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authorAl Viro <viro@zeniv.linux.org.uk>2011-03-13 10:51:11 +0300
committerAl Viro <viro@zeniv.linux.org.uk>2011-03-15 09:21:45 +0300
commit1abf0c718f15a56a0a435588d1b104c7a37dc9bd (patch)
tree91a6fae3218686b9a945569a7fa7fad120f64e94 /include/linux/file.h
parentf2fa2ffc2046fdc35f96366d1ec8675f4d578522 (diff)
downloadlinux-1abf0c718f15a56a0a435588d1b104c7a37dc9bd.tar.xz
New kind of open files - "location only".
New flag for open(2) - O_PATH. Semantics: * pathname is resolved, but the file itself is _NOT_ opened as far as filesystem is concerned. * almost all operations on the resulting descriptors shall fail with -EBADF. Exceptions are: 1) operations on descriptors themselves (i.e. close(), dup(), dup2(), dup3(), fcntl(fd, F_DUPFD), fcntl(fd, F_DUPFD_CLOEXEC, ...), fcntl(fd, F_GETFD), fcntl(fd, F_SETFD, ...)) 2) fcntl(fd, F_GETFL), for a common non-destructive way to check if descriptor is open 3) "dfd" arguments of ...at(2) syscalls, i.e. the starting points of pathname resolution * closing such descriptor does *NOT* affect dnotify or posix locks. * permissions are checked as usual along the way to file; no permission checks are applied to the file itself. Of course, giving such thing to syscall will result in permission checks (at the moment it means checking that starting point of ....at() is a directory and caller has exec permissions on it). fget() and fget_light() return NULL on such descriptors; use of fget_raw() and fget_raw_light() is needed to get them. That protects existing code from dealing with those things. There are two things still missing (they come in the next commits): one is handling of symlinks (right now we refuse to open them that way; see the next commit for semantics related to those) and another is descriptor passing via SCM_RIGHTS datagrams. Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Diffstat (limited to 'include/linux/file.h')
-rw-r--r--include/linux/file.h2
1 files changed, 2 insertions, 0 deletions
diff --git a/include/linux/file.h b/include/linux/file.h
index e85baebf6279..21a79958541c 100644
--- a/include/linux/file.h
+++ b/include/linux/file.h
@@ -29,6 +29,8 @@ static inline void fput_light(struct file *file, int fput_needed)
extern struct file *fget(unsigned int fd);
extern struct file *fget_light(unsigned int fd, int *fput_needed);
+extern struct file *fget_raw(unsigned int fd);
+extern struct file *fget_raw_light(unsigned int fd, int *fput_needed);
extern void set_close_on_exec(unsigned int fd, int flag);
extern void put_filp(struct file *);
extern int alloc_fd(unsigned start, unsigned flags);