On Wed, Feb 17, 2016 at 2:53 PM, Dave Hansen <dave@xxxxxxxx> wrote: > On 02/17/2016 02:17 PM, Andy Lutomirski wrote: >>> > Is there a way to detect this feature's availability without userspace >>> > having to set up a segv handler and attempting to read a >>> > PROT_EXEC-only region? (i.e. cpu flag for protection keys, or a way to >>> > check the protection to see if PROT_READ got added automatically, >>> > etc?) >>> > >> We could add an HWCAP. > > I'll bite. What's an HWCAP? It's a CPU capability vector that's passed to every program as an auxv entry. On x86, ELF_HWCAP is useless (it's already fully used up for pointless purposes for CPUID stuff), but ELF_HWCAP2 could be added and a bit could be defined like HWCAP2_PROT_EXEC_ONLY. Some day, WRFSBASE, etc will be advertised via ELF_HWCAP2, I suspect. --Andy -- Andy Lutomirski AMA Capital Management, LLC -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>