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 7E872C433F5 for ; Mon, 7 Feb 2022 23:03:12 +0000 (UTC) Received: from localhost ([::1]:45694 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1nHD2N-000791-Gs for qemu-devel@archiver.kernel.org; Mon, 07 Feb 2022 18:03:11 -0500 Received: from eggs.gnu.org ([209.51.188.92]:35882) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1nHCvf-0000kH-UR for qemu-devel@nongnu.org; Mon, 07 Feb 2022 17:56:15 -0500 Received: from kylie.crudebyte.com ([5.189.157.229]:45839) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1nHCvd-0007zC-PL for qemu-devel@nongnu.org; Mon, 07 Feb 2022 17:56:15 -0500 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=V/veNjeb63bgrUfjGzzUVR29/f6CXeLyHE37pzA9okI=; b=U7cmmCUc1Lc/7xmMrij5lwjJDw dfpR9TopcwLu29ds1fRgjvVDf4oyvd7VxWQCJSExkVc9XhGx67cNvhSbLRxqAS9AkmgbwxFhHiNyD STQJymdiPIJNfU60Z1IHGcivf73hgxnF8XfpeRVZKmoDks/nSuBmvM7A+2fQXwdIpJ+neRB9pfcdx 0HuioHzZcMNA6ECb8GQusa9zFV46lcA00dZcfl5AQg337S0zZTfzwgg5xT77XIwGtktlMi+ebDvze g9hjbpcKkVTQxhHUXqCd8q/paTC09aUTixh/OfFN1aJ/fSr8MqF87RG4ZO4MUzmXgPEePw6n40QkH xyHOeA17iEYn09wssjqct9ajFb0v7Y2iHsLaaVW8TTqB0l55Ck5HKzWiPzVD2hCl0s7WTLSbpMugO Bn6I0vUQHc7vY0uB7CZL9ViBalsJbSPMFcV810mWa4yUNYjsBw45cFIEaGg7q9BK5dJpXPyMydjWY rXq055FtWGKpYvYb7c/9nlCDvhfB3iUS60pArYpWzBQAvabVo8WE2tVogxNO8k8+59hgIgbJ1GGBY RiPdHVbFgx7FpGiIPnIJ3gHMfiVCVa4fhK7djORKIZX2wduuB71+NJEmSWpq7ae9c7W9vDSTZR9dZ QTYDzXD0DdoXpiM2B7ilxwrETQwwc5BV/81OUKdmw=; From: Christian Schoenebeck To: Will Cohen Cc: qemu-devel@nongnu.org, hi@alyssa.is, Greg Kurz , Paolo Bonzini , Thomas Huth , Laurent Vivier , Keno Fischer , Michael Roitzsch Subject: Re: [PATCH v5 09/11] 9p: darwin: Implement compatibility for mknodat Date: Mon, 07 Feb 2022 23:56:10 +0100 Message-ID: <2714656.jhBehFKKHS@silver> In-Reply-To: <20220207224024.87745-10-wwcohen@gmail.com> References: <20220207224024.87745-1-wwcohen@gmail.com> <20220207224024.87745-10-wwcohen@gmail.com> 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 Montag, 7. Februar 2022 23:40:22 CET Will Cohen wrote: > From: Keno Fischer > > Darwin does not support mknodat. However, to avoid race conditions > with later setting the permissions, we must avoid using mknod on > the full path instead. We could try to fchdir, but that would cause > problems if multiple threads try to call mknodat at the same time. > However, luckily there is a solution: Darwin includes a function > that sets the cwd for the current thread only. > This should suffice to use mknod safely. > > This function (pthread_fchdir_np) is protected by a check in > meson in a patch later in tihs series. > > Signed-off-by: Keno Fischer > Signed-off-by: Michael Roitzsch > [Will Cohen: - Adjust coding style > - Replace clang references with gcc > - Note radar filed with Apple for missing syscall > - Replace direct syscall with pthread_fchdir_np and > adjust patch notes accordingly > - Move qemu_mknodat from 9p-util to osdep and os-posix] > Signed-off-by: Will Cohen > --- Like already mentioned by me moments ago on previous v4 (just echoing) ... > hw/9pfs/9p-local.c | 4 ++-- > include/qemu/osdep.h | 10 ++++++++++ > os-posix.c | 34 ++++++++++++++++++++++++++++++++++ > 3 files changed, 46 insertions(+), 2 deletions(-) > > diff --git a/hw/9pfs/9p-local.c b/hw/9pfs/9p-local.c > index a0d08e5216..d42ce6d8b8 100644 > --- a/hw/9pfs/9p-local.c > +++ b/hw/9pfs/9p-local.c > @@ -682,7 +682,7 @@ static int local_mknod(FsContext *fs_ctx, V9fsPath > *dir_path, > > if (fs_ctx->export_flags & V9FS_SM_MAPPED || > fs_ctx->export_flags & V9FS_SM_MAPPED_FILE) { > - err = mknodat(dirfd, name, fs_ctx->fmode | S_IFREG, 0); > + err = qemu_mknodat(dirfd, name, fs_ctx->fmode | S_IFREG, 0); > if (err == -1) { > goto out; > } > @@ -697,7 +697,7 @@ static int local_mknod(FsContext *fs_ctx, V9fsPath > *dir_path, } > } else if (fs_ctx->export_flags & V9FS_SM_PASSTHROUGH || > fs_ctx->export_flags & V9FS_SM_NONE) { > - err = mknodat(dirfd, name, credp->fc_mode, credp->fc_rdev); > + err = qemu_mknodat(dirfd, name, credp->fc_mode, credp->fc_rdev); > if (err == -1) { > goto out; > } > diff --git a/include/qemu/osdep.h b/include/qemu/osdep.h > index d1660d67fa..f3a8367ece 100644 > --- a/include/qemu/osdep.h > +++ b/include/qemu/osdep.h > @@ -810,3 +810,13 @@ static inline int > platform_does_not_support_system(const char *command) #endif > > #endif > + > +/* > + * As long as mknodat is not available on macOS, this workaround > + * using pthread_fchdir_np is needed. qemu_mknodat is defined in > + * os-posix.c > + */ > +#ifdef CONFIG_DARWIN > +int pthread_fchdir_np(int fd); > +#endif I would make that: #ifdef CONFIG_DARWIN int pthread_fchdir_np(int fd) API_AVAILABLE(macosx(10.12)); #endif here and ... > +int qemu_mknodat(int dirfd, const char *filename, mode_t mode, dev_t dev); > diff --git a/os-posix.c b/os-posix.c > index ae6c9f2a5e..95c1607065 100644 > --- a/os-posix.c > +++ b/os-posix.c > @@ -24,6 +24,7 @@ > */ > > #include "qemu/osdep.h" > +#include > #include > #include > #include > @@ -332,3 +333,36 @@ int os_mlock(void) > return -ENOSYS; > #endif > } > + > +/* > + * As long as mknodat is not available on macOS, this workaround > + * using pthread_fchdir_np is needed. > + * > + * Radar filed with Apple for implementing mknodat: > + * rdar://FB9862426 (https://openradar.appspot.com/FB9862426) > + */ > +#ifdef CONFIG_DARWIN > + > +int pthread_fchdir_np(int fd) API_AVAILABLE(macosx(10.12)); ... drop the duplicate declaration of pthread_fchdir_np() here. > + > +int qemu_mknodat(int dirfd, const char *filename, mode_t mode, dev_t dev) > +{ > + int preserved_errno, err; > + if (pthread_fchdir_np(dirfd) < 0) { > + return -1; > + } > + err = mknod(filename, mode, dev); > + preserved_errno = errno; > + /* Stop using the thread-local cwd */ > + pthread_fchdir_np(-1); > + if (err < 0) { > + errno = preserved_errno; > + } > + return err; > +} > +#else > +int qemu_mknodat(int dirfd, const char *filename, mode_t mode, dev_t dev) > +{ > + return mknodat(dirfd, filename, mode, dev); > +} > +#endif