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

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Message-ID: <alpine.LSU.2.21.2204201755580.1205@pobox.suse.cz>
Date:   Wed, 20 Apr 2022 19:25:16 +0200 (CEST)
From:   Miroslav Benes <mbenes@...e.cz>
To:     Josh Poimboeuf <jpoimboe@...hat.com>
cc:     x86@...nel.org, Peter Zijlstra <peterz@...radead.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 15/25] objtool: Rework ibt and extricate from stack
 validation

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.

Miroslav