z/TPF Backtrace Translation and Processing Fixes

z/TPF Symbol Names and Modules names from dladdr are
returned as EBCDIC characters sets.  These values need
to be translated before being stored in the backtrace
frame control structure otherwise they are printed out
as garbage characters.  Furthermore the top of stack for
z/TPF is a dummy invalid frame, and needs to be pruned
from the backtrace otherwise unexpected behaviour occurs.

Signed-off-by: James D Johnston <[email protected]>

port/ztpf/omrosbacktrace_impl.c

@@ -1,5 +1,5 @@
 /*******************************************************************************
- * Copyright (c) 1991, 2017 IBM Corp. and others
+ * Copyright (c) 1991, 2018 IBM Corp. and others
  *
  * This program and the accompanying materials are made available under
  * the terms of the Eclipse Public License 2.0 which accompanies this
@@ -38,6 +38,8 @@
 
 #include "omrintrospect.h"
 
+#include <atoe.h>
+
 uintptr_t protectedBacktrace(struct OMRPortLibrary *port, void *arg);
 uintptr_t backtrace_sigprotect(struct OMRPortLibrary *portLibrary,
 	J9PlatformThread *threadInfo, void **address_array, int capacity);
@@ -149,6 +151,12 @@ omrintrospect_backtrace_thread_raw(struct OMRPortLibrary *portLibrary,
 	ret = backtrace_sigprotect(portLibrary, threadInfo, addresses,
 		sizeof(addresses) / sizeof(void*));
 
+	/*
+	 * z/TPF Stack grows down.  The top-of-stack has a dummy frame which should be ignored.
+	 * Therefore reducing stack frame count by one.
+	 */
+	ret--;
+
 	nextFrame = &threadInfo->callstack;
 	for (i = 0; i < ret; i++) {
 		if (heap != NULL) {
@@ -246,6 +254,8 @@ omrintrospect_backtrace_symbols_raw(struct OMRPortLibrary *portLibrary,
 		uintptr_t symbol_offset = 0;
 		uintptr_t module_offset = 0;
 		const char *symbol_name = "";
+		char asciiSymbolBuffer[512];
+		char asciiModuleBuffer[512];
 		const char *module_name = "<unknown>";
 		short symbol_length = 0;
 
@@ -285,9 +295,10 @@ omrintrospect_backtrace_symbols_raw(struct OMRPortLibrary *portLibrary,
 
 		/* symbol_name+offset (id, instruction_pointer [module+offset]) */
 		if (symbol_length > 0) {
+			e2a_len(symbol_name, asciiSymbolBuffer, symbol_length+1);
 			cursor += omrstr_printf(portLibrary, cursor,
 				sizeof(output_buf) - (cursor - output_buf), "%.*s",
-				symbol_length, symbol_name);
+				symbol_length, asciiSymbolBuffer);
 			cursor += omrstr_printf(portLibrary, cursor,
 				sizeof(output_buf) - (cursor - output_buf), "+0x%x ",
 				symbol_offset);
@@ -296,9 +307,10 @@ omrintrospect_backtrace_symbols_raw(struct OMRPortLibrary *portLibrary,
 			sizeof(output_buf) - (cursor - output_buf), "(0x%p",
 			frame->instruction_pointer);
 		if (module_name[0] != '\0') {
+			e2a_len(module_name, asciiModuleBuffer, strlen(module_name)+1);
 			cursor += omrstr_printf(portLibrary, cursor,
 				sizeof(output_buf) - (cursor - output_buf), " [%s+0x%x]",
-				module_name, module_offset);
+				asciiModuleBuffer, module_offset);
 		}
 		*(cursor++) = ')';
 		*cursor = 0;