229 lines
6.7 KiB
C
229 lines
6.7 KiB
C
/* SPDX-License-Identifier: LGPL-2.1+ */
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/***
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This file is part of systemd.
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Copyright 2010 Lennart Poettering
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systemd is free software; you can redistribute it and/or modify it
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under the terms of the GNU Lesser General Public License as published by
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the Free Software Foundation; either version 2.1 of the License, or
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(at your option) any later version.
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systemd is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public License
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along with systemd; If not, see <http://www.gnu.org/licenses/>.
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***/
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#include <errno.h>
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#include <fcntl.h>
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#include <linux/stat.h>
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#include <stdint.h>
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#include <stdlib.h>
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#include <string.h>
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#include <sys/time.h>
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#include <sys/xattr.h>
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#include "alloc-util.h"
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#include "fd-util.h"
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#include "macro.h"
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#include "missing.h"
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#include "sparse-endian.h"
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#include "stdio-util.h"
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#include "string-util.h"
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#include "time-util.h"
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#include "xattr-util.h"
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int getxattr_malloc(const char *path, const char *name, char **value, bool allow_symlink) {
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char *v;
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size_t l;
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ssize_t n;
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assert(path);
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assert(name);
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assert(value);
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for (l = 100; ; l = (size_t) n + 1) {
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v = new0(char, l);
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if (!v)
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return -ENOMEM;
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if (allow_symlink)
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n = lgetxattr(path, name, v, l);
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else
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n = getxattr(path, name, v, l);
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if (n >= 0 && (size_t) n < l) {
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*value = v;
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return n;
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}
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free(v);
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if (n < 0 && errno != ERANGE)
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return -errno;
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if (allow_symlink)
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n = lgetxattr(path, name, NULL, 0);
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else
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n = getxattr(path, name, NULL, 0);
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if (n < 0)
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return -errno;
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}
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}
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int fgetxattr_malloc(int fd, const char *name, char **value) {
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char *v;
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size_t l;
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ssize_t n;
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assert(fd >= 0);
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assert(name);
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assert(value);
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for (l = 100; ; l = (size_t) n + 1) {
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v = new0(char, l);
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if (!v)
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return -ENOMEM;
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n = fgetxattr(fd, name, v, l);
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if (n >= 0 && (size_t) n < l) {
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*value = v;
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return n;
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}
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free(v);
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if (n < 0 && errno != ERANGE)
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return -errno;
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n = fgetxattr(fd, name, NULL, 0);
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if (n < 0)
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return -errno;
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}
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}
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ssize_t fgetxattrat_fake(int dirfd, const char *filename, const char *attribute, void *value, size_t size, int flags) {
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char fn[STRLEN("/proc/self/fd/") + DECIMAL_STR_MAX(int) + 1];
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_cleanup_close_ int fd = -1;
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ssize_t l;
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/* The kernel doesn't have a fgetxattrat() command, hence let's emulate one */
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if (flags & ~(AT_SYMLINK_NOFOLLOW|AT_EMPTY_PATH))
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return -EINVAL;
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if (isempty(filename)) {
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if (!(flags & AT_EMPTY_PATH))
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return -EINVAL;
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xsprintf(fn, "/proc/self/fd/%i", dirfd);
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} else {
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fd = openat(dirfd, filename, O_CLOEXEC|O_PATH|(flags & AT_SYMLINK_NOFOLLOW ? O_NOFOLLOW : 0));
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if (fd < 0)
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return -errno;
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xsprintf(fn, "/proc/self/fd/%i", fd);
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}
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l = getxattr(fn, attribute, value, size);
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if (l < 0)
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return -errno;
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return l;
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}
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static int parse_crtime(le64_t le, usec_t *usec) {
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uint64_t u;
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assert(usec);
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u = le64toh(le);
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if (IN_SET(u, 0, (uint64_t) -1))
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return -EIO;
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*usec = (usec_t) u;
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return 0;
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}
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int fd_getcrtime_at(int dirfd, const char *name, usec_t *ret, int flags) {
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struct statx sx;
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usec_t a, b;
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le64_t le;
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ssize_t n;
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int r;
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assert(ret);
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if (flags & ~(AT_EMPTY_PATH|AT_SYMLINK_NOFOLLOW))
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return -EINVAL;
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/* So here's the deal: the creation/birth time (crtime/btime) of a file is a relatively newly supported concept
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* on Linux (or more strictly speaking: a concept that only recently got supported in the API, it was
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* implemented on various file systems on the lower level since a while, but never was accessible). However, we
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* needed a concept like that for vaccuuming algorithms and such, hence we emulated it via a user xattr for a
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* long time. Starting with Linux 4.11 there's statx() which exposes the timestamp to userspace for the first
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* time, where it is available. Thius function will read it, but it tries to keep some compatibility with older
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* systems: we try to read both the crtime/btime and the xattr, and then use whatever is older. After all the
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* concept is useful for determining how "old" a file really is, and hence using the older of the two makes
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* most sense. */
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if (statx(dirfd, strempty(name), flags|AT_STATX_DONT_SYNC, STATX_BTIME, &sx) >= 0 &&
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(sx.stx_mask & STATX_BTIME) &&
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sx.stx_btime.tv_sec != 0)
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a = (usec_t) sx.stx_btime.tv_sec * USEC_PER_SEC +
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(usec_t) sx.stx_btime.tv_nsec / NSEC_PER_USEC;
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else
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a = USEC_INFINITY;
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n = fgetxattrat_fake(dirfd, name, "user.crtime_usec", &le, sizeof(le), flags);
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if (n < 0)
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r = -errno;
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else if (n != sizeof(le))
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r = -EIO;
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else
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r = parse_crtime(le, &b);
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if (r < 0) {
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if (a != USEC_INFINITY) {
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*ret = a;
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return 0;
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}
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return r;
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}
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if (a != USEC_INFINITY)
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*ret = MIN(a, b);
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else
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*ret = b;
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return 0;
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}
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int fd_getcrtime(int fd, usec_t *ret) {
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return fd_getcrtime_at(fd, NULL, ret, AT_EMPTY_PATH);
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}
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int path_getcrtime(const char *p, usec_t *ret) {
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return fd_getcrtime_at(AT_FDCWD, p, ret, 0);
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}
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int fd_setcrtime(int fd, usec_t usec) {
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le64_t le;
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assert(fd >= 0);
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if (IN_SET(usec, 0, USEC_INFINITY))
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usec = now(CLOCK_REALTIME);
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le = htole64((uint64_t) usec);
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if (fsetxattr(fd, "user.crtime_usec", &le, sizeof(le), 0) < 0)
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return -errno;
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return 0;
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}
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