ARM VFPv3 and VFPv4 do not support trapping floating-point exceptions;
VFPv2, VFPv3U and VFPv4U do. The lack of support causes the glibc
math/test-fenv test to fail on VFPv3 and VFPv4 systems.
The natural fix for that would be for fesetenv (FE_NOMASK_ENV) to fail on
hardware not supporting trapping exceptions. There is, however, no HWCAP
bit to indicate whether trapping floating-point exceptions is supported.
Could one be added to the kernel, or is there a good way fesetenv could
detect this from userspace without a new HWCAP bit?