[Bug binutils/29737] strip: section attributes to indicate strip or persistent sections

[guillermo.e.martinez at oracle dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=29737

--- Comment #6 from Guillermo E. Martinez <guillermo.e.martinez at oracle dot 
com> ---
(In reply to Nick Clifton from comment #5)
> (In reply to Guillermo E. Martinez from comment #4)
> Hi Guillermo,
>  

Hi Nick,

> > > Are you asking for strip to be able to keep or remove sections based upon
> > > their attributes, rather than their names ?   
> > 
> > Exactly. This bugzilla is to provide the feedback and support triggered by
> > the discussion for standardize a way to indicates whether sections should be
> > preserved or not after binutils strip/eu-strip execution without need to use
> > special arguments,  
> 
> OK, so lets assume that we restrict this to ELF format files only.
> 
> Basically the idea is, (I think...), we define a new section flag, eg:
> 
>   SHF_GNU_CAN_BE_STRIPPED
> 
> which would be set by the linker on any section that it believes is not
> necessary for proper execution of the binary.  (ie debug info sections,
> notes that are not needed by the loader, etc).  In addition tools like
> objcopy should be able to add or remove this flag from specific 
> sections at the behest of the user.
> 

Yes, that's right.

> The purpose of the flag is to tell tools like strip and eu-strip that the
> section can and should be removed or preserved when stripping or creating
> a debuginfo file.  (At the moment this decision is made by heuristics
> built into these tools, and the heuristics differ...)
> 

Yes. So basically sections in binutils strip are removed whether SEC_DEBUGGING
is set, it happens because section name contains: .debug,
.gnu.debuglto_.debug_,.gnu.linkonce.wi., .zdebug, .line, .stab, .gdb_index,
excluding: .gnu_debuglink and .gnu_debugaltlink. So, there is not a section
attribute to indicates if this section will removed or preserved.

> In order to support backwards compatibility with files that do not use
> this scheme, it will probably also be necessary to define a second flag:
> 
>   SHF_GNU_DO_NOT_STRIP
> 

Yes, I think so.

> Then the tools can detect sections which have not been annotated with this
> new feature and fall back on their old heuristics instead.
> 

Correct.

> -------------------------------------------------------------------------
> 
> Does that sound about right ?  
> 

Yes!.

> If so then I think that the proper way to proceed with this idea is to
> present it on the GNU gABI list (gnu-gabi@sourceware.org) rather than 
> discussing it inside a binutils PR.  Do you agree ?
> 

Agree, of course!. What will be next step to start working on it?

> Cheers
>   Nick

Thanks Nick,
guillermo

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