From 89e987b22ecd3dd38d6d519485421374016f30b1 Mon Sep 17 00:00:00 2001
From: Norman Feske <norman.feske@genode-labs.com>
Date: Thu, 16 Oct 2014 20:23:22 +0200
Subject: [PATCH] base/x86_32: preserve EBX value in crt0

---
 repos/base/src/platform/x86_32/crt0.s | 20 ++++++++++++--------
 1 file changed, 12 insertions(+), 8 deletions(-)

diff --git a/repos/base/src/platform/x86_32/crt0.s b/repos/base/src/platform/x86_32/crt0.s
index efedf4aca4..9b1dbd86cb 100644
--- a/repos/base/src/platform/x86_32/crt0.s
+++ b/repos/base/src/platform/x86_32/crt0.s
@@ -23,16 +23,17 @@
 	.global _start
 	_start:
 
-	/* initialize GOT pointer in EBX */
+	/* save initial register values using GOT-relative addressing */
 	3:
-	movl $., %ebx
-	addl $_GLOBAL_OFFSET_TABLE_ + (. - 3b) , %ebx
-	movl %esp, __initial_sp@GOTOFF(%ebx)
+	movl $., %ecx
+	addl $_GLOBAL_OFFSET_TABLE_ + (. - 3b) , %ecx
+	movl %esp, __initial_sp@GOTOFF(%ecx)
+	movl %eax, __initial_ax@GOTOFF(%ecx)
+	movl %ebx, __initial_bx@GOTOFF(%ecx)
+	movl %edi, __initial_di@GOTOFF(%ecx)
 
-	/* make initial value of some registers available to higher-level code */
-	mov %esp, __initial_sp
-	mov %eax, __initial_ax
-	mov %edi, __initial_di
+	/* initialize GOT pointer in EBX as expected by the tool chain */
+	mov %ecx, %ebx
 
 	/*
 	 * Install initial temporary environment that is replaced later by the
@@ -74,6 +75,9 @@
 	.global __initial_ax
 	__initial_ax:
 	.space 4
+	.global __initial_bx
+	__initial_bx:
+	.space 4
 	.global __initial_di
 	__initial_di:
 	.space 4