From fe17f22d7fd0e344ef6447238f799bb49f670c6f Mon Sep 17 00:00:00 2001
From: Al Viro <viro@zeniv.linux.org.uk>
Date: Tue, 21 Aug 2012 11:48:11 -0400
Subject: take purely descriptor-related stuff from fcntl.c to file.c

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---
 fs/file.c | 132 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 132 insertions(+)

(limited to 'fs/file.c')

diff --git a/fs/file.c b/fs/file.c
index 92197dd9fdc8..7f29544755d0 100644
--- a/fs/file.c
+++ b/fs/file.c
@@ -6,6 +6,7 @@
  *  Manage the dynamic fd arrays in the process files_struct.
  */
 
+#include <linux/syscalls.h>
 #include <linux/export.h>
 #include <linux/fs.h>
 #include <linux/mm.h>
@@ -794,3 +795,134 @@ struct file *fget_raw_light(unsigned int fd, int *fput_needed)
 
 	return file;
 }
+
+void set_close_on_exec(unsigned int fd, int flag)
+{
+	struct files_struct *files = current->files;
+	struct fdtable *fdt;
+	spin_lock(&files->file_lock);
+	fdt = files_fdtable(files);
+	if (flag)
+		__set_close_on_exec(fd, fdt);
+	else
+		__clear_close_on_exec(fd, fdt);
+	spin_unlock(&files->file_lock);
+}
+
+bool get_close_on_exec(unsigned int fd)
+{
+	struct files_struct *files = current->files;
+	struct fdtable *fdt;
+	bool res;
+	rcu_read_lock();
+	fdt = files_fdtable(files);
+	res = close_on_exec(fd, fdt);
+	rcu_read_unlock();
+	return res;
+}
+
+SYSCALL_DEFINE3(dup3, unsigned int, oldfd, unsigned int, newfd, int, flags)
+{
+	int err = -EBADF;
+	struct file * file, *tofree;
+	struct files_struct * files = current->files;
+	struct fdtable *fdt;
+
+	if ((flags & ~O_CLOEXEC) != 0)
+		return -EINVAL;
+
+	if (newfd >= rlimit(RLIMIT_NOFILE))
+		return -EMFILE;
+
+	spin_lock(&files->file_lock);
+	err = expand_files(files, newfd);
+	file = fcheck(oldfd);
+	if (unlikely(!file))
+		goto Ebadf;
+	if (unlikely(err < 0)) {
+		if (err == -EMFILE)
+			goto Ebadf;
+		goto out_unlock;
+	}
+	/*
+	 * We need to detect attempts to do dup2() over allocated but still
+	 * not finished descriptor.  NB: OpenBSD avoids that at the price of
+	 * extra work in their equivalent of fget() - they insert struct
+	 * file immediately after grabbing descriptor, mark it larval if
+	 * more work (e.g. actual opening) is needed and make sure that
+	 * fget() treats larval files as absent.  Potentially interesting,
+	 * but while extra work in fget() is trivial, locking implications
+	 * and amount of surgery on open()-related paths in VFS are not.
+	 * FreeBSD fails with -EBADF in the same situation, NetBSD "solution"
+	 * deadlocks in rather amusing ways, AFAICS.  All of that is out of
+	 * scope of POSIX or SUS, since neither considers shared descriptor
+	 * tables and this condition does not arise without those.
+	 */
+	err = -EBUSY;
+	fdt = files_fdtable(files);
+	tofree = fdt->fd[newfd];
+	if (!tofree && fd_is_open(newfd, fdt))
+		goto out_unlock;
+	get_file(file);
+	rcu_assign_pointer(fdt->fd[newfd], file);
+	__set_open_fd(newfd, fdt);
+	if (flags & O_CLOEXEC)
+		__set_close_on_exec(newfd, fdt);
+	else
+		__clear_close_on_exec(newfd, fdt);
+	spin_unlock(&files->file_lock);
+
+	if (tofree)
+		filp_close(tofree, files);
+
+	return newfd;
+
+Ebadf:
+	err = -EBADF;
+out_unlock:
+	spin_unlock(&files->file_lock);
+	return err;
+}
+
+SYSCALL_DEFINE2(dup2, unsigned int, oldfd, unsigned int, newfd)
+{
+	if (unlikely(newfd == oldfd)) { /* corner case */
+		struct files_struct *files = current->files;
+		int retval = oldfd;
+
+		rcu_read_lock();
+		if (!fcheck_files(files, oldfd))
+			retval = -EBADF;
+		rcu_read_unlock();
+		return retval;
+	}
+	return sys_dup3(oldfd, newfd, 0);
+}
+
+SYSCALL_DEFINE1(dup, unsigned int, fildes)
+{
+	int ret = -EBADF;
+	struct file *file = fget_raw(fildes);
+
+	if (file) {
+		ret = get_unused_fd();
+		if (ret >= 0)
+			fd_install(ret, file);
+		else
+			fput(file);
+	}
+	return ret;
+}
+
+int f_dupfd(unsigned int from, struct file *file, unsigned flags)
+{
+	int err;
+	if (from >= rlimit(RLIMIT_NOFILE))
+		return -EINVAL;
+	err = alloc_fd(from, flags);
+	if (err >= 0) {
+		get_file(file);
+		fd_install(err, file);
+	}
+	return err;
+}
-- 
cgit