linux-kernel - Re: [PATCH v2 15/25] objtool: Rework ibt and extricate from stack validation

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Message-ID: <alpine.LSU.2.21.2204250826540.25526@pobox.suse.cz>
Date:   Mon, 25 Apr 2022 08:27:17 +0200 (CEST)
From:   Miroslav Benes <mbenes@...e.cz>
To:     Peter Zijlstra <peterz@...radead.org>
cc:     Josh Poimboeuf <jpoimboe@...hat.com>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 15/25] objtool: Rework ibt and extricate from stack
 validation

On Fri, 22 Apr 2022, Peter Zijlstra wrote:

> On Wed, Apr 20, 2022 at 07:25:16PM +0200, Miroslav Benes wrote:
> > A nit and it was there even before this patch...
> > 
> > > -static struct instruction *
> > > -validate_ibt_reloc(struct objtool_file *file, struct reloc *reloc)
> > > -{
> > > -	struct instruction *dest;
> > > -	struct section *sec;
> > > -	unsigned long off;
> > > -
> > > -	sec = reloc->sym->sec;
> > > -	off = reloc->sym->offset;
> > > -
> > > -	if ((reloc->sec->base->sh.sh_flags & SHF_EXECINSTR) &&
> > > -	    (reloc->type == R_X86_64_PC32 || reloc->type == R_X86_64_PLT32))
> > > -		off += arch_dest_reloc_offset(reloc->addend);
> > 
> > here...
> > 
> > > +static int validate_ibt_insn(struct objtool_file *file, struct instruction *insn)
> > > +{
> > 
> > ...
> > > +		off = reloc->sym->offset;
> > > +		if (reloc->type == R_X86_64_PC32 || reloc->type == R_X86_64_PLT32)
> > > +			off += arch_dest_reloc_offset(reloc->addend);
> > > +		else
> > > +			off += reloc->addend;
> > 
> > it looks kind of strange to have arch_dest_reloc_offset() and still 
> > reference arch-specific relocation types here. On the other hand it seems 
> > difficult to achieve complete arch-agnostic code, so take it just as a 
> > note and maybe someone porting objtool to a different architecture will 
> > split the code, make it all arch-independent and all will be nice and 
> > shiny.
> 
> Something like so perhaps? Seems to build and boot x86_64-defconfig.

Yes, that looks good. Thanks.

Miroslav