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Re: [PATCH, MIPS] Support shared library debug with MIPS PIE
- From: "Maciej W. Rozycki" <macro at linux-mips dot org>
- To: Matthew Fortune <Matthew dot Fortune at imgtec dot com>
- Cc: "binutils at sourceware dot org" <binutils at sourceware dot org>
- Date: Tue, 23 Jun 2015 17:14:20 +0100 (BST)
- Subject: Re: [PATCH, MIPS] Support shared library debug with MIPS PIE
- Authentication-results: sourceware.org; auth=none
- References: <6D39441BF12EF246A7ABCE6654B0235321175C6A at LEMAIL01 dot le dot imgtec dot org>
On Tue, 23 Jun 2015, Matthew Fortune wrote:
> New dynamic tag:
> DT_MIPS_RLD_MAP2 - 0x70000035
> This member is used by debugging. It contains a relative offset from the tag's
> runtime location of a 32-bit word in the .data section which is supplied by the
> compilation environment. The word's contents are not specified and programs
> using this value are not ABI - compliant.
> I have considered the suggestion from Roland and Maciej about making this a GNU
> tag. MIPS needs this feature because of the way the psABI is defined and will
> therefore need this for any OS which may well then lead to needing more tags.
> If the tag were in the completely generic range (like DT_DEBUG) then I wouldn't
> be concerned at all.
We've been using GNU extensions (e.g. GNU ELF attributes) for other
purposes with no concern whatsoever about other OSes. And they are free
to adopt them. So what is your specific concern about DT_GNU_RLD_MAP?
With that in mind and given that this is a generic feature to support PIE
while keeping the dynamic segment r/o, do you maintain it would better go
with the ELF gABI rather than as a GNU extension? I suspect with a good
justification, that I believe we have here, reserving a dynamic tag number
with the gABI maintainers shouldn't take a lot of time or effort.