mm, page_alloc: do not rely on the order of page_poison and init_on_alloc/free parameters

mm, page_alloc: do not rely on the order of page_poison and init_on_alloc/free parameters

Patch series "cleanup page poisoning", v3.

I have identified a number of issues and opportunities for cleanup with
CONFIG_PAGE_POISON and friends:

 - interaction with init_on_alloc and init_on_free parameters depends on
   the order of parameters (Patch 1)

 - the boot time enabling uses static key, but inefficienty (Patch 2)

 - sanity checking is incompatible with hibernation (Patch 3)

 - CONFIG_PAGE_POISONING_NO_SANITY can be removed now that we have
   init_on_free (Patch 4)

 - CONFIG_PAGE_POISONING_ZERO can be most likely removed now that we
   have init_on_free (Patch 5)

This patch (of 5):

Enabling page_poison=1 together with init_on_alloc=1 or init_on_free=1
produces a warning in dmesg that page_poison takes precedence.  However,
as these warnings are printed in early_param handlers for
init_on_alloc/free, they are not printed if page_poison is enabled later
on the command line (handlers are called in the order of their
parameters), or when init_on_alloc/free is always enabled by the
respective config option - before the page_poison early param handler is
called, it is not considered to be enabled.  This is inconsistent.

We can remove the dependency on order by making the init_on_* parameters
only set a boolean variable, and postponing the evaluation after all early
params have been processed.  Introduce a new
init_mem_debugging_and_hardening() function for that, and move the related
debug_pagealloc processing there as well.

As a result init_mem_debugging_and_hardening() knows always accurately if
init_on_* and/or page_poison options were enabled.  Thus we can also
optimize want_init_on_alloc() and want_init_on_free().  We don't need to
check page_poisoning_enabled() there, we can instead not enable the
init_on_* static keys at all, if page poisoning is enabled.  This results
in a simpler and more effective code.

Link: https://lkml.kernel.org/r/20201113104033.22907-1-vbabka@suse.cz
Link: https://lkml.kernel.org/r/20201113104033.22907-2-vbabka@suse.cz
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Mike Rapoport <rppt@linux.ibm.com>
Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Mateusz Nosek <mateusznosek0@gmail.com>
Cc: Laura Abbott <labbott@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>