From: David Daney <ddaney@avtrex.com>
To: Thiemo Seufer <ths@networkno.de>
Cc: Daniel Jacobowitz <drow@false.org>, binutils@sourceware.org
Subject: Re: MIPS textrel fix
Date: Fri, 19 May 2006 09:26:00 -0000 [thread overview]
Message-ID: <446D11C7.2040008@avtrex.com> (raw)
In-Reply-To: <20060519001101.GA1073@networkno.de>
Thiemo Seufer wrote:
> David Daney wrote:
>
>>Daniel Jacobowitz wrote:
>>
>>>While stuck offline earlier today, I revisited the textrel-1 MIPS
>>>failure. Eric originally tried setting DF_TEXTREL during section
>>>relocation, but it's too late: we add the entry in size_dynamic_sections.
>>>But I couldn't see any other way to get it right, since there's no
>>>hook to predict whether elf-eh-frame.c will eliminate a relocation.
>>>
>>>The easiest approach I found was to annul the DT_TEXTREL and DT_FLAGS
>>>changes in finish_dynamic_sections if no text relocations were
>>>actually generated. This is not immensely pretty, but does work.
>>>OK?
>>>
>>>For background, the problem arises from the use of absolute addresses
>>>in .eh_frame. In this case, they're being produced by gas CFI
>>>directives. Is there a reason we can't mix and match encodings?
>>>i.e. why not have gas use a PC-relative format? I'm sure there's
>>>a reason, but I can't think of it...
>>>
>>
>>Could it be related to the reason that GCC no longer generates a
>>PC-relative .eh_frame?
>>
>>I never fully understood the reason, but I think it has to do with
>>MIPS-ELF specifications not allowing the needed relocation types (even
>>though they work well in binutils/glibc/linux).
>
>
> The needed relocation types were originally defined for embedded PIC
> MIPS and are not available in the ABI spec, their use for eh_frame
> was an accident. When the removal of embedded PIC support broke the
> toolchain, the fix chosen was to become ABI compatible again.
>
Not to beat a dead horse, but it would be nice to have a gnu extension
that allows us to have read-only eh_frame sections. Large C++ shared
libraries have way to many relocations. It is a lot of dirty pages in
the name of ABI compliance.
David Daney.
next prev parent reply other threads:[~2006-05-19 0:31 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-05-19 0:37 Daniel Jacobowitz
2006-05-19 0:50 ` Daniel Jacobowitz
2006-05-19 6:09 ` Eric Christopher
2006-05-19 9:03 ` David Daney
2006-05-19 9:12 ` Thiemo Seufer
2006-05-19 9:26 ` David Daney [this message]
2006-05-19 10:18 ` Eric Christopher
2006-05-22 20:28 ` Daniel Jacobowitz
2006-05-22 20:28 ` Thiemo Seufer
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=446D11C7.2040008@avtrex.com \
--to=ddaney@avtrex.com \
--cc=binutils@sourceware.org \
--cc=drow@false.org \
--cc=ths@networkno.de \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).