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pc-bios/s390-ccw: zero out bss section

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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)

Let's fix this once and forever by letting the BIOS zero the bss itself.

Suggested-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Message-Id: <20171122142627.73170-3-borntraeger@de.ibm.com>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Cornelia Huck <cohuck@redhat.com>
This commit is contained in:
Christian Borntraeger 2017-11-22 15:26:27 +01:00 committed by Cornelia Huck
parent 39b28b26cf
commit 339686a358
1 changed files with 27 additions and 3 deletions
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30
pc-bios/s390-ccw/start.S
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@ -3,7 +3,7 @@
* into the pc-bios directory of qemu.
*
* Copyright (c) 2013 Alexander Graf <agraf@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)