diff options
Diffstat (limited to 'lib/getcwd.c')
| -rw-r--r-- | lib/getcwd.c | 567 |
1 files changed, 567 insertions, 0 deletions
diff --git a/lib/getcwd.c b/lib/getcwd.c new file mode 100644 index 0000000..28f6913 --- /dev/null +++ b/lib/getcwd.c @@ -0,0 +1,567 @@ +/* Copyright (C) 1991-2023 Free Software Foundation, Inc. + This file is part of the GNU C Library. + + This file is free software: you can redistribute it and/or modify + it under the terms of the GNU General Public License as published + by the Free Software Foundation, either version 3 of the License, + or (at your option) any later version. + + This file 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 General Public License for more details. + + You should have received a copy of the GNU General Public License + along with this program. If not, see <https://www.gnu.org/licenses/>. */ + +#if !_LIBC +# include <config.h> +# include <stdio.h> +# include <unistd.h> +# include "pathmax.h" +#else +# define HAVE_OPENAT 1 +# define D_INO_IN_DIRENT 1 +# define HAVE_MSVC_INVALID_PARAMETER_HANDLER 0 +# define HAVE_MINIMALLY_WORKING_GETCWD 0 +#endif + +#include <errno.h> +#include <sys/types.h> +#include <sys/stat.h> +#include <stddef.h> + +#include <fcntl.h> /* For AT_FDCWD on Solaris 9. */ + +/* If this host provides the openat function or if we're using the + gnulib replacement function with a native fdopendir, then enable + code below to make getcwd more efficient and robust. */ +#if defined HAVE_OPENAT || (defined GNULIB_OPENAT && defined HAVE_FDOPENDIR) +# define HAVE_OPENAT_SUPPORT 1 +#else +# define HAVE_OPENAT_SUPPORT 0 +#endif + +#ifndef __set_errno +# define __set_errno(val) (errno = (val)) +#endif + +#include <dirent.h> +#ifndef _D_EXACT_NAMLEN +# define _D_EXACT_NAMLEN(d) strlen ((d)->d_name) +#endif +#ifndef _D_ALLOC_NAMLEN +# define _D_ALLOC_NAMLEN(d) (_D_EXACT_NAMLEN (d) + 1) +#endif + +#include <unistd.h> +#include <stdlib.h> +#include <string.h> + +#if _LIBC +# ifndef mempcpy +# define mempcpy __mempcpy +# endif +#endif + +#ifndef MAX +# define MAX(a, b) ((a) < (b) ? (b) : (a)) +#endif +#ifndef MIN +# define MIN(a, b) ((a) < (b) ? (a) : (b)) +#endif + +/* In this file, PATH_MAX only serves as a threshold for choosing among two + algorithms. */ +#ifndef PATH_MAX +# define PATH_MAX 8192 +#endif + +#if D_INO_IN_DIRENT +# define MATCHING_INO(dp, ino) ((dp)->d_ino == (ino)) +#else +# define MATCHING_INO(dp, ino) true +#endif + +#if HAVE_MSVC_INVALID_PARAMETER_HANDLER +# include "msvc-inval.h" +#endif + +#if !_LIBC +# define GETCWD_RETURN_TYPE char * +# define __close_nocancel_nostatus close +# define __getcwd_generic rpl_getcwd +# undef stat64 +# define stat64 stat +# define __fstat64 fstat +# define __fstatat64 fstatat +# define __lstat64 lstat +# define __closedir closedir +# define __opendir opendir +# define __readdir64 readdir +# define __fdopendir fdopendir +# define __openat openat +# define __rewinddir rewinddir +# define __openat64 openat +# define dirent64 dirent +#else +# include <not-cancel.h> +#endif + +/* The results of opendir() in this file are not used with dirfd and fchdir, + and we do not leak fds to any single-threaded code that could use stdio, + therefore save some unnecessary recursion in fchdir.c. + FIXME - if the kernel ever adds support for multi-thread safety for + avoiding standard fds, then we should use opendir_safer and + openat_safer. */ +#ifdef GNULIB_defined_DIR +# undef DIR +# undef opendir +# undef closedir +# undef readdir +# undef rewinddir +#else +# ifdef GNULIB_defined_opendir +# undef opendir +# endif +# ifdef GNULIB_defined_closedir +# undef closedir +# endif +#endif + +#if defined _WIN32 && !defined __CYGWIN__ +# if HAVE_MSVC_INVALID_PARAMETER_HANDLER +static char * +getcwd_nothrow (char *buf, size_t size) +{ + char *result; + + TRY_MSVC_INVAL + { + result = _getcwd (buf, size); + } + CATCH_MSVC_INVAL + { + result = NULL; + errno = ERANGE; + } + DONE_MSVC_INVAL; + + return result; +} +# else +# define getcwd_nothrow _getcwd +# endif +# define getcwd_system getcwd_nothrow +#else +# define getcwd_system getcwd +#endif + +/* Get the name of the current working directory, and put it in SIZE + bytes of BUF. Returns NULL with errno set if the directory couldn't be + determined or SIZE was too small. If successful, returns BUF. In GNU, + if BUF is NULL, an array is allocated with 'malloc'; the array is SIZE + bytes long, unless SIZE == 0, in which case it is as big as necessary. */ + +GETCWD_RETURN_TYPE +__getcwd_generic (char *buf, size_t size) +{ + /* Lengths of big file name components and entire file names, and a + deep level of file name nesting. These numbers are not upper + bounds; they are merely large values suitable for initial + allocations, designed to be large enough for most real-world + uses. */ + enum + { + BIG_FILE_NAME_COMPONENT_LENGTH = 255, + BIG_FILE_NAME_LENGTH = MIN (4095, PATH_MAX - 1), + DEEP_NESTING = 100 + }; + +#if HAVE_OPENAT_SUPPORT + int fd = AT_FDCWD; + bool fd_needs_closing = false; +# if defined __linux__ + bool proc_fs_not_mounted = false; +# endif +#else + char dots[DEEP_NESTING * sizeof ".." + BIG_FILE_NAME_COMPONENT_LENGTH + 1]; + char *dotlist = dots; + size_t dotsize = sizeof dots; + size_t dotlen = 0; +#endif + DIR *dirstream = NULL; + dev_t rootdev, thisdev; + ino_t rootino, thisino; + char *dir; + register char *dirp; + struct stat64 st; + size_t allocated = size; + size_t used; + +#if HAVE_MINIMALLY_WORKING_GETCWD + /* If AT_FDCWD is not defined, the algorithm below is O(N**2) and + this is much slower than the system getcwd (at least on + GNU/Linux). So trust the system getcwd's results unless they + look suspicious. + + Use the system getcwd even if we have openat support, since the + system getcwd works even when a parent is unreadable, while the + openat-based approach does not. + + But on AIX 5.1..7.1, the system getcwd is not even minimally + working: If the current directory name is slightly longer than + PATH_MAX, it omits the first directory component and returns + this wrong result with errno = 0. */ + +# undef getcwd + dir = getcwd_system (buf, size); + if (dir || (size && errno == ERANGE)) + return dir; + + /* Solaris getcwd (NULL, 0) fails with errno == EINVAL, but it has + internal magic that lets it work even if an ancestor directory is + inaccessible, which is better in many cases. So in this case try + again with a buffer that's almost always big enough. */ + if (errno == EINVAL && buf == NULL && size == 0) + { + char big_buffer[BIG_FILE_NAME_LENGTH + 1]; + dir = getcwd_system (big_buffer, sizeof big_buffer); + if (dir) + return strdup (dir); + } + +# if HAVE_PARTLY_WORKING_GETCWD + /* The system getcwd works, except it sometimes fails when it + shouldn't, setting errno to ERANGE, ENAMETOOLONG, or ENOENT. */ + if (errno != ERANGE && errno != ENAMETOOLONG && errno != ENOENT) + return NULL; +# endif +#endif + if (size == 0) + { + if (buf != NULL) + { + __set_errno (EINVAL); + return NULL; + } + + allocated = BIG_FILE_NAME_LENGTH + 1; + } + + if (buf == NULL) + { + dir = malloc (allocated); + if (dir == NULL) + return NULL; + } + else + dir = buf; + + dirp = dir + allocated; + *--dirp = '\0'; + + if (__lstat64 (".", &st) < 0) + goto lose; + thisdev = st.st_dev; + thisino = st.st_ino; + + if (__lstat64 ("/", &st) < 0) + goto lose; + rootdev = st.st_dev; + rootino = st.st_ino; + + while (!(thisdev == rootdev && thisino == rootino)) + { + struct dirent64 *d; + dev_t dotdev; + ino_t dotino; + bool mount_point; + int parent_status; + size_t dirroom; + size_t namlen; + bool use_d_ino = true; + + /* Look at the parent directory. */ +#if HAVE_OPENAT_SUPPORT + fd = __openat64 (fd, "..", O_RDONLY); + if (fd < 0) + goto lose; + fd_needs_closing = true; + parent_status = __fstat64 (fd, &st); +#else + dotlist[dotlen++] = '.'; + dotlist[dotlen++] = '.'; + dotlist[dotlen] = '\0'; + parent_status = __lstat64 (dotlist, &st); +#endif + if (parent_status != 0) + goto lose; + + if (dirstream && __closedir (dirstream) != 0) + { + dirstream = NULL; + goto lose; + } + + /* Figure out if this directory is a mount point. */ + dotdev = st.st_dev; + dotino = st.st_ino; + mount_point = dotdev != thisdev; + + /* Search for the last directory. */ +#if HAVE_OPENAT_SUPPORT + dirstream = __fdopendir (fd); + if (dirstream == NULL) + goto lose; + fd_needs_closing = false; +#else + dirstream = __opendir (dotlist); + if (dirstream == NULL) + goto lose; + dotlist[dotlen++] = '/'; +#endif + for (;;) + { + /* Clear errno to distinguish EOF from error if readdir returns + NULL. */ + __set_errno (0); + d = __readdir64 (dirstream); + + /* When we've iterated through all directory entries without finding + one with a matching d_ino, rewind the stream and consider each + name again, but this time, using lstat. This is necessary in a + chroot on at least one system (glibc-2.3.6 + linux 2.6.12), where + .., ../.., ../../.., etc. all had the same device number, yet the + d_ino values for entries in / did not match those obtained + via lstat. */ + if (d == NULL && errno == 0 && use_d_ino) + { + use_d_ino = false; + __rewinddir (dirstream); + d = __readdir64 (dirstream); + } + + if (d == NULL) + { + if (errno == 0) + /* EOF on dirstream, which can mean e.g., that the current + directory has been removed. */ + __set_errno (ENOENT); + goto lose; + } + if (d->d_name[0] == '.' && + (d->d_name[1] == '\0' || + (d->d_name[1] == '.' && d->d_name[2] == '\0'))) + continue; + + if (use_d_ino) + { + bool match = (MATCHING_INO (d, thisino) || mount_point); + if (! match) + continue; + } + + { + int entry_status; +#if HAVE_OPENAT_SUPPORT + entry_status = __fstatat64 (fd, d->d_name, &st, AT_SYMLINK_NOFOLLOW); +#else + /* Compute size needed for this file name, or for the file + name ".." in the same directory, whichever is larger. + Room for ".." might be needed the next time through + the outer loop. */ + size_t name_alloc = _D_ALLOC_NAMLEN (d); + size_t filesize = dotlen + MAX (sizeof "..", name_alloc); + + if (filesize < dotlen) + goto memory_exhausted; + + if (dotsize < filesize) + { + /* My, what a deep directory tree you have, Grandma. */ + size_t newsize = MAX (filesize, dotsize * 2); + size_t i; + if (newsize < dotsize) + goto memory_exhausted; + if (dotlist != dots) + free (dotlist); + dotlist = malloc (newsize); + if (dotlist == NULL) + goto lose; + dotsize = newsize; + + i = 0; + do + { + dotlist[i++] = '.'; + dotlist[i++] = '.'; + dotlist[i++] = '/'; + } + while (i < dotlen); + } + + memcpy (dotlist + dotlen, d->d_name, _D_ALLOC_NAMLEN (d)); + entry_status = __lstat64 (dotlist, &st); +#endif + /* We don't fail here if we cannot stat() a directory entry. + This can happen when (network) file systems fail. If this + entry is in fact the one we are looking for we will find + out soon as we reach the end of the directory without + having found anything. */ + if (entry_status == 0 && S_ISDIR (st.st_mode) + && st.st_dev == thisdev && st.st_ino == thisino) + break; + } + } + + dirroom = dirp - dir; + namlen = _D_EXACT_NAMLEN (d); + + if (dirroom <= namlen) + { + if (size != 0) + { + __set_errno (ERANGE); + goto lose; + } + else + { + char *tmp; + size_t oldsize = allocated; + + allocated += MAX (allocated, namlen); + if (allocated < oldsize + || ! (tmp = realloc (dir, allocated))) + goto memory_exhausted; + + /* Move current contents up to the end of the buffer. + This is guaranteed to be non-overlapping. */ + dirp = memcpy (tmp + allocated - (oldsize - dirroom), + tmp + dirroom, + oldsize - dirroom); + dir = tmp; + } + } + dirp -= namlen; + memcpy (dirp, d->d_name, namlen); + *--dirp = '/'; + + thisdev = dotdev; + thisino = dotino; + +#if HAVE_OPENAT_SUPPORT + /* On some platforms, a system call returns the directory that FD points + to. This is useful if some of the ancestor directories of the + directory are unreadable, because in this situation the loop that + climbs up the ancestor hierarchy runs into an EACCES error. + For example, in some Android app, /data/data/com.termux is readable, + but /data/data and /data are not. */ +# if defined __linux__ + /* On Linux, in particular, if /proc is mounted, + readlink ("/proc/self/fd/<fd>") + returns the directory, if its length is < 4096. (If the length is + >= 4096, it fails with error ENAMETOOLONG, even if the buffer that we + pass to the readlink function would be large enough.) */ + if (!proc_fs_not_mounted) + { + char namebuf[14 + 10 + 1]; + sprintf (namebuf, "/proc/self/fd/%u", (unsigned int) fd); + char linkbuf[4096]; + ssize_t linklen = readlink (namebuf, linkbuf, sizeof linkbuf); + if (linklen < 0) + { + if (errno != ENAMETOOLONG) + /* If this call was not successful, the next one will likely be + not successful either. */ + proc_fs_not_mounted = true; + } + else + { + dirroom = dirp - dir; + if (dirroom < linklen) + { + if (size != 0) + { + __set_errno (ERANGE); + goto lose; + } + else + { + char *tmp; + size_t oldsize = allocated; + + allocated += linklen - dirroom; + if (allocated < oldsize + || ! (tmp = realloc (dir, allocated))) + goto memory_exhausted; + + /* Move current contents up to the end of the buffer. */ + dirp = memmove (tmp + dirroom + (allocated - oldsize), + tmp + dirroom, + oldsize - dirroom); + dir = tmp; + } + } + dirp -= linklen; + memcpy (dirp, linkbuf, linklen); + break; + } + } +# endif +#endif + } + + if (dirstream && __closedir (dirstream) != 0) + { + dirstream = NULL; + goto lose; + } + + if (dirp == &dir[allocated - 1]) + *--dirp = '/'; + +#if ! HAVE_OPENAT_SUPPORT + if (dotlist != dots) + free (dotlist); +#endif + + used = dir + allocated - dirp; + memmove (dir, dirp, used); + + if (size == 0) + /* Ensure that the buffer is only as large as necessary. */ + buf = (used < allocated ? realloc (dir, used) : dir); + + if (buf == NULL) + /* Either buf was NULL all along, or 'realloc' failed but + we still have the original string. */ + buf = dir; + + return buf; + + memory_exhausted: + __set_errno (ENOMEM); + lose: + { + int save = errno; + if (dirstream) + __closedir (dirstream); +#if HAVE_OPENAT_SUPPORT + if (fd_needs_closing) + __close_nocancel_nostatus (fd); +#else + if (dotlist != dots) + free (dotlist); +#endif + if (buf == NULL) + free (dir); + __set_errno (save); + } + return NULL; +} + +#if defined _LIBC && !defined GETCWD_RETURN_TYPE +libc_hidden_def (__getcwd) +weak_alias (__getcwd, getcwd) +#endif |