The QEMU ELF loader does not zero the bss segment.
This resulted in several bugs, e.g. see
commit 5d739a4787a5 (s390-ccw.img: Fix sporadic errors with ccw boot image -
initialize css)
commit 6a40fa2669d3 (s390-ccw.img: Initialize next_idx)
commit 8775d91a0f42 (pc-bios/s390-ccw: Fix problem with invalid virtio-scsi LUN
when rebooting)
Lets fix this once and forever by letting the BIOS zero the bss itself.
Suggested-by: Alexander Graf <ag...@suse.de>
Signed-off-by: Christian Borntraeger <borntrae...@de.ibm.com>
---
pc-bios/s390-ccw/start.S | 30 +++++++++++++++++++++++++++---
1 file changed, 27 insertions(+), 3 deletions(-)
diff --git a/pc-bios/s390-ccw/start.S b/pc-bios/s390-ccw/start.S
index 43f9bd2..eb8d024 100644
--- a/pc-bios/s390-ccw/start.S
+++ b/pc-bios/s390-ccw/start.S
@@ -3,7 +3,7 @@
* into the pc-bios directory of qemu.
*
* Copyright (c) 2013 Alexander Graf <ag...@suse.de>
- * Copyright 2013 IBM Corp.
+ * Copyright IBM Corp. 2013, 2017
*
* This work is licensed under the terms of the GNU GPL, version 2 or (at
* your option) any later version. See the COPYING file in the top-level
@@ -13,8 +13,32 @@
.globl _start
_start:
-larl %r15, stack + 0x8000 /* Set up stack */
-j main /* And call C */
+ larl %r15, stack + 0x8000 /* Set up stack */
+
+ /* clear bss */
+ larl %r2, __bss_start
+ larl %r3, _end
+ slgr %r3, %r2 /* get sizeof bss */
+ ltgr %r3,%r3 /* bss emtpy? */
+ jz done
+ aghi %r3,-1
+ srlg %r4,%r3,8 /* how many 256 byte chunks? */
+ ltgr %r4,%r4
+ lgr %r1,%r2
+ jz remainder
+loop:
+ xc 0(256,%r1),0(%r1)
+ la %r1,256(%r1)
+ brctg %r4,loop
+remainder:
+ larl %r2,memsetxc
+ ex %r3,0(%r2)
+done:
+ j main /* And call C */
+
+memsetxc:
+ xc 0(1,%r1),0(%r1)
+
/*
* void disabled_wait(void)
--
2.9.4
