Re: taint/module: Clean up global and module taint flags handling

[Jessica Yu]

+++ 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@xxxxxxxxxx
>
> 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@xxxxxxxx>
> ---
> 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@xxxxxxxxxx>

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?