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Re: [Qemu-devel] [PATCH v2 0/2] s390x: Make the s390-ccw BIOS relocatabl
From: |
Christian Borntraeger |
Subject: |
Re: [Qemu-devel] [PATCH v2 0/2] s390x: Make the s390-ccw BIOS relocatable |
Date: |
Mon, 09 Mar 2015 16:21:40 +0100 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.5.0 |
Am 09.03.2015 um 11:12 schrieb Thomas Huth:
> Currently, our s390-ccw.img sits at the fix address 126 MiB in memory.
> This has two big disadvantages: 1) We can not start guests with less
> than 128 MiB RAM and 2) if the guest uses a really huge ramdisk > 126 MiB,
> the s390-ccw BIOS gets overwritten and the boot silently crashes.
>
> These two patches now fix these problems by relocating the s390-ccw
> BIOS to the end of the RAM. The basic idea here is to compile the
> BIOS with the "-fpie" compiler option to create position independent
> code. Sounds easy at a first glance - however, with -fpie, we only
> get position independent _code_ - and a so called GOT (global offset
> table) which contains absolute references to global variables again
> (this is normally needed for supporting dynamic libraries - in our
> s390-ccw BIOS, it's just bad luck that we get a GOT).
>
> So to be able to really move around our s390-ccw.img in RAM, we've got
> to relocate the entries in the GOT, too. This is what the first patch
> is good for. I've changed the ELF loader there to parse the reloc section
> of the ELF file. I only included the bare minimum of relocation types
> (R_390_RELATIVE) in the patch so far, but this can easily be extended
> in case we need more (with different compiler version etc.).
>
> The second patch then adds the required changes to the s390-ccw BIOS
> Makefile and our s390 ipl code in QEMU.
>
> v2:
> - Fixed endianess issues in the ELF relocation function
>
> Thomas Huth (2):
> elf-loader: Provide the possibility to relocate s390 ELF files
> s390/bios: Make the s390-ccw.img relocatable
>
> hw/core/loader.c | 2 +
> hw/s390x/ipl.c | 23 ++++++++++++-
> include/elf.h | 2 +
> include/hw/elf_ops.h | 78
> +++++++++++++++++++++++++++++++++++++++++++++
> pc-bios/s390-ccw/Makefile | 11 +++---
> 5 files changed, 109 insertions(+), 7 deletions(-)
>
Applied to s390-next.
Thanks