglier than the disease ;-)

  Ralf