[PATCH] D79038: [objdump][ELF] Handle sections not contained in PT_LOAD segments

[Fangrui Song via Phabricator via llvm-commits]

MaskRay added a comment.

In D79038#2013052 <https://reviews.llvm.org/D79038#2013052>, @LemonBoy wrote:

> > What is actually the difference between them here?
>
> The difference doesn't really matter here as the segment PAddr and VAddr are zero, the test case passes by simply avoiding the `Sec.Addr` assigment for sections with non-PT_LOAD segments, that's why it's been suggested to patch `setParentSegment` and keep the old logic.
>  The added logic takes into account one more edge case, as explained by this comment in BFD:
>
>   /* We used to use the same adjustment for SEC_LOAD
>   		   sections, but that doesn't work if the segment
>   		   is packed with code from multiple VMAs.
>   		   Instead we calculate the section LMA based on
>   		   the segment LMA.  It is assumed that the
>   		   segment will contain sections with contiguous
>   		   LMAs, even if the VMAs are not.  */
>
>
> If you prefer a less-invasive patch I can simply go for the `setParentSegment` route.


I did some shallow analysis of bfd/elf.c's rules related to bfd_section::lma/file offset/etc. They are overly complex and I am pretty sure we can do better than them. Their distinction of PT_LOAD ver non-PT_LOAD is artificial and can really be simplified if they don't do that. I second to James that we should not make PT_LOAD different.

Unfortunately, the PT_GNU_RELRO use case (p_vaddr=p_paddr=0, large p_memsz) means we still have to specialize something. It seems that we can simply treat PT_GNU_RELRO as an (ugly) exception.


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