linux-kernel - Re: inline asm semantics: output constraint width smaller than input

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Message-ID: <jebptw4gex.fsf@sykes.suse.de>
Date:	Sat, 24 Jan 2009 21:07:02 +0100
From:	Andreas Schwab <schwab@...e.de>
To:	Török Edwin <edwintorok@...il.com>
Cc:	Ingo Molnar <mingo@...e.hu>, Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	LLVM Developers Mailing List <llvmdev@...uiuc.edu>
Subject: Re: inline asm semantics: output constraint width smaller than input

Török Edwin <edwintorok@...il.com> writes:

> @@ -239,11 +239,13 @@ extern void __put_user_8(void);
>   */
>  #define put_user(x, ptr)                    \
>  ({                                \
> -    int __ret_pu;                        \
> +    __typeof__(*(ptr)) __ret_pu;                \
>      __typeof__(*(ptr)) __pu_val;                \
>      __chk_user_ptr(ptr);                    \
>      might_fault();                        \
>      __pu_val = x;                        \
> +       /* return value is 0 or -EFAULT, both fit in 1 byte, and \
> +    * are sign-extendable to int */                \

That does not work when *ptr is unsigned (char or short).

Andreas.

-- 
Andreas Schwab, SuSE Labs, schwab@...e.de
SuSE Linux Products GmbH, Maxfeldstraße 5, 90409 Nürnberg, Germany
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