Implement a close_range(2) syscall

close_range(min, max, flags) allows for a range of descriptors to be
closed. The Python folk have indicated that they would much prefer this
interface to closefrom(2), as the case may be that they/someone have special
fds dup'd to higher in the range and they can't necessarily closefrom(min)
because they don't want to hit the upper range, but relocating them to lower
isn't necessarily feasible.

sys_closefrom has been rewritten to use kern_close_range() using ~0U to
indicate closing to the end of the range. This was chosen rather than
requiring callers of kern_close_range() to hold FILEDESC_SLOCK across the
call to kern_close_range for simplicity.

The flags argument of close_range(2) is currently unused, so any flags set
is currently EINVAL. It was added to the interface in Linux so that future
flags could be added for, e.g., "halt on first error" and things of this
nature.

This patch is based on a syscall of the same design that is expected to be
merged into Linux.

Reviewed by:	kib, markj, vangyzen (all slightly earlier revisions)
Differential Revision:	https://reviews.freebsd.org/D21627

1 files changed, 1 insertions, 0 deletions

diff --git a/include/unistd.h b/include/unistd.h
index 5a4991ef9fe1..02df2515eaaa 100644
--- a/include/unistd.h
+++ b/include/unistd.h
@@ -494,6 +494,7 @@ struct crypt_data {
 int	 acct(const char *);
 int	 async_daemon(void);
 int	 check_utility_compat(const char *);
+int	 close_range(unsigned int, unsigned int, int);
 ssize_t	 copy_file_range(int, off_t *, int, off_t *, size_t, unsigned int);
 const char *
 	 crypt_get_format(void);