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Re: [PATCH] x86/boot: adjust text gap/diff to work with 64-bytes alignment too
- To: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Thu, 9 Jan 2025 15:50:52 +0100
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- Cc: Frediano Ziglio <frediano.ziglio@xxxxxxxxx>, Roger Pau Monné <roger.pau@xxxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxxx, Marek Marczykowski-Górecki <marmarek@xxxxxxxxxxxxxxxxxxxxxx>
- Delivery-date: Thu, 09 Jan 2025 14:50:59 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 09.01.2025 14:44, Andrew Cooper wrote:
> On 09/01/2025 1:23 pm, Jan Beulich wrote:
>> On 09.01.2025 14:15, Marek Marczykowski-Górecki wrote:
>>> Xen compiled with -mtune=generic has .text alignment set to 64-bytes.
>>> Having text_diff non-64-bytes-aligned breaks stuff:
>>>
>>> Traceback (most recent call last):
>>> File
>>> "/builddir/build/BUILD/xen-4.20.0-build/xen-4.20.0-rc0/xen/./tools/combine_two_binaries.py",
>>> line 96, in <module>
>>> raise Exception('File sizes do not match')
>>> Exception: File sizes do not match: 70160 != 4080 + 66048
>>>
>>> Adjust the numbers as suggested by Frediano to work with 64-bytes and
>>> even 128-bytes alignment.
>> And then breaking at 256? As indicated on Matrix, imo we should be able to
>> cope with anything up to at least PAGE_SIZE. Or we should reduce .text
>> alignment before linking.
>
> Do you have a concrete proposal on how to do this?
The latter suggestion would involve objcopy's --set-section-alignment,
the former would involve using constants with the low 12 bits clear.
> Because if not, we've had 2 downstreams hit by this build failure, and
> we probably ought to take this patch as a stopgap fix, and see about
> doing the better fix for 4.20.
4.21 that is, I guess. I never like such very much, because it's too
likely that it'll then be forgotten.
Jan
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