linux-kernel - [PATCH] livepatch: Remove not longer valid limitations from the documentation

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Message-Id: <20180523074742.20171-1-pmladek@suse.com>
Date:   Wed, 23 May 2018 09:47:42 +0200
From:   Petr Mladek <pmladek@...e.com>
To:     Jiri Kosina <jikos@...nel.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Miroslav Benes <mbenes@...e.cz>
Cc:     Joe Lawrence <joe.lawrence@...hat.com>,
        Jessica Yu <jeyu@...nel.org>, live-patching@...r.kernel.org,
        linux-kernel@...r.kernel.org, Petr Mladek <pmladek@...e.com>
Subject: [PATCH] livepatch: Remove not longer valid limitations from the documentation

Semantic changes are possible since the commit d83a7cb375eec21f04
("livepatch: change to a per-task consistency model").

Also data structures can be patched since the commit 439e7271dc2b63de37
("livepatch: introduce shadow variable API").

It is a high time we removed these limitations from the documentation.

Signed-off-by: Petr Mladek <pmladek@...e.com>
---
I have found this when working on v12 of the atomic replace. It looks
like a no-brainer and does not conflict with the patchset, so ... ;-)

 Documentation/livepatch/livepatch.txt | 24 ------------------------
 1 file changed, 24 deletions(-)

diff --git a/Documentation/livepatch/livepatch.txt b/Documentation/livepatch/livepatch.txt
index 1ae2de758c08..2d7ed09dbd59 100644
--- a/Documentation/livepatch/livepatch.txt
+++ b/Documentation/livepatch/livepatch.txt
@@ -429,30 +429,6 @@ See Documentation/ABI/testing/sysfs-kernel-livepatch for more details.
 
 The current Livepatch implementation has several limitations:
 
-
-  + The patch must not change the semantic of the patched functions.
-
-    The current implementation guarantees only that either the old
-    or the new function is called. The functions are patched one
-    by one. It means that the patch must _not_ change the semantic
-    of the function.
-
-
-  + Data structures can not be patched.
-
-    There is no support to version data structures or anyhow migrate
-    one structure into another. Also the simple consistency model does
-    not allow to switch more functions atomically.
-
-    Once there is more complex consistency mode, it will be possible to
-    use some workarounds. For example, it will be possible to use a hole
-    for a new member because the data structure is aligned. Or it will
-    be possible to use an existing member for something else.
-
-    There are no plans to add more generic support for modified structures
-    at the moment.
-
-
   + Only functions that can be traced could be patched.
 
     Livepatch is based on the dynamic ftrace. In particular, functions
-- 
2.13.6