llvm dev - Nov 2011 - [LLVMdev] How to get ELF section virtual starting address from MCSymbolRefExpr?

I have a case where I the expression (MCSymbolRefExpr) is the offset from the
beginning of the section.

The need is to combine that offset to the virtual address of the section it
belongs, in this case .text, but it could be any section.

I can get a MCSectionELF class object from MCSymbol that I get from
MCSymbolRefExpr:

  int Kind = Value->getKind();
  if (Kind == MCExpr::SymbolRef) {
    const MCSymbol &Sym = SRE->getSymbol();
    const MCSectionELF = dyn_cast_or_null<MCSectionELF>(Sym.getSection());
  }

But can't see how to get the virtual address of the section. This is odd
since I would have expected methods for accessing every part of the ELF section
header entry.

How does one get the virtual address (sh_addr in ELF) starting from a
MCSymbolRefExpr?

Thanks,

Jack
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On 11-11-17 12:32 PM, Carter, Jack wrote:
> I have a case where I the expression (MCSymbolRefExpr) is the offset
> from the beginning of the section.
>
> The need is to combine that offset to the virtual address of the section
> it belongs, in this case .text, but it could be any section.
>
> I can get a MCSectionELF class object from MCSymbol that I get from
> MCSymbolRefExpr:
>
> int Kind = Value->getKind();
> if (Kind == MCExpr::SymbolRef) {
> const MCSymbol &Sym = SRE->getSymbol();
> const MCSectionELF =
dyn_cast_or_null<MCSectionELF>(Sym.getSection());
> }
>
> But can't see how to get the virtual address of the section. This is
odd
> since I would have expected methods for accessing every part of the ELF
> section header entry.
>
> How does one get the virtual address (sh_addr in ELF) starting from a
> MCSymbolRefExpr?
The offset is not know until relaxation. You probably want an expression 
that is (cur_label - label_at_section_start), no?
> Thanks,
>
> Jack
>
Cheers,
Rafael