available by Hewlett-Packard under the MIT license. The unwinder is
small, clean and fast and needed little adaptation for use in the
kernel.
This import has embedded in it the changes needed to make it build
in a kernel environment.
To optimize the common case, the kernel will minimize the number
of registers saved by not saving the preserved registers. In case
access to preserved registers is needed (signal handling, ptrace)
the kernel will unwind to the context of the syscall or exception.
For this we need an unwinder.
Approved by: re (blanket)
