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Re: [GOLD] PowerPC recreate eh_frame for stubs on each relax pass
- From: Cary Coutant <ccoutant at gmail dot com>
- To: Alan Modra <amodra at gmail dot com>
- Cc: Binutils <binutils at sourceware dot org>
- Date: Mon, 31 Jul 2017 11:26:17 -0700
- Subject: Re: [GOLD] PowerPC recreate eh_frame for stubs on each relax pass
- Authentication-results: sourceware.org; auth=none
- References: <20170731101950.GI1956@bubble.grove.modra.org>
> There is a very small but non-zero probability that a stub group
> contains stubs on one relax pass, but does not on the next. In that
> case we would get an FDE covering a zero length address range.
> (Actually, it's even worse. Alignment padding for stubs can mean the
> address for the non-existent stubs is past the end of the original
> section to which stubs are attached, and due to the way
> do_plt_fde_location calculates the length we can get a negative
> length.) Fixing this properly requires removing the FDE.
>
> Also, I have been implementing the __tls_get_addr_opt support for
> gold, and that stub needs something other than the default FDE. The
> necessary FDE will depend on the offset to the __tls_get_addr_opt
> stub, which of course can change during relaxation. That means at the
> very least, rewriting the FDE on each pass, possibly changing the FDE
> size. I think that is better done by completely recreating PLT
> eh_frame FDEs.
>
> OK?
>
> * ehframe.cc (Fde::operator==): New.
> (Cie::remove_fde, Eh_frame::remove_ehframe_for_plt): New.
> * ehframe.h (Fde::operator==): Declare.
> (Cie::remove_fde, Eh_frame::remove_ehframe_for_plt): Likewise.
> * layout.cc (Layout::remove_eh_frame_for_plt): New.
> * layout.h (Layout::remove_eh_frame_for_plt): Declare.
> * powerpc.cc (Target_powerpc::do_relax): Remove old eh_frame FDEs.
> (Stub_table::add_eh_frame): Delete eh_frame_added_ condition.
> Don't add eh_frame for empty stub section.
> (Stub_table::remove_eh_frame): New.
This is OK. Thanks!
-cary