Re: [PATCH] EFI: strip xen.efi when putting it on the EFI partition

[Jan Beulich <jbeulich@xxxxxxxx>]

On 07.07.2022 13:58, Wei Chen wrote:
> Hi Jan,
> 
> On 2022/7/6 13:44, Henry Wang wrote:
>> Hi Jan,
>>
>>> -----Original Message-----
>>> Subject: Re: [PATCH] EFI: strip xen.efi when putting it on the EFI partition
>>>
>>> On 09.06.2022 17:52, Jan Beulich wrote:
>>>> With debug info retained, xen.efi can be quite large. Unlike for xen.gz
>>>> there's no intermediate step (mkelf32 there) involved which would strip
>>>> debug info kind of as a side effect. While the installing of xen.efi on
>>>> the EFI partition is an optional step (intended to be a courtesy to the
>>>> developer), adjust it also for the purpose of documenting what distros
>>>> would be expected to do during boot loader configuration (which is what
>>>> would normally put xen.efi into the EFI partition).
>>>>
>>>> Model the control over stripping after Linux'es module installation,
>>>> except that the stripped executable is constructed in the build area
>>>> instead of in the destination location. This is to conserve on space
>>>> used there - EFI partitions tend to be only a few hundred Mb in size.
>>>>
>>>> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
>>>> ---
>>>> GNU strip 2.38 appears to have issues when acting on a PE binary:
>>>> - file name symbols are also stripped; while there is a separate
>>>>    --keep-file-symbols option (which I would have thought to be on by
>>>>    default anyway), its use so far makes no difference,
>>>> - the string table grows in size, when one would expect it to retain its
>>>>    size (or shrink),
>>>> - linker version is changed in and timestamp zapped from the header.
>>>> Older GNU strip (observed with 2.35.1) doesn't work at all ("Data
>>>> Directory size (1c) exceeds space left in section (8)").
>>>>
>>>> Future GNU strip is going to honor --keep-file-symbols (and will also
>>>> have the other issues fixed). Question is whether we should use that
>>>> option (for the symbol table as a whole to make sense), or whether
>>>> instead we should (by default) strip the symbol table as well.
>>>
>>> Without any feedback / ack I guess I'll consider this of no interest
>>> (despite having heard otherwise, triggering me to put together the
>>> patch in the first place), and put on the pile of effectively
>>> rejected patches.
>>
>> I did a test for this patch on my x86 machine and I think this patch is
>> doing the correct thing, so:
>>
>> Tested-by: Henry Wang <Henry.Wang@xxxxxxx>
>>
> 
> Because there was no Arm EFI environment in hand at the time, Henry only 
> tested the x86 part.I have setup an Arm platform with UEFI v2.70 (EDK 
> II, 0x00010000) today, and this patch works well when boot Xen as an EFI 
> application from UEFI shell.
> 
> But the binaries sizes are the same with/without this patch. Is it expected?
> I have enabled:
> CONFIG_DEBUG=y
> CONFIG_DEBUG_INFO=y

Well, the way "xen" is built (and "xen.efi" only being an alias
thereof), debug info is stripped in the course. That's quite
different from x86, where - with a new enough linker - debug info
is retained while linking (and it is truly linking by which
xen.efi is built), and hence can make sense to strip while
installing.

> Is there anything I should be aware to test this patch?
> 
> -rwxrwxr-x 1 weic weic 1081504 Jul  7 18:43 xen
> -rwxrwxr-x 1 weic weic 1081504 Jul  7 19:43 xen
> 
> Tested-by (Arm only): Wei Chen <Wei.Chen@xxxxxxx>

Thanks. Btw the proper form of the tag, as of a couple of months
ago, is

Tested-by: Wei Chen <Wei.Chen@xxxxxxx> # arm

Jan