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Re: .debug_frame section - incorrect relocations?
- From: Alexey Neyman <stilor at att dot net>
- To: Ian Lance Taylor <iant at google dot com>
- Cc: Binutils <binutils at sourceware dot org>
- Date: Fri, 06 Dec 2013 22:40 -0800
- Subject: Re: .debug_frame section - incorrect relocations?
- Authentication-results: sourceware.org; auth=none
- References: <1466157 dot ehQ2qqM5T4 at mistral> <CAKOQZ8wuE+fB_Fj5t24QcDU+0x0m7ctLTJSDo4Xk2iNEF-Ndhg at mail dot gmail dot com>
On Friday, December 06, 2013 07:44:32 AM Ian Lance Taylor wrote:
> On Thu, Dec 5, 2013 at 11:38 PM, Alexey Neyman <stilor@att.net> wrote:
> > So, the question is, is it possible to express the behavior described by
> > DWARF spec ("insert an address that is offset of the specified symbol
> > from the start of the specified output section") in x86-64 and i386
> > relocations? If it is, shouldn't gas generate such relocations?
>
> There is no straightforward way to express that in an object file.
>
> > If not - are there any solutions to have .debug_frame at non-zero address,
> > yet with DWARF-conformat CIE links?
>
> I'm not aware of any. DWARF sections are normally at address zero.
Thanks. Actually, this gave me an idea how to handle this using the AT(...)
attribute in the linker script:
__debug_frame_start = ALIGN(8);
.debug_frame 0 : AT(__debug_frame_start) { *(.debug_frame) }
. = __debug_frame_start + SIZEOF(.debug_frame);
__debug_frame_end = .;
> If you are really only concerned about the .debug_frame section, you
> should be looking instead at the .eh_frame section, which is loaded
> into memory, and uses a slightly different format. I don't know if it
> will provide everything you need, though.
>
> If you do need full debug info, then you'll have to tweak your DWARF
> reader to adjust by the base of the debug sections as appropriate.
No, I've just started with .debug_frame, but I'll need other .debug_* sections
as well. They have the same issue, as far as I understand, so the linker
script above seems to be more general solution (than tweak all specifications
of "offset from the start of the section").
Regards,
Alexey.
>
> Ian