sysctl: deprecate sys_sysctl in a user space visible fashion.
After adding checking to register_sysctl_table and finding a whole new set
of bugs. Missed by countless code reviews and testers I have finally lost
patience with the binary sysctl interface.
The binary sysctl interface has been sort of deprecated for years and
finding a user space program that uses the syscall is more difficult then
finding a needle in a haystack. Problems continue to crop up, with the in
kernel implementation. So since supporting something that no one uses is
silly, deprecate sys_sysctl with a sufficient grace period and notice that
the handful of user space applications that care can be fixed or replaced.
The /proc/sys sysctl interface that people use will continue to be
supported indefinitely.
This patch moves the tested warning about sysctls from the path where
sys_sysctl to a separate path called from both implementations of
sys_sysctl, and it adds a proper entry into
Documentation/feature-removal-schedule.
Allowing us to revisit this in a couple years time and actually kill
sys_sysctl.
[lethal@linux-sh.org: sysctl: Fix syscall disabled build]
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/Documentation/feature-removal-schedule.txt b/Documentation/feature-removal-schedule.txt
index 280ec06..5b25162 100644
--- a/Documentation/feature-removal-schedule.txt
+++ b/Documentation/feature-removal-schedule.txt
@@ -82,6 +82,41 @@
---------------------------
+What: sys_sysctl
+When: September 2010
+Option: CONFIG_SYSCTL_SYSCALL
+Why: The same information is available in a more convenient from
+ /proc/sys, and none of the sysctl variables appear to be
+ important performance wise.
+
+ Binary sysctls are a long standing source of subtle kernel
+ bugs and security issues.
+
+ When I looked several months ago all I could find after
+ searching several distributions were 5 user space programs and
+ glibc (which falls back to /proc/sys) using this syscall.
+
+ The man page for sysctl(2) documents it as unusable for user
+ space programs.
+
+ sysctl(2) is not generally ABI compatible to a 32bit user
+ space application on a 64bit and a 32bit kernel.
+
+ For the last several months the policy has been no new binary
+ sysctls and no one has put forward an argument to use them.
+
+ Binary sysctls issues seem to keep happening appearing so
+ properly deprecating them (with a warning to user space) and a
+ 2 year grace warning period will mean eventually we can kill
+ them and end the pain.
+
+ In the mean time individual binary sysctls can be dealt with
+ in a piecewise fashion.
+
+Who: Eric Biederman <ebiederm@xmission.com>
+
+---------------------------
+
What: a.out interpreter support for ELF executables
When: 2.6.25
Files: fs/binfmt_elf.c