[XTENSA] Add support for configurable registers and coprocessors

The Xtensa architecture allows to define custom instructions and
registers. Registers that are bound to a coprocessor are only
accessible if the corresponding enable bit is set, which allows
to implement a 'lazy' context switch mechanism. Other registers
needs to be saved and restore at the time of the context switch
or during interrupt handling.

This patch adds support for these additional states:

- save and restore registers that are used by the compiler upon
  interrupt entry and exit.
- context switch additional registers unbound to any coprocessor
- 'lazy' context switch of registers bound to a coprocessor
- ptrace interface to provide access to additional registers
- update configuration files in include/asm-xtensa/variant-fsf

Signed-off-by: Chris Zankel <chris@zankel.net>

1 files changed, 1 insertions, 0 deletions

diff --git a/include/asm-xtensa/sigcontext.h b/include/asm-xtensa/sigcontext.h
index dff3c54a3c12..03383af8c3b7 100644
--- a/include/asm-xtensa/sigcontext.h
+++ b/include/asm-xtensa/sigcontext.h
@@ -22,6 +22,7 @@ struct sigcontext {
 	unsigned long sc_acclo;
 	unsigned long sc_acchi;
 	unsigned long sc_a[16];
+	void *sc_xtregs;
 };
 
 #endif /* _XTENSA_SIGCONTEXT_H */