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Re: [RFC] Aligning segments in gold
- From: Cary Coutant <ccoutant at google dot com>
- To: Ian Lance Taylor <iant at google dot com>
- Cc: Binutils <binutils at sourceware dot org>
- Date: Fri, 9 Jan 2015 15:01:49 -0800
- Subject: Re: [RFC] Aligning segments in gold
- Authentication-results: sourceware.org; auth=none
- References: <CAHACq4r+uun3awgdM3VBybWF9+eC66C12mcMS2CyHm0k43bBPg at mail dot gmail dot com> <CAKOQZ8y2pjt=d0YgGRznmqXUPH=xUrVTW7bxaURa3D_o8op1bA at mail dot gmail dot com>
> (*p)->maximum_alignment is going to feed into the p_align field. It
> sounds like you are saying that it's OK if a phdr is not aligned
> according to what its p_align field says. Is that right?
Right. Segments aren't expected to begin at p_align boundaries (and
typically don't). From the gABI:
As ``Program Loading'' describes in this chapter of the processor
supplement, loadable process segments must have congruent values for
p_vaddr and p_offset, modulo the page size. This member gives the
value to which the segments are aligned in memory and in the file.
Values 0 and 1 mean no alignment is required. Otherwise, p_align
should be a positive, integral power of 2, and p_vaddr should equal
p_offset, modulo p_align.
While "This member gives the value to which the segments are aligned
in memory and in the file" might be read to imply otherwise, I think
the last sentence is generally understood to mean that p_offset and
p_vaddr are not individually required to be aligned at a p_align