Implement db_print_backtrace() if DDB is compiled into the kernel. This

MD function is just a wrapper around db_stack_trace_cmd() that prints out
a backtrace of curthread.  Currently, this function is only implemented
on i386 and alpha (and the alpha version isn't quite tested yet, will do
that in a bit).  Other changes:

- For i386, fix a bug in the raw frame address case.  The eip we extract
  from the passed in frame address does not match the frame we received.
  Thus, instead of printing a bogus frame with the wrong eip, go ahead
  and advance frame down to the same frame as the eip we are using.
- For alpha, attempt to add a way of doing a raw trace for alpha.  Instead
  of passing a frame address in 'addr', pass in a pointer to a structure
  containing PC and KSP and use those to start the backtrace.  The alpha
  db_print_backtrace() uses asm to read in the current PC and KSP values
  into such a request.

Tested on:	i386
Requested by:	many

1 files changed, 3 insertions, 0 deletions

diff --git a/sys/ddb/ddb.h b/sys/ddb/ddb.h
index ce3ffc41278a..1eb87ba0ce27 100644
--- a/sys/ddb/ddb.h
+++ b/sys/ddb/ddb.h
@@ -134,6 +134,9 @@ db_cmdfcn_t	ipc_port_print;
 db_cmdfcn_t	vm_page_print;
 #endif
 
+/* Scare the user with backtrace of curthread to console. */
+void		db_print_backtrace(void);
+
 /*
  * Command table.
  */