Per architecture restorer trampolines

Some architectures like ppc64 requires a trampoline to be called prior to
the standard restorer services.

This patch introduces 3 trampolines which can be overwritten by
architectures in arch/x/include/asm/restore.h:
 - arch_export_restore_thread
 - arch_export_restore_task
 - arch_export_unmap

The architecture which doesn't need to overwrite them, has nothing to do.
Signed-off-by: Laurent Dufour <ldufour@linux.vnet.ibm.com>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

arch/ppc64/include/asm/restore.h

@@ -30,4 +30,7 @@
 
 int restore_fpu(struct rt_sigframe *sigframe, CoreEntry *core);
 
+#define arch_export_restore_task	__export_restore_task_trampoline
+#define arch_export_unmap		__export_unmap_trampoline
+
 #endif /* __CR_ASM_RESTORE_H__ */

cr-restore.c

@@ -90,6 +90,18 @@
 
 #include "cr-errno.h"
 
+#ifndef arch_export_restore_thread
+#define arch_export_restore_thread	__export_restore_thread
+#endif
+
+#ifndef arch_export_restore_task
+#define arch_export_restore_task	__export_restore_task
+#endif
+
+#ifndef arch_export_unmap
+#define arch_export_unmap		__export_unmap
+#endif
+
 static struct pstree_item *current;
 
 static int restore_task_with_children(void *);
@@ -2750,14 +2762,9 @@ static int sigreturn_restore(pid_t pid, CoreEntry *core)
 	 * Prepare a memory map for restorer. Note a thread space
 	 * might be completely unused so it's here just for convenience.
 	 */
-	restore_thread_exec_start	= restorer_sym(exec_mem_hint, __export_restore_thread);
-#ifdef CONFIG_PPC64
-	restore_task_exec_start		= restorer_sym(exec_mem_hint, __export_restore_task_trampoline);
-	rsti(current)->munmap_restorer	= restorer_sym(exec_mem_hint, __export_unmap_trampoline);
-#else
-	restore_task_exec_start		= restorer_sym(exec_mem_hint, __export_restore_task);
-	rsti(current)->munmap_restorer	= restorer_sym(exec_mem_hint, __export_unmap);
-#endif
+	restore_thread_exec_start	= restorer_sym(exec_mem_hint, arch_export_restore_thread);
+	restore_task_exec_start		= restorer_sym(exec_mem_hint, arch_export_restore_task);
+	rsti(current)->munmap_restorer	= restorer_sym(exec_mem_hint, arch_export_unmap);
 
 	exec_mem_hint += restorer_len;
 

include/restorer.h

@@ -195,6 +195,8 @@ enum {
 
 
 /* the restorer_blob_offset__ prefix is added by gen_offsets.sh */
-#define restorer_sym(rblob, name)	((void *)(rblob) + restorer_blob_offset__##name)
+#define __blob_offset(name)	restorer_blob_offset__ ## name
+#define _blob_offset(name)	__blob_offset(name)
+#define restorer_sym(rblob, name)	(void*)(rblob + _blob_offset(name))
 
 #endif /* __CR_RESTORER_H__ */