perf dwarf-aux: Fix die_get_typename() for void *

The die_get_typename() is to return a C-like type name from DWARF debug
entry and it follows data type if the target entry is a pointer type.

But I found that void pointers don't have the type attribute to follow
and then the function returns an error for that case.  This results in a
broken type string for void pointer types.

For example, the following type entries are pointer types.

 <1><48c>: Abbrev Number: 4 (DW_TAG_pointer_type)
    <48d>   DW_AT_byte_size   : 8
    <48d>   DW_AT_type        : <0x481>
 <1><491>: Abbrev Number: 211 (DW_TAG_pointer_type)
    <493>   DW_AT_byte_size   : 8
 <1><494>: Abbrev Number: 4 (DW_TAG_pointer_type)
    <495>   DW_AT_byte_size   : 8
    <495>   DW_AT_type        : <0x49e>

The first one at offset 48c and the third one at offset 494 have type
information.  Then they are pointer types for the referenced types.  But
the second one at offset 491 doesn't have the type attribute.

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: linux-toolchains@vger.kernel.org
Cc: linux-trace-devel@vger.kernel.org
Link: https://lore.kernel.org/r/20231110000012.3538610-5-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

1 files changed, 8 insertions, 1 deletions

diff --git a/tools/perf/util/dwarf-aux.c b/tools/perf/util/dwarf-aux.c
index 2941d88f2199..4849c3bbfd95 100644
--- a/tools/perf/util/dwarf-aux.c
+++ b/tools/perf/util/dwarf-aux.c
@@ -1090,7 +1090,14 @@ int die_get_typename(Dwarf_Die *vr_die, struct strbuf *buf)
 		return strbuf_addf(buf, "%s%s", tmp, name ?: "");
 	}
 	ret = die_get_typename(&type, buf);
-	return ret ? ret : strbuf_addstr(buf, tmp);
+	if (ret < 0) {
+		/* void pointer has no type attribute */
+		if (tag == DW_TAG_pointer_type && ret == -ENOENT)
+			return strbuf_addf(buf, "void*");
+
+		return ret;
+	}
+	return strbuf_addstr(buf, tmp);
 }
 
 /**