Re: [RFC][PATCH 00/36] objtool: Make recordmcount a subcommand

[Julien Thierry]

On 4/14/20 2:35 PM, Steven Rostedt wrote:
> On Tue, 14 Apr 2020 08:24:15 +0100
> Julien Thierry <jthierry@xxxxxxxxxx> wrote:
>
> > If all you need from objtool it the elf parsing code, wouldn't it make
> > more sense to move that out of objtool, as a utility library that both
> > objtool and recordmcount could use (and perhaps other tools in the future?)
> >
> > In patch 3 you seem to mention that other tools already have their own
> > code to parse elf. So instead of converting everything as an objtool
> > subcommand, maybe just have the library with the required functionality.
> >
> > Any opinions on the above? What do people prefer?
>
> I think we discussed this before (and originally that was the plan), but I
> believe one of the goals for bringing recordmcount into objtool is to speed
> up the processing. Instead of having to read the elf sections for each use
> case, we do it once, and then execute all the necessary operations for that
> build.
>
> If we just have a elf parsing library, then each object file is going to
> have that read redundantly for each operation that is done on it.
>
> I was hoping to have objtool handle all the operations needed that required
> reading elf headers.

That makes sense, however, having each operation as an objtool 
subcommand doesn't solve that issue, right? Each invocation of objtool 
will re-read the elf object.

I guess having all the relevant code in objtool as subcommand would be a 
first step towards that goal.

> But if that's not what objtool maintainers want, then we can certainly go
> back to looking at pulling out the elf headers, and have each tool be a
> standalone again.

I'm no maintainer nor know their feeling about this and I haven't been 
part of the initial discussion. My main concern was about the approach 
of moving existing subcommand code to arch specific folders.

Thanks for the explanations.

Cheers,

--
Julien Thierry