Corinna Vinschen wrote:
Hi Christian,
On Jan 15 09:56, Christian Franke wrote:
Christian Franke wrote:
Jon Turney wrote:
On 14/01/2024 16:07, Christian Franke wrote:
Recently I learned about the existence and usefulness of close_range():
https://github.com/smartmontools/smartmontools/issues/235
https://man.freebsd.org/cgi/man.cgi?query=close_range&sektion=2
https://man7.org/linux/man-pages/man2/close_range.2.html
Note that the above Linux man page is not fully correct. The
include file "linux/close_range.h" exists, but provides only the
defines. It is sufficient to include "unistd.h" as on FreeBSD.
The attached patch adds this to Cygwin. It does not implement
the Linux-specific CLOSE_RANGE_UNSHARE as I have no idea how to
do this :-)
This API should also be mentioned in the
"System interfaces compatible with GNU or Linux extensions" section
of doc/posix.xml
Thanks for the info. I used the recent "Cygwin: introduce fallocate(2)"
patch as a blueprint for which other files should be changed (fallocate
is also missing in the posix.xml file).
I will provide a new patch soon which also fixes an unlikely but
possible corner case: Pass a value larger than MAX_INT as lower limit.
Attached. I also decided to simply ignore CLOSE_RANGE_UNSHARE for now.
After reading up on this issue, I think we should not ignore
CLOSE_RANGE_UNSHARE, but quite explicitely not implement it as a valid
flag.
The whole idea behind CLOSE_RANGE_UNSHARE depends on the way the Linux
kernel creates threads and (forked) processes and the fact that it has a
wide range of ways to share parts of the execution context between
parent and child process/thread.
So on Linux, a process/thread can actually decide if they share or not
share the descriptor table with the created process/thread. That's
what the CLONE_FILES flag to clone(2) and unshare(2) manage.
However, just as in FreeBSD, there's no such thing in Cygwin. Threads
always share descriptors, processes never share file desriptors.
The bottom line is, I think the decision of the FreeBSD developer not to
expose the CLOSE_RANGE_UNSHARE flag at all, was the right decision.
We should not claim that we even remotely have a way of doing this
the Linux way.
Does that make sense?
Yes - new patch attached.
From 3d538a35732b1e8cd3d7e7921e06dfdffc6d28db Mon Sep 17 00:00:00 2001
From: Christian Franke <christian.fra...@t-online.de>
Date: Mon, 15 Jan 2024 12:13:30 +0100
Subject: [PATCH] Cygwin: introduce close_range(2)
This function closes or sets the close-on-exec flag for a specified
range of file descriptors. It is available on FreeBSD and Linux.
Signed-off-by: Christian Franke <christian.fra...@t-online.de>
---
newlib/libc/include/sys/unistd.h | 6 ++++
winsup/cygwin/cygwin.din | 1 +
winsup/cygwin/include/cygwin/version.h | 3 +-
winsup/cygwin/release/3.5.0 | 2 ++
winsup/cygwin/syscalls.cc | 42 ++++++++++++++++++++++++++
winsup/doc/new-features.xml | 4 +++
winsup/doc/posix.xml | 5 +++
7 files changed, 62 insertions(+), 1 deletion(-)
diff --git a/newlib/libc/include/sys/unistd.h b/newlib/libc/include/sys/unistd.h
index 25532251c..00901540f 100644
--- a/newlib/libc/include/sys/unistd.h
+++ b/newlib/libc/include/sys/unistd.h
@@ -26,6 +26,12 @@ int chown (const char *__path, uid_t __owner, gid_t
__group);
int chroot (const char *__path);
#endif
int close (int __fildes);
+#if defined(__CYGWIN__) && (__BSD_VISIBLE || __GNU_VISIBLE)
+/* Available on FreeBSD (__BSD_VISIBLE) and Linux (__GNU_VISIBLE). */
+int close_range (unsigned int __firstfd, unsigned int __lastfd, int
__flags);
+/* CLOSE_RANGE_UNSHARE (1 << 1) */ /* Linux-specific, not supported. */
+#define CLOSE_RANGE_CLOEXEC (1 << 2)
+#endif
#if __POSIX_VISIBLE >= 199209
size_t confstr (int __name, char *__buf, size_t __len);
#endif
diff --git a/winsup/cygwin/cygwin.din b/winsup/cygwin/cygwin.din
index 9b76ce67a..9e354acc6 100644
--- a/winsup/cygwin/cygwin.din
+++ b/winsup/cygwin/cygwin.din
@@ -347,6 +347,7 @@ clog10l NOSIGFE
clogf NOSIGFE
clogl NOSIGFE
close SIGFE
+close_range SIGFE
closedir SIGFE
closelog SIGFE
cnd_broadcast SIGFE
diff --git a/winsup/cygwin/include/cygwin/version.h
b/winsup/cygwin/include/cygwin/version.h
index c8177c2b1..3036878c4 100644
--- a/winsup/cygwin/include/cygwin/version.h
+++ b/winsup/cygwin/include/cygwin/version.h
@@ -484,12 +484,13 @@ details. */
347: Add c16rtomb, c32rtomb, mbrtoc16, mbrtoc32.
348: Add c8rtomb, mbrtoc.
349: Add fallocate.
+ 350: Add close_range.
Note that we forgot to bump the api for ualarm, strtoll, strtoull,
sigaltstack, sethostname. */
#define CYGWIN_VERSION_API_MAJOR 0
-#define CYGWIN_VERSION_API_MINOR 349
+#define CYGWIN_VERSION_API_MINOR 350
/* There is also a compatibity version number associated with the shared memory
regions. It is incremented when incompatible changes are made to the shared
diff --git a/winsup/cygwin/release/3.5.0 b/winsup/cygwin/release/3.5.0
index d0a6c2fc8..6209064a6 100644
--- a/winsup/cygwin/release/3.5.0
+++ b/winsup/cygwin/release/3.5.0
@@ -43,6 +43,8 @@ What's new:
- New API calls: c8rtomb, c16rtomb, c32rtomb, mbrtoc8, mbrtoc16, mbrtoc32.
+- New API call: close_range (available on FreeBSD and Linux).
+
- New API call: fallocate (Linux-specific).
- Implement OSS-based sound mixer device (/dev/mixer).
diff --git a/winsup/cygwin/syscalls.cc b/winsup/cygwin/syscalls.cc
index 486db1db6..9d88b60b0 100644
--- a/winsup/cygwin/syscalls.cc
+++ b/winsup/cygwin/syscalls.cc
@@ -85,6 +85,48 @@ close_all_files (bool norelease)
cygheap->fdtab.unlock ();
}
+/* Close or set the close-on-exec flag for all open file descriptors
+ from firstfd to lastfd. CLOSE_RANGE_UNSHARE is not supported.
+ Available on FreeBSD since 13 and Linux since 5.9 */
+extern "C" int
+close_range (unsigned int firstfd, unsigned int lastfd, int flags)
+{
+ pthread_testcancel ();
+
+ if (!(firstfd <= lastfd && !(flags & ~CLOSE_RANGE_CLOEXEC)))
+ {
+ set_errno (EINVAL);
+ return -1;
+ }
+
+ cygheap->fdtab.lock ();
+
+ unsigned int size = (lastfd < cygheap->fdtab.size ? lastfd + 1 :
+ cygheap->fdtab.size);
+
+ for (unsigned int i = firstfd; i < size; i++)
+ {
+ cygheap_fdget cfd ((int) i, false, false);
+ if (cfd < 0)
+ continue;
+
+ if (flags & CLOSE_RANGE_CLOEXEC)
+ {
+ syscall_printf ("set FD_CLOEXEC on fd %u", i);
+ cfd->fcntl (F_SETFD, FD_CLOEXEC);
+ }
+ else
+ {
+ syscall_printf ("closing fd %u", i);
+ cfd->close_with_arch ();
+ cfd.release ();
+ }
+ }
+
+ cygheap->fdtab.unlock ();
+ return 0;
+}
+
extern "C" int
dup (int fd)
{
diff --git a/winsup/doc/new-features.xml b/winsup/doc/new-features.xml
index 6ae420031..0abe1c41c 100644
--- a/winsup/doc/new-features.xml
+++ b/winsup/doc/new-features.xml
@@ -74,6 +74,10 @@ posix_spawn_file_actions_addfchdir_np.
New API calls: c8rtomb, c16rtomb, c32rtomb, mbrtoc8, mbrtoc16, mbrtoc32.
</para></listitem>
+<listitem><para>
+New API call: close_range (available on FreeBSD and Linux).
+</para></listitem>
+
<listitem><para>
New API call: fallocate (Linux-specific).
</para></listitem>
diff --git a/winsup/doc/posix.xml b/winsup/doc/posix.xml
index 1a4eee1ab..89056915b 100644
--- a/winsup/doc/posix.xml
+++ b/winsup/doc/posix.xml
@@ -1143,6 +1143,7 @@ also IEEE Std 1003.1-2017 (POSIX.1-2017).</para>
cfmakeraw
cfsetspeed
clearerr_unlocked
+ close_range
daemon
dn_comp
dn_expand
@@ -1297,6 +1298,7 @@ also IEEE Std 1003.1-2017 (POSIX.1-2017).</para>
clog10
clog10f
clog10l
+ close_range (see <xref linkend="std-notes">chapter
"Implementation Notes"</xref>)
crypt_r (available in external "crypt" library)
dladdr (see <xref linkend="std-notes">chapter
"Implementation Notes"</xref>)
dremf
@@ -1656,6 +1658,9 @@ CLOCK_REALTIME and CLOCK_MONOTONIC.
<function>clock_setres</function>,
<function>clock_settime</function>, and <function>timer_create</function>
currently support only CLOCK_REALTIME.</para>
+<para><function>close_range</function> does not support the Linux-specific
+flag CLOSE_RANGE_UNSHARE.</para>
+
<para>POSIX file locks via <function>fcntl</function> or
<function>lockf</function>, as well as BSD <function>flock</function> locks
are advisory locks. They don't interact with Windows mandatory locks, nor
--
2.42.1
