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Re: [PATCH 1/2] Add support for O32 FPXX ABI
- From: Richard Sandiford <rdsandiford at googlemail dot com>
- To: Matthew Fortune <Matthew dot Fortune at imgtec dot com>
- Cc: "macro\ at codesourcery dot com" <macro at codesourcery dot com>, "Joseph Myers \(joseph\ at codesourcery dot com\)" <joseph at codesourcery dot com>, "binutils\ at sourceware dot org" <binutils at sourceware dot org>, Rich Fuhler <Rich dot Fuhler at imgtec dot com>
- Date: Thu, 10 Apr 2014 09:30:44 +0100
- Subject: Re: [PATCH 1/2] Add support for O32 FPXX ABI
- Authentication-results: sourceware.org; auth=none
- References: <6D39441BF12EF246A7ABCE6654B023534DAAAB at LEMAIL01 dot le dot imgtec dot org> <87a9c0xkje dot fsf at talisman dot default> <6D39441BF12EF246A7ABCE6654B023534DC37D at LEMAIL01 dot le dot imgtec dot org> <87ha655s3i dot fsf at sandifor-thinkpad dot stglab dot manchester dot uk dot ibm dot com> <6D39441BF12EF246A7ABCE6654B023534DC8CF at LEMAIL01 dot le dot imgtec dot org> <871tx9z35k dot fsf at sandifor-thinkpad dot stglab dot manchester dot uk dot ibm dot com> <6D39441BF12EF246A7ABCE6654B023534DFC40 at LEMAIL01 dot le dot imgtec dot org>
Matthew Fortune <Matthew.Fortune@imgtec.com> writes:
> Richard Sandiford <firstname.lastname@example.org> writes:
>> Matthew Fortune <Matthew.Fortune@imgtec.com> writes:
>> > Perhaps call it PT_MIPS_ATTRIBUTES or PT_GNU_ATTRIBUTES if this were
>> > done for all architectures.
>> Yeah. Might as well make it PT_GNU_ATTRIBUTES, even if it's something
>> that targets have to buy into. Probably worth sending a separate RFC to
>> the list for that.
> I've had some discussion about this with Rich (now on cc). The current
> thinking is that we don't want to have the MIPS ABI any more dependent on
> the GNU attribute section but instead would prefer to migrate to a MIPS
> attribute section. In order to achieve the migration then we would have to
> do something like:
> 1) use the same attribute numbers for the FP abi and MSA abi as used in the
> GNU attributes section
> 2) At link time, if the FP or MSA attribute is set in the gnu attribute
> section then copy it to the MIPS attribute section (or if already set
> check they match)
> 3) In the output object only emit the MIPS attribute section (though I
> guess it would do no harm to emit both).
> 4) Perhaps emit both gnu and MIPS attributes in the assembler for
> backwards compatibility with older linkers. I think it would be
> sufficient to just do this when inferring an attribute from module options.
> The explicit .gnu_attribute and .mips_attribute would just set their
> Respective attributes but we would be phasing out the explicit use of such
> attributes anyway.
> How does that sound? If it is OK would you be happy to review other aspects
> of the patch under the assumption that the linker would use this newly
> proposed program header scheme on the executables? It will take a few days
> to rework this as I have to educate glibc about parsing attribute sections
> and retest.
I understand why you'd prefer a MIPS gloss to the section names but it
seems a bit late to change it now. Having the same information under
two different section names is just going to create a lot of unnecessary
Maybe the others on cc: feel more positively about it than me though.
Since the program header is new, calling it PT_MIPS_ATTRIBUTES would be
fine with me. I slightly prefered PT_GNU_ATTRIBUTES for consistency
with the section name but at least there'd be no compatibility problem
with treating as a MIPS-specific header. The meaning of the attributes
is target-dependent anyway.