From owner-freebsd-current@freebsd.org Tue Aug 27 13:38:22 2019 Return-Path: Delivered-To: freebsd-current@mailman.nyi.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mailman.nyi.freebsd.org (Postfix) with ESMTP id A7659D5F8B for ; Tue, 27 Aug 2019 13:38:22 +0000 (UTC) (envelope-from kostikbel@gmail.com) Received: from kib.kiev.ua (kib.kiev.ua [IPv6:2001:470:d5e7:1::1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) server-signature RSA-PSS (4096 bits)) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id 46HqhD6f5qz3P1y for ; Tue, 27 Aug 2019 13:38:20 +0000 (UTC) (envelope-from kostikbel@gmail.com) Received: from tom.home (kib@localhost [127.0.0.1]) by kib.kiev.ua (8.15.2/8.15.2) with ESMTPS id x7RDcBnA006667 (version=TLSv1.3 cipher=TLS_AES_256_GCM_SHA384 bits=256 verify=NO); Tue, 27 Aug 2019 16:38:14 +0300 (EEST) (envelope-from kostikbel@gmail.com) DKIM-Filter: OpenDKIM Filter v2.10.3 kib.kiev.ua x7RDcBnA006667 Received: (from kostik@localhost) by tom.home (8.15.2/8.15.2/Submit) id x7RDcBaH006666; Tue, 27 Aug 2019 16:38:11 +0300 (EEST) (envelope-from kostikbel@gmail.com) X-Authentication-Warning: tom.home: kostik set sender to kostikbel@gmail.com using -f Date: Tue, 27 Aug 2019 16:38:11 +0300 From: Konstantin Belousov To: Maksim Yevmenkin Cc: "mms.vanbreukelingen@gmail.com" , Warner Losh , Hans Petter Selasky , "freebsd-current@freebsd.org" Subject: Re: Kernel-Crash when working with ubt0 Message-ID: <20190827133811.GU71821@kib.kiev.ua> References: <47509401.1440476.1566796167857.ref@mail.yahoo.com> <47509401.1440476.1566796167857@mail.yahoo.com> <5aa8faeb-5e8e-38be-4301-81f3d82c494a@selasky.org> <00E772F0-7231-44C4-B314-26730CC7DF21@gmail.com> <20190827071052.GT71821@kib.kiev.ua> <233039408.1857163.1566892977201@mail.yahoo.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.12.1 (2019-06-15) X-Spam-Status: No, score=-1.0 required=5.0 tests=ALL_TRUSTED,BAYES_00, DKIM_ADSP_CUSTOM_MED,FORGED_GMAIL_RCVD,FREEMAIL_FROM, NML_ADSP_CUSTOM_MED autolearn=no autolearn_force=no version=3.4.2 X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on tom.home X-Rspamd-Queue-Id: 46HqhD6f5qz3P1y X-Spamd-Bar: -- Authentication-Results: mx1.freebsd.org; dkim=none; dmarc=fail reason="No valid SPF, No valid DKIM" header.from=gmail.com (policy=none); spf=softfail (mx1.freebsd.org: 2001:470:d5e7:1::1 is neither permitted nor denied by domain of kostikbel@gmail.com) smtp.mailfrom=kostikbel@gmail.com X-Spamd-Result: default: False [-2.98 / 15.00]; TO_DN_EQ_ADDR_SOME(0.00)[]; RCVD_COUNT_TWO(0.00)[2]; TO_DN_SOME(0.00)[]; FREEMAIL_FROM(0.00)[gmail.com]; HAS_XAW(0.00)[]; R_SPF_SOFTFAIL(0.00)[~all]; RCPT_COUNT_FIVE(0.00)[5]; NEURAL_HAM_SHORT(-0.98)[-0.978,0]; FREEMAIL_TO(0.00)[gmail.com]; FROM_EQ_ENVFROM(0.00)[]; MIME_TRACE(0.00)[0:+]; R_DKIM_NA(0.00)[]; FREEMAIL_ENVFROM(0.00)[gmail.com]; ASN(0.00)[asn:6939, ipnet:2001:470::/32, country:US]; ARC_NA(0.00)[]; NEURAL_HAM_MEDIUM(-1.00)[-1.000,0]; FROM_HAS_DN(0.00)[]; NEURAL_HAM_LONG(-1.00)[-1.000,0]; TAGGED_RCPT(0.00)[]; MIME_GOOD(-0.10)[text/plain]; IP_SCORE_FREEMAIL(0.00)[]; TO_MATCH_ENVRCPT_SOME(0.00)[]; IP_SCORE(0.00)[ip: (-2.63), ipnet: 2001:470::/32(-4.45), asn: 6939(-3.09), country: US(-0.05)]; FREEMAIL_CC(0.00)[gmail.com]; RCVD_TLS_ALL(0.00)[]; DMARC_POLICY_SOFTFAIL(0.10)[gmail.com : No valid SPF, No valid DKIM,none] X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Discussions about the use of FreeBSD-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 27 Aug 2019 13:38:22 -0000 On Tue, Aug 27, 2019 at 06:03:46AM -0700, Maksim Yevmenkin wrote: > > > Hmm... interesting.... > > > > > > I only took a brief look at it. I suppose I can ensure user space address is wired and then copyout() can be called with mutex held > > > > >No, you cannot do this, at least without making the kernel to panic. > > User might unmap the wired mapping at any time still. > > Kostik, > > i was thinking along the lines of vslock/vsunlock and copyout_nofault. > basically similar to the sysctl code. do you think this would not > work? This would probably work, but at least causes fragmentation of userspace vm_map entries. If it is supposed to be used on high-frequency data path, then it would cause significant blow up of the VM structures used to keep user data map.