[PATCH] ARM: poison initmem when it is freed

[Nicolas Pitre]

On Tue, 5 Jul 2011, Russell King - ARM Linux wrote:

> When the initmem is freed, we can no longer rely on its contents.  In
> lightly loaded systems, this memory may persist for some time, making
> it harder discover run-time issues (caused by the build warnings being
> ignored.)
> 
> Poison the initmem at the point where it is freed to encourage run-time
> problems when initmem is dereferenced as an aid to finding such problems.
> 
> Signed-off-by: Russell King <rmk+kernel at arm.linux.org.uk>

The default poison doesn't appear to be a judicious choice for ARM.

include/linux/poison.h:#define POISON_FREE_INITMEM      0xcc

   0:   cccccccc        stclgt  12, cr12, [ip], {204}   ; 0xcc

So if the gt condition is false this will execute nops until it falls 
out of the initmem section.  Would be nicer if a fault could be 
generated right at the accessed address which could be looked up.


Nicolas