This modification is required to fix debugging function for m32r targets
with !CONFIG_ISA_DSP_LEVEL2, by unifying 'struct pt_regs' and 'struct
sigcontext' size for all M32R ISA.

Some m32r processor core with !CONFIG_ISA_DSP_LEVEL2 configuration has only
single accumulator a0 (ex.  VDEC2 core, M32102 core, etc.), the others with
CONFIG_ISA_DSP_LEVEL2 has two accumulators, a0 and a1.

This means there are two variations of thread context.  So far, we reduced
and changed stackframe size at a syscall for their context size.  However,
this causes a problem that a GDB for processors with CONFIG_ISA_DSP_LEVEL2
cannot be used for processors with !CONFIG_ISA_DSP_LEVEL2.

From the viewpoint of GDB support, we should reduce such variation of
stackframe size for simplicity.

In this patch, dummy members are added to 'struct pt_regs' and 'struct
sigcontext' to adjust their size for !CONFIG_ISA_DSP_LEVEL2.

This modification is also a one step for a GDB update in future.
Currently, on the m32r, GDB can access process's context by using ptrace
functions in a simple way of register by register access.  By unifying
stackframe size, we have a possibility to make use of ptrace functions of
not only a single register access but also block register access,
PTRACE_{GETREGS,PUTREGS}.

However, for this purpose, we might have to modify stackframe structure
some more; for example, PSW (processor status word) register should be
pre-processed before pushing to stack at a syscall, and so on.  In this
case, we must update carefully both kernel and GDB at a time...

Signed-off-by: Hayato Fujiwara <fujiwara@linux-m32r.org>
Signed-off-by: Hirokazu Takata <takata@linux-m32r.org>
Cc: Kei Sakamoto <ksakamot@linux-m32r.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>