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/* SPDX-License-Identifier: LGPL-2.1-or-later */
#include <errno.h>
#include <fcntl.h>
#include <stdint.h>
#include <stdlib.h>
#include <sys/time.h>
#include <sys/xattr.h>
#include "alloc-util.h"
#include "errno-util.h"
#include "fd-util.h"
#include "macro.h"
#include "missing_syscall.h"
#include "sparse-endian.h"
#include "stat-util.h"
#include "stdio-util.h"
#include "string-util.h"
#include "time-util.h"
#include "xattr-util.h"
int getxattr_at_malloc(
int fd,
const char *path,
const char *name,
int flags,
char **ret) {
_cleanup_close_ int opened_fd = -1;
unsigned n_attempts = 7;
bool by_procfs = false;
size_t l = 100;
assert(fd >= 0 || fd == AT_FDCWD);
assert(name);
assert((flags & ~(AT_SYMLINK_FOLLOW|AT_EMPTY_PATH)) == 0);
assert(ret);
/* So, this is single function that does what getxattr()/lgetxattr()/fgetxattr() does, but in one go,
* and with additional bells and whistles. Specifically:
*
* 1. This works on O_PATH fds (which fgetxattr() does not)
* 2. Provides full openat()-style semantics, i.e. by-fd, by-path and combination thereof
* 3. As extension to openat()-style semantics implies AT_EMPTY_PATH if path is NULL.
* 4. Does a malloc() loop, automatically sizing the allocation
* 5. NUL-terminates the returned buffer (for safety)
*/
if (!path) /* If path is NULL, imply AT_EMPTY_PATH. – But if it's "", don't — for safety reasons. */
flags |= AT_EMPTY_PATH;
if (isempty(path)) {
if (!FLAGS_SET(flags, AT_EMPTY_PATH))
return -EINVAL;
if (fd == AT_FDCWD) /* Both unspecified? Then operate on current working directory */
path = ".";
else
path = NULL;
} else if (fd != AT_FDCWD) {
/* If both have been specified, then we go via O_PATH */
opened_fd = openat(fd, path, O_PATH|O_CLOEXEC|(FLAGS_SET(flags, AT_SYMLINK_FOLLOW) ? 0 : O_NOFOLLOW));
if (opened_fd < 0)
return -errno;
fd = opened_fd;
path = NULL;
by_procfs = true; /* fgetxattr() is not going to work, go via /proc/ link right-away */
}
for(;;) {
_cleanup_free_ char *v = NULL;
ssize_t n;
if (n_attempts == 0) /* If someone is racing against us, give up eventually */
return -EBUSY;
n_attempts--;
v = new0(char, l+1);
if (!v)
return -ENOMEM;
l = MALLOC_ELEMENTSOF(v) - 1;
if (path)
n = FLAGS_SET(flags, AT_SYMLINK_FOLLOW) ? getxattr(path, name, v, l) : lgetxattr(path, name, v, l);
else
n = by_procfs ? getxattr(FORMAT_PROC_FD_PATH(fd), name, v, l) : fgetxattr(fd, name, v, l);
if (n < 0) {
if (errno == EBADF) {
if (by_procfs || path)
return -EBADF;
by_procfs = true; /* Might be an O_PATH fd, try again via /proc/ link */
continue;
}
if (errno != ERANGE)
return -errno;
} else {
v[n] = 0; /* NUL terminate */
*ret = TAKE_PTR(v);
return (int) n;
}
if (path)
n = FLAGS_SET(flags, AT_SYMLINK_FOLLOW) ? getxattr(path, name, NULL, 0) : lgetxattr(path, name, NULL, 0);
else
n = by_procfs ? getxattr(FORMAT_PROC_FD_PATH(fd), name, NULL, 0) : fgetxattr(fd, name, NULL, 0);
if (n < 0)
return -errno;
if (n > INT_MAX) /* We couldn't return this as 'int' anymore */
return -E2BIG;
l = (size_t) n;
}
}
static int parse_crtime(le64_t le, usec_t *usec) {
uint64_t u;
assert(usec);
u = le64toh(le);
if (IN_SET(u, 0, UINT64_MAX))
return -EIO;
*usec = (usec_t) u;
return 0;
}
int fd_getcrtime_at(
int fd,
const char *path,
int flags,
usec_t *ret) {
_cleanup_free_ le64_t *le = NULL;
STRUCT_STATX_DEFINE(sx);
usec_t a, b;
int r;
assert(fd >= 0 || fd == AT_FDCWD);
assert((flags & ~(AT_SYMLINK_FOLLOW|AT_EMPTY_PATH)) == 0);
assert(ret);
if (!path)
flags |= AT_EMPTY_PATH;
/* So here's the deal: the creation/birth time (crtime/btime) of a file is a relatively newly supported concept
* on Linux (or more strictly speaking: a concept that only recently got supported in the API, it was
* implemented on various file systems on the lower level since a while, but never was accessible). However, we
* needed a concept like that for vaccuuming algorithms and such, hence we emulated it via a user xattr for a
* long time. Starting with Linux 4.11 there's statx() which exposes the timestamp to userspace for the first
* time, where it is available. Thius function will read it, but it tries to keep some compatibility with older
* systems: we try to read both the crtime/btime and the xattr, and then use whatever is older. After all the
* concept is useful for determining how "old" a file really is, and hence using the older of the two makes
* most sense. */
if (statx(fd, strempty(path),
(flags & ~AT_SYMLINK_FOLLOW)|(FLAGS_SET(flags, AT_SYMLINK_FOLLOW) ? 0 : AT_SYMLINK_NOFOLLOW)|AT_STATX_DONT_SYNC,
STATX_BTIME,
&sx) >= 0 &&
(sx.stx_mask & STATX_BTIME) &&
sx.stx_btime.tv_sec != 0)
a = (usec_t) sx.stx_btime.tv_sec * USEC_PER_SEC +
(usec_t) sx.stx_btime.tv_nsec / NSEC_PER_USEC;
else
a = USEC_INFINITY;
r = getxattr_at_malloc(fd, path, "user.crtime_usec", flags, (char**) &le);
if (r >= 0) {
if (r != sizeof(*le))
r = -EIO;
else
r = parse_crtime(*le, &b);
}
if (r < 0) {
if (a != USEC_INFINITY) {
*ret = a;
return 0;
}
return r;
}
if (a != USEC_INFINITY)
*ret = MIN(a, b);
else
*ret = b;
return 0;
}
int fd_setcrtime(int fd, usec_t usec) {
le64_t le;
assert(fd >= 0);
if (!timestamp_is_set(usec))
usec = now(CLOCK_REALTIME);
le = htole64((uint64_t) usec);
return RET_NERRNO(fsetxattr(fd, "user.crtime_usec", &le, sizeof(le), 0));
}
int listxattr_at_malloc(
int fd,
const char *path,
int flags,
char **ret) {
_cleanup_close_ int opened_fd = -1;
bool by_procfs = false;
unsigned n_attempts = 7;
size_t l = 100;
assert(fd >= 0 || fd == AT_FDCWD);
assert((flags & ~(AT_SYMLINK_FOLLOW|AT_EMPTY_PATH)) == 0);
assert(ret);
/* This is to listxattr()/llistattr()/flistattr() what getxattr_at_malloc() is to getxattr()/… */
if (!path) /* If path is NULL, imply AT_EMPTY_PATH. – But if it's "", don't. */
flags |= AT_EMPTY_PATH;
if (isempty(path)) {
if (!FLAGS_SET(flags, AT_EMPTY_PATH))
return -EINVAL;
if (fd == AT_FDCWD) /* Both unspecified? Then operate on current working directory */
path = ".";
else
path = NULL;
} else if (fd != AT_FDCWD) {
/* If both have been specified, then we go via O_PATH */
opened_fd = openat(fd, path, O_PATH|O_CLOEXEC|(FLAGS_SET(flags, AT_SYMLINK_FOLLOW) ? 0 : O_NOFOLLOW));
if (opened_fd < 0)
return -errno;
fd = opened_fd;
path = NULL;
by_procfs = true;
}
for (;;) {
_cleanup_free_ char *v = NULL;
ssize_t n;
if (n_attempts == 0) /* If someone is racing against us, give up eventually */
return -EBUSY;
n_attempts--;
v = new(char, l+1);
if (!v)
return -ENOMEM;
l = MALLOC_ELEMENTSOF(v) - 1;
if (path)
n = FLAGS_SET(flags, AT_SYMLINK_FOLLOW) ? listxattr(path, v, l) : llistxattr(path, v, l);
else
n = by_procfs ? listxattr(FORMAT_PROC_FD_PATH(fd), v, l) : flistxattr(fd, v, l);
if (n < 0) {
if (errno == EBADF) {
if (by_procfs || path)
return -EBADF;
by_procfs = true; /* Might be an O_PATH fd, try again via /proc/ link */
continue;
}
if (errno != ERANGE)
return -errno;
} else {
v[n] = 0; /* NUL terminate */
*ret = TAKE_PTR(v);
return (int) n;
}
if (path)
n = FLAGS_SET(flags, AT_SYMLINK_FOLLOW) ? listxattr(path, NULL, 0) : llistxattr(path, NULL, 0);
else
n = by_procfs ? listxattr(FORMAT_PROC_FD_PATH(fd), NULL, 0) : flistxattr(fd, NULL, 0);
if (n < 0)
return -errno;
if (n > INT_MAX) /* We couldn't return this as 'int' anymore */
return -E2BIG;
l = (size_t) n;
}
}
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