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| author | Adhemerval Zanella <adhemerval.zanella@linaro.org> | 2021-03-10 12:26:32 -0300 |
|---|---|---|
| committer | Adhemerval Zanella <adhemerval.zanella@linaro.org> | 2021-07-08 14:08:14 -0300 |
| commit | 607449506f197cc9514408908f41f22537a47a8c (patch) | |
| tree | 9d4304b8a8a1ccdef78a305433d845bcd3e08ae6 /posix/unistd.h | |
| parent | 286286283e9bdc7ef894306e2dbcf4c115b97ba2 (diff) | |
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io: Add closefrom [BZ #10353]
The function closes all open file descriptors greater than or equal to
input argument. Negative values are clamped to 0, i.e, it will close
all file descriptors.
As indicated by the bug report, this is a common symbol provided by
different systems (Solaris, OpenBSD, NetBSD, FreeBSD) and, although
its has inherent issues with not taking in consideration internal libc
file descriptors (such as syslog), this is also a common feature used
in multiple projects [1][2][3][4][5].
The Linux fallback implementation iterates over /proc and close all
file descriptors sequentially. Although it was raised the questioning
whether getdents on /proc/self/fd might return disjointed entries
when file descriptor are closed; it does not seems the case on my
testing on multiple kernel (v4.18, v5.4, v5.9) and the same strategy
is used on different projects [1][2][3][5].
Also, the interface is set a fail-safe meaning that a failure in the
fallback results in a process abort.
Checked on x86_64-linux-gnu and i686-linux-gnu on kernel 5.11 and 4.15.
[1] https://github.com/systemd/systemd/blob/5238e9575906297608ff802a27e2ff9effa3b338/src/basic/fd-util.c#L217
[2] https://github.com/lxc/lxc/blob/ddf4b77e11a4d08f09b7b9cd13e593f8c047edc5/src/lxc/start.c#L236
[3] https://github.com/python/cpython/blob/9e4f2f3a6b8ee995c365e86d976937c141d867f8/Modules/_posixsubprocess.c#L220
[4] https://github.com/rust-lang/rust/blob/5f47c0613ed4eb46fca3633c1297364c09e5e451/src/libstd/sys/unix/process2.rs#L303-L308
[5] https://github.com/openjdk/jdk/blob/master/src/java.base/unix/native/libjava/childproc.c#L82
Diffstat (limited to 'posix/unistd.h')
| -rw-r--r-- | posix/unistd.h | 6 |
1 files changed, 6 insertions, 0 deletions
diff --git a/posix/unistd.h b/posix/unistd.h index 217c6c5363..3dca65732f 100644 --- a/posix/unistd.h +++ b/posix/unistd.h @@ -357,6 +357,12 @@ extern __off64_t lseek64 (int __fd, __off64_t __offset, int __whence) __THROW. */ extern int close (int __fd); +#ifdef __USE_MISC +/* Close all open file descriptors greater than or equal to LOWFD. + Negative LOWFD is clamped to 0. */ +extern void closefrom (int __lowfd) __THROW; +#endif + /* Read NBYTES into BUF from FD. Return the number read, -1 for errors or 0 for EOF. |