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-rw-r--r--src/shared/base-filesystem.c210
1 files changed, 210 insertions, 0 deletions
diff --git a/src/shared/base-filesystem.c b/src/shared/base-filesystem.c
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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 "architecture.h"
+#include "base-filesystem.h"
+#include "errno-util.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 existence of this file */
+ bool ignore_failure;
+} BaseFilesystem;
+
+static const BaseFilesystem table[] = {
+ { "bin", 0, "usr/bin\0", NULL },
+ { "lib", 0, "usr/lib\0", NULL },
+ { "root", 0750, NULL, NULL, true },
+ { "sbin", 0, "usr/sbin\0", NULL },
+ { "usr", 0755, NULL, NULL },
+ { "var", 0755, NULL, NULL },
+ { "etc", 0755, NULL, NULL },
+ { "proc", 0555, NULL, NULL, true },
+ { "sys", 0555, NULL, NULL, true },
+ { "dev", 0555, NULL, NULL, true },
+ { "run", 0555, NULL, NULL, true },
+ /* We don't add /tmp/ here for now (even though it's necessary for regular operation), because we
+ * want to support both cases where /tmp/ is a mount of its own (in which case we probably should set
+ * the mode to 1555, to indicate that no one should write to it, not even root) and when it's part of
+ * the rootfs (in which case we should set mode 1777), and we simply don't know what's right. */
+
+ /* 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 and Arch-style multilib too. */
+#if defined(__aarch64__)
+ /* aarch64 ELF ABI actually says dynamic loader is in /lib/, but Fedora puts it in /lib64/ anyway and
+ * just symlinks /lib/ld-linux-aarch64.so.1 to ../lib64/ld-linux-aarch64.so.1. For this to work
+ * correctly, /lib64/ must be symlinked to /usr/lib64/. */
+ { "lib64", 0, "usr/lib/"LIB_ARCH_TUPLE"\0"
+ "usr/lib64\0"
+ "usr/lib\0", "ld-linux-aarch64.so.1" },
+# define KNOW_LIB64_DIRS 1
+#elif defined(__alpha__)
+#elif defined(__arc__) || defined(__tilegx__)
+#elif defined(__arm__)
+ /* No /lib64 on arm. The linker is /lib/ld-linux-armhf.so.3. */
+# define KNOW_LIB64_DIRS 1
+#elif defined(__i386__) || defined(__x86_64__)
+ { "lib64", 0, "usr/lib/"LIB_ARCH_TUPLE"\0"
+ "usr/lib64\0"
+ "usr/lib\0", "ld-linux-x86-64.so.2" },
+# define KNOW_LIB64_DIRS 1
+#elif defined(__ia64__)
+#elif defined(__loongarch_lp64)
+# define KNOW_LIB64_DIRS 1
+# if defined(__loongarch_double_float)
+ { "lib64", 0, "usr/lib/"LIB_ARCH_TUPLE"\0"
+ "usr/lib64\0"
+ "usr/lib\0", "ld-linux-loongarch-lp64d.so.1" },
+# elif defined(__loongarch_single_float)
+ { "lib64", 0, "usr/lib/"LIB_ARCH_TUPLE"\0"
+ "usr/lib64\0"
+ "usr/lib\0", "ld-linux-loongarch-lp64f.so.1" },
+# elif defined(__loongarch_soft_float)
+ { "lib64", 0, "usr/lib/"LIB_ARCH_TUPLE"\0"
+ "usr/lib64\0"
+ "usr/lib\0", "ld-linux-loongarch-lp64s.so.1" },
+# else
+# error "Unknown LoongArch ABI"
+# endif
+#elif defined(__m68k__)
+ /* No link needed. */
+# define KNOW_LIB64_DIRS 1
+#elif defined(_MIPS_SIM)
+# if _MIPS_SIM == _MIPS_SIM_ABI32
+# elif _MIPS_SIM == _MIPS_SIM_NABI32
+# elif _MIPS_SIM == _MIPS_SIM_ABI64
+# else
+# error "Unknown MIPS ABI"
+# endif
+#elif defined(__powerpc__)
+# if defined(__PPC64__) && __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
+ { "lib64", 0, "usr/lib/"LIB_ARCH_TUPLE"\0"
+ "usr/lib64\0"
+ "usr/lib\0", "ld64.so.2" },
+# define KNOW_LIB64_DIRS 1
+# elif defined(__powerpc64__) && __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
+ /* powerpc64-linux-gnu */
+# else
+ /* powerpc-linux-gnu */
+# endif
+#elif defined(__riscv)
+# if __riscv_xlen == 32
+# elif __riscv_xlen == 64
+ /* Same situation as for aarch64 */
+ { "lib64", 0, "usr/lib/"LIB_ARCH_TUPLE"\0"
+ "usr/lib64\0"
+ "usr/lib\0", "ld-linux-riscv64-lp64d.so.1" },
+# define KNOW_LIB64_DIRS 1
+# else
+# error "Unknown RISC-V ABI"
+# endif
+#elif defined(__s390__)
+ /* s390-linux-gnu */
+#elif defined(__s390x__)
+ { "lib64", 0, "usr/lib/"LIB_ARCH_TUPLE"\0"
+ "usr/lib64\0"
+ "usr/lib\0", "ld-lsb-s390x.so.3" },
+# define KNOW_LIB64_DIRS 1
+#elif defined(__sparc__)
+#endif
+ /* gcc doesn't allow pragma to be used within constructs, hence log about this separately below */
+};
+
+#ifndef KNOW_LIB64_DIRS
+# pragma message "Please add an entry above specifying whether your architecture uses /lib64/, /lib32/, or no such links."
+#endif
+
+int base_filesystem_create_fd(int fd, const char *root, uid_t uid, gid_t gid) {
+ int r;
+
+ assert(fd >= 0);
+ assert(root);
+
+ /* The "root" parameter is decoration only – it's only used as part of log messages */
+
+ 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) { /* Create as symlink? */
+ const char *target = NULL;
+
+ /* 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;
+
+ r = RET_NERRNO(symlinkat(target, fd, table[i].dir));
+ } else {
+ /* Create as directory. */
+ WITH_UMASK(0000)
+ r = RET_NERRNO(mkdirat(fd, table[i].dir, table[i].mode));
+ }
+ if (r < 0) {
+ bool ignore = IN_SET(r, -EEXIST, -EROFS) || table[i].ignore_failure;
+ log_full_errno(ignore ? LOG_DEBUG : LOG_ERR, r,
+ "Failed to create %s/%s: %m", root, table[i].dir);
+ if (ignore)
+ continue;
+
+ return r;
+ }
+
+ 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 %s/%s: %m", root, table[i].dir);
+ }
+
+ return 0;
+}
+
+int base_filesystem_create(const char *root, uid_t uid, gid_t gid) {
+ _cleanup_close_ int fd = -EBADF;
+
+ fd = open(ASSERT_PTR(root), O_DIRECTORY|O_CLOEXEC);
+ if (fd < 0)
+ return log_error_errno(errno, "Failed to open root file system: %m");
+
+ return base_filesystem_create_fd(fd, root, uid, gid);
+}
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