docs: make kptr_restrict and hash_pointers reference each other

vsprintf.c uses a mix of the `kernel.kptr_restrict` sysctl and the
`hash_pointers` boot param to control pointer hashing. But that wasn't
possible to tell without looking at the source code.

They have a different focus and purpose. To avoid wasting the time of
users trying to use one instead of the other, simply have them reference
each other in the Documentation.

Signed-off-by: Marc Herbert <marc.herbert@linux.intel.com>
Acked-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Message-ID: <20260107-doc-hash-ptr-v2-1-cb4c161218d7@linux.intel.com>

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index f4a2bf906bf3ccbfc0635ad71e97c3f7a676b393..8e3738d9588a6c78b573281d09edc0e19facbb4c 100644 (file)
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -1969,6 +1969,9 @@ Kernel parameters
                                 param "no_hash_pointers" is an alias for
                                 this mode.
 
+                       For controlling hashing dynamically at runtime,
+                       use the "kernel.kptr_restrict" sysctl instead.
+
        hashdist=       [KNL,NUMA] Large hashes allocated during boot
                        are distributed across NUMA nodes.  Defaults on
                        for 64-bit NUMA, off otherwise.

diff --git a/Documentation/admin-guide/sysctl/kernel.rst b/Documentation/admin-guide/sysctl/kernel.rst
index 239da22c4e28f192d654667776e5c7f5dfee134f..0315eb7ee6d409856bcc2785981cf60187cd06cb 100644 (file)
--- a/Documentation/admin-guide/sysctl/kernel.rst
+++ b/Documentation/admin-guide/sysctl/kernel.rst
@@ -591,6 +591,9 @@ if leaking kernel pointer values to unprivileged users is a concern.
 When ``kptr_restrict`` is set to 2, kernel pointers printed using
 %pK will be replaced with 0s regardless of privileges.
 
+For disabling these security restrictions early at boot time (and once
+for all), use the ``hash_pointers`` boot parameter instead.
+
 softlockup_sys_info & hardlockup_sys_info
 =========================================
 A comma separated list of extra system information to be dumped when