From owner-freebsd-hackers@FreeBSD.ORG Thu Apr 29 19:21:01 2010 Return-Path: Delivered-To: freebsd-hackers@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 30393106567C for ; Thu, 29 Apr 2010 19:21:01 +0000 (UTC) (envelope-from czerner.lukas@gmail.com) Received: from fg-out-1718.google.com (fg-out-1718.google.com [72.14.220.153]) by mx1.freebsd.org (Postfix) with ESMTP id ACF728FC20 for ; Thu, 29 Apr 2010 19:21:00 +0000 (UTC) Received: by fg-out-1718.google.com with SMTP id l26so2035374fgb.13 for ; Thu, 29 Apr 2010 12:21:00 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:received:received:date:from:x-x-sender:to:cc :subject:in-reply-to:message-id:references:user-agent:mime-version :content-type; bh=MOD0JkEpfjeIisdc0HkudzOk6eZFikY1T4OmCfb+Vyg=; b=DSM3cnJIvqvCR6jnJNz4JgZPmOsW2llf91hljpuk4YFlCDGOLTsvT26+aPzt2l4X0+ vu3+zzLsD8bEkQetQ1VxuUO62N2nxdKp0yLa3BnUmL9pN2AP3Y82LNbBWs9H8UImUidy Wvq6EVEhGG5XCc4a2AVi8iUFJwrJ9DzM43hnE= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=date:from:x-x-sender:to:cc:subject:in-reply-to:message-id :references:user-agent:mime-version:content-type; b=wv4KxyOEhSDS7FngTZSCQyv3VssgRNDvV9Q9zwAEEkMVCSvXd+84ZfSMOZ5wJhs5+2 yfwzNxunH3i3p3KU/nsMtG11qh2Afm0pMdwbb7NZHAA07tPEhJzsJfrUPgbPeXfk4H3Z GcXZTL98emHtE5IQiunhS+miZ4wxkGleO1d/8= Received: by 10.86.6.37 with SMTP id 37mr2159859fgf.7.1272568858299; Thu, 29 Apr 2010 12:20:58 -0700 (PDT) Received: from a04-0215a.kn.vutbr.cz (a04-0215a.kn.vutbr.cz [147.229.216.20]) by mx.google.com with ESMTPS id d4sm3074983fga.25.2010.04.29.12.20.57 (version=TLSv1/SSLv3 cipher=RC4-MD5); Thu, 29 Apr 2010 12:20:57 -0700 (PDT) Date: Thu, 29 Apr 2010 21:21:00 +0200 (CEST) From: "=?ISO-8859-15?Q?Luk=E1=A8_Czerner?=" X-X-Sender: bratt@a04-0215a.kn.vutbr.cz To: John Baldwin In-Reply-To: <201004291418.09768.jhb@freebsd.org> Message-ID: References: <201004291418.09768.jhb@freebsd.org> User-Agent: Alpine 1.10 (DEB 962 2008-03-14) MIME-Version: 1.0 Content-Type: MULTIPART/MIXED; BOUNDARY="8323329-1225407102-1272568861=:30007" Cc: freebsd-hackers@freebsd.org, =?ISO-8859-15?Q?Luk=E1=A8_Czerner?= Subject: Re: ioctl, copy string from user X-BeenThere: freebsd-hackers@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Technical Discussions relating to FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 29 Apr 2010 19:21:01 -0000 This message is in MIME format. The first part should be readable text, while the remaining parts are likely unreadable without MIME-aware tools. --8323329-1225407102-1272568861=:30007 Content-Type: TEXT/PLAIN; charset=utf-8 Content-Transfer-Encoding: 8BIT On Thu, 29 Apr 2010, John Baldwin wrote: > Date: Thu, 29 Apr 2010 14:18:09 -0400 > From: John Baldwin > To: freebsd-hackers@freebsd.org > Cc: Lukáš Czerner > Subject: Re: ioctl, copy string from user > > On Thursday 29 April 2010 1:52:45 pm Lukáš Czerner wrote: > > Hi, > > > > I know that there are plenty of examples in the kernel code, but I > > just can not get it working, so maybe I am doing some stupid mistake > > I am not aware of. Please give me a hint if you can. > > > > What I want to do is simply call the ioctl from the userspace with > > (char *) argument. Then, in kernel ioctl handling function copy the > > string argument into the kernel space. I have tried it various ways, > > everything without any success. > > > > *** Userspace *** > > char name[MAXLEN]; > > > > strncpy(name, argv[1], MAXLEN); > > fprintf(stdout,"Name: %s\n",name); > > > > if (ioctl(fd, MYIOCTL, name)) { > > On BSD systems, ioctl() copies the data into the kernel for you ahead of time. > What does the definition of MYIOCTL look like? #define MYIOCTL _IOW('M', 0, char *) > > > And the second question. I have commented that I can allocate buffer > > dynamically, but I suppose that there will be some locks involved so > > I think I can not just use M_WAITOK, am I right ? > > malloc() and free() acquire their own locks internally, you do not need to > hold any locks to call them. I probably does not express what I meant very clearly. My concern is that when I am calling malloc with M_WAITOK I can sleep (be rescheduled) and it may be bad thing if I am holding some lock, because I can block others, am I right ? --8323329-1225407102-1272568861=:30007--