From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id B1FF5C4167E for ; Fri, 29 Apr 2022 13:52:04 +0000 (UTC) Received: from localhost ([::1]:52352 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1nkR2R-00026C-DD for qemu-devel@archiver.kernel.org; Fri, 29 Apr 2022 09:52:03 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:50732) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1nkQzH-000891-WC; Fri, 29 Apr 2022 09:48:51 -0400 Received: from kylie.crudebyte.com ([5.189.157.229]:41741) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1nkQzE-00086N-Hz; Fri, 29 Apr 2022 09:48:47 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=crudebyte.com; s=kylie; h=Content-Type:Content-Transfer-Encoding: MIME-Version:References:In-Reply-To:Message-ID:Date:Subject:Cc:To:From: Content-ID:Content-Description; bh=wPGm045tvgpxK58RLzlZPFnbcISEU9PtxokDoa8+qOU=; b=mMMucSURvZL2oSoaoT95fgg6Ag AYUpXk3DRE/MZhFrOfPfvS9AndsUnawfFeEW039WL8wpRAlD/CsxpyFx037s+I9ZW+SYNxhxD6+zA sYgN+qTNoSHYxrUHDiYUsXBseCMNTRkk4rkihc8wUegJEBaISx+PUiroOkp9GSzgQoDSFJexvc0SN uN5DEG4HXd+0NgizfZ4IkLi8iWB/m4bDjfVmlgEsq0mPZAiRARc9xx3+6j1bTD8xnWJVEwN2wt8TU JeNhas4iQ68M5gL/e5bxM+pA1vj2JlM8n0MBnwCSJ7b96uBEmYkTAAlQ4aWLbw9Pi/iq1RLqoIsH9 RX911ygU9RrfJKK0kxkpTXok9RMsrJgNM1V9xZAmq9HTYewVVcS/wWGqtsj2mye8d96o5gtcE0I33 ZIfE57eKZyINpWVFm44JrITp96aKgA2Jv6QbTg2sRmt+ljwKl3bq+h8XCFvLTqkC0mXQXuuCj4Mk/ Rvkwm3+BNGneKr/uAwJUC8lvB/lnFU3PCp2Nl1j8KDQW9wzs2h2pz0cfzhxNpzlZRB9bytpTjve4C hhsuWaU1AunaxfgU/XQRHtjha/8MffeJOjOnF+zshxAcvkkakdbPvI/ZAUR9Fucr058kcWikoD0Ua z6OpTTXbwjsdjpxVvSdym0U/a9ZT8k4hJwFPJ7Pa4=; From: Christian Schoenebeck To: Bin Meng Cc: qemu-devel@nongnu.org, Michael Roitzsch , qemu-stable@nongnu.org, Keno Fischer , Will Cohen , Guohuai Shi , Akihiko Odaki , Greg Kurz Subject: Re: [PATCH v5 4/6] 9pfs: fix wrong errno being sent to Linux client on macOS host Date: Fri, 29 Apr 2022 15:48:16 +0200 Message-ID: <2182756.uObvtyB7Eu@silver> In-Reply-To: <20220429152915.7beb6545@bahia> References: <20220429152915.7beb6545@bahia> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" Received-SPF: pass client-ip=5.189.157.229; envelope-from=qemu_oss@crudebyte.com; helo=kylie.crudebyte.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Freitag, 29. April 2022 15:29:15 CEST Greg Kurz wrote: > On Fri, 29 Apr 2022 21:19:51 +0800 > > Bin Meng wrote: > > On Fri, Apr 29, 2022 at 9:08 PM Greg Kurz wrote: > > > On Fri, 29 Apr 2022 14:46:26 +0200 > > > > > > Christian Schoenebeck wrote: > > > > On Freitag, 29. April 2022 13:28:39 CEST Bin Meng wrote: > > > > > On Fri, Apr 29, 2022 at 7:16 PM Christian Schoenebeck > > > > > > > > > > wrote: > > > > > > Linux and macOS only share some errno definitions with equal macro > > > > > > name and value. In fact most mappings for errno are completely > > > > > > different on the two systems. > > > > > > > > > > > > This patch converts some important errno values from macOS host to > > > > > > corresponding Linux errno values before eventually sending such > > > > > > error > > > > > > codes along with 'Rlerror' replies (if 9p2000.L is used that is). > > > > > > Not > > > > > > having translated errnos before violated the 9p2000.L protocol > > > > > > spec, > > > > > > > > > > > > which says: > > > > > > " > > > > > > size[4] Rlerror tag[2] ecode[4] > > > > > > > > > > > > ... ecode is a numerical Linux errno. > > > > > > " > > > > > > > > > > > > https://github.com/chaos/diod/wiki/protocol#lerror----return-err > > > > > > or-code > > > > > > > > > > > > This patch fixes a bunch of misbehaviours when running a Linux > > > > > > client > > > > > > > > > > > > on macOS host. For instance this patch fixes: > > > > > > mount -t 9p -o posixacl ... > > > > > > > > > > > > on Linux guest if security_mode=mapped was used for 9p server, > > > > > > which > > > > > > refused to mount successfully, because macOS returned ENOATTR==93 > > > > > > when client tried to retrieve POSIX ACL xattrs, because errno 93 > > > > > > is defined as EPROTONOSUPPORT==93 on Linux, so Linux client > > > > > > believed > > > > > > that xattrs were not supported by filesystem on host in general. > > > > > > > > > > This issue looks exact the same issue we were trying to fix when > > > > > supporting 9p on Windows host, > > > > > > > > > > What we did is like this: > > > > > http://patchwork.ozlabs.org/project/qemu-devel/patch/20220425142705. > > > > > 2099270-> 10-bmeng.cn@gmail.com/ > > > > > > > > > > But we had some questions in mind (see the commit message of our > > > > > patch, and below) > > > > > > > > > > > Signed-off-by: Christian Schoenebeck > > > > > > Link: > > > > > > https://lore.kernel.org/qemu-devel/20220421124835.3e664669@bahia/ > > > > > > Reviewed-by: Greg Kurz > > > > > > --- > > > > > > > > > > > > hw/9pfs/9p-util.h | 30 ++++++++++++++++++++++++++++++ > > > > > > hw/9pfs/9p.c | 2 ++ > > > > > > 2 files changed, 32 insertions(+) > > > > > > > > > > > > diff --git a/hw/9pfs/9p-util.h b/hw/9pfs/9p-util.h > > > > > > index 2cc9a5dbfb..c3526144c9 100644 > > > > > > --- a/hw/9pfs/9p-util.h > > > > > > +++ b/hw/9pfs/9p-util.h > > > > > > @@ -58,6 +58,36 @@ static inline uint64_t > > > > > > host_dev_to_dotl_dev(dev_t dev) > > > > > > > > > > > > #endif > > > > > > } > > > > > > > > > > > > +/* Translates errno from host -> Linux if needed */ > > > > > > +static inline int errno_to_dotl(int err) { > > > > > > +#if defined(CONFIG_LINUX) > > > > > > + /* nothing to translate (Linux -> Linux) */ > > > > > > +#elif defined(CONFIG_DARWIN) > > > > > > + /* > > > > > > + * translation mandatory for macOS hosts > > > > > > + * > > > > > > + * FIXME: Only most important errnos translated here yet, > > > > > > this should > > > > > > be + * extended to as many errnos being translated as possible > > > > > > in > > > > > > future. + */ > > > > > > + if (err == ENAMETOOLONG) { > > > > > > + err = 36; /* ==ENAMETOOLONG on Linux */ > > > > > > + } else if (err == ENOTEMPTY) { > > > > > > + err = 39; /* ==ENOTEMPTY on Linux */ > > > > > > + } else if (err == ELOOP) { > > > > > > + err = 40; /* ==ELOOP on Linux */ > > > > > > + } else if (err == ENOATTR) { > > > > > > + err = 61; /* ==ENODATA on Linux */ > > > > > > + } else if (err == ENOTSUP) { > > > > > > + err = 95; /* ==EOPNOTSUPP on Linux */ > > > > > > + } else if (err == EOPNOTSUPP) { > > > > > > + err = 95; /* ==EOPNOTSUPP on Linux */ > > > > > > + } > > > > > > > > > > What happens if a macOS guest is running on QEMU from a macOS host? > > > > > Here all macOS errnos are translated to the Linux errnos. Will macOS > > > > > be happy? > > > > > > > > Look at the commit log of this patch: it is a matter of which protocol > > > > is used> > > > > > > (currently there are 3 [1] protocol versions): > > > > * 9p2000: nothing to translate here, as this protocol version does > > > > not > > > > > > > > return a numeric error code, it only returns an error string (and > > > > we are > > > > no longer supporting 9p2000 version in QEMU anyway BTW [1]): > > > > http://ericvh.github.io/9p-rfc/rfc9p2000.html#anchor27 > > > > > > > > * 9p2000.L: errno *must* be in Linux errno mapping: > > > > https://github.com/chaos/diod/wiki/protocol#lerror----return-erro > > > > r-code > > > > > > > > * 9p2000.u: this one returns both an error code and error string, > > > > and it > > > > > > > > says the error string should be preferred being interpreted by > > > > client: > > > > http://ericvh.github.io/9p-rfc/rfc9p2000.u.html#anchor15 > > > > > > > > In this patch here I only translated errno for 9p2000.L, whereas you > > > > are > > > > always translating it, no matter wich protocol version is used. You > > > > might > > > > argue that there should be a translation for 9p2000.u as well, but in > > > > the end we don't know the OS running on guest in this case. It could > > > > be Linux or something else. > > > > > > In the case of 9p2000.u the spec says "to provide a hint of the > > > underlying > > > UNIX error number which caused the error on the server" and even > > > mentions > > > "consistency problems of mapping error numbers betweeen different > > > versions > > > of UNIX"... this basically means that errno in 9p2000.u is undefined > > > since > > > it depends on the host. It is thus unusable unless the guest runs a > > > compatible UNIX variant. In any case, there's really nothing to > > > translate. > > > > > > > [1] https://wiki.qemu.org/Documentation/9p#9p_Protocol > > > > Thanks for the clarifications and pointers to different protocols! It > > looks what we did in our Windows patch is correct. Like I said, you are translating it for all protocol version, whereas this patch here translates errnos for 9p2000.L version only. > > I have another question, does this mean the current 9pfs client on > > macOS is broken since it does not use any translation? With this > > patch, now the 9p server returns the translated linux errno so the 9p > > client on macOS should complain. > > I don't now the macOS client but if it doesn't expect linux errnos > then it is infringing 9p2000.L and should be fixed. Agreed, if you are using 9p2000.L with that macOS client and client does not translate errnos Linux -> macOS, then client is broken. In the end it matters what the protocol documentation specified. Which client is that? Is it from Apple or from a third party? And are you sure you were actually using 9p2000.L and not 9p2000.u? Best regards, Christian Schoenebeck