Break out stack(9) from ddb(4):

- Introduce per-architecture stack_machdep.c to hold stack_save(9).
- Introduce per-architecture machine/stack.h to capture any common
  definitions required between db_trace.c and stack_machdep.c.
- Add new kernel option "options STACK"; we will build in stack(9) if it is
  defined, or also if "options DDB" is defined to provide compatibility
  with existing users of stack(9).

Add new stack_save_td(9) function, which allows the capture of a stacktrace
of another thread rather than the current thread, which the existing
stack_save(9) was limited to.  It requires that the thread be neither
swapped out nor running, which is the responsibility of the consumer to
enforce.

Update stack(9) man page.

Build tested:	amd64, arm, i386, ia64, powerpc, sparc64, sun4v
Runtime tested:	amd64 (rwatson), arm (cognet), i386 (rwatson)

1 files changed, 2 insertions, 0 deletions

diff --git a/sys/kern/subr_stack.c b/sys/kern/subr_stack.c
index e3cf156..db03ccf 100644
--- a/sys/kern/subr_stack.c
+++ b/sys/kern/subr_stack.c
@@ -105,6 +105,7 @@ stack_print(struct stack *st)
 	}
 }
 
+#ifdef DDB
 void
 stack_print_ddb(struct stack *st)
 {
@@ -120,6 +121,7 @@ stack_print_ddb(struct stack *st)
 		    namebuf, offset);
 	}
 }
+#endif
 
 /*
  * Two print routines -- one for use from DDB and DDB-like contexts, the