[PATCH 2/4] LD: Support fixed-size sections some psABIs may require

Maciej W. Rozycki macro@mips.com
Mon Feb 5 15:05:00 GMT 2018


Hi Nick,

> > Define a SEC_FIXED_SIZE section flag for target backends to use for 
> > output sections whose size has been fixed in the psABI.  The size of 
> > such sections will not be changed anyhow by the generic linker and it is 
> > up to the target backend to get their size right.
> 
> One thing that worries me is - should the linker issue a warning/error
> message if the user does attempt to change the size of a fixed-size section ?
> Or maybe only issue the message if the size change would make the section
> bigger than is allowed ?

 An error would defeat the purpose of this change, as what the change does 
is to ensure the size is fixed, by truncating or padding out the section 
concerned as required.  We currently abort, with an error, in the MIPS 
backend if one of the fixed-size sections turns out not to have the right 
size, and this patch changes it.

 A warning might make sense, although given how linker processing is done 
it would require keeping track of section size update attempts and only 
issue the warning if the final one ends up with a size mismatch.  I'll see 
if I can look into it, but given my other commitments right now I may not 
be able to do anything about it.

> Hmm, actually, going one step further - do we need to support a FIXED_SIZE(<vale>)
> section attribute for linker scripts, so that these sections can be defined 
> there too ?

 I don't know, I would have to think about a use case.  Maybe someone else 
can chime in.

  Maciej



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