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From:   David Laight <David.Laight@ACULAB.COM>
To:     'Peter Zijlstra' <peterz@infradead.org>,
        Mikulas Patocka <mpatocka@redhat.com>
CC:     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
Thread-Topic: [PATCH] objtool: fix objtool regression on x32 systems
Thread-Index: AQHYaWt5OldbokCz9EWxs3iZW4E54K0iu3XQ
Date:   Tue, 17 May 2022 08:26:42 +0000
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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.

Immediates can be 64bit (but not if the addressing mode
includes an offset).

	David

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