Using section flags to indicate strip or persistent sections

Using section flags to indicate strip or persistent sections

[Nick Clifton]

Hi Guys,

   We would like to suggest an extension the ELF section flags which can be
   used to indicate sections that should, or should not, be stripped when
   removing debug information.

   The problem we are trying to address is that different stripping tools
   (strip, eu-strip, llvm-strip) have different heuristics for deciding
   which sections should be removed when stripping debug information.  In
   order to fix this we are proposing two new section flags:

     GNU_SHF_CAN_BE_STRIPPED
     GNU_SHF_DO_NOT_STRIP

   These would be set by the assembler and/or linker to indicate sections
   that should be removed when stripping and sections which must not be
   removed when stripping.  It would be an error if both flags were present
   on a given section, and if neither flag is present then the stripping
   tool would fall back on its built in heuristics.

   In addition we need new flags for the assembler's .section directive
   (suggestion: 'D': can be stripped, 'K' do not strip).
   This email is to ask if you think that this idea has merit, and if so,
   are there any guidelines for writing and submitting a formal specification ?

Cheers
   Nick

Re: Using section flags to indicate strip or persistent sections

[Florian Weimer]

* Nick Clifton via Gnu-gabi:

>   We would like to suggest an extension the ELF section flags which can be
>   used to indicate sections that should, or should not, be stripped when
>   removing debug information.
>
>   The problem we are trying to address is that different stripping tools
>   (strip, eu-strip, llvm-strip) have different heuristics for deciding
>   which sections should be removed when stripping debug information.  In
>   order to fix this we are proposing two new section flags:
>
>     GNU_SHF_CAN_BE_STRIPPED
>     GNU_SHF_DO_NOT_STRIP
>
>   These would be set by the assembler and/or linker to indicate sections
>   that should be removed when stripping and sections which must not be
>   removed when stripping.  It would be an error if both flags were present
>   on a given section, and if neither flag is present then the stripping
>   tool would fall back on its built in heuristics.
>
>   In addition we need new flags for the assembler's .section directive
>   (suggestion: 'D': can be stripped, 'K' do not strip).
>   This email is to ask if you think that this idea has merit, and if so,
>   are there any guidelines for writing and submitting a formal specification ?

(Cc: list fixed, hence full quote.)

I think making this explicit is a good idea in principle.  However, I'm
not sure if the flags convey sufficient information to decide whether a
section should be removed as part of debuginfo stripping.  I think that
needs at least one flag that says, “this section should be removed or
separated as part of default debuginfo processing”.

Some use-cases involve non-removable non-allocated sections, too, but
that would be something different.

Thanks,
Florian

Re: Using section flags to indicate strip or persistent sections

[Jose E. Marchesi]

> * Nick Clifton via Gnu-gabi:
>
>>   We would like to suggest an extension the ELF section flags which can be
>>   used to indicate sections that should, or should not, be stripped when
>>   removing debug information.
>>
>>   The problem we are trying to address is that different stripping tools
>>   (strip, eu-strip, llvm-strip) have different heuristics for deciding
>>   which sections should be removed when stripping debug information.  In
>>   order to fix this we are proposing two new section flags:
>>
>>     GNU_SHF_CAN_BE_STRIPPED
>>     GNU_SHF_DO_NOT_STRIP

I think the "can be" in the GNU_SHF_CAN_BE_STRIPPED name is confusing
given the indicated semantics.

Wouldn't be better to call that flag GNU_SHF_STRIP instead?

>>   These would be set by the assembler and/or linker to indicate sections
>>   that should be removed when stripping and sections which must not be
>>   removed when stripping.  It would be an error if both flags were present
>>   on a given section, and if neither flag is present then the stripping
>>   tool would fall back on its built in heuristics.
>>
>>   In addition we need new flags for the assembler's .section directive
>>   (suggestion: 'D': can be stripped, 'K' do not strip).
>>   This email is to ask if you think that this idea has merit, and if so,
>>   are there any guidelines for writing and submitting a formal specification ?
>
> (Cc: list fixed, hence full quote.)
>
> I think making this explicit is a good idea in principle.  However, I'm
> not sure if the flags convey sufficient information to decide whether a
> section should be removed as part of debuginfo stripping.  I think that
> needs at least one flag that says, “this section should be removed or
> separated as part of default debuginfo processing”.
>
> Some use-cases involve non-removable non-allocated sections, too, but
> that would be something different.
>
> Thanks,
> Florian

Re: Using section flags to indicate strip or persistent sections

[Jose E. Marchesi]

> Hi Guys,
>
>   We would like to suggest an extension the ELF section flags which can be
>   used to indicate sections that should, or should not, be stripped when
>   removing debug information.
>
>   The problem we are trying to address is that different stripping tools
>   (strip, eu-strip, llvm-strip) have different heuristics for deciding
>   which sections should be removed when stripping debug information.  In
>   order to fix this we are proposing two new section flags:
>
>     GNU_SHF_CAN_BE_STRIPPED
>     GNU_SHF_DO_NOT_STRIP
>
>   These would be set by the assembler and/or linker to indicate sections
>   that should be removed when stripping and sections which must not be
>   removed when stripping.  It would be an error if both flags were present
>   on a given section, and if neither flag is present then the stripping
>   tool would fall back on its built in heuristics.

I think the "can be" in the GNU_SHF_CAN_BE_STRIPPED name is confusing
given the indicated semantics.

Wouldn't be better to call that flag GNU_SHF_STRIP instead?

>   In addition we need new flags for the assembler's .section directive
>   (suggestion: 'D': can be stripped, 'K' do not strip).
>   This email is to ask if you think that this idea has merit, and if so,
>   are there any guidelines for writing and submitting a formal specification ?
>
> Cheers
>   Nick