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* [musl] [PATCH] add close_range() syscall wrapper
@ 2023-09-01  8:02 Natanael Copa
  2023-09-01 13:57 ` Rich Felker
  0 siblings, 1 reply; 5+ messages in thread
From: Natanael Copa @ 2023-09-01  8:02 UTC (permalink / raw)
  To: musl; +Cc: Natanael Copa

close_range() is a syscall present in FreeBSD 8.0 and Linux 5.9. glibc
2.34 added a wrapper.

Expose it under _GNU_SOURCE similar to what GNU libc does. Also expose
it under _BSD_SOURCE since it is also a FreeBSD function.

This is a re-take of close_range() syscall wrapper. It was previously
discussed in mailing list:

Difference from previous submission:

- Set errno on errors.
- Drop the (unsigned int) cast for flags, as it raised questions last

I think it is a good idea to add this to musl because it is difficult to
the close before exec properly without it. 

Most workaounrds currently out there are either parsing /proc or try to
close everything to maxfd reported by getrlimit(), sysconf() or

opendir("/proc/self/fd") is problematic becase 1) /proc may not be
mounted and 2) some versions of musl hangs on malloc between fork and 

Trying to close everything between a maxfd is also problematic. On some
systems (under docker for example) the maxfd can be 1G, which
effectively results in a hang. (See

I think its better to encourage the use of close_range().

See also:

 include/unistd.h        | 3 +++
 src/linux/close_range.c | 8 ++++++++
 2 files changed, 11 insertions(+)
 create mode 100644 src/linux/close_range.c

diff --git a/include/unistd.h b/include/unistd.h
index 5bc7f798..d89e3d4c 100644
--- a/include/unistd.h
+++ b/include/unistd.h
@@ -161,6 +161,9 @@ unsigned ualarm(unsigned, unsigned);
 #define L_INCR 1
 #define L_XTND 2
 int brk(void *);
+#define CLOSE_RANGE_UNSHARE	(1U << 1)
+#define CLOSE_RANGE_CLOEXEC	(1U << 2)
+int close_range(unsigned int, unsigned int, int);
 void *sbrk(intptr_t);
 pid_t vfork(void);
 int vhangup(void);
diff --git a/src/linux/close_range.c b/src/linux/close_range.c
new file mode 100644
index 00000000..258ba8bd
--- /dev/null
+++ b/src/linux/close_range.c
@@ -0,0 +1,8 @@
+#define _GNU_SOURCE
+#include <unistd.h>
+#include "syscall.h"
+int close_range(unsigned int first, unsigned int last, int flags)
+	return __syscall_ret(syscall(SYS_close_range, first, last, flags));

^ permalink raw reply	[flat|nested] 5+ messages in thread

end of thread, other threads:[~2023-09-01 15:06 UTC | newest]

Thread overview: 5+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2023-09-01  8:02 [musl] [PATCH] add close_range() syscall wrapper Natanael Copa
2023-09-01 13:57 ` Rich Felker
2023-09-01 14:55   ` Natanael Copa
2023-09-01 15:06     ` Rich Felker
2023-09-01 14:58   ` [musl] [PATCH v2] " Natanael Copa

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