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
Date: Tue, 17 May 2022 11:42:12 +0200 [thread overview]
Message-ID: <YoNt9GhFdKKqjuiu@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <738a941ba2ff4e2db8f2268b281d9bd5@AcuMS.aculab.com>
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.
next prev parent reply other threads:[~2022-05-17 9:43 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-05-16 15:06 [PATCH] objtool: fix objtool regression on x32 systems Mikulas Patocka
2022-05-16 15:41 ` Peter Zijlstra
2022-05-16 15:56 ` Mikulas Patocka
2022-05-16 21:25 ` Peter Zijlstra
2022-05-17 8:26 ` David Laight
2022-05-17 9:42 ` Peter Zijlstra [this message]
2022-05-18 13:28 ` [PATCH v2] " Mikulas Patocka
2022-05-18 18:08 ` Josh Poimboeuf
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