[musl] Re: Thread pointer changes

* Russell King - ARM Linux [off-list ref] [2014-06-27 23:17:44 +0100]:

I think you're are missing one obvious solution to this which you can do:
you are passed the HWCAP fields in the ELF auxinfo.  This will tell you
if the CPU has TLS support or not.  If it has TLS support, then you don't
need to use the kuser helpers, and you know that it is a CPU which is ARM
architecture v6k or later, and it has things like the CP15 barrier
instructions.  If you want to know that the CPU supports the DMB
instruction rather than the CP15 barrier instruction, then you have to
check the uname details, or read /proc/cpuinfo (but I'd rather you
didn't.)

but cp15 barrier is deprecated on armv7+

and i think the kernel can avoid the barriers on non-smp systems making
kuser helpers possibly preferable even if TLS HWCAP flag is set