From: Nicholas Piggin
> Sent: 12 October 2023 02:19
...
> It is a kernel crash, so we need something for stable. But In a case
> like this there's not one single problem. Linux kernel stack use has
> always been pretty dumb - "don't use too much", for some values of
> too much, and just cross fingers config and compiler and worlkoad
> doesn't hit some overflow case.
I think it ought to be possible to use a FINE_IBT (I think that
is what it is called) compile to get indirect calls grouped
and change objtool to output the stack offset of every call.
It is then a simple (for some definition of simple) process
to work out the static maximum stack usage.
Any recursion causes grief (the stack depth for each
loop can be reported).
Also I suspect the compiler will need an enhancement to
add a constant into the hash to disambiguate indirect
calls with the same argument list.
My suspicion (from doing this exercise on an embedded system
a long time ago) is that the stack will be blown somewhere
inside printk() in some error path.
David
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