restore: Add restoration of alternative signal stack

To restore SAS we have two ways:
- call for sigaltstack explicitly in restorer.c right before we call for sigreturn
- pass stack value to sigreturn call and allow the kernel to restore stack for us

Since second way is a simplier one -- we stick with it.

[alekskartashov@: use RT_SIGFRAME_UC]
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
CC: Alexander Kartashov <alekskartashov@parallels.com>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

include/sigframe.h

@@ -5,6 +5,9 @@
 #ifndef __CR_SIGFRAME_H__
 #define __CR_SIGFRAME_H__
 
+#include "asm/types.h"
+#include "protobuf/core.pb-c.h"
+
 struct rt_sigframe;
 
 #ifndef __ARCH_SI_PREAMBLE_SIZE
@@ -43,4 +46,18 @@ extern int construct_sigframe(struct rt_sigframe *sigframe,
 			      struct rt_sigframe *rsigframe,
 			      CoreEntry *core);
 
+/*
+ * FIXME Convert it to inline helper, which requires
+ *	 to unweave types mess we've generated for
+ *	 run-time data.
+ */
+#define setup_sas(sigframe, sas)											\
+do {															\
+	if ((sas)) {													\
+		RT_SIGFRAME_UC((sigframe)).uc_stack.ss_sp	= (void *)decode_pointer((sas)->ss_sp);			\
+		RT_SIGFRAME_UC((sigframe)).uc_stack.ss_flags	= (int)(sas)->ss_flags;					\
+		RT_SIGFRAME_UC((sigframe)).uc_stack.ss_size	= (size_t)(sas)->ss_size;				\
+	}														\
+} while (0)
+
 #endif /* __CR_SIGFRAME_H__ */

sigframe.c

@@ -31,5 +31,7 @@ int construct_sigframe(struct rt_sigframe *sigframe,
 	if (restore_gpregs(sigframe, CORE_THREAD_ARCH_INFO(core)->gpregs))
 		return -1;
 
+	setup_sas(sigframe, core->thread_core->sas);
+
 	return 0;
 }