lkml.org 
[lkml]   [2016]   [Apr]   [13]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
Subject[PATCH v4 0/3] vfs: Define new syscall umask2 [formerly getumask]
Date
v3 -> v4:

- Rename the syscall: getumask becomes umask2.

- Add flags parameter, with one flag (UMASK_GET_MASK).

- Expand the rationale for this change in the first commit message.

- Add a selftest.

- Retest everything.

--------------------

It's not possible to read the process umask without also modifying it,
which is what umask(2) does. A library cannot read umask safely,
especially if the main program might be multithreaded.

This patch series adds a new system call "umask2". This adds a flags
parameter. Specifying flags=UMASK_GET_MASK allows the umask of the
current process to be read without modifying it.

This leaves open the possibility in future of adding a per-thread
umask, set or read with other flags. This is not implemented.

Another approach to this has been attempted before, adding something
to /proc, although it didn't go anywhere. See:

http://comments.gmane.org/gmane.linux.kernel/1292109

Another way to solve this would be to add a thread-safe getumask to
glibc. Since glibc could own the mutex, this would permit libraries
linked to this glibc to read umask safely. I should also note that
man-pages documents getumask(3), but no version of glibc has ever
implemented it.

Rich.

\
 
 \ /
  Last update: 2016-04-13 21:21    [W:0.073 / U:0.520 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site