kamil 05ffc73c35 Add new ptrace(2) API: PT_SETSTEP & PT_CLEARSTEP
These operations allow to mark thread as a single-stepping one.

This allows to i.a.:
 - single step and emit a signal (PT_SETSTEP & PT_CONTINUE)
 - single step and trace syscall entry and exit (PT_SETSTEP & PT_SYSCALL)

The former is useful for debuggers like GDB or LLDB. The latter can be used
to singlestep a usermode kernel. These examples don't limit use-cases of
this interface.

Define PT_*STEP only for platforms defining PT_STEP.

Add new ATF tests setstep[1234].

These ptrace(2) operations first appeared in FreeBSD.

Sponsored by <The NetBSD Foundation>
2017-04-08 00:25:49 +00:00
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