[PATCH 0/3] Handle lack of F_DUPFD_CLOEXEC support

[PATCH 0/3] Handle lack of F_DUPFD_CLOEXEC support

[Guillem Jover]

Hi!

These patches make the code gracefully handle missing F_DUPFD_CLOEXEC
support at build and run-time. This affects at least current GNU/kFreeBSD
systems. I've included the last patch so that GNU/kFreeBSD systems can
immediately benefit from F_DUPFD_CLOEXEC before glibc is updated there,
but if you prefer to omit that one out of disgust, that would be fine I
guess.

While the actual problem is that sysfs code is being built and used on
non-Linux systems, it is too entrenched to get rid of it w/o substantial
amounts of work. Also GNU/kFreeBSD does have limited sysfs support via
the compat linsysfs, so it might not be entirely useless there. But it
certainly is not useful on GNU/Hurd though, at least not currently.

The patches were tested by Steven Chamberlain.

Thanks,
Guillem

Guillem Jover (3):
  lib/fileutils: Add new dup_fd_cloexec function
  lib/sysfs: Use dup_fd_cloexec instead of direct call to fcntl
  include/c: Define F_DUPFD_CLOEXEC on kFreeBSD systems if missing

 include/c.h         |  6 ++++++
 include/fileutils.h |  1 +
 lib/fileutils.c     | 30 ++++++++++++++++++++++++++++++
 lib/sysfs.c         |  2 +-
 4 files changed, 38 insertions(+), 1 deletion(-)

-- 
2.2.1.209.g41e5f3a

[PATCH 1/3] lib/fileutils: Add new dup_fd_cloexec function

[Guillem Jover]

This function duplicates and marks a file descriptor as close-on-exec.
Takes care of build and run-time support for the fcntl F_DUPFD_CLOEXEC
command, and other errors.

Signed-off-by: Guillem Jover <guillem@hadrons.org>
---
 include/fileutils.h |  1 +
 lib/fileutils.c     | 30 ++++++++++++++++++++++++++++++
 2 files changed, 31 insertions(+)

diff --git a/include/fileutils.h b/include/fileutils.h
index 3353f69..e0e2ece 100644
--- a/include/fileutils.h
+++ b/include/fileutils.h
@@ -25,6 +25,7 @@ static inline FILE *xfmkstemp(char **tmpname, char *dir)
 	return ret;
 }
 
+extern int dup_fd_cloexec(int oldfd, int lowfd);
 extern int get_fd_tabsize(void);
 
 extern int mkdir_p(const char *path, mode_t mode);
diff --git a/lib/fileutils.c b/lib/fileutils.c
index bffa8ff..81b38ad 100644
--- a/lib/fileutils.c
+++ b/lib/fileutils.c
@@ -50,6 +50,36 @@ int xmkstemp(char **tmpname, char *dir)
 	return fd;
 }
 
+int dup_fd_cloexec(int oldfd, int lowfd)
+{
+	int fd, flags, errno_save;
+
+#ifdef F_DUPFD_CLOEXEC
+	fd = fcntl(oldfd, F_DUPFD_CLOEXEC, lowfd);
+	if (fd >= 0)
+		return fd;
+#endif
+
+	fd = dup(oldfd);
+	if (fd < 0)
+		return fd;
+
+	flags = fcntl(fd, F_GETFD);
+	if (flags < 0)
+		goto unwind;
+	if (fcntl(fd, F_SETFD, flags | FD_CLOEXEC) < 0)
+		goto unwind;
+
+	return fd;
+
+unwind:
+	errno_save = errno;
+	close(fd);
+	errno = errno_save;
+
+	return -1;
+}
+
 /*
  * portable getdtablesize()
  */
-- 
2.2.1.209.g41e5f3a

[PATCH 2/3] lib/sysfs: Use dup_fd_cloexec instead of direct call to fcntl

[Guillem Jover]

Signed-off-by: Guillem Jover <guillem@hadrons.org>
---
 lib/sysfs.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/sysfs.c b/lib/sysfs.c
index 07b6b56..caf89bf 100644
--- a/lib/sysfs.c
+++ b/lib/sysfs.c
@@ -267,7 +267,7 @@ DIR *sysfs_opendir(struct sysfs_cxt *cxt, const char *attr)
 		 * -- we cannot use cxt->sysfs_fd directly, because closedir()
 		 * will close this our persistent file descriptor.
 		 */
-		fd = fcntl(cxt->dir_fd, F_DUPFD_CLOEXEC, STDERR_FILENO + 1);
+		fd = dup_fd_cloexec(cxt->dir_fd, STDERR_FILENO + 1);
 
 	if (fd < 0)
 		return NULL;
-- 
2.2.1.209.g41e5f3a

[PATCH 3/3] include/c: Define F_DUPFD_CLOEXEC on kFreeBSD systems if missing

[Guillem Jover]

The kernel of FreeBSD version 10 and higher supports this fcntl command,
but the system libc, in this case glibc, might not yet know about it.

Signed-off-by: Guillem Jover <guillem@hadrons.org>
---
 include/c.h | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/include/c.h b/include/c.h
index a72e264..1eda75f 100644
--- a/include/c.h
+++ b/include/c.h
@@ -231,6 +231,12 @@ static inline int dirfd(DIR *d)
 #define O_CLOEXEC 0
 #endif
 
+#ifdef __FreeBSD_kernel__
+#ifndef F_DUPFD_CLOEXEC
+#define F_DUPFD_CLOEXEC	17	/* Like F_DUPFD, but FD_CLOEXEC is set */
+#endif
+#endif
+
 
 #ifndef AI_ADDRCONFIG
 #define AI_ADDRCONFIG 0x0020
-- 
2.2.1.209.g41e5f3a

Re: [PATCH 0/3] Handle lack of F_DUPFD_CLOEXEC support

[Karel Zak]

> Guillem Jover (3):
>   lib/fileutils: Add new dup_fd_cloexec function
>   lib/sysfs: Use dup_fd_cloexec instead of direct call to fcntl
>   include/c: Define F_DUPFD_CLOEXEC on kFreeBSD systems if missing

 Applied, thanks.

-- 
 Karel Zak  <kzak@redhat.com>
 http://karelzak.blogspot.com