[LLVMdev] [lld] How do I prevent .note sections from being eliminated?

[Tom Stellard]

On Tue, Jun 16, 2015 at 12:05:39PM +0300, Simon Atanasyan wrote:
> On Mon, Jun 15, 2015 at 6:12 PM, Tom Stellard <tom at stellard.net> wrote:
> > ELFFile::handleSectionWithNoSymbols() returns false for SHT_NOTE.  This
> > means that ELFFile::createAtoms() never creates an atom for .note sections.
> > It seems like even if I use something like SDataSection, then I will still
> > need to modify ELFFIle::handleSectionWithNoSymbols().  What is the best
> > way to do this?  Should I make the function virtual and override it in
> > AMDGPUELFFile.cpp?
> 
> Yes, you can make handleSectionWithNoSymbols() virtual and override it
> in ELFFile class descendant.
> 
> > In ELFDefinedAtom::doContentType(), SHT_NOTE sections are only assigned
> > the typeR[OW]Note ContentType if they have the SHF_ALLOC flag.  This is
> > because any section without SHF_ALLOC is assigned the typeNoAlloc
> > ContentType before the section type is ever considered.  Is this a bug
> > or are SHT_NOTE sections required to have the SHF_ALLOC flag?
> 
> It depends on your ABI requirement. If a .note section does not need
> to occupy memory during a process execution it should not have
> the SHF_ALLOC flag.
> 

What I want to do is emit a .note section *without* SHF_ALLOC.  However,
the current implementation won't let me do this, because it assigns the
section a content type of typeNoAlloc, rather than typeR[OW]Note.
I'm just wondering the best way to fix this.

-Tom

> -- 
> Simon Atanasyan