1 files changed, 52 insertions, 24 deletions

diff --git a/runtime/stack-i386.c b/runtime/stack-i386.c
index b46ff06b..ad101889 100644
--- a/runtime/stack-i386.c
+++ b/runtime/stack-i386.c
@@ -8,40 +8,68 @@
  * later version.
  */
 
-static inline int _stp_valid_stack_ptr(unsigned long context, unsigned long p)
+static int _stp_valid_stack_ptr(unsigned long context, unsigned long p)
 {
 	return	p > context && p < context + THREAD_SIZE - 3;
 }
 
+/* DWARF unwinder failed.  Just dump intereting addresses on kernel stack. */
+static void _stp_stack_print_fallback(unsigned long context, unsigned long stack, int verbose, int levels)
+{
+	unsigned long addr;
+	while (levels && _stp_valid_stack_ptr(context, stack)) {
+		if (unlikely(_stp_read_address(addr, (unsigned long *)stack, KERNEL_DS))) {
+			/* cannot access stack.  give up. */
+			return;
+		}
+		if (_stp_func_print(addr, verbose, 0))
+			levels--;
+		stack++;
+	}
+}
+
 static void __stp_stack_print (struct pt_regs *regs, int verbose, int levels)
 {
-	unsigned long *stack = (unsigned long *)&REG_SP(regs);
-	unsigned long context = (unsigned long)stack & ~(THREAD_SIZE - 1);
+	unsigned long context = (unsigned long)&REG_SP(regs) & ~(THREAD_SIZE - 1);
+
+#ifdef	STP_USE_FRAME_POINTER
 	unsigned long addr;
+	unsigned long next_fp, fp = REG_FP(regs);
 
-#ifdef	CONFIG_FRAME_POINTER
-	{
-                #ifdef STAPCONF_X86_UNIREGS
-                unsigned long ebp = regs->bp;
-                #else
-		unsigned long ebp = regs->ebp;
-		#endif
-		
-		while (_stp_valid_stack_ptr(context, (unsigned long)ebp)) {
-			addr = *(unsigned long *)(ebp + 4);
-			if (verbose) {
-				_stp_print_char(' ');
-				_stp_symbol_print (addr);
-				_stp_print_char('\n');
-			} else
-				_stp_printf ("0x%08lx ", addr);
-			ebp = *(unsigned long *)ebp;
+	while (levels && _stp_valid_stack_ptr(context, (unsigned long)fp)) {
+		if (unlikely(_stp_read_address(addr, (unsigned long *)(fp + 4), KERNEL_DS))) {
+			/* cannot access stack.  give up. */
+			return;
+		}
+		_stp_func_print(addr, verbose, 1);
+		if (unlikely(_stp_read_address(next_fp, (unsigned long *)fp, KERNEL_DS))) {
+			/* cannot access stack.  give up. */
+			return;
 		}
+		levels--;
+
+		/* frame pointers move upwards */
+		if (next_fp <= fp)
+			break;
+		fp = next_fp;
 	}
 #else
-	while (_stp_valid_stack_ptr(context, (unsigned long)stack)) {
-		addr = *stack++;
-		_stp_func_print(addr, verbose, 1);
+	struct unwind_frame_info info;
+	arch_unw_init_frame_info(&info, regs);
+	
+	while (levels && !arch_unw_user_mode(&info)) {
+		int ret = unwind(&info);
+		dbug_unwind(1, "ret=%d PC=%lx SP=%lx\n", ret, UNW_PC(&info), UNW_SP(&info));
+		if (ret == 0) {
+			_stp_func_print(UNW_PC(&info), verbose, 1);
+			levels--;
+			continue;
+		}
+		/* If an error happened or we hit a kretprobe trampoline, use fallback backtrace */
+		/* FIXME: is there a way to unwind across kretprobe trampolines? */
+		if (ret < 0 || (ret > 0 && UNW_PC(&info) == _stp_kretprobe_trampoline))
+			_stp_stack_print_fallback(context, UNW_SP(&info), verbose, levels);
+		break;
 	}
-#endif
+#endif /* STP_USE_FRAME_POINTER */
 }