diff options
Diffstat (limited to 'gl/lib/at-func2.c')
| -rw-r--r-- | gl/lib/at-func2.c | 289 |
1 files changed, 289 insertions, 0 deletions
diff --git a/gl/lib/at-func2.c b/gl/lib/at-func2.c new file mode 100644 index 0000000..8a0882e --- /dev/null +++ b/gl/lib/at-func2.c @@ -0,0 +1,289 @@ +/* Define 2-FD at-style functions like linkat or renameat. + Copyright (C) 2006, 2009-2022 Free Software Foundation, Inc. + + This program 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 program 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/>. */ + +/* written by Jim Meyering and Eric Blake */ + +#include <config.h> + +#include "openat-priv.h" + +#include <errno.h> +#include <stdlib.h> +#include <string.h> +#include <unistd.h> + +#include "filename.h" /* solely for definition of IS_ABSOLUTE_FILE_NAME */ +#include "filenamecat.h" +#include "openat.h" +#include "same-inode.h" +#include "save-cwd.h" + +/* Call FUNC to operate on a pair of files, where FILE1 is relative to FD1, + and FILE2 is relative to FD2. If possible, do it without changing the + working directory. Otherwise, resort to using save_cwd/fchdir, + FUNC, restore_cwd (up to two times). If either the save_cwd or the + restore_cwd fails, then give a diagnostic and exit nonzero. */ +int +at_func2 (int fd1, char const *file1, + int fd2, char const *file2, + int (*func) (char const *file1, char const *file2)) +{ + struct saved_cwd saved_cwd; + int saved_errno; + int err; + char *file1_alt; + char *file2_alt; + struct stat st1; + struct stat st2; + + /* There are 16 possible scenarios, based on whether an fd is + AT_FDCWD or real, and whether a file is absolute or relative: + + fd1 file1 fd2 file2 action + 0 cwd abs cwd abs direct call + 1 cwd abs cwd rel direct call + 2 cwd abs fd abs direct call + 3 cwd abs fd rel chdir to fd2 + 4 cwd rel cwd abs direct call + 5 cwd rel cwd rel direct call + 6 cwd rel fd abs direct call + 7 cwd rel fd rel convert file1 to abs, then case 3 + 8 fd abs cwd abs direct call + 9 fd abs cwd rel direct call + 10 fd abs fd abs direct call + 11 fd abs fd rel chdir to fd2 + 12 fd rel cwd abs chdir to fd1 + 13 fd rel cwd rel convert file2 to abs, then case 12 + 14 fd rel fd abs chdir to fd1 + 15a fd1 rel fd1 rel chdir to fd1 + 15b fd1 rel fd2 rel chdir to fd1, then case 7 + + Try some optimizations to reduce fd to AT_FDCWD, or to at least + avoid converting an absolute name or doing a double chdir. */ + + if ((fd1 == AT_FDCWD || IS_ABSOLUTE_FILE_NAME (file1)) + && (fd2 == AT_FDCWD || IS_ABSOLUTE_FILE_NAME (file2))) + return func (file1, file2); /* Case 0-2, 4-6, 8-10. */ + + /* If /proc/self/fd works, we don't need any stat or chdir. */ + { + char proc_buf1[OPENAT_BUFFER_SIZE]; + char *proc_file1 = ((fd1 == AT_FDCWD || IS_ABSOLUTE_FILE_NAME (file1)) + ? (char *) file1 + : openat_proc_name (proc_buf1, fd1, file1)); + if (proc_file1) + { + char proc_buf2[OPENAT_BUFFER_SIZE]; + char *proc_file2 = ((fd2 == AT_FDCWD || IS_ABSOLUTE_FILE_NAME (file2)) + ? (char *) file2 + : openat_proc_name (proc_buf2, fd2, file2)); + if (proc_file2) + { + int proc_result = func (proc_file1, proc_file2); + int proc_errno = errno; + if (proc_file1 != proc_buf1 && proc_file1 != file1) + free (proc_file1); + if (proc_file2 != proc_buf2 && proc_file2 != file2) + free (proc_file2); + /* If the syscall succeeds, or if it fails with an unexpected + errno value, then return right away. Otherwise, fall through + and resort to using save_cwd/restore_cwd. */ + if (0 <= proc_result) + return proc_result; + if (! EXPECTED_ERRNO (proc_errno)) + { + errno = proc_errno; + return proc_result; + } + } + else if (proc_file1 != proc_buf1 && proc_file1 != file1) + free (proc_file1); + } + } + + /* Cases 3, 7, 11-15 remain. Time to normalize directory fds, if + possible. */ + if (IS_ABSOLUTE_FILE_NAME (file1)) + fd1 = AT_FDCWD; /* Case 11 reduced to 3. */ + else if (IS_ABSOLUTE_FILE_NAME (file2)) + fd2 = AT_FDCWD; /* Case 14 reduced to 12. */ + + /* Cases 3, 7, 12, 13, 15 remain. */ + + if (fd1 == AT_FDCWD) /* Cases 3, 7. */ + { + if (stat (".", &st1) == -1 || fstat (fd2, &st2) == -1) + return -1; + if (!S_ISDIR (st2.st_mode)) + { + errno = ENOTDIR; + return -1; + } + if (SAME_INODE (st1, st2)) /* Reduced to cases 1, 5. */ + return func (file1, file2); + } + else if (fd2 == AT_FDCWD) /* Cases 12, 13. */ + { + if (stat (".", &st2) == -1 || fstat (fd1, &st1) == -1) + return -1; + if (!S_ISDIR (st1.st_mode)) + { + errno = ENOTDIR; + return -1; + } + if (SAME_INODE (st1, st2)) /* Reduced to cases 4, 5. */ + return func (file1, file2); + } + else if (fd1 != fd2) /* Case 15b. */ + { + if (fstat (fd1, &st1) == -1 || fstat (fd2, &st2) == -1) + return -1; + if (!S_ISDIR (st1.st_mode) || !S_ISDIR (st2.st_mode)) + { + errno = ENOTDIR; + return -1; + } + if (SAME_INODE (st1, st2)) /* Reduced to case 15a. */ + { + fd2 = fd1; + if (stat (".", &st1) == 0 && SAME_INODE (st1, st2)) + return func (file1, file2); /* Further reduced to case 5. */ + } + } + else /* Case 15a. */ + { + if (fstat (fd1, &st1) == -1) + return -1; + if (!S_ISDIR (st1.st_mode)) + { + errno = ENOTDIR; + return -1; + } + if (stat (".", &st2) == 0 && SAME_INODE (st1, st2)) + return func (file1, file2); /* Reduced to case 5. */ + } + + /* Catch invalid arguments before changing directories. */ + if (file1[0] == '\0' || file2[0] == '\0') + { + errno = ENOENT; + return -1; + } + + /* Cases 3, 7, 12, 13, 15a, 15b remain. With all reductions in + place, it is time to start changing directories. */ + + if (save_cwd (&saved_cwd) != 0) + openat_save_fail (errno); + + if (fd1 != AT_FDCWD && fd2 != AT_FDCWD && fd1 != fd2) /* Case 15b. */ + { + if (fchdir (fd1) != 0) + { + saved_errno = errno; + free_cwd (&saved_cwd); + errno = saved_errno; + return -1; + } + fd1 = AT_FDCWD; /* Reduced to case 7. */ + } + + /* Cases 3, 7, 12, 13, 15a remain. Convert one relative name to + absolute, if necessary. */ + + file1_alt = (char *) file1; + file2_alt = (char *) file2; + + if (fd1 == AT_FDCWD && !IS_ABSOLUTE_FILE_NAME (file1)) /* Case 7. */ + { + /* It would be nicer to use: + file1_alt = file_name_concat (xgetcwd (), file1, NULL); + but libraries should not call xalloc_die. */ + char *cwd = getcwd (NULL, 0); + if (!cwd) + { + saved_errno = errno; + free_cwd (&saved_cwd); + errno = saved_errno; + return -1; + } + file1_alt = mfile_name_concat (cwd, file1, NULL); + if (!file1_alt) + { + saved_errno = errno; + free (cwd); + free_cwd (&saved_cwd); + errno = saved_errno; + return -1; + } + free (cwd); /* Reduced to case 3. */ + } + else if (fd2 == AT_FDCWD && !IS_ABSOLUTE_FILE_NAME (file2)) /* Case 13. */ + { + char *cwd = getcwd (NULL, 0); + if (!cwd) + { + saved_errno = errno; + free_cwd (&saved_cwd); + errno = saved_errno; + return -1; + } + file2_alt = mfile_name_concat (cwd, file2, NULL); + if (!file2_alt) + { + saved_errno = errno; + free (cwd); + free_cwd (&saved_cwd); + errno = saved_errno; + return -1; + } + free (cwd); /* Reduced to case 12. */ + } + + /* Cases 3, 12, 15a remain. Change to the correct directory. */ + if (fchdir (fd1 == AT_FDCWD ? fd2 : fd1) != 0) + { + saved_errno = errno; + free_cwd (&saved_cwd); + if (file1 != file1_alt) + free (file1_alt); + else if (file2 != file2_alt) + free (file2_alt); + errno = saved_errno; + return -1; + } + + /* Finally safe to perform the user's function, then clean up. */ + + err = func (file1_alt, file2_alt); + saved_errno = (err < 0 ? errno : 0); + + if (file1 != file1_alt) + free (file1_alt); + else if (file2 != file2_alt) + free (file2_alt); + + if (restore_cwd (&saved_cwd) != 0) + openat_restore_fail (errno); + + free_cwd (&saved_cwd); + + if (saved_errno) + errno = saved_errno; + return err; +} +#undef CALL_FUNC +#undef FUNC_RESULT |