Add ubacktrace(), print_ustack() and print_ubacktrace().

* runtime/sym.c (_stp_usymbol_print): New function.
* tapset/ucontext-unwind.stp (print_ubacktrace): New tapset function.
  (ubacktrace): Likewise.
* tapset/ucontext-symbols.stp (print_ustack): Likewise.
* testsuite/buildok/ustack.stp: New test for above three functions.

4 files changed, 111 insertions, 0 deletions

diff --git a/runtime/sym.c b/runtime/sym.c
index fe9b800c..013edd0c 100644
--- a/runtime/sym.c
+++ b/runtime/sym.c
@@ -329,6 +329,32 @@ static void _stp_symbol_print(unsigned long address)
 	}
 }
 
+/** Print an user space address from a specific task symbolically.
+ * @param address The address to lookup.
+ * @param task The address to lookup.
+ * @note Symbolic lookups should not normally be done within
+ * a probe because it is too time-consuming. Use at module exit time.
+ */
+
+static void _stp_usymbol_print(unsigned long address, struct task_struct *task)
+{
+	const char *modname;
+	const char *name;
+	unsigned long offset, size;
+
+	name = _stp_kallsyms_lookup(address, &size, &offset, &modname, NULL,
+                                    task);
+
+	_stp_printf("%p", (int64_t) address);
+
+	if (name) {
+		if (modname && *modname)
+			_stp_printf(" : %s+%#lx/%#lx [%s]", name, offset, size, modname);
+		else
+			_stp_printf(" : %s+%#lx/%#lx", name, offset, size);
+	}
+}
+
 /* Like _stp_symbol_print, except only print if the address is a valid function address */
 static int _stp_func_print(unsigned long address, int verbose, int exact,
                            struct task_struct *task)
diff --git a/tapset/ucontext-symbols.stp b/tapset/ucontext-symbols.stp
index 3813a8bf..2e7ad25b 100644
--- a/tapset/ucontext-symbols.stp
+++ b/tapset/ucontext-symbols.stp
@@ -50,3 +50,26 @@ function usymdata:string (addr: long) %{ /* pure */
 	 _stp_symbol_snprint(THIS->__retvalue, MAXSTRINGLEN, THIS->addr,
 			     current, 1);
 %}
+
+/**
+ * sfunction print_ustack - Print out stack for the current task from string.
+ * @stk: String with list of hexidecimal addresses for the current task.
+ *
+ *  Perform a symbolic lookup of the addresses in the given string,
+ *  which is assumed to be the result of a prior call to 
+ *  <command>ubacktrace()</command> for the current task.
+ * 
+ *  Print one line per address, including the address, the
+ *  name  of the function containing the address, and an estimate of
+ *  its position within that function.  Return nothing.
+ */
+function print_ustack(stk:string) %{
+        char *ptr = THIS->stk;
+        char *tok = strsep(&ptr, " ");
+        while (tok && *tok) {
+                _stp_print_char(' ');
+                _stp_usymbol_print (simple_strtol(tok, NULL, 16), current);
+                _stp_print_char('\n');
+                tok = strsep(&ptr, " ");
+        }
+%}
diff --git a/tapset/ucontext-unwind.stp b/tapset/ucontext-unwind.stp
new file mode 100644
index 00000000..b70f6da7
--- /dev/null
+++ b/tapset/ucontext-unwind.stp
@@ -0,0 +1,52 @@
+// User context unwind tapset
+// Copyright (C) 2009 Red Hat Inc.
+//
+// This file is part of systemtap, and is free software.  You can
+// redistribute it and/or modify it under the terms of the GNU General
+// Public License (GPL); either version 2, or (at your option) any
+// later version.
+
+%{
+#ifndef STP_NEED_UNWIND_DATA
+#define STP_NEED_UNWIND_DATA 1
+#endif
+#ifndef STP_NEED_SYMBOL_DATA
+#define STP_NEED_SYMBOL_DATA 1
+#endif
+#ifndef STP_NEED_VMA_TRACKER
+#define STP_NEED_VMA_TRACKER 1
+#endif
+%}
+
+/**
+ * sfunction print_ubacktrace - Print stack back trace for current task.
+ *
+ *  Equivalent to <command>print_ustack(ubacktrace())</command>, 
+ *  except that deeper stack nesting may be supported.  Return nothing.
+ */
+function print_ubacktrace () %{
+	if (CONTEXT->regs) {
+		_stp_stack_print(CONTEXT->regs, 1, CONTEXT->pi, MAXTRACE,
+				 current);
+	} else {
+		_stp_printf("Systemtap probe: %s\n", CONTEXT->probe_point);
+	}
+%}
+
+/**
+ * sfunction ubacktrace - Hex backtrace of current task stack.
+ *
+ *  Return a string of hex addresses that are a backtrace of the 
+ *  stack of the current task.  Output may be truncated as per maximum
+ *  string length. Returns empty string when current probe point cannot
+ *  determine user backtrace.
+ */
+
+function ubacktrace:string () %{ /* pure */
+	if (CONTEXT->regs)
+		_stp_stack_snprint (THIS->__retvalue, MAXSTRINGLEN,
+				    CONTEXT->regs, 0, CONTEXT->pi, MAXTRACE,
+				    current);
+	else 
+		strlcpy (THIS->__retvalue, "", MAXSTRINGLEN);
+%}
diff --git a/testsuite/buildok/ustack.stp b/testsuite/buildok/ustack.stp
new file mode 100755
index 00000000..23af0bff
--- /dev/null
+++ b/testsuite/buildok/ustack.stp
@@ -0,0 +1,10 @@
+#! stap -p4
+#
+# Test the translatability for ubacktrace(), print_ustack()
+# and print_ubacktrace()
+#
+probe begin
+{
+   print_ustack(ubacktrace());
+   print_ubacktrace();
+}