Messages in this thread | | | Subject | Re: [PATCH 1/3] mm, page_alloc: do not rely on the order of page_poison and init_on_alloc/free parameters | From | Vlastimil Babka <> | Date | Tue, 27 Oct 2020 10:58:16 +0100 |
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On 10/27/20 10:03 AM, David Hildenbrand wrote: > On 26.10.20 18:33, Vlastimil Babka wrote: >> Enabling page_poison=1 together with init_on_alloc=1 or init_on_free=1 produces >> a warning in dmesg that page_poison takes precendence. 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() function for that, >> and move the related debug_pagealloc processing there as well. > > init_mem_debugging() is somewhat sub-optimal - init_on_alloc=1 or > init_on_free=1 are rather security hardening mechanisms.
Well yeah, init_mem_debugging_and_hardening()?
> ... I wondered if this could be the place to initialize any kind of mm > parameters in the future. Like init_mem_params() or so.
Maybe. In practice you often find out that different things have to be hooked in different points of the init process, and a single function might not be enough. I tried to group stuff that's really inter-related and can be initialized at the same time.
>> >> As a result init_mem_debugging() 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_* tracepoint at all, if page poisoning is >> enabled. This results in a simpler and more effective code. > > LGTM > > Reviewed-by: David Hildenbrand <david@redhat.com>
Thanks!
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