tracing: Add recursion protection in kernel stack trace recording

In the Linux kernel, the following vulnerability has been resolved:

tracing: Add recursion protection in kernel stack trace recording

A bug was reported about an infinite recursion caused by tracing the rcu

events with the kernel stack trace trigger enabled. The stack trace code

called back into RCU which then called the stack trace again.

Expand the ftrace recursion protection to add a set of bits to protect

events from recursion. Each bit represents the context that the event is

in (normal, softirq, interrupt and NMI).

Have the stack trace code use the interrupt context to protect against

recursion.

Note, the bug showed an issue in both the RCU code as well as the tracing

stacktrace code. This only handles the tracing stack trace side of the

bug. The RCU fix will be handled separately.