restore: Preliminary scheme for restore

Signed-off-by: Cyrill Gorcunov <gorcunov@gmail.com>

include/restorer.h

@@ -4,7 +4,7 @@
 #include "image.h"
 
 #define RESTORER_ARGS_SIZE	512
-#define RESTORER_SIZE		4096
+#define RESTORER_SIZE		8192
 
 long restorer(long cmd);
 
@@ -14,6 +14,7 @@ enum {
 	RESTORER_CMD__NONE,
 	RESTORER_CMD__GET_ARG_OFFSET,
 	RESTORER_CMD__PR_ARG_STRING,
+	RESTORER_CMD__RESTORE_CORE,
 	RESTORER_CMD__MAX,
 };
 

restorer.c

@@ -56,6 +56,41 @@ long restorer(long cmd)
 			: "memory");
 		break;
 
+	/*
+	 * This one is very special, we never return there
+	 * but use sigreturn facility to restore core registers
+	 * and jump execution to some predefined ip read from
+	 * core file.
+	 */
+	case RESTORER_CMD__RESTORE_CORE:
+	{
+		/*
+		 * Unmap all but self, note that we reply on
+		 * caller that it has placed this execution
+		 * code at the VMA which we can keep mapped.
+		 */
+
+		/*
+		 * Map VMAs we will need.
+		 */
+
+		/*
+		 * Threads here with registers and pids
+		 * we need.
+		 */
+
+		/*
+		 * Setup a sigreturn frame.
+		 */
+
+		/* Finally call for sigreturn */
+		sys_rt_sigreturn();
+	}
+		break;
+
+	default:
+		ret = -1;
+		break;
 	}
 
 	asm volatile(".align "__stringify(RESTORER_SIZE));