svn commit: r280038 - head/sys/cddl/dev/dtrace/arm

[Robert Watson]

Author: rwatson
Date: Sun Mar 15 15:17:34 2015
New Revision: 280038
URL: https://svnweb.freebsd.org/changeset/base/280038

Log:
  On ARM, unlike some other architectures, saved $pc values from in-kernel
  traps do appear in the regular call stack, rather than only in a special
  trap frame, so we don't need to inject the trap-frame $pc into a returned
  stack trace in DTrace.
  
  MFC after:	3 days
  Sponsored by:	DARPA, AFRL

Modified:
  head/sys/cddl/dev/dtrace/arm/dtrace_isa.c

Modified: head/sys/cddl/dev/dtrace/arm/dtrace_isa.c
==============================================================================
--- head/sys/cddl/dev/dtrace/arm/dtrace_isa.c	Sun Mar 15 14:57:11 2015	(r280037)
+++ head/sys/cddl/dev/dtrace/arm/dtrace_isa.c	Sun Mar 15 15:17:34 2015	(r280038)
@@ -73,7 +73,6 @@ dtrace_getpcstack(pc_t *pcstack, int pcs
 	register_t sp;
 	int scp_offset;
 	int depth = 0;
-	pc_t caller = (pc_t) solaris_cpu[curcpu].cpu_dtrace_caller;
 
 	if (intrpc != 0)
 		pcstack[depth++] = (pc_t) intrpc;
@@ -92,13 +91,14 @@ dtrace_getpcstack(pc_t *pcstack, int pcs
 
 		done = unwind_stack_one(&state, 1);
 
+		/*
+		 * NB: Unlike some other architectures, we don't need to
+		 * explicitly insert cpu_dtrace_caller as it appears in the
+		 * normal kernel stack trace rather than a special trap frame.
+		 */
 		if (aframes > 0) {
 			aframes--;
-			if ((aframes == 0) && (caller != 0)) {
-				pcstack[depth++] = caller;
-			}
-		}
-		else {
+		} else {
 			pcstack[depth++] = state.registers[PC];
 		}