From patchwork Fri Nov 15 15:35:52 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jeff Layton X-Patchwork-Id: 13876506 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id C06A81E261B; Fri, 15 Nov 2024 15:36:05 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1731684965; cv=none; b=ea2UHIPMFifiWVC+Y23cjxNQclonPfCiZTYmvw4y++G6nWC6gZLp8Oc4rYd2eKoSAqjtEtV6vdKGp79/f9hC4O3ox1VkgoPqjvF/iWRLKTIYWbGEuBbPP5FMB6PQUiaZ5o4jy7hvxXEdA8+Tf9eELgQt01e6eEogFQin0+Vyhmw= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1731684965; c=relaxed/simple; bh=Nz2g6aX7kYZa3fV4pgIXbRXHWIhB0kmiRiHE/o+ZHCE=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=AYdDf7T6LNHp5yJB7ekr2p01s/jv1tgGT/Ly9qP9RQBVlSarf9uZo3nvWllhBjPg4Vi/Euv/b7M/HVYtd3/w9fWvYyK2rlpdEL25OPu/rGI7PhKONotLheBDYSA7wk04nks+GPpiPULmaFKioi55tcVbbuf2QBqiFsFkCctzPmQ= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=UrOJatHg; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="UrOJatHg" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 30BA8C4CED6; Fri, 15 Nov 2024 15:36:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1731684965; bh=Nz2g6aX7kYZa3fV4pgIXbRXHWIhB0kmiRiHE/o+ZHCE=; h=From:Date:Subject:References:In-Reply-To:To:Cc:From; b=UrOJatHg4QKDUXg+rxYShXR2g6j3E/rsFfxJMd3ZG3woilx3x0NlYNQkighSV1k7N eB1vHnzF+E4LlrkSg8DzS62fO7vf1KyTbIB1sm8lbWF9qB2nR+E1xloy1XrB5ADkJO kI0aPOpVpUYFiH6VHKlu/muORWAeeo6L/bg7udReQjDPP6WtcrwmQoYK5ROqgDUNqO QG72GkJJzpvYfubXVOq0nqEBEu8zg+hTkFDozsCe9hqMutUQ1fY5DobgRfzVw7mMtE WVYv+NvlLCgyoqe9KaPW1mqIJt0PVVKRuCsBcxFITH7m+KBDh1COvry30PczdwGDqr +M6tyFLlFp/bg== From: Jeff Layton Date: Fri, 15 Nov 2024 10:35:52 -0500 Subject: [PATCH v2 1/2] samples: add a mountinfo program to demonstrate statmount()/listmount() Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Message-Id: <20241115-statmount-v2-1-cd29aeff9cbb@kernel.org> References: <20241115-statmount-v2-0-cd29aeff9cbb@kernel.org> In-Reply-To: <20241115-statmount-v2-0-cd29aeff9cbb@kernel.org> To: Christian Brauner , Alexander Viro , Jan Kara Cc: Josef Bacik , Miklos Szeredi , Ian Kent , David Howells , Amir Goldstein , Paul Moore , Karel Zak , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, Jeff Layton X-Mailer: b4 0.14.2 X-Developer-Signature: v=1; a=openpgp-sha256; l=8545; i=jlayton@kernel.org; h=from:subject:message-id; bh=Nz2g6aX7kYZa3fV4pgIXbRXHWIhB0kmiRiHE/o+ZHCE=; b=owEBbAKT/ZANAwAIAQAOaEEZVoIVAcsmYgBnN2piO47W0bewypcjon+glLvkfsamv33yeuqlH NwxQQ6Q2RyJAjIEAAEIAB0WIQRLwNeyRHGyoYTq9dMADmhBGVaCFQUCZzdqYgAKCRAADmhBGVaC FY3TD/USu9O917a6rJF0c5mDPDM85AN5n2Ff8lvrH8V+xnRxICI+kWB3BECP51jg300JniXsxol TQ87eVhtSAwHPNtCjKU3ugnaw6bVrJNVUXizAF53KJpXeJJEgq34w8VJLU1t/d5szutCqN/YTc8 vZZn9tvc/QT25Air9kcL+JMBZqOkGrcLbq65bYZaLqNN8FaFauRjvu5n+V/WNoQh1l1gZmNEN/5 C6QGdtKIQoiJNFv2++kKGlUmm9+JnCAjWB4deRx7xgxak4Yk4dnjPNiZ8xwCXOoAHBbVpWxQjRd k0DMic4/n/WgwR6YKGEeW7TZ1a+ViU5Npjd8xqfs8aEjufPmYnFkOkRmr29nuzW8zP3ZMzeiCDE Tn9QSsOmGn4JehTa04ghFFKGte/Cx3yiRTTkZmMsQsZF3nr1A8A31DYKWh2gk9vM0yWj2hFfyoc JStXxgtGd/quhf1748ldNKgrjC74t3PA2OXpx72BaBHNoOB3xA6QJEXXXngg8OFFajaLQEflIMF 46EH0JF2fMyOs7sAs4WlCa1PpECZgkMpkn3WQN5bSzXsrT2ZB69wjg3qa0TOU9FLYxXJG7+GBQP 0xizGJALuQ3D74zBRPoxopdcPpc2XJopjT9ivT4cMVE54f84tZ4VpAb6RFeoSCy9nHgtHGjLvlz WsUAtwVoK/ZTY X-Developer-Key: i=jlayton@kernel.org; a=openpgp; fpr=4BC0D7B24471B2A184EAF5D3000E684119568215 Add a new "mountinfo" sample userland program that demonstrates how to use statmount() and listmount() to get at the same info that /proc/pid/mountinfo provides. The output of the program tries to mimic the mountinfo procfile contents. With the -p flag, it can be pointed at an arbitrary pid to print out info about its mount namespace. With the -r flag it will attempt to walk all of the namespaces under the pid's mount namespace and dump out mount info from all of them. Signed-off-by: Jeff Layton --- samples/vfs/.gitignore | 1 + samples/vfs/Makefile | 2 +- samples/vfs/mountinfo.c | 271 ++++++++++++++++++++++++++++++++++++++++++++++++ 3 files changed, 273 insertions(+), 1 deletion(-) diff --git a/samples/vfs/.gitignore b/samples/vfs/.gitignore index 79212d91285bca72b0ff85f28aaccd2e803ac092..33a03cffe072fe2466c9df30ad47e9c58b0eea7c 100644 --- a/samples/vfs/.gitignore +++ b/samples/vfs/.gitignore @@ -1,3 +1,4 @@ # SPDX-License-Identifier: GPL-2.0-only /test-fsmount /test-statx +/mountinfo diff --git a/samples/vfs/Makefile b/samples/vfs/Makefile index 6377a678134acf0d682151d751d2f5042dbf5e0a..fb9bb33fdc751556e806aa897f0dbd48f7e3a4d8 100644 --- a/samples/vfs/Makefile +++ b/samples/vfs/Makefile @@ -1,4 +1,4 @@ # SPDX-License-Identifier: GPL-2.0-only -userprogs-always-y += test-fsmount test-statx +userprogs-always-y += test-fsmount test-statx mountinfo userccflags += -I usr/include diff --git a/samples/vfs/mountinfo.c b/samples/vfs/mountinfo.c new file mode 100644 index 0000000000000000000000000000000000000000..d9f21113a93b7aa7606de2edfce5ad0d5bcf2056 --- /dev/null +++ b/samples/vfs/mountinfo.c @@ -0,0 +1,271 @@ +// SPDX-License-Identifier: GPL-2.0-or-later + +/* + * Use pidfds, nsfds, listmount() and statmount() mimic the + * contents of /proc/self/mountinfo. + */ +#define _GNU_SOURCE +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include + +/* max mounts per listmount call */ +#define MAXMOUNTS 1024 + +/* size of struct statmount (including trailing string buffer) */ +#define STATMOUNT_BUFSIZE 4096 + +static bool ext_format; + +/* + * There are no bindings in glibc for listmount() and statmount() (yet), + * make our own here. + */ +static int statmount(uint64_t mnt_id, uint64_t mnt_ns_id, uint64_t mask, + struct statmount *buf, size_t bufsize, + unsigned int flags) +{ + struct mnt_id_req req = { + .size = MNT_ID_REQ_SIZE_VER0, + .mnt_id = mnt_id, + .param = mask, + }; + + if (mnt_ns_id) { + req.size = MNT_ID_REQ_SIZE_VER1; + req.mnt_ns_id = mnt_ns_id; + } + + return syscall(__NR_statmount, &req, buf, bufsize, flags); +} + +static ssize_t listmount(uint64_t mnt_id, uint64_t mnt_ns_id, + uint64_t last_mnt_id, uint64_t list[], size_t num, + unsigned int flags) +{ + struct mnt_id_req req = { + .size = MNT_ID_REQ_SIZE_VER0, + .mnt_id = mnt_id, + .param = last_mnt_id, + }; + + if (mnt_ns_id) { + req.size = MNT_ID_REQ_SIZE_VER1; + req.mnt_ns_id = mnt_ns_id; + } + + return syscall(__NR_listmount, &req, list, num, flags); +} + +static void show_mnt_attrs(uint64_t flags) +{ + printf("%s", flags & MOUNT_ATTR_RDONLY ? "ro" : "rw"); + + if (flags & MOUNT_ATTR_NOSUID) + printf(",nosuid"); + if (flags & MOUNT_ATTR_NODEV) + printf(",nodev"); + if (flags & MOUNT_ATTR_NOEXEC) + printf(",noexec"); + + switch (flags & MOUNT_ATTR__ATIME) { + case MOUNT_ATTR_RELATIME: + printf(",relatime"); + break; + case MOUNT_ATTR_NOATIME: + printf(",noatime"); + break; + case MOUNT_ATTR_STRICTATIME: + /* print nothing */ + break; + } + + if (flags & MOUNT_ATTR_NOSYMFOLLOW) + printf(",nosymfollow"); + if (flags & MOUNT_ATTR_IDMAP) + printf(",idmapped"); +} + +static void show_propagation(struct statmount *sm) +{ + if (sm->mnt_propagation & MS_SHARED) + printf(" shared:%llu", sm->mnt_peer_group); + if (sm->mnt_propagation & MS_SLAVE) { + printf(" master:%llu", sm->mnt_master); + if (sm->mnt_master) + printf(" propagate_from:%llu", sm->propagate_from); + } + if (sm->mnt_propagation & MS_UNBINDABLE) + printf(" unbindable"); +} + +static void show_sb_flags(uint64_t flags) +{ + printf("%s", flags & MS_RDONLY ? "ro" : "rw"); + if (flags & MS_SYNCHRONOUS) + printf(",sync"); + if (flags & MS_DIRSYNC) + printf(",dirsync"); + if (flags & MS_MANDLOCK) + printf(",mand"); + if (flags & MS_LAZYTIME) + printf(",lazytime"); +} + +static int dump_mountinfo(uint64_t mnt_id, uint64_t mnt_ns_id) +{ + int ret; + struct statmount *buf = alloca(STATMOUNT_BUFSIZE); + const uint64_t mask = STATMOUNT_SB_BASIC | STATMOUNT_MNT_BASIC | + STATMOUNT_PROPAGATE_FROM | STATMOUNT_FS_TYPE | + STATMOUNT_MNT_ROOT | STATMOUNT_MNT_POINT | + STATMOUNT_MNT_OPTS | STATMOUNT_FS_SUBTYPE | + STATMOUNT_SB_SOURCE; + + ret = statmount(mnt_id, mnt_ns_id, mask, buf, STATMOUNT_BUFSIZE, 0); + if (ret < 0) { + perror("statmount"); + return 1; + } + + if (ext_format) + printf("0x%lx 0x%lx 0x%llx ", mnt_ns_id, mnt_id, buf->mnt_parent_id); + + printf("%u %u %u:%u %s %s ", buf->mnt_id_old, buf->mnt_parent_id_old, + buf->sb_dev_major, buf->sb_dev_minor, + &buf->str[buf->mnt_root], + &buf->str[buf->mnt_point]); + show_mnt_attrs(buf->mnt_attr); + show_propagation(buf); + + printf(" - %s", &buf->str[buf->fs_type]); + if (buf->mask & STATMOUNT_FS_SUBTYPE) + printf(".%s", &buf->str[buf->fs_subtype]); + if (buf->mask & STATMOUNT_SB_SOURCE) + printf(" %s ", &buf->str[buf->sb_source]); + else + printf(" :none "); + + show_sb_flags(buf->sb_flags); + if (buf->mask & STATMOUNT_MNT_OPTS) + printf(",%s", &buf->str[buf->mnt_opts]); + printf("\n"); + return 0; +} + +static int dump_mounts(uint64_t mnt_ns_id) +{ + uint64_t mntid[MAXMOUNTS]; + uint64_t last_mnt_id = 0; + ssize_t count; + int i; + + /* + * Get a list of all mntids in mnt_ns_id. If it returns MAXMOUNTS + * mounts, then go again until we get everything. + */ + do { + count = listmount(LSMT_ROOT, mnt_ns_id, last_mnt_id, mntid, MAXMOUNTS, 0); + if (count < 0 || count > MAXMOUNTS) { + errno = count < 0 ? errno : count; + perror("listmount"); + return 1; + } + + /* Walk the returned mntids and print info about each */ + for (i = 0; i < count; ++i) { + int ret = dump_mountinfo(mntid[i], mnt_ns_id); + + if (ret != 0) + return ret; + } + /* Set up last_mnt_id to pick up where we left off */ + last_mnt_id = mntid[count - 1]; + } while (count == MAXMOUNTS); + return 0; +} + +static void usage(const char * const prog) +{ + printf("Usage:\n"); + printf("%s [-e] [-p pid] [-r] [-h]\n", prog); + printf(" -e: extended format\n"); + printf(" -h: print usage message\n"); + printf(" -p: get mount namespace from given pid\n"); + printf(" -r: recursively print all mounts in all child namespaces\n"); +} + +int main(int argc, char * const *argv) +{ + struct mnt_ns_info mni = { .size = MNT_NS_INFO_SIZE_VER0 }; + int pidfd, mntns, ret, opt; + pid_t pid = getpid(); + bool recursive = false; + + while ((opt = getopt(argc, argv, "ehp:r")) != -1) { + switch (opt) { + case 'e': + ext_format = true; + break; + case 'h': + usage(argv[0]); + return 0; + case 'p': + pid = atoi(optarg); + break; + case 'r': + recursive = true; + break; + } + } + + /* Get a pidfd for pid */ + pidfd = syscall(SYS_pidfd_open, pid, 0); + if (pidfd < 0) { + perror("pidfd_open"); + return 1; + } + + /* Get the mnt namespace for pidfd */ + mntns = ioctl(pidfd, PIDFD_GET_MNT_NAMESPACE, NULL); + if (mntns < 0) { + perror("PIDFD_GET_MNT_NAMESPACE"); + return 1; + } + close(pidfd); + + /* get info about mntns. In particular, the mnt_ns_id */ + ret = ioctl(mntns, NS_MNT_GET_INFO, &mni); + if (ret < 0) { + perror("NS_MNT_GET_INFO"); + return 1; + } + + do { + int ret; + + ret = dump_mounts(mni.mnt_ns_id); + if (ret) + return ret; + + if (!recursive) + break; + + /* get the next mntns (and overwrite the old mount ns info) */ + ret = ioctl(mntns, NS_MNT_GET_NEXT, &mni); + close(mntns); + mntns = ret; + } while (mntns >= 0); + + return 0; +}