ptrace: Why does PTRACE_PEEKUSER not allow reading of FPU registers on x86?

[tartanllama]

Hey folks,

Looking at arch/x86/kernel/ptrace.c, I can see that reading with
PTRACE_PEEKUSER is only supported within the user::regs and user::u_debugreg
fields. What's the reason that reading from user::i387 is disallowed?

Thanks,
Sy Brand