Re: [Minios-devel] [UNIKRAFT PATCH 1/2] plat: Add the eh_frame and eh_frame_hdr sections

[Florian Schmidt <Florian.Schmidt@xxxxxxxxx>]

Hi Vlad,

On 12/13/18 8:53 PM, Vlad-Andrei BĂDOIU (78692) wrote:
> Hey Florian,
>
> On 12/13/18 11:55 AM, Florian Schmidt wrote:
> > Hi Vlad,
> >
> > thanks for the patch! I have one question:
> >
> > On 12/12/18 6:08 PM, Vlad-Andrei BĂDOIU (78692) wrote:
> > > This patch adds the eh_frame and eh_frame hdr sections to
> > > the linker script for both XEN and KVM.
> > >
> > > A new linker script has been created plat/common/x86/link64.lds in
> > > order to avoid code duplication.
> > >
> > > This patch adds the frames to the linker scripts.
> > >
> > > Signed-off-by: Vlad-Andrei Badoiu <vlad_andrei.badoiu@xxxxxxxxxxxxxxx>
> > > ---
> > >    plat/common/x86/link64.lds | 51 ++++++++++++++++++++++++++++++++++++++
> > >    plat/kvm/x86/link64.lds    |  2 ++
> > >    plat/xen/x86/link64.lds    |  2 ++
> > >    3 files changed, 55 insertions(+)
> > >    create mode 100644 plat/common/x86/link64.lds
> > >
> > > diff --git a/plat/common/x86/link64.lds b/plat/common/x86/link64.lds
> > > new file mode 100644
> > > index 0000000..1b809c4
> > > --- /dev/null
> > > +++ b/plat/common/x86/link64.lds
> > > @@ -0,0 +1,51 @@
> > > +/* SPDX-License-Identifier: BSD-3-Clause */
> > > +/*
> > > + * Authors: Vlad-Andrei Badoiu <vlad_andrei.badoiu@xxxxxxxxxxxxxxx>
> > > + *
> > > + * Copyright (c) 2018, NEC Europe Ltd., NEC Corporation. All rights
> > > reserved.
> > > + *
> > > + * Redistribution and use in source and binary forms, with or without
> > > + * modification, are permitted provided that the following conditions
> > > + * are met:
> > > + *
> > > + * 1. Redistributions of source code must retain the above copyright
> > > + *    notice, this list of conditions and the following disclaimer.
> > > + * 2. Redistributions in binary form must reproduce the above copyright
> > > + *    notice, this list of conditions and the following disclaimer
> > > in the
> > > + *    documentation and/or other materials provided with the
> > > distribution.
> > > + * 3. Neither the name of the copyright holder nor the names of its
> > > + *    contributors may be used to endorse or promote products
> > > derived from
> > > + *    this software without specific prior written permission.
> > > + *
> > > + * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
> > > CONTRIBUTORS "AS IS"
> > > + * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
> > > TO, THE
> > > + * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
> > > PARTICULAR PURPOSE
> > > + * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR
> > > CONTRIBUTORS BE
> > > + * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
> > > + * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
> > > + * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
> > > BUSINESS
> > > + * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
> > > WHETHER IN
> > > + * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
> > > OTHERWISE)
> > > + * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
> > > ADVISED OF THE
> > > + * POSSIBILITY OF SUCH DAMAGE.
> > > + *
> > > + * THIS HEADER MAY NOT BE EXTRACTED OR MODIFIED IN ANY WAY.
> > > + */
> > > +
> > > +. = ALIGN(0x1000);
> > > +__eh_frame_start = .;
> > > +.eh_frame :
> > > +{
> > > +    *(.eh_frame)
> > > +    *(.eh_frame.*)
> > > +}
> > > +__eh_frame_end = .;
> > > +
> > > +. = ALIGN(0x1000);
> > I understand that the first alignment is probably necessary to make
> > sure you don't share a page with the read-write data coming before it
> > in the layout, but do you need such a large alignment before the hdr?
> > Can't the hdr and the frame share a page?
> Yes, hdr and eh_frame could share a page. I'll send a v2 of this patch
> with the in-between alignment removed, is that all right?
Yes, please. However, I would maybe wait for a review for the other 
file. It looks good to me, but I'd like Simon to give it just a 1-minute 
cursory look, because I'm not completely familiar with the logic of the 
memory regions code. So in case he has a remark, you can roll that into 
v2, too.
> > > +__eh_frame_hdr_start = .;
> > > +.eh_frame_hdr :
> > > +{
> > > +    *(.eh_frame_hdr)
> > > +    *(.eh_frame_hdr.*)
> > > +}
> > > +__eh_frame_hdr_end = .;
> > > diff --git a/plat/kvm/x86/link64.lds b/plat/kvm/x86/link64.lds
> > > index 60b5d21..c96f750 100644
> > > --- a/plat/kvm/x86/link64.lds
> > > +++ b/plat/kvm/x86/link64.lds
> > > @@ -41,6 +41,8 @@ SECTIONS
> > >        }
> > >        _etext = .;
> > >    +    INCLUDE plat/common/x86/link64.lds
> > > +
> > >        /* Read-only data */
> > >        . = ALIGN(0x1000);
> > >        _rodata = .;
> > > diff --git a/plat/xen/x86/link64.lds b/plat/xen/x86/link64.lds
> > > index 5391dbd..2e83de4 100644
> > > --- a/plat/xen/x86/link64.lds
> > > +++ b/plat/xen/x86/link64.lds
> > > @@ -39,6 +39,8 @@ SECTIONS
> > >          _etext = .;            /* End of text section */
> > >    +    INCLUDE plat/common/x86/link64.lds
> > > +
> > >        _rodata = .;
> > >        .rodata : {
> > >            *(.rodata)
--
Dr. Florian Schmidt
フローリアン・シュミット
Research Scientist,
Systems and Machine Learning Group
NEC Laboratories Europe
Kurfürsten-Anlage 36, D-69115 Heidelberg
Tel.     +49 (0)6221 4342-265
Fax:     +49 (0)6221 4342-155
e-mail:  florian.schmidt@xxxxxxxxx
============================================================
Registered at Amtsgericht Mannheim, Germany, HRB728558

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