From: Nick Alcock <nick.alcock@oracle.com>
Date: Tue, 4 Jul 2017 00:09:01 +0000 (+0100)
Subject: ctf: handle the bit_offset in members with a DW_FORM_block data_member_location
X-Git-Tag: v4.1.12-117.0_27200813_3~345^2~5
X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=77c57a8ad70e4052a986d3dc76f30de7c3f03393;p=users%2Fjedix%2Flinux-maple.git

ctf: handle the bit_offset in members with a DW_FORM_block data_member_location

When building a SPARC kernel with GCC 6, the following failure is observed at
CTF generation time:

Internal error: within file arch/sparc/built-in.o, module vmlinux, type at
DIE offset 3fe447 with ID ////unsigned int:23:0  was not already noted by
detect_duplicates().

This is because the bit-field in question
(include/math-emu/single.h:_FP_UNION_S.frac) is at offset 1, not 0: the type
ID being emitted should be ////unsigned int:23:1.  We are not correctly
handling the case where a bit-field at nonzero offset has its
data_member_location represented by a DW_FORM_block: we were erroneously only
considering the bit offset when the form was DW_FORM_*data* (i.e. a simple
constant), because I assumed that in this situation the
DW_AT_data_member_location would track the location at bit granularity.
This is obviously wrong: no matter what form it's in, the
data_member_location is a count of bytes.  It can't suddenly turn into a
count of bits just because it's not being represented as a simple
constant!

So promote the bit-offset handling to apply to all
data_member_locations, regardless of form.

Signed-off-by: Nick Alcock <nick.alcock@oracle.com>
Reviewed-by: Tomas Jedlicka <tomas.jedlicka@oracle.com>
Orabug: 26387109
---

diff --git a/scripts/dwarf2ctf/dwarf2ctf.c b/scripts/dwarf2ctf/dwarf2ctf.c
index 96272364067d..59f3ad02c88f 100644
--- a/scripts/dwarf2ctf/dwarf2ctf.c
+++ b/scripts/dwarf2ctf/dwarf2ctf.c
@@ -3888,16 +3888,6 @@ static ctf_id_t assemble_ctf_su_member(const char *module_name,
 				dwarf_formudata(&location_attr, &location);
 				offset = location * 8;
 			}
-
-			if (private_dwarf_hasattr(die, DW_AT_bit_offset)) {
-				Dwarf_Attribute bit_attr;
-				Dwarf_Word bit;
-
-				private_dwarf_attr(die, DW_AT_bit_offset,
-					   &bit_attr);
-				dwarf_formudata(&bit_attr, &bit);
-				bit_offset = bit;
-			}
 			break;
 		}
 		case DW_FORM_block1:
@@ -3958,7 +3948,20 @@ static ctf_id_t assemble_ctf_su_member(const char *module_name,
 			exit(1);
 		}
 		}
-		/* Fall through. */
+
+		/*
+		 * Handle the bit offset.
+		 */
+		if (private_dwarf_hasattr(die, DW_AT_bit_offset)) {
+			Dwarf_Attribute bit_attr;
+			Dwarf_Word bit;
+
+			private_dwarf_attr(die, DW_AT_bit_offset,
+					   &bit_attr);
+			dwarf_formudata(&bit_attr, &bit);
+			bit_offset = bit;
+		}
+
 	} else { /* No offset beyond any override.  */
 		die_override_t *o;