[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>

arch/xtensa/kernel/asm-offsets.c

@@ -63,6 +63,8 @@ int main(void)
 	DEFINE(PT_SIZE, sizeof(struct pt_regs));
 	DEFINE(PT_AREG_END, offsetof (struct pt_regs, areg[XCHAL_NUM_AREGS]));
 	DEFINE(PT_USER_SIZE, offsetof(struct pt_regs, areg[XCHAL_NUM_AREGS]));
+	DEFINE(PT_XTREGS_OPT, offsetof(struct pt_regs, xtregs_opt));
+	DEFINE(XTREGS_OPT_SIZE, sizeof(xtregs_opt_t));
 
 	/* struct task_struct */
 	DEFINE(TASK_PTRACE, offsetof (struct task_struct, ptrace));
@@ -76,7 +78,19 @@ int main(void)
 	/* struct thread_info (offset from start_struct) */
 	DEFINE(THREAD_RA, offsetof (struct task_struct, thread.ra));
 	DEFINE(THREAD_SP, offsetof (struct task_struct, thread.sp));
-	DEFINE(THREAD_CP_SAVE, offsetof (struct task_struct, thread.cp_save));
+	DEFINE(THREAD_CPENABLE, offsetof (struct thread_info, cpenable));
+#if XTENSA_HAVE_COPROCESSORS
+	DEFINE(THREAD_XTREGS_CP0, offsetof (struct thread_info, xtregs_cp));
+	DEFINE(THREAD_XTREGS_CP1, offsetof (struct thread_info, xtregs_cp));
+	DEFINE(THREAD_XTREGS_CP2, offsetof (struct thread_info, xtregs_cp));
+	DEFINE(THREAD_XTREGS_CP3, offsetof (struct thread_info, xtregs_cp));
+	DEFINE(THREAD_XTREGS_CP4, offsetof (struct thread_info, xtregs_cp));
+	DEFINE(THREAD_XTREGS_CP5, offsetof (struct thread_info, xtregs_cp));
+	DEFINE(THREAD_XTREGS_CP6, offsetof (struct thread_info, xtregs_cp));
+	DEFINE(THREAD_XTREGS_CP7, offsetof (struct thread_info, xtregs_cp));
+#endif
+	DEFINE(THREAD_XTREGS_USER, offsetof (struct thread_info, xtregs_user));
+	DEFINE(XTREGS_USER_SIZE, sizeof(xtregs_user_t));
 	DEFINE(THREAD_CURRENT_DS, offsetof (struct task_struct, thread.current_ds));
 
 	/* struct mm_struct */