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authorAdhemerval Zanella <adhemerval.zanella@linaro.org>2021-03-10 12:26:33 -0300
committerAdhemerval Zanella <adhemerval.zanella@linaro.org>2021-07-08 14:08:15 -0300
commit882d6e17bc44db687c8de9b357e5ce6c6d501f28 (patch)
tree950be2a02a8fed36f09491c1ad9dbb64497a781b /include
parent607449506f197cc9514408908f41f22537a47a8c (diff)
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posix: Add posix_spawn_file_actions_addclosefrom_np
This patch adds a way to close a range of file descriptors on posix_spawn as a new file action. The API is similar to the one provided by Solaris 11 [1], where the file action causes the all open file descriptors greater than or equal to input on to be closed when the new process is spawned. The function posix_spawn_file_actions_addclosefrom_np is safe to be implemented by iterating over /proc/self/fd, since the Linux spawni.c helper process does not use CLONE_FILES, so its has own file descriptor table and any failure (in /proc operation) aborts the process creation and returns an error to the caller. I am aware that this file action might be redundant to the current approach of POSIX in promoting O_CLOEXEC in more interfaces. However O_CLOEXEC is still not the default and for some specific usages, the caller needs to close all possible file descriptors to avoid them leaking. Some examples are CPython (discussed in BZ#10353) and OpenJDK jspawnhelper [2] (where OpenJDK spawns a helper process to exactly closes all file descriptors). Most likely any environment which calls functions that might open file descriptor under the hood and aim to use posix_spawn might face the same requirement. Checked on x86_64-linux-gnu and i686-linux-gnu on kernel 5.11 and 4.15. [1] https://docs.oracle.com/cd/E36784_01/html/E36874/posix-spawn-file-actions-addclosefrom-np-3c.html [2] https://github.com/openjdk/jdk/blob/master/src/java.base/unix/native/libjava/childproc.c#L82
Diffstat (limited to 'include')
-rw-r--r--include/unistd.h2
1 files changed, 1 insertions, 1 deletions
diff --git a/include/unistd.h b/include/unistd.h
index 114a431..7849562 100644
--- a/include/unistd.h
+++ b/include/unistd.h
@@ -158,7 +158,7 @@ extern int __brk (void *__addr) attribute_hidden;
extern int __close (int __fd);
libc_hidden_proto (__close)
extern int __libc_close (int __fd);
-extern _Bool __closefrom_fallback (int __lowfd) attribute_hidden;
+extern _Bool __closefrom_fallback (int __lowfd, _Bool) attribute_hidden;
extern ssize_t __read (int __fd, void *__buf, size_t __nbytes);
libc_hidden_proto (__read)
extern ssize_t __write (int __fd, const void *__buf, size_t __n);