Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Date:   Tue, 17 May 2022 11:42:12 +0200
From:   Peter Zijlstra <peterz@infradead.org>
To:     David Laight <David.Laight@aculab.com>
Cc:     Mikulas Patocka <mpatocka@redhat.com>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Josh Poimboeuf <jpoimboe@redhat.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] objtool: fix objtool regression on x32 systems
Message-ID: <YoNt9GhFdKKqjuiu@hirez.programming.kicks-ass.net>
References: <alpine.LRH.2.02.2205161041260.11556@file01.intranet.prod.int.rdu2.redhat.com>
 <YoJwtCeVzYUm6Uhg@hirez.programming.kicks-ass.net>
 <alpine.LRH.2.02.2205161145070.30905@file01.intranet.prod.int.rdu2.redhat.com>
 <20220516212517.GP76023@worktop.programming.kicks-ass.net>
 <738a941ba2ff4e2db8f2268b281d9bd5@AcuMS.aculab.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <738a941ba2ff4e2db8f2268b281d9bd5@AcuMS.aculab.com>
Precedence: bulk

On Tue, May 17, 2022 at 08:26:42AM +0000, David Laight wrote:
> From: Peter Zijlstra
> > Sent: 16 May 2022 22:25
> ...
> > A quick look seems to suggest at least all the 'offset' fields should be
> > u64 or something. The only reason that works is because -mcmodel=kernel
> > keeps everything in the 2G range to make s32 immediates work. But it
> > isn't right.
> 
> Offsets in instructions are only 8bit or 32bit.
> The mod/reg/rm and SiB encodings don't support anything else.
> If offsets might be large then they have to be loaded into
> registers - which will slow things down.

Not relevant; these are Elf64_Addr fields, objtool currently uses
'unsigned long' for them, but that goes sideways if ILP32.