linux-kernel - Re: taint/module: Clean up global and module taint flags handling

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Date:   Fri, 23 Sep 2016 00:48:40 -0400
From:   Jessica Yu <jeyu@...hat.com>
To:     Petr Mladek <pmladek@...e.com>
Cc:     Rusty Russell <rusty@...tcorp.com.au>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Jiri Kosina <jkosina@...e.cz>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        live-patching@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: taint/module: Clean up global and module taint flags handling

+++ Petr Mladek [21/09/16 13:47 +0200]:
>The commit 66cc69e34e86a231 ("Fix: module signature vs tracepoints:
>add new TAINT_UNSIGNED_MODULE") updated module_taint_flags() to
>potentially print one more character. But it did not increase the
>size of the corresponding buffers in m_show() and print_modules().
>
>We have recently done the same mistake when adding a taint flag
>for livepatching, see
>https://lkml.kernel.org/g/cfba2c823bb984690b73572aaae1db596b54a082.1472137475.git.jpoimboe@redhat.com
>
>Also struct module uses an incompatible type for mod-taints flags.
>It survived from the commit 2bc2d61a9638dab670d ("[PATCH] list module
>taint flags in Oops/panic"). There was used "int" for the global taint
>flags at these times. But only the global tain flags was later changed
>to "unsigned long" by the commit 25ddbb18aae33ad2 ("Make the taint
>flags reliable").
>
>This patch defines TAINT_FLAGS_COUNT that can be used to create
>arrays and buffers of the right size. Note that we could not use
>enum because the taint flag indexes are used also in assembly code.
>
>Then it reworks the table that describes the taint flags. The TAINT_*
>numbers can be used as the index. Instead, we add information
>if the taint flag is also shown per-module.
>
>Finally, it uses "unsigned long", bit operations, and the updated
>taint_flags table also for mod->taints.
>
>It is not optimal because only few taint flags can be printed by
>module_taint_flags(). But better be on the safe side. IMHO, it is
>not worth the optimization and this is a good compromise.
>
>Signed-off-by: Petr Mladek <pmladek@...e.com>
>---
>Changes against v2:
>
>  + fixed a typo in a comment
>
>  + rebased on top of for-next branch from git/jikos/livepatching.git
>    that has the commit commit 2992ef29ae01af9983 ("livepatch/module:
>     make TAINT_LIVEPATCH module-specific").

Reviewed-by: Jessica Yu <jeyu@...hat.com>

Hm, quick question, which tree would this patch go to? Though the
cleanup is for modules, there is an indirect cross-tree dependency
(taint_flag.module needs to be true for TAINT_LIVEPATCH for Josh's
patch to still work as intended). The least complicated thing to do
would be to just take this through the livepatch tree (with Rusty's
approval :-)), no?