We expect that a kernel with CONFIG_FPU=y can still support no-FPU
machines. To do so, the kernel should first examine the existence of a
FPU, then do nothing if a FPU does exist; otherwise, it should
disable/bypass all FPU-related functions.

In this patch, a new global variable, has_fpu, is created and determined
when parsing the hardware capability from device tree during booting.
This variable is used in those FPU-related functions.

Signed-off-by: Alan Kao <alankao@andestech.com>
Cc: Greentime Hu <greentime@andestech.com>
Cc: Vincent Chen <vincentc@andestech.com>
Cc: Zong Li <zong@andestech.com>
Cc: Nick Hu <nickhu@andestech.com>
Signed-off-by: Palmer Dabbelt <palmer@sifive.com>

FPU codes have been separated from common part in previous patches.
This patch add the CONFIG_FPU option and some stubs, so that a no-FPU
configuration is allowed.

Signed-off-by: Alan Kao <alankao@andestech.com>
Cc: Greentime Hu <greentime@andestech.com>
Cc: Vincent Chen <vincentc@andestech.com>
Cc: Zong Li <zong@andestech.com>
Cc: Nick Hu <nickhu@andestech.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Palmer Dabbelt <palmer@sifive.com>

Pull asm/uaccess.h whack-a-mole from Al Viro:
 "It's linux/uaccess.h, damnit... Oh, well - eventually they'll stop
  cropping up..."

* 'work.whack-a-mole' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
  asm-prototypes.h: use linux/uaccess.h, not asm/uaccess.h
  riscv: use linux/uaccess.h, not asm/uaccess.h...
  ppc: for put_user() pull linux/uaccess.h, not asm/uaccess.h

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Palmer Dabbelt <palmer@sifive.com>

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

This patch contains the implementation of tasks on RISC-V, most of which
is involved in task switching.

Signed-off-by: Palmer Dabbelt <palmer@dabbelt.com>