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, 9 insertions, 0 deletions

diff --git a/sys/i386/i386/db_trace.c b/sys/i386/i386/db_trace.c
index 8ac4c01..f3688c5 100644
--- a/sys/i386/i386/db_trace.c
+++ b/sys/i386/i386/db_trace.c
@@ -350,6 +350,7 @@ db_stack_trace_cmd(addr, have_addr, count, modif)
 		p = NULL;
 		frame = (struct i386_frame *)addr;
 		callpc = (db_addr_t)db_get_value((int)&frame->f_retaddr, 4, FALSE);
+		frame = frame->f_frame;
 	}
 
 	first = TRUE;
@@ -470,6 +471,14 @@ DB_DRX_FUNC(dr6)
 DB_DRX_FUNC(dr7)
 
 
+void
+db_print_backtrace(void)
+{
+	register_t ebp;
+
+	__asm __volatile("mov %%ebp,%0\n" : "=r" (ebp));
+	db_stack_trace_cmd(ebp, 1, -1, NULL);
+}
 
 int
 i386_set_watch(watchnum, watchaddr, size, access, d)