[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, 2 insertions, 11 deletions

diff --git a/include/asm-xtensa/processor.h b/include/asm-xtensa/processor.h
index 96408f4366..4918a4e96d 100644
--- a/include/asm-xtensa/processor.h
+++ b/include/asm-xtensa/processor.h
@@ -103,10 +103,6 @@ struct thread_struct {
         unsigned long dbreaka[XCHAL_NUM_DBREAK];
         unsigned long dbreakc[XCHAL_NUM_DBREAK];
 
-        /* Allocate storage for extra state and coprocessor state. */
-        unsigned char cp_save[XTENSA_CP_EXTRA_SIZE]
-                __attribute__ ((aligned(XTENSA_CP_EXTRA_ALIGN)));
-
         /* Make structure 16 bytes aligned. */
         int align[0] __attribute__ ((aligned(16)));
 };
@@ -162,21 +158,16 @@ struct thread_struct {
 struct task_struct;
 struct mm_struct;
 
-// FIXME: do we need release_thread for CP??
 /* Free all resources held by a thread. */
 #define release_thread(thread) do { } while(0)
 
-// FIXME: do we need prepare_to_copy (lazy status) for CP??
 /* Prepare to copy thread state - unlazy all lazy status */
-#define prepare_to_copy(tsk)    do { } while (0)
+extern void prepare_to_copy(struct task_struct*);
 
-/*
- * create a kernel thread without removing it from tasklists
- */
+/* Create a kernel thread without removing it from tasklists */
 extern int kernel_thread(int (*fn)(void *), void * arg, unsigned long flags);
 
 /* Copy and release all segment info associated with a VM */
-
 #define copy_segments(p, mm)    do { } while(0)
 #define release_segments(mm)    do { } while(0)
 #define forget_segments()       do { } while (0)