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/* SPDX-License-Identifier: LGPL-2.1-or-later */
#include <errno.h>
#include <fcntl.h>
#include <stdbool.h>
#include <stdlib.h>
#include <sys/stat.h>
#include <syslog.h>
#include <unistd.h>
#include "alloc-util.h"
#include "base-filesystem.h"
#include "fd-util.h"
#include "log.h"
#include "macro.h"
#include "nulstr-util.h"
#include "path-util.h"
#include "string-util.h"
#include "umask-util.h"
#include "user-util.h"
typedef struct BaseFilesystem {
const char *dir; /* directory or symlink to create */
mode_t mode;
const char *target; /* if non-NULL create as symlink to this target */
const char *exists; /* conditionalize this entry on existance of this file */
bool ignore_failure;
} BaseFilesystem;
static const BaseFilesystem table[] = {
{ "bin", 0, "usr/bin\0", NULL },
{ "lib", 0, "usr/lib\0", NULL },
{ "root", 0755, NULL, NULL, true },
{ "sbin", 0, "usr/sbin\0", NULL },
{ "usr", 0755, NULL, NULL },
{ "var", 0755, NULL, NULL },
{ "etc", 0755, NULL, NULL },
{ "proc", 0755, NULL, NULL, true },
{ "sys", 0755, NULL, NULL, true },
{ "dev", 0755, NULL, NULL, true },
#if defined(__i386__) || defined(__x86_64__)
/* Various architecture ABIs define the path to the dynamic loader via the /lib64/ subdirectory of
* the root directory. When booting from an otherwise empty root file system (where only /usr/ has
* been mounted into) it is thus necessary to create a symlink pointing to the right subdirectory of
* /usr/ first — otherwise we couldn't invoke any dynamic binary. Let's detect this case here, and
* create the symlink as needed should it be missing. We prefer doing this consistently with Debian's
* multiarch logic, but support Fedora-style multilib too.*/
{ "lib64", 0, "usr/lib/x86_64-linux-gnu\0"
"usr/lib64\0", "ld-linux-x86-64.so.2" },
#else
/* gcc doesn't allow pragma to be used within constructs, hence log about this separately below */
# define WARN_LIB64 1
#endif
};
#ifdef WARN_LIB64
#pragma message "If your architecture knows a /lib64/ or /lib32/ directory, please add an entry creating it here."
/* And if your architecture doesn't know these directories, make sure to add ifdeffery here to
* suppress this pragma message. */
#endif
int base_filesystem_create(const char *root, uid_t uid, gid_t gid) {
_cleanup_close_ int fd = -1;
int r;
fd = open(root, O_RDONLY|O_NONBLOCK|O_DIRECTORY|O_CLOEXEC|O_NOFOLLOW);
if (fd < 0)
return log_error_errno(errno, "Failed to open root file system: %m");
for (size_t i = 0; i < ELEMENTSOF(table); i++) {
if (faccessat(fd, table[i].dir, F_OK, AT_SYMLINK_NOFOLLOW) >= 0)
continue;
if (table[i].target) {
const char *target = NULL, *s;
/* check if one of the targets exists */
NULSTR_FOREACH(s, table[i].target) {
if (faccessat(fd, s, F_OK, AT_SYMLINK_NOFOLLOW) < 0)
continue;
/* check if a specific file exists at the target path */
if (table[i].exists) {
_cleanup_free_ char *p = NULL;
p = path_join(s, table[i].exists);
if (!p)
return log_oom();
if (faccessat(fd, p, F_OK, AT_SYMLINK_NOFOLLOW) < 0)
continue;
}
target = s;
break;
}
if (!target)
continue;
if (symlinkat(target, fd, table[i].dir) < 0) {
log_full_errno(IN_SET(errno, EEXIST, EROFS) || table[i].ignore_failure ? LOG_DEBUG : LOG_ERR, errno,
"Failed to create symlink at %s/%s: %m", root, table[i].dir);
if (IN_SET(errno, EEXIST, EROFS) || table[i].ignore_failure)
continue;
return -errno;
}
if (uid_is_valid(uid) || gid_is_valid(gid))
if (fchownat(fd, table[i].dir, uid, gid, AT_SYMLINK_NOFOLLOW) < 0)
return log_error_errno(errno, "Failed to chown symlink at %s/%s: %m", root, table[i].dir);
continue;
}
RUN_WITH_UMASK(0000)
r = mkdirat(fd, table[i].dir, table[i].mode);
if (r < 0) {
log_full_errno(IN_SET(errno, EEXIST, EROFS) || table[i].ignore_failure ? LOG_DEBUG : LOG_ERR, errno,
"Failed to create directory at %s/%s: %m", root, table[i].dir);
if (IN_SET(errno, EEXIST, EROFS) || table[i].ignore_failure)
continue;
return -errno;
}
if (uid != UID_INVALID || gid != UID_INVALID)
if (fchownat(fd, table[i].dir, uid, gid, AT_SYMLINK_NOFOLLOW) < 0)
return log_error_errno(errno, "Failed to chown directory at %s/%s: %m", root, table[i].dir);
}
return 0;
}
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