um: stop polluting the namespace with registers.h contents

Only one extern in there is needed in processor-generic.h, and it's
not needed anywhere else. So move it over there and get rid of
the include in processor-generic.h, adding includes of registers.h
to the few files that need the declarations in it.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Richard Weinberger <richard@nod.at>

um: Fix FP register size for XSTATE/XSAVE

Hard code max size. Taken from
https://sourceware.org/git/?p=binutils-gdb.git;a=blob;f=gdb/common/x86-xstate.h

Signed-off-by: Thomas Meyer <thomas@m3y3r.de>
Signed-off-by: Richard Weinberger <richard@nod.at>

um: Allow building and running on older hosts

Commit a78ff1112263 ("um: add extended processor state save/restore
support") and b6024b21fec8 ("um: extend fpstate to _xstate to support
YMM registers") forced the use of the x86 FP _xstate and
PTRACE_GETREGSET/SETREGSET. On older hosts, we would neither be able to
build UML nor run it anymore with these two commits applied because we
don't have definitions for struct _xstate nor these two ptrace requests.

We can determine at build time which fp context structure to check
against, just like we can keep using the old i387 fp save/restore if
PTRACE_GETRESET/SETREGSET are not defined.

Fixes: a78ff1112263 ("um: add extended processor state save/restore support")
Fixes: b6024b21fec8 ("um: extend fpstate to _xstate to support YMM registers")
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: Richard Weinberger <richard@nod.at>

um: add extended processor state save/restore support

This patch extends save_fp_registers() and restore_fp_registers() to use
PTRACE_GETREGSET and PTRACE_SETREGSET with the XSTATE note type, adding
support for new processor state extensions between context switches.

When the new ptrace requests are unavailable, it falls back to the old
PTRACE_GETFPREGS and PTRACE_SETFPREGS methods, which have been renamed to
save_i387_registers() and restore_i387_registers().

Now these functions expect *fp_regs to have the space of an _xstate struct.
Thus, this also makes ptrace in UML responde to PTRACE_GETFPREGS/_SETFPREG
requests with a user_i387_struct (thus independent from HOST_FP_SIZE), and
by calling save_i387_registers() and restore_i387_registers() instead of
the extended save_fp_registers() and restore_fp_registers() functions.

Signed-off-by: Eli Cooper <elicooper@gmx.com>

um: get rid of pointless include "..." where include <...> will do

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Richard Weinberger <richard@nod.at>

um: we need sys/user.h only on i386

Signed-off-by: Richard Weinberger <richard@nod.at>

um: unify KSTK_...

... and switch get_thread_register() to HOST_... for register numbers

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Richard Weinberger <richard@nod.at>

um: take arch/um/sys-x86 to arch/x86/um

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Richard Weinberger <richard@nod.at>