On Tue, Nov 13, 2007 at 03:37:39PM +0100, Kevin D. Kissell wrote: > True, though it should perhaps be noted that currently it's only on 4KSc/Sd > systems (which I know you work on) where it's even possible for the stack > *not* to have exec permissions, since the classical MIPS MMU gives > execute permission to any page that is readable.
Disabling PROT_EXEC on a mapping tells the kernel it doesn't need to take care of I-cache coherency. So it's somewhat beneficial even in absence of a protection bit in the actual TLB hardware. Some of these performance optimizations are impossible because the kernel can't have definate knowledge that certain addresses have never entered the I-cache. Ralf
