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.
... I wondered if this could be the place to initialize any kind of mm parameters in the future. Like init_mem_params() or so.
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@xxxxxxxxxx> -- Thanks, David / dhildenb
