From owner-freebsd-net@freebsd.org Wed Jul 29 22:26:54 2015 Return-Path: Delivered-To: freebsd-net@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id 9E5CC9AEAEB for ; Wed, 29 Jul 2015 22:26:54 +0000 (UTC) (envelope-from laurie_jennings_1977@yahoo.com) Received: from nm5-vm0.bullet.mail.bf1.yahoo.com (nm5-vm0.bullet.mail.bf1.yahoo.com [98.139.213.150]) (using TLSv1 with cipher ECDHE-RSA-RC4-SHA (128/128 bits)) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id 50F88157 for ; Wed, 29 Jul 2015 22:26:54 +0000 (UTC) (envelope-from laurie_jennings_1977@yahoo.com) Received: from [66.196.81.174] by nm5.bullet.mail.bf1.yahoo.com with NNFMP; 29 Jul 2015 22:26:47 -0000 Received: from [98.139.215.228] by tm20.bullet.mail.bf1.yahoo.com with NNFMP; 29 Jul 2015 22:26:47 -0000 Received: from [127.0.0.1] by omp1068.mail.bf1.yahoo.com with NNFMP; 29 Jul 2015 22:26:47 -0000 X-Yahoo-Newman-Property: ymail-3 X-Yahoo-Newman-Id: 106695.40234.bm@omp1068.mail.bf1.yahoo.com Received: (qmail 17989 invoked by uid 60001); 29 Jul 2015 22:26:47 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=yahoo.com; s=s1024; t=1438208807; bh=7WDKzIN1WXF9Cc+I9ez4VrzNMMzieSReGim4+Ue/n9Q=; h=Message-ID:Date:From:Subject:To:Cc:In-Reply-To:MIME-Version:Content-Type; b=OD73Zm7vGS2X8WsLe+lSWm/E+Teb2lvtiGgyq9YszaLtPPSONUbS7sNTnXdpEJbDAS7ghgxHm6CBACLS1NH49zFdRmsqDkk7Bk5vMnuIKykgnn4q5pvp8DdKu8w0o90/PIVxb+a9PX1f3dBNdNTN/qnzLdKq+7nVWznfwnx27Yw= X-YMail-OSG: w75ogAUVM1moCXDM0jakSpizbFLWxat7PPcw4xBYa5dqxYM UgaR_g.g.7vIrcRN323bwue9luYWZRWbX4qjIKnjaQIYVH6d2XeXbdxcqfo7 aPtO5oMq.zMBIZAvREuUyssojP.DrvsX0evcZTfoQiJDBoo.tAOTrKne0Akc iKx.9LjdSK86p_liCTuNdhA7qptOmbg.W_PRGsK_SAIR7GIjX_sZ3FTVOa_w .3cS7Vv.xs05mCF_evSBF79RaFv0H6wAoNGV9GDDGNq83TErdzogSAfWbiw3 HLc.vlwg5NIA32jkOieLpreVcfzErWnpVj6oL7p2p8LSTfPxn7Qtu12Jv4Wr CYnzpSxIFRHsAC76dq9zRdcHqJD_4RyvZLWIS.3.T0414ioUfZ9NDRrdKbmt zp_t4qpXERPCPr9V94mhax8unqw4cVh5ApfP8kYPyOPVmw_zspqprKfZGmYL Wrz7Bm013bfHAcsZyytxUVbcOlsyLRaVknr6feZpwGHL.M8iCyBnGemRkXTY hfgXbtRL59NwZkBy.TGk- Received: from [73.0.96.254] by web141505.mail.bf1.yahoo.com via HTTP; Wed, 29 Jul 2015 15:26:46 PDT X-Rocket-MIMEInfo: 002.001, DQpJIGhhdmUgYSBwcm9ibGVtIGFuZCBJIGNhbid0IHF1aXRlIGZpZ3VyZSBvdXQgd2hlcmUgdG8gbG9vay4gVGhpcyBpcyB3aGF0IEltIGRvaW5nOg0KDQpJIGhhdmUgYW4gSU9DVEwgdG8gcmVhZCBhIGJsb2NrIG9mIGRhdGEsIGJ1dCB0aGUgZGF0YSBpcyB0b28gbGFyZ2UgdG8gcmV0dXJuIHZpYSBpb2N0bC4gU28gdG8gZ2V0IHRoZSBkYXRhLA0KSSBhbGxvY2F0ZSBhIGJsb2NrIGluIGEga2VybmVsIG1vZHVsZToNCg0KZm9vID0gbWFsbG9jKDEwMjQwMDAsTV9ERVZCVUYsTV9XQUlUT0spOw0KDQogSSBwYXMBMAEBAQE- X-Mailer: YahooMailBasic/600 YahooMailWebService/0.8.203.802 Message-ID: <1438208806.66724.YahooMailBasic@web141505.mail.bf1.yahoo.com> Date: Wed, 29 Jul 2015 15:26:46 -0700 From: Laurie Jennings Subject: Locking Memory Question To: John Baldwin Cc: freebsd-net@freebsd.org In-Reply-To: <201310151521.25231.jhb@freebsd.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii X-BeenThere: freebsd-net@freebsd.org X-Mailman-Version: 2.1.20 Precedence: list List-Id: Networking and TCP/IP with FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 29 Jul 2015 22:26:54 -0000 I have a problem and I can't quite figure out where to look. This is what Im doing: I have an IOCTL to read a block of data, but the data is too large to return via ioctl. So to get the data, I allocate a block in a kernel module: foo = malloc(1024000,M_DEVBUF,M_WAITOK); I pass up a pointer and in user space map it using /dev/kmem: fd = open("/dev/kmem",O_RDWR); if (fd > 0){ memp = mmap(0,1024000,PROT_READ,MAP_SHARED,fd,p); and then grab the data from memp (It's a stringified object). The problem is that sometimes it's garbage. 95% of the time it works fine. I figured that the memory wasn't wired and I've been trying to wire it but not having much success. kmem_alloc() and kmem_malloc() panic in vm_map_lock, so Im guessing that you can't do this in an IOCTL call? So my questions: 1) Shouldn't kmem mapped memory be wired? how else could you reliable read kernel memory? 2) Why does kmem_alloc() panic kmem_alloc(kernel_map, 1024000); 3) is there a function to allocate and free a wired block? 4) how could I reliably wire a block allocated with malloc. Can it be done somehow with vm_map_wire()? I can't get it to work. 5) What does MAP_PREFAULT_READ do and would it solve this problem? Thanks, Laurie