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Re: [PATCH] x86: fold sections in final binaries
- To: "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Wed, 2 Mar 2022 09:50:50 +0100
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- Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Wei Liu <wl@xxxxxxx>, Roger Pau Monné <roger.pau@xxxxxxxxxx>
- Delivery-date: Wed, 02 Mar 2022 08:51:02 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 01.03.2022 09:55, Jan Beulich wrote:
> --- a/xen/arch/x86/xen.lds.S
> +++ b/xen/arch/x86/xen.lds.S
> @@ -194,6 +194,7 @@ SECTIONS
> #endif
> _sinittext = .;
> *(.init.text)
> + *(.text.startup)
> _einittext = .;
> /*
> * Here are the replacement instructions. The linker sticks them
> @@ -258,9 +259,10 @@ SECTIONS
>
> . = ALIGN(8);
> __ctors_start = .;
> - *(.ctors)
> + *(SORT_BY_INIT_PRIORITY(.init_array.*))
> + *(SORT_BY_INIT_PRIORITY(.ctors.*))
> *(.init_array)
> - *(SORT(.init_array.*))
> + *(.ctors)
> __ctors_end = .;
> } PHDR(text)
While I did commit the change with Roger's R-b, on the basis that it's not
going to make things worse, I don't think what we have here and what we do
in init_constructors() is quite right: For one .init_array and .ctors are
supposed to be processed in, respectively, opposite order - the former
forwards, the latter backwards. See e.g. gcc's libgcc/gbl-ctors.h. And
then both variants also shouldn't be intermixed; we ought to expect only
one of the two kinds, and aiui for now it's always going to be .ctors.
The processing in wrong order looks to not be a problem in the builds I
can check, as there's only ever a single priority used. But we're at risk
of this breaking down the road ...
Finally, if we consider .init_array might appear, we ought to also
discard (rather than leaving orphaned) .fini_array.
Jan
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