From 433a2169193a1c568b4d5e02f0604e51339b6085 Mon Sep 17 00:00:00 2001
From: Sebastian Sumpf <sebastian.sumpf@genode-labs.com>
Date: Thu, 20 Feb 2014 11:27:26 +0100
Subject: [PATCH] base: Fix stack pointer alignment for ARM

After some research we found that the stack pointer on ARM platforms must be
at least double word aligned (See: "Procedure Call Standard for the ARM
Architecture" - 5.2.1.1). Since a 'call' on ARM will not result in a stack pointer
change (like on x86), the current behavior resulted in a 4 Byte aligned stack
only.

Follow up to #1043
---
 base/include/arm/cpu/consts.h | 27 +++++++++++++++++++++++++++
 base/include/base/thread.h    |  5 +++--
 base/include/x86/cpu/consts.h |  9 +++++++++
 3 files changed, 39 insertions(+), 2 deletions(-)
 create mode 100644 base/include/arm/cpu/consts.h

diff --git a/base/include/arm/cpu/consts.h b/base/include/arm/cpu/consts.h
new file mode 100644
index 0000000000..39758f6ba5
--- /dev/null
+++ b/base/include/arm/cpu/consts.h
@@ -0,0 +1,27 @@
+/*
+ * \brief  Constants definitions for the ARM architecture.
+ * \author Sebastian Sumpf
+ * \date   2014-02-20
+ */
+
+/*
+ * Copyright (C) 2011-2013 Genode Labs GmbH
+ *
+ * This file is part of the Genode OS framework, which is distributed
+ * under the terms of the GNU General Public License version 2.
+ */
+
+#ifndef _INCLUDE__ARM__CPU__CONSTS_H_
+#define _INCLUDE__ARM__CPU__CONSTS_H_
+
+#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; }
+}
+
+#endif /* _INCLUDE__ARM__CPU__CONSTS_H_ */
diff --git a/base/include/base/thread.h b/base/include/base/thread.h
index 4f1799a7b4..7fbb96845a 100644
--- a/base/include/base/thread.h
+++ b/base/include/base/thread.h
@@ -59,6 +59,7 @@
 #include <base/lock.h>
 #include <base/native_types.h>
 #include <base/trace/logger.h>
+#include <cpu/consts.h>
 #include <util/string.h>
 #include <util/bit_allocator.h>
 #include <ram_session/ram_session.h>  /* for 'Ram_dataspace_capability' type */
@@ -103,12 +104,12 @@ namespace Genode {
 				 * Top of stack
 				 *
 				 * The alignment matches an initial stack frame, which is
-				 * sufficient for the AMD64 ABI (stack top + 8 is 16-byte
+				 * sufficient for the AMD64 ABI (stack top + adjustment is 16-byte
 				 * aligned).
 				 */
 				addr_t stack_top() const
 				{
-					return ((addr_t)_stack & ~0xf) - sizeof(addr_t);
+					return ((addr_t)_stack & ~0xf) - Abi::stack_adjustment();
 				}
 
 				/**
diff --git a/base/include/x86/cpu/consts.h b/base/include/x86/cpu/consts.h
index 1b3d89b772..d8c6edef2a 100644
--- a/base/include/x86/cpu/consts.h
+++ b/base/include/x86/cpu/consts.h
@@ -14,6 +14,8 @@
 #ifndef _INCLUDE__X86__CPU__CONSTS_H_
 #define _INCLUDE__X86__CPU__CONSTS_H_
 
+#include <base/stdint.h>
+
 namespace X86 {
 
 		enum Eflags_masks {
@@ -32,4 +34,11 @@ namespace X86 {
 
 }
 
+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); }
+}
+
 #endif /* _INCLUDE__X86__CPU__CONSTS_H_ */