Dwarf 5, 7.3.1 "A DWARF expression may contain a DW_OP_addr (see Section 2.5.1.1 on 31 page 26) which contains a location within the virtual address space of the 32 program, and require relocation."
On Mon, Sep 24, 2018 at 10:35 AM Robert Harris via Dwarf-Discuss < dwarf-discuss@lists.dwarfstd.org> wrote: > > > > On 24 Sep 2018, at 16:59, Greg Clayton <clayb...@gmail.com> wrote: > > > > > > > >> On Sep 24, 2018, at 8:44 AM, Robert Harris <robert.m.har...@oracle.com> > wrote: > >> > >> > >> > >>> On 24 Sep 2018, at 15:33, Greg Clayton <clayb...@gmail.com> wrote: > >>> > >>> > >>> > >>>> On Sep 24, 2018, at 7:15 AM, Robert Harris via Dwarf-Discuss < > dwarf-discuss@lists.dwarfstd.org> wrote: > >>>> > >>>> I'd like some clarification regarding what precisely needs to be > relocated relative to > >>>> the object load address when interpreting .debug_frame. I'm > interested in versions > >>>> 2, 3 and 4. > >>>> > >>>> I think the only explicit mention of relocation in DWARF 4 is ยง 6.4.1: > >>>> > >>>> Abstractly, this mechanism describes a very large table... > >>>> ... > >>>> The first column indicates an address for every location that > contains > >>>> code in a program. (In shared objects, this is an object-relative > offset.) > >>>> > >>>> Thus adjustments need to be made to only > >>>> > >>>> An FDE's initial_location field > >>>> DW_CFA_set_loc's operand > >>>> > >>>> Have I missed anything? I see some ambiguity in the definition of > >>>> DW_CFA_def_cfa_expression and it's making me wonder if there are any > >>>> other occasions when a result would require relocation. > >>> > >>> Any DWARF expression can contain a DW_OP_addr, which has an address > argument, and would need to be relocated. > >> > >> Do you mean that DW_OP_addr's argument should be relocated in all > instances > >> of a DWARF expression, i.e. in other .debug_ sections, or just in the > context of > >> .debug_frame? > > > > I was specifically talking about DWARF expressions in any .debug_frame > info. > > Well, that would preclude relocating the *result* of any DWARF expression > in > .debug_frame. For some expressions, e.g. DW_CFA_expression, the use > of the CFA to initialise the stack implies as much but this would be a > useful > blanket constraint. > > > > But in general, yes, any DWARF expression that contains a DW_OP_addr > might need a relocation for its address argument. > > Are you aware of where in the standard this is documented? It sounds > reasonable > but I'm returning to this after a long time and I don't remember my way > around as > well as I used to. > > _______________________________________________ > Dwarf-Discuss mailing list > Dwarf-Discuss@lists.dwarfstd.org > http://lists.dwarfstd.org/listinfo.cgi/dwarf-discuss-dwarfstd.org >
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