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author | Lorry Tar Creator <lorry-tar-importer@lorry> | 2007-03-22 21:23:21 +0000 |
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committer | Lorry Tar Creator <lorry-tar-importer@lorry> | 2007-03-22 21:23:21 +0000 |
commit | cbf5993c43f49281173f185863577d86bfac6eae (patch) | |
tree | 90737c96cf15b97273a2bdc5950b3cf09f1d94ca /lib/openat.c | |
download | coreutils-tarball-cbf5993c43f49281173f185863577d86bfac6eae.tar.gz |
coreutils-6.9coreutils-6.9
Diffstat (limited to 'lib/openat.c')
-rw-r--r-- | lib/openat.c | 270 |
1 files changed, 270 insertions, 0 deletions
diff --git a/lib/openat.c b/lib/openat.c new file mode 100644 index 0000000..cd49654 --- /dev/null +++ b/lib/openat.c @@ -0,0 +1,270 @@ +/* provide a replacement openat function + Copyright (C) 2004, 2005, 2006 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 2, 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, write to the Free Software Foundation, + Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */ + +/* written by Jim Meyering */ + +#include <config.h> + +#include "openat.h" + +#include <stdarg.h> +#include <stddef.h> + +#include "dirname.h" /* solely for definition of IS_ABSOLUTE_FILE_NAME */ +#include "fcntl--.h" +#include "lchown.h" +#include "lstat.h" +#include "openat-priv.h" +#include "save-cwd.h" + +/* Replacement for Solaris' openat function. + <http://www.google.com/search?q=openat+site:docs.sun.com> + First, try to simulate it via open ("/proc/self/fd/FD/FILE"). + Failing that, simulate it by doing save_cwd/fchdir/open/restore_cwd. + If either the save_cwd or the restore_cwd fails (relatively unlikely), + then give a diagnostic and exit nonzero. + Otherwise, upon failure, set errno and return -1, as openat does. + Upon successful completion, return a file descriptor. */ +int +openat (int fd, char const *file, int flags, ...) +{ + mode_t mode = 0; + + if (flags & O_CREAT) + { + va_list arg; + va_start (arg, flags); + + /* If mode_t is narrower than int, use the promoted type (int), + not mode_t. Use sizeof to guess whether mode_t is narrower; + we don't know of any practical counterexamples. */ + mode = (sizeof (mode_t) < sizeof (int) + ? va_arg (arg, int) + : va_arg (arg, mode_t)); + + va_end (arg); + } + + return openat_permissive (fd, file, flags, mode, NULL); +} + +/* Like openat (FD, FILE, FLAGS, MODE), but if CWD_ERRNO is + nonnull, set *CWD_ERRNO to an errno value if unable to save + or restore the initial working directory. This is needed only + the first time remove.c's remove_dir opens a command-line + directory argument. + + If a previous attempt to restore the current working directory + failed, then we must not even try to access a `.'-relative name. + It is the caller's responsibility not to call this function + in that case. */ + +int +openat_permissive (int fd, char const *file, int flags, mode_t mode, + int *cwd_errno) +{ + struct saved_cwd saved_cwd; + int saved_errno; + int err; + bool save_ok; + + if (fd == AT_FDCWD || IS_ABSOLUTE_FILE_NAME (file)) + return open (file, flags, mode); + + { + char buf[OPENAT_BUFFER_SIZE]; + char *proc_file = openat_proc_name (buf, fd, file); + if (proc_file) + { + int open_result = open (proc_file, flags, mode); + int open_errno = errno; + if (proc_file != buf) + free (proc_file); + /* 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 <= open_result || ! EXPECTED_ERRNO (open_errno)) + { + errno = open_errno; + return open_result; + } + } + } + + save_ok = (save_cwd (&saved_cwd) == 0); + if (! save_ok) + { + if (! cwd_errno) + openat_save_fail (errno); + *cwd_errno = errno; + } + + err = fchdir (fd); + saved_errno = errno; + + if (! err) + { + err = open (file, flags, mode); + saved_errno = errno; + if (save_ok && restore_cwd (&saved_cwd) != 0) + { + if (! cwd_errno) + openat_restore_fail (errno); + *cwd_errno = errno; + } + } + + free_cwd (&saved_cwd); + errno = saved_errno; + return err; +} + +/* Return true if our openat implementation must resort to + using save_cwd and restore_cwd. */ +bool +openat_needs_fchdir (void) +{ + bool needs_fchdir = true; + int fd = open ("/", O_RDONLY); + + if (0 <= fd) + { + char buf[OPENAT_BUFFER_SIZE]; + char *proc_file = openat_proc_name (buf, fd, "."); + if (proc_file) + { + needs_fchdir = false; + if (proc_file != buf) + free (proc_file); + } + close (fd); + } + + return needs_fchdir; +} + +#if !HAVE_FDOPENDIR + +/* Replacement for Solaris' function by the same name. + <http://www.google.com/search?q=fdopendir+site:docs.sun.com> + First, try to simulate it via opendir ("/proc/self/fd/FD"). Failing + that, simulate it by doing save_cwd/fchdir/opendir(".")/restore_cwd. + If either the save_cwd or the restore_cwd fails (relatively unlikely), + then give a diagnostic and exit nonzero. + Otherwise, this function works just like Solaris' fdopendir. + + W A R N I N G: + Unlike the other fd-related functions here, this one + effectively consumes its FD parameter. The caller should not + close or otherwise manipulate FD if this function returns successfully. */ +DIR * +fdopendir (int fd) +{ + struct saved_cwd saved_cwd; + int saved_errno; + DIR *dir; + + char buf[OPENAT_BUFFER_SIZE]; + char *proc_file = openat_proc_name (buf, fd, "."); + if (proc_file) + { + dir = opendir (proc_file); + saved_errno = errno; + } + else + { + dir = NULL; + saved_errno = EOPNOTSUPP; + } + + /* If the syscall fails with an expected errno value, resort to + save_cwd/restore_cwd. */ + if (! dir && EXPECTED_ERRNO (saved_errno)) + { + if (save_cwd (&saved_cwd) != 0) + openat_save_fail (errno); + + if (fchdir (fd) != 0) + { + dir = NULL; + saved_errno = errno; + } + else + { + dir = opendir ("."); + saved_errno = errno; + + if (restore_cwd (&saved_cwd) != 0) + openat_restore_fail (errno); + } + + free_cwd (&saved_cwd); + } + + if (dir) + close (fd); + if (proc_file != buf) + free (proc_file); + errno = saved_errno; + return dir; +} + +#endif + +/* Replacement for Solaris' function by the same name. + <http://www.google.com/search?q=fstatat+site:docs.sun.com> + First, try to simulate it via l?stat ("/proc/self/fd/FD/FILE"). + Failing that, simulate it via save_cwd/fchdir/(stat|lstat)/restore_cwd. + If either the save_cwd or the restore_cwd fails (relatively unlikely), + then give a diagnostic and exit nonzero. + Otherwise, this function works just like Solaris' fstatat. */ + +#define AT_FUNC_NAME fstatat +#define AT_FUNC_F1 lstat +#define AT_FUNC_F2 stat +#define AT_FUNC_USE_F1_COND flag == AT_SYMLINK_NOFOLLOW +#define AT_FUNC_POST_FILE_PARAM_DECLS , struct stat *st, int flag +#define AT_FUNC_POST_FILE_ARGS , st +#include "at-func.c" +#undef AT_FUNC_NAME +#undef AT_FUNC_F1 +#undef AT_FUNC_F2 +#undef AT_FUNC_USE_F1_COND +#undef AT_FUNC_POST_FILE_PARAM_DECLS +#undef AT_FUNC_POST_FILE_ARGS + +/* Replacement for Solaris' function by the same name. + <http://www.google.com/search?q=unlinkat+site:docs.sun.com> + First, try to simulate it via (unlink|rmdir) ("/proc/self/fd/FD/FILE"). + Failing that, simulate it via save_cwd/fchdir/(unlink|rmdir)/restore_cwd. + If either the save_cwd or the restore_cwd fails (relatively unlikely), + then give a diagnostic and exit nonzero. + Otherwise, this function works just like Solaris' unlinkat. */ + +#define AT_FUNC_NAME unlinkat +#define AT_FUNC_F1 rmdir +#define AT_FUNC_F2 unlink +#define AT_FUNC_USE_F1_COND flag == AT_REMOVEDIR +#define AT_FUNC_POST_FILE_PARAM_DECLS , int flag +#define AT_FUNC_POST_FILE_ARGS /* empty */ +#include "at-func.c" +#undef AT_FUNC_NAME +#undef AT_FUNC_F1 +#undef AT_FUNC_F2 +#undef AT_FUNC_USE_F1_COND +#undef AT_FUNC_POST_FILE_PARAM_DECLS +#undef AT_FUNC_POST_FILE_ARGS |