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

[Florian Schmidt <Florian.Schmidt@xxxxxxxxx>]

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?
> +__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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