On Tue, Oct 15, 2013 at 02:16:28PM -0400, Carlos O'Donell wrote:
There is no effective security difference between accessing the randomized stack guard value from a global variable or a value stored in the dynamic thread vector.
It is only a performance optimization. The choice of a global variable vs. DTV offset has only to do with the speed of access of the stack guard.
DTV access is of course going to be expensive, after all, that is a function call, the question was about reserving a word at fixed constant offset from the TLS base and how expensive that is vs. global variable access. For soft FP I guess global variable access must win, for -mtp=cp15 ]it depends on how fast the mrc instruction is.
Jakub