char xstateregs[X86_XSTATE_MAX_SIZE];
struct iovec iov;
+ /* Pre-4.14 kernels have a bug (fixed by commit 0852b374173b
+ "x86/fpu: Add FPU state copying quirk to handle XRSTOR failure on
+ Intel Skylake CPUs") that sometimes causes the mxcsr location in
+ xstateregs not to be copied by PTRACE_GETREGSET. Make sure that
+ the location is at least initialized with a defined value. */
+ memset (xstateregs, 0, sizeof (xstateregs));
iov.iov_base = xstateregs;
iov.iov_len = sizeof (xstateregs);
if (ptrace (PTRACE_GETREGSET, tid,