File support-DW_TAG_unspecified_type.patch of Package elfutils

From f638ab839a5c0a6fdfa666acdf6839ed827f0897 Mon Sep 17 00:00:00 2001
From: Mark Wielaard <mark@klomp.org>
Date: Thu, 26 Jan 2023 18:19:15 +0100
Subject: [PATCH] backends: Handle DW_TAG_unspecified_type in
 dwarf_peeled_die_type

binutils 2.40 introduces DW_TAG_unspecified_type for assembly
functions with an unknown return type. This breaks the
run-funcretval.sh testcase because dwfl_module_return_value_location
returns an error for such functions because it cannot determine the
return value location. Fix that by treating DW_TAG_unspecified_type
as if the DIE doesn't have a DW_AT_type.

Also update the testcase to explicitly checking for
DW_TAG_unspecified_type and printing "returns unspecified type".

https://sourceware.org/bugzilla/show_bug.cgi?id=30047

Signed-off-by: Mark Wielaard <mark@klomp.org>
---
 NEWS                  |  5 +++++
 backends/ChangeLog    |  5 +++++
 backends/libebl_CPU.h | 14 ++++++++++++--
 tests/ChangeLog       |  4 ++++
 tests/funcretval.c    | 14 +++++++++++++-
 5 files changed, 39 insertions(+), 3 deletions(-)

diff --git a/backends/libebl_CPU.h b/backends/libebl_CPU.h
index 0e507bd3..a2898a1f 100644
--- a/backends/libebl_CPU.h
+++ b/backends/libebl_CPU.h
@@ -1,5 +1,6 @@
 /* Common interface for libebl modules.
    Copyright (C) 2000, 2001, 2002, 2003, 2005, 2013, 2014 Red Hat, Inc.
+   Copyright (C) 2023 Mark J. Wielaard <mark@klomp.org>
    This file is part of elfutils.
 
    This file is free software; you can redistribute it and/or modify
@@ -53,7 +54,9 @@ extern bool (*generic_debugscn_p) (const char *) attribute_hidden;
      dwarf_tag (_die); })
 
 /* Get a type die corresponding to DIE.  Peel CV qualifiers off
-   it.  */
+   it.  Returns zero if the DIE doesn't have a type, or the type
+   is DW_TAG_unspecified_type.  Returns -1 on error.  Otherwise
+   returns the result tag DW_AT value.  */
 static inline int
 dwarf_peeled_die_type (Dwarf_Die *die, Dwarf_Die *result)
 {
@@ -69,7 +72,14 @@ dwarf_peeled_die_type (Dwarf_Die *die, Dwarf_Die *result)
   if (dwarf_peel_type (result, result) != 0)
     return -1;
 
-  return DWARF_TAG_OR_RETURN (result);
+  if (result == NULL)
+    return -1;
+
+  int tag = dwarf_tag (result);
+  if (tag == DW_TAG_unspecified_type)
+    return 0; /* Treat an unspecified type as if there was no type.  */
+
+  return tag;
 }
 
 #endif	/* libebl_CPU.h */
diff --git a/tests/funcretval.c b/tests/funcretval.c
index 16cd1a44..41198ab7 100644
--- a/tests/funcretval.c
+++ b/tests/funcretval.c
@@ -1,5 +1,6 @@
 /* Test program for dwfl_module_return_value_location.
    Copyright (C) 2005 Red Hat, Inc.
+   Copyright (C) 2023 Mark J. Wielaard <mark@klomp.org>
    This file is part of elfutils.
 
    This file is free software; you can redistribute it and/or modify
@@ -67,7 +68,18 @@ handle_function (Dwarf_Die *funcdie, void *arg)
     error (EXIT_FAILURE, 0, "dwfl_module_return_value_location: %s",
 	   dwfl_errmsg (-1));
   else if (nlocops == 0)
-    puts ("returns no value");
+    {
+      // Check if this is the special unspecified type
+      // https://sourceware.org/bugzilla/show_bug.cgi?id=30047
+      Dwarf_Die die_mem, *typedie = &die_mem;
+      Dwarf_Attribute attr_mem, *attr;
+      attr = dwarf_attr_integrate (funcdie, DW_AT_type, &attr_mem);
+      if (dwarf_formref_die (attr, typedie) != NULL
+	  && dwarf_tag (typedie) == DW_TAG_unspecified_type)
+	puts ("returns unspecified type");
+      else
+	puts ("returns no value");
+    }
   else
     {
       printf ("return value location:");
-- 
2.39.1