sysctl: allow for strict write position handling

[uclinux-h8/linux.git] / Documentation / sysctl / kernel.txt

diff --git a/Documentation/sysctl/kernel.txt b/Documentation/sysctl/kernel.txt
index 9886c3d..708bb7f 100644 (file)
--- a/Documentation/sysctl/kernel.txt
+++ b/Documentation/sysctl/kernel.txt
@@ -77,6 +77,7 @@ show up in /proc/sys/kernel:
 - shmmni
 - stop-a                      [ SPARC only ]
 - sysrq                       ==> Documentation/sysrq.txt
+- sysctl_writes_strict
 - tainted
 - threads-max
 - unknown_nmi_panic
@@ -762,6 +763,26 @@ without users and with a dead originative process will be destroyed.
 
 ==============================================================
 
+sysctl_writes_strict:
+
+Control how file position affects the behavior of updating sysctl values
+via the /proc/sys interface:
+
+  -1 - Legacy per-write sysctl value handling, with no printk warnings.
+       Each write syscall must fully contain the sysctl value to be
+       written, and multiple writes on the same sysctl file descriptor
+       will rewrite the sysctl value, regardless of file position.
+   0 - (default) Same behavior as above, but warn about processes that
+       perform writes to a sysctl file descriptor when the file position
+       is not 0.
+   1 - Respect file position when writing sysctl strings. Multiple writes
+       will append to the sysctl value buffer. Anything past the max length
+       of the sysctl value buffer will be ignored. Writes to numeric sysctl
+       entries must always be at file position 0 and the value must be
+       fully contained in the buffer sent in the write syscall.
+
+==============================================================
+
 tainted:
 
 Non-zero if the kernel has been tainted.  Numeric values, which