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Re: [Qemu-devel] [PATCH 2/2] pc-bios/s390-ccw: zero out bss section
From: |
Cornelia Huck |
Subject: |
Re: [Qemu-devel] [PATCH 2/2] pc-bios/s390-ccw: zero out bss section |
Date: |
Wed, 22 Nov 2017 15:45:19 +0100 |
On Wed, 22 Nov 2017 15:26:27 +0100
Christian Borntraeger <address@hidden> wrote:
> 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.
s/Lets/Let's/
:)
>
> Suggested-by: Alexander Graf <address@hidden>
> Signed-off-by: Christian Borntraeger <address@hidden>
> ---
> 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 <address@hidden>
> - * 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)
This looks like the right thing to do.
- [Qemu-devel] [PATCH 0/2] s390x fixes (post 2.11), Christian Borntraeger, 2017/11/22
- [Qemu-devel] [PATCH 1/2] s390x/migration: use zero flag parameter, Christian Borntraeger, 2017/11/22
- [Qemu-devel] [PATCH 2/2] pc-bios/s390-ccw: zero out bss section, Christian Borntraeger, 2017/11/22
- Re: [Qemu-devel] [PATCH 0/2] s390x fixes (post 2.11), Cornelia Huck, 2017/11/22
- Re: [Qemu-devel] [PATCH 0/2] s390x fixes (post 2.11), Cornelia Huck, 2017/11/22
- Re: [Qemu-devel] [PATCH 0/2] s390x fixes (post 2.11), no-reply, 2017/11/22