picnoir
/
Systemd
1
0
Fork 0
Code Issues Pull Requests Projects Releases Wiki Activity
Systemd/src/basic/path-util.c

939 lines
26 KiB
C
Raw Blame History

/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
/***
This file is part of systemd.
Copyright 2010-2012 Lennart Poettering
systemd is free software; you can redistribute it and/or modify it
under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation; either version 2.1 of the License, or
(at your option) any later version.
systemd is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public License
along with systemd; If not, see <http://www.gnu.org/licenses/>.
***/
#include <errno.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/statvfs.h>
#include <unistd.h>
#include "fd-util.h"
#include "fileio.h"
#include "log.h"
#include "macro.h"
#include "missing.h"
#include "path-util.h"
#include "string-util.h"
#include "strv.h"
#include "util.h"
bool path_is_absolute(const char *p) {
return p[0] == '/';
}
bool is_path(const char *p) {
return !!strchr(p, '/');
}
int path_get_parent(const char *path, char **_r) {
const char *e, *a = NULL, *b = NULL, *p;
char *r;
bool slash = false;
assert(path);
assert(_r);
if (!*path)
return -EINVAL;
for (e = path; *e; e++) {
if (!slash && *e == '/') {
a = b;
b = e;
slash = true;
} else if (slash && *e != '/')
slash = false;
}
if (*(e-1) == '/')
p = a;
else
p = b;
if (!p)
return -EINVAL;
if (p == path)
r = strdup("/");
else
r = strndup(path, p-path);
if (!r)
return -ENOMEM;
*_r = r;
return 0;
}
int path_split_and_make_absolute(const char *p, char ***ret) {
char **l;
int r;
assert(p);
assert(ret);
l = strv_split(p, ":");
if (!l)
return NULL;
r = path_strv_make_absolute_cwd(l);
if (r < 0) {
strv_free(l);
return r;
}
*ret = l;
return r;
}
char *path_make_absolute(const char *p, const char *prefix) {
assert(p);
/* Makes every item in the list an absolute path by prepending
* the prefix, if specified and necessary */
if (path_is_absolute(p) || !prefix)
return strdup(p);
return strjoin(prefix, "/", p, NULL);
}
int path_make_absolute_cwd(const char *p, char **ret) {
char *c;
assert(p);
assert(ret);
/* Similar to path_make_absolute(), but prefixes with the
* current working directory. */
if (path_is_absolute(p))
c = strdup(p);
else {
_cleanup_free_ char *cwd = NULL;
cwd = get_current_dir_name();
if (!cwd)
return -errno;
c = strjoin(cwd, "/", p, NULL);
}
if (!c)
return -ENOMEM;
*ret = c;
return 0;
}
int path_make_relative(const char *from_dir, const char *to_path, char **_r) {
char *r, *p;
unsigned n_parents;
assert(from_dir);
assert(to_path);
assert(_r);
/* Strips the common part, and adds ".." elements as necessary. */
if (!path_is_absolute(from_dir))
return -EINVAL;
if (!path_is_absolute(to_path))
return -EINVAL;
/* Skip the common part. */
for (;;) {
size_t a;
size_t b;
from_dir += strspn(from_dir, "/");
to_path += strspn(to_path, "/");
if (!*from_dir) {
if (!*to_path)
/* from_dir equals to_path. */
r = strdup(".");
else
/* from_dir is a parent directory of to_path. */
r = strdup(to_path);
if (!r)
return -ENOMEM;
path_kill_slashes(r);
*_r = r;
return 0;
}
if (!*to_path)
break;
a = strcspn(from_dir, "/");
b = strcspn(to_path, "/");
if (a != b)
break;
if (memcmp(from_dir, to_path, a) != 0)
break;
from_dir += a;
to_path += b;
}
/* If we're here, then "from_dir" has one or more elements that need to
* be replaced with "..". */
/* Count the number of necessary ".." elements. */
for (n_parents = 0;;) {
from_dir += strspn(from_dir, "/");
if (!*from_dir)
break;
from_dir += strcspn(from_dir, "/");
n_parents++;
}
r = malloc(n_parents * 3 + strlen(to_path) + 1);
if (!r)
return -ENOMEM;
for (p = r; n_parents > 0; n_parents--, p += 3)
memcpy(p, "../", 3);
strcpy(p, to_path);
path_kill_slashes(r);
*_r = r;
return 0;
}
int path_strv_make_absolute_cwd(char **l) {
char **s;
int r;
/* Goes through every item in the string list and makes it
* absolute. This works in place and won't rollback any
* changes on failure. */
STRV_FOREACH(s, l) {
char *t;
r = path_make_absolute_cwd(*s, &t);
if (r < 0)
return r;
free(*s);
*s = t;
}
return 0;
}
char **path_strv_resolve(char **l, const char *prefix) {
char **s;
unsigned k = 0;
bool enomem = false;
if (strv_isempty(l))
return l;
/* Goes through every item in the string list and canonicalize
* the path. This works in place and won't rollback any
* changes on failure. */
STRV_FOREACH(s, l) {
char *t, *u;
_cleanup_free_ char *orig = NULL;
if (!path_is_absolute(*s)) {
free(*s);
continue;
}
if (prefix) {
orig = *s;
t = strappend(prefix, orig);
if (!t) {
enomem = true;
continue;
}
} else
t = *s;
errno = 0;
u = canonicalize_file_name(t);
if (!u) {
if (errno == ENOENT) {
if (prefix) {
u = orig;
orig = NULL;
free(t);
} else
u = t;
} else {
free(t);
if (errno == ENOMEM || errno == 0)
enomem = true;
continue;
}
} else if (prefix) {
char *x;
free(t);
x = path_startswith(u, prefix);
if (x) {
/* restore the slash if it was lost */
if (!startswith(x, "/"))
*(--x) = '/';
t = strdup(x);
free(u);
if (!t) {
enomem = true;
continue;
}
u = t;
} else {
/* canonicalized path goes outside of
* prefix, keep the original path instead */
free(u);
u = orig;
orig = NULL;
}
} else
free(t);
l[k++] = u;
}
l[k] = NULL;
if (enomem)
return NULL;
return l;
}
char **path_strv_resolve_uniq(char **l, const char *prefix) {
if (strv_isempty(l))
return l;
if (!path_strv_resolve(l, prefix))
return NULL;
return strv_uniq(l);
}
char *path_kill_slashes(char *path) {
char *f, *t;
bool slash = false;
/* Removes redundant inner and trailing slashes. Modifies the
* passed string in-place.
*
* ///foo///bar/ becomes /foo/bar
*/
for (f = path, t = path; *f; f++) {
if (*f == '/') {
slash = true;
continue;
}
if (slash) {
slash = false;
*(t++) = '/';
}
*(t++) = *f;
}
/* Special rule, if we are talking of the root directory, a
trailing slash is good */
if (t == path && slash)
*(t++) = '/';
*t = 0;
return path;
}
char* path_startswith(const char *path, const char *prefix) {
assert(path);
assert(prefix);
if ((path[0] == '/') != (prefix[0] == '/'))
return NULL;
for (;;) {
size_t a, b;
path += strspn(path, "/");
prefix += strspn(prefix, "/");
if (*prefix == 0)
return (char*) path;
if (*path == 0)
return NULL;
a = strcspn(path, "/");
b = strcspn(prefix, "/");
if (a != b)
return NULL;
if (memcmp(path, prefix, a) != 0)
return NULL;
path += a;
prefix += b;
}
}
int path_compare(const char *a, const char *b) {
int d;
assert(a);
assert(b);
/* A relative path and an abolute path must not compare as equal.
* Which one is sorted before the other does not really matter.
* Here a relative path is ordered before an absolute path. */
d = (a[0] == '/') - (b[0] == '/');
if (d)
return d;
for (;;) {
size_t j, k;
a += strspn(a, "/");
b += strspn(b, "/");
if (*a == 0 && *b == 0)
return 0;
/* Order prefixes first: "/foo" before "/foo/bar" */
if (*a == 0)
return -1;
if (*b == 0)
return 1;
j = strcspn(a, "/");
k = strcspn(b, "/");
/* Alphabetical sort: "/foo/aaa" before "/foo/b" */
d = memcmp(a, b, MIN(j, k));
if (d)
return (d > 0) - (d < 0); /* sign of d */
/* Sort "/foo/a" before "/foo/aaa" */
d = (j > k) - (j < k); /* sign of (j - k) */
if (d)
return d;
a += j;
b += k;
}
}
bool path_equal(const char *a, const char *b) {
return path_compare(a, b) == 0;
}
bool path_equal_or_files_same(const char *a, const char *b) {
return path_equal(a, b) || files_same(a, b) > 0;
}
char* path_join(const char *root, const char *path, const char *rest) {
assert(path);
if (!isempty(root))
return strjoin(root, endswith(root, "/") ? "" : "/",
path[0] == '/' ? path+1 : path,
rest ? (endswith(path, "/") ? "" : "/") : NULL,
rest && rest[0] == '/' ? rest+1 : rest,
NULL);
else
return strjoin(path,
rest ? (endswith(path, "/") ? "" : "/") : NULL,
rest && rest[0] == '/' ? rest+1 : rest,
NULL);
}
static int fd_fdinfo_mnt_id(int fd, const char *filename, int flags, int *mnt_id) {
char path[strlen("/proc/self/fdinfo/") + DECIMAL_STR_MAX(int)];
_cleanup_free_ char *fdinfo = NULL;
_cleanup_close_ int subfd = -1;
char *p;
int r;
if ((flags & AT_EMPTY_PATH) && isempty(filename))
xsprintf(path, "/proc/self/fdinfo/%i", fd);
else {
subfd = openat(fd, filename, O_RDONLY|O_CLOEXEC|O_NOCTTY|O_PATH);
if (subfd < 0)
return -errno;
xsprintf(path, "/proc/self/fdinfo/%i", subfd);
}
r = read_full_file(path, &fdinfo, NULL);
if (r == -ENOENT) /* The fdinfo directory is a relatively new addition */
return -EOPNOTSUPP;
if (r < 0)
return -errno;
p = startswith(fdinfo, "mnt_id:");
if (!p) {
p = strstr(fdinfo, "\nmnt_id:");
if (!p) /* The mnt_id field is a relatively new addition */
return -EOPNOTSUPP;
p += 8;
}
p += strspn(p, WHITESPACE);
p[strcspn(p, WHITESPACE)] = 0;
return safe_atoi(p, mnt_id);
}
int fd_is_mount_point(int fd, const char *filename, int flags) {
union file_handle_union h = FILE_HANDLE_INIT, h_parent = FILE_HANDLE_INIT;
int mount_id = -1, mount_id_parent = -1;
bool nosupp = false, check_st_dev = true;
struct stat a, b;
int r;
assert(fd >= 0);
assert(filename);
/* First we will try the name_to_handle_at() syscall, which
* tells us the mount id and an opaque file "handle". It is
* not supported everywhere though (kernel compile-time
* option, not all file systems are hooked up). If it works
* the mount id is usually good enough to tell us whether
* something is a mount point.
*
* If that didn't work we will try to read the mount id from
* /proc/self/fdinfo/<fd>. This is almost as good as
* name_to_handle_at(), however, does not return the
* opaque file handle. The opaque file handle is pretty useful
* to detect the root directory, which we should always
* consider a mount point. Hence we use this only as
* fallback. Exporting the mnt_id in fdinfo is a pretty recent
* kernel addition.
*
* As last fallback we do traditional fstat() based st_dev
* comparisons. This is how things were traditionally done,
* but unionfs breaks breaks this since it exposes file
* systems with a variety of st_dev reported. Also, btrfs
* subvolumes have different st_dev, even though they aren't
* real mounts of their own. */
r = name_to_handle_at(fd, filename, &h.handle, &mount_id, flags);
if (r < 0) {
if (errno == ENOSYS)
/* This kernel does not support name_to_handle_at()
* fall back to simpler logic. */
goto fallback_fdinfo;
else if (errno == EOPNOTSUPP)
/* This kernel or file system does not support
* name_to_handle_at(), hence let's see if the
* upper fs supports it (in which case it is a
* mount point), otherwise fallback to the
* traditional stat() logic */
nosupp = true;
else
return -errno;
}
r = name_to_handle_at(fd, "", &h_parent.handle, &mount_id_parent, AT_EMPTY_PATH);
if (r < 0) {
if (errno == EOPNOTSUPP) {
if (nosupp)
/* Neither parent nor child do name_to_handle_at()?
We have no choice but to fall back. */
goto fallback_fdinfo;
else
/* The parent can't do name_to_handle_at() but the
* directory we are interested in can?
* If so, it must be a mount point. */
return 1;
} else
return -errno;
}
/* The parent can do name_to_handle_at() but the
* directory we are interested in can't? If so, it
* must be a mount point. */
if (nosupp)
return 1;
/* If the file handle for the directory we are
* interested in and its parent are identical, we
* assume this is the root directory, which is a mount
* point. */
if (h.handle.handle_bytes == h_parent.handle.handle_bytes &&
h.handle.handle_type == h_parent.handle.handle_type &&
memcmp(h.handle.f_handle, h_parent.handle.f_handle, h.handle.handle_bytes) == 0)
return 1;
return mount_id != mount_id_parent;
fallback_fdinfo:
r = fd_fdinfo_mnt_id(fd, filename, flags, &mount_id);
if (r == -EOPNOTSUPP)
goto fallback_fstat;
if (r < 0)
return r;
r = fd_fdinfo_mnt_id(fd, "", AT_EMPTY_PATH, &mount_id_parent);
if (r < 0)
return r;
if (mount_id != mount_id_parent)
return 1;
/* Hmm, so, the mount ids are the same. This leaves one
* special case though for the root file system. For that,
* let's see if the parent directory has the same inode as we
* are interested in. Hence, let's also do fstat() checks now,
* too, but avoid the st_dev comparisons, since they aren't
* that useful on unionfs mounts. */
check_st_dev = false;
fallback_fstat:
/* yay for fstatat() taking a different set of flags than the other
* _at() above */
if (flags & AT_SYMLINK_FOLLOW)
flags &= ~AT_SYMLINK_FOLLOW;
else
flags |= AT_SYMLINK_NOFOLLOW;
if (fstatat(fd, filename, &a, flags) < 0)
return -errno;
if (fstatat(fd, "", &b, AT_EMPTY_PATH) < 0)
return -errno;
/* A directory with same device and inode as its parent? Must
* be the root directory */
if (a.st_dev == b.st_dev &&
a.st_ino == b.st_ino)
return 1;
return check_st_dev && (a.st_dev != b.st_dev);
}
/* flags can be AT_SYMLINK_FOLLOW or 0 */
int path_is_mount_point(const char *t, int flags) {
_cleanup_close_ int fd = -1;
_cleanup_free_ char *canonical = NULL, *parent = NULL;
int r;
assert(t);
if (path_equal(t, "/"))
return 1;
/* we need to resolve symlinks manually, we can't just rely on
* fd_is_mount_point() to do that for us; if we have a structure like
* /bin -> /usr/bin/ and /usr is a mount point, then the parent that we
* look at needs to be /usr, not /. */
if (flags & AT_SYMLINK_FOLLOW) {
canonical = canonicalize_file_name(t);
if (!canonical)
return -errno;
t = canonical;
}
r = path_get_parent(t, &parent);
if (r < 0)
return r;
fd = openat(AT_FDCWD, parent, O_RDONLY|O_NONBLOCK|O_DIRECTORY|O_CLOEXEC|O_PATH);
if (fd < 0)
return -errno;
return fd_is_mount_point(fd, basename(t), flags);
}
int path_is_read_only_fs(const char *path) {
struct statvfs st;
assert(path);
if (statvfs(path, &st) < 0)
return -errno;
if (st.f_flag & ST_RDONLY)
return true;
/* On NFS, statvfs() might not reflect whether we can actually
* write to the remote share. Let's try again with
* access(W_OK) which is more reliable, at least sometimes. */
if (access(path, W_OK) < 0 && errno == EROFS)
return true;
return false;
}
int path_is_os_tree(const char *path) {
char *p;
int r;
/* We use /usr/lib/os-release as flag file if something is an OS */
p = strjoina(path, "/usr/lib/os-release");
r = access(p, F_OK);
if (r >= 0)
return 1;
/* Also check for the old location in /etc, just in case. */
p = strjoina(path, "/etc/os-release");
r = access(p, F_OK);
return r >= 0;
}
int find_binary(const char *name, char **ret) {
int last_error, r;
const char *p;
assert(name);
if (is_path(name)) {
if (access(name, X_OK) < 0)
return -errno;
if (ret) {
r = path_make_absolute_cwd(name, ret);
if (r < 0)
return r;
}
return 0;
}
/**
* Plain getenv, not secure_getenv, because we want
* to actually allow the user to pick the binary.
*/
p = getenv("PATH");
if (!p)
p = DEFAULT_PATH;
last_error = -ENOENT;
for (;;) {
_cleanup_free_ char *j = NULL, *element = NULL;
r = extract_first_word(&p, &element, ":", EXTRACT_RELAX|EXTRACT_DONT_COALESCE_SEPARATORS);
if (r < 0)
return r;
if (r == 0)
break;
if (!path_is_absolute(element))
continue;
j = strjoin(element, "/", name, NULL);
if (!j)
return -ENOMEM;
if (access(j, X_OK) >= 0) {
/* Found it! */
if (ret) {
*ret = path_kill_slashes(j);
j = NULL;
}
return 0;
}
last_error = -errno;
}
return last_error;
}
bool paths_check_timestamp(const char* const* paths, usec_t *timestamp, bool update) {
bool changed = false;
const char* const* i;
assert(timestamp);
if (paths == NULL)
return false;
STRV_FOREACH(i, paths) {
struct stat stats;
usec_t u;
if (stat(*i, &stats) < 0)
continue;
u = timespec_load(&stats.st_mtim);
/* first check */
if (*timestamp >= u)
continue;
log_debug("timestamp of '%s' changed", *i);
/* update timestamp */
if (update) {
*timestamp = u;
changed = true;
} else
return true;
}
return changed;
}
static int binary_is_good(const char *binary) {
_cleanup_free_ char *p = NULL, *d = NULL;
int r;
r = find_binary(binary, &p);
if (r == -ENOENT)
return 0;
if (r < 0)
return r;
/* An fsck that is linked to /bin/true is a non-existent
* fsck */
r = readlink_malloc(p, &d);
if (r == -EINVAL) /* not a symlink */
return 1;
if (r < 0)
return r;
return !path_equal(d, "true") &&
!path_equal(d, "/bin/true") &&
!path_equal(d, "/usr/bin/true") &&
!path_equal(d, "/dev/null");
}
int fsck_exists(const char *fstype) {
const char *checker;
assert(fstype);
if (streq(fstype, "auto"))
return -EINVAL;
checker = strjoina("fsck.", fstype);
return binary_is_good(checker);
}
int mkfs_exists(const char *fstype) {
const char *mkfs;
assert(fstype);
if (streq(fstype, "auto"))
return -EINVAL;
mkfs = strjoina("mkfs.", fstype);
return binary_is_good(mkfs);
}
char *prefix_root(const char *root, const char *path) {
char *n, *p;
size_t l;
/* If root is passed, prefixes path with it. Otherwise returns
* it as is. */
assert(path);
/* First, drop duplicate prefixing slashes from the path */
while (path[0] == '/' && path[1] == '/')
path++;
if (isempty(root) || path_equal(root, "/"))
return strdup(path);
l = strlen(root) + 1 + strlen(path) + 1;
n = new(char, l);
if (!n)
return NULL;
p = stpcpy(n, root);
while (p > n && p[-1] == '/')
p--;
if (path[0] != '/')
*(p++) = '/';
strcpy(p, path);
return n;
}
int parse_path_argument_and_warn(const char *path, bool suppress_root, char **arg) {
char *p;
int r;
/*
* This function is intended to be used in command line
* parsers, to handle paths that are passed in. It makes the
* path absolute, and reduces it to NULL if omitted or
* root (the latter optionally).
*
* NOTE THAT THIS WILL FREE THE PREVIOUS ARGUMENT POINTER ON
* SUCCESS! Hence, do not pass in uninitialized pointers.
*/
if (isempty(path)) {
*arg = mfree(*arg);
return 0;
}
r = path_make_absolute_cwd(path, &p);
if (r < 0)
return log_error_errno(r, "Failed to parse path \"%s\" and make it absolute: %m", path);
path_kill_slashes(p);
if (suppress_root && path_equal(p, "/"))
p = mfree(p);
free(*arg);
*arg = p;
return 0;
}
Reference in New Issue View Git Blame Copy Permalink