linux-kernel - Re: [PATCH] x86/entry/ia32: Ensure s32 is sign extended to s64

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Message-ID: <875yuletsw.fsf@oldenburg.str.redhat.com>
Date:   Mon, 27 Sep 2021 20:51:11 +0200
From:   Florian Weimer <fweimer@...hat.com>
To:     Richard Palethorpe <rpalethorpe@...e.com>
Cc:     x86@...nel.org, Heiko Carstens <hca@...ux.ibm.com>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        Christian Borntraeger <borntraeger@...ibm.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>, linux-s390@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-api@...r.kernel.org,
        Arnd Bergmann <arnd@...db.de>, rpalethorpe@...hiejp.com,
        Dominik Brodowski <linux@...inikbrodowski.net>,
        ltp@...ts.linux.it
Subject: Re: [PATCH] x86/entry/ia32: Ensure s32 is sign extended to s64

* Richard Palethorpe:

> +#define __SC_COMPAT_CAST(t, a)						\
> +	(__typeof(__builtin_choose_expr(__TYPE_IS_L(t), 0, 0U)))	\
> +	(unsigned int)a

So this casts to int (triggering sign extension) if the type on the
64-bit kernel side is long?  But not in other cases (unsigned long,
pointer)?  Just double-checking.

Thanks,
Florian