1 /* Define at-style functions like fstatat, unlinkat, fchownat, etc. 2 Copyright (C) 2006, 2009-2022 Free Software Foundation, Inc. 3 4 This program is free software: you can redistribute it and/or modify 5 it under the terms of the GNU General Public License as published by 6 the Free Software Foundation, either version 3 of the License, or 7 (at your option) any later version. 8 9 This program is distributed in the hope that it will be useful, 10 but WITHOUT ANY WARRANTY; without even the implied warranty of 11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 12 GNU General Public License for more details. 13 14 You should have received a copy of the GNU General Public License 15 along with this program. If not, see <https://www.gnu.org/licenses/>. */ 16 17 /* written by Jim Meyering */ 18 19 #include "filename.h" /* solely for definition of IS_ABSOLUTE_FILE_NAME */ 20 21 #ifdef GNULIB_SUPPORT_ONLY_AT_FDCWD 22 # include <errno.h> 23 # ifndef ENOTSUP 24 # define ENOTSUP EINVAL 25 # endif 26 #else 27 # include "openat.h" 28 # include "openat-priv.h" 29 # include "save-cwd.h" 30 #endif 31 32 #ifdef AT_FUNC_USE_F1_COND 33 # define CALL_FUNC(F) \ 34 (flag == AT_FUNC_USE_F1_COND \ 35 ? AT_FUNC_F1 (F AT_FUNC_POST_FILE_ARGS) \ 36 : AT_FUNC_F2 (F AT_FUNC_POST_FILE_ARGS)) 37 # define VALIDATE_FLAG(F) \ 38 if (flag & ~AT_FUNC_USE_F1_COND) \ 39 { \ 40 errno = EINVAL; \ 41 return FUNC_FAIL; \ 42 } 43 #else 44 # define CALL_FUNC(F) (AT_FUNC_F1 (F AT_FUNC_POST_FILE_ARGS)) 45 # define VALIDATE_FLAG(F) /* empty */ 46 #endif 47 48 #ifdef AT_FUNC_RESULT 49 # define FUNC_RESULT AT_FUNC_RESULT 50 #else 51 # define FUNC_RESULT int 52 #endif 53 54 #ifdef AT_FUNC_FAIL 55 # define FUNC_FAIL AT_FUNC_FAIL 56 #else 57 # define FUNC_FAIL -1 58 #endif 59 60 /* Call AT_FUNC_F1 to operate on FILE, which is in the directory 61 open on descriptor FD. If AT_FUNC_USE_F1_COND is defined to a value, 62 AT_FUNC_POST_FILE_PARAM_DECLS must include a parameter named flag; 63 call AT_FUNC_F2 if FLAG is 0 or fail if FLAG contains more bits than 64 AT_FUNC_USE_F1_COND. Return int and fail with -1 unless AT_FUNC_RESULT 65 or AT_FUNC_FAIL are defined. If possible, do it without changing the 66 working directory. Otherwise, resort to using save_cwd/fchdir, 67 then AT_FUNC_F?/restore_cwd. If either the save_cwd or the restore_cwd 68 fails, then give a diagnostic and exit nonzero. */ 69 FUNC_RESULT 70 AT_FUNC_NAME (int fd, char const *file AT_FUNC_POST_FILE_PARAM_DECLS) 71 { 72 VALIDATE_FLAG (flag); 73 74 if (fd == AT_FDCWD || IS_ABSOLUTE_FILE_NAME (file)) 75 return CALL_FUNC (file); 76 77 #ifdef GNULIB_SUPPORT_ONLY_AT_FDCWD 78 errno = ENOTSUP; 79 return FUNC_FAIL; 80 #else 81 { 82 /* Be careful to choose names unlikely to conflict with 83 AT_FUNC_POST_FILE_PARAM_DECLS. */ 84 struct saved_cwd saved_cwd; 85 int saved_errno; 86 FUNC_RESULT err; 87 88 { 89 char proc_buf[OPENAT_BUFFER_SIZE]; 90 char *proc_file = openat_proc_name (proc_buf, fd, file); 91 if (proc_file) 92 { 93 FUNC_RESULT proc_result = CALL_FUNC (proc_file); 94 int proc_errno = errno; 95 if (proc_file != proc_buf) 96 free (proc_file); 97 /* If the syscall succeeds, or if it fails with an unexpected 98 errno value, then return right away. Otherwise, fall through 99 and resort to using save_cwd/restore_cwd. */ 100 if (FUNC_FAIL != proc_result) 101 return proc_result; 102 if (! EXPECTED_ERRNO (proc_errno)) 103 { 104 errno = proc_errno; 105 return proc_result; 106 } 107 } 108 } 109 110 if (save_cwd (&saved_cwd) != 0) 111 openat_save_fail (errno); 112 if (0 <= fd && fd == saved_cwd.desc) 113 { 114 /* If saving the working directory collides with the user's 115 requested fd, then the user's fd must have been closed to 116 begin with. */ 117 free_cwd (&saved_cwd); 118 errno = EBADF; 119 return FUNC_FAIL; 120 } 121 122 if (fchdir (fd) != 0) 123 { 124 saved_errno = errno; 125 free_cwd (&saved_cwd); 126 errno = saved_errno; 127 return FUNC_FAIL; 128 } 129 130 err = CALL_FUNC (file); 131 saved_errno = (err == FUNC_FAIL ? errno : 0); 132 133 if (restore_cwd (&saved_cwd) != 0) 134 openat_restore_fail (errno); 135 136 free_cwd (&saved_cwd); 137 138 if (saved_errno) 139 errno = saved_errno; 140 return err; 141 } 142 #endif 143 } 144 #undef CALL_FUNC 145 #undef FUNC_RESULT 146 #undef FUNC_FAIL 147