[Dwarf-Discuss] _starting address_ in eh_frame FDE encoding

Francesco Zappa Nardelli francesco.zappa.nardelli at gmail.com
Thu Mar 24 06:56:21 PDT 2016


Dear all

I have a question about the FDE encoding in eh_frame (and not dwarf_frame)
tables.

This document (I could not find a better description of eh_frame)

  http://www.airs.com/blog/archives/460

states that:

  "An FDE starts with the length and ID described above, and then continues
as follows.   1 The _starting address_ to which this FDE applies. This is
encoded using the FDE encoding specified by the associated CIE.”

In a sample elf file, the associated CIE augmentation data state reports:

   DW_EH_PE_pcrel, DW_EH_PE_sdata4

and the untranslated starting address value in the FDE is fffffe88
(according to readelf this should be translated to 4004d0).  I do not
understand what “value is PC relative” means here, as we are actually
defining the range of PC values.

Can somebody explain me how to interpret this _starting address_ field?

Thank you in advance.

-francesco
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