base: ABI specific stack creation

ref #1042

base/include/arm/cpu/consts.h

@@ -17,11 +17,17 @@
 #include <base/stdint.h>
 
 namespace Abi {
+
 	/**
 	 * On ARM a call (or branch) will not change the stack pointer, so we do not
 	 * need stack adjustment
 	 */
 	static constexpr Genode::size_t stack_adjustment() { return 0; }
+
+	/**
+	 * Do ABI specific initialization to a freshly created stack
+	 */
+	inline void init_stack(Genode::addr_t) { }
 }
 
 #endif /* _INCLUDE__ARM__CPU__CONSTS_H_ */

base/include/x86/cpu/consts.h

@@ -39,6 +39,20 @@ namespace Abi {
 	 * On x86 a call will result in a growth of the stack by machine word size
 	 */
 	static constexpr Genode::size_t stack_adjustment() { return sizeof(Genode::addr_t); }
+
+	/**
+	 * Do ABI specific initialization to a freshly created stack
+	 *
+	 * \param stack_top  top of the stack
+	 */
+	inline void init_stack(Genode::addr_t const stack_top)
+	{
+		/*
+		 * The value at the top of the stack might get interpreted as return
+		 * address of the thread start function by GDB, so we set it to 0.
+		 */
+		*(Genode::addr_t *)stack_top = 0;
+	}
 }
 
 #endif /* _INCLUDE__X86__CPU__CONSTS_H_ */

base/src/base/thread/thread.cc

@@ -91,12 +91,7 @@ Thread_base::_alloc_context(size_t stack_size, bool main_thread)
 	context->stack_base  = ds_addr;
 	context->ds_cap      = ds_cap;
 
-	/*
-	 * The value at the top of the stack might get interpreted as return
-	 * address of the thread start function by GDB, so we set it to 0.
-	 */
-	*(addr_t*)context->stack_top() = 0;
-
+	Abi::init_stack(context->stack_top());
 	return context;
 }