From owner-freebsd-hackers  Fri Jul 13  8:16:16 2001
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From: "Eugene L. Vorokov" <vel@bugz.infotecs.ru>
Message-Id: <200107131529.f6DFTZI00705@bugz.infotecs.ru>
Subject: Re: Some questions about kernel programming
In-Reply-To: <20010712212809.F6664@sneakerz.org> "from Alfred Perlstein at Jul
 12, 2001 09:28:09 pm"
To: Alfred Perlstein <bright@sneakerz.org>
Date: Fri, 13 Jul 2001 19:29:35 +0400 (MSD)
Cc: freebsd-hackers@freebsd.org
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> /*
>  * return number of characters in a userland address string
>  * or -1 if an illegal access occurs.
>  */
> int
> user_strlen(uaddr)
> 	char *uaddr;
> {
> 	int ret;
> 
> 	ret = -1;
> 	do {
> 		ch = fubyte(uaddr);
> 		ret++;
> 	} while (ch != 0 && ch != -1);
> 
> 	return (ch == -1 ? -1 : ret);
> }

Then I don't get it. Won't this piece of code cycle forever fetching
first byte of the string again and again ? According to fetch(9)
fubyte() doesn't change uaddr, or am I missing something again ?
Am I allowed to do uaddr++ for userspace addresses in such a case ?

Regards,
Eugene


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