commit 581fc63dc05041e9c17445a1e55b59e6dfb431ee
author George Rimar <grimar@accesssoftek.com> Thu Oct 25 10:56:44 2018 +0000
committer George Rimar <grimar@accesssoftek.com> Thu Oct 25 10:56:44 2018 +0000
tree 286be52d342883ecc9fde77611a13b18d8dc85da
parent 071e82218f505396535b2d4abcf008117feb5685

[llvm-dwarfdump] - Fix incorrect parsing of the DW_LLE_startx_length

As was already mentioned in comments for D53364, DWARF 5
spec says about DW_LLE_startx_length:

"This is a form of bounded location description that has two unsigned ULEB operands.
The first value is an address index (into the .debug_addr section) that indicates the beginning of the address range
over which the location is valid. The second value is the length of the range. ")

Currently, the length is always parsed as U32.
Patch change the behavior to parse DW_LLE_startx_length as ULEB128 for DWARF 5
and keeps it as U32 for DWARF4+(pre-DWARF5) for compatibility.

Differential revision: https://reviews.llvm.org/D53564

llvm-svn: 345254

llvm/lib/DebugInfo/DWARF/DWARFContext.cpp

diff --git a/llvm/lib/DebugInfo/DWARF/DWARFContext.cpp b/llvm/lib/DebugInfo/DWARF/DWARFContext.cpp
index 1f37538..a29c9c2 100644
--- a/llvm/lib/DebugInfo/DWARF/DWARFContext.cpp
+++ b/llvm/lib/DebugInfo/DWARF/DWARFContext.cpp
@@ -309,7 +309,7 @@
   DataExtractor LocData(Data.getData().drop_front(Offset),
                         Data.isLittleEndian(), Header.getAddrSize());
 
-  Loclists.parse(LocData);
+  Loclists.parse(LocData, Header.getVersion());
   Loclists.dump(OS, 0, MRI, DumpOffset);
 }
 
@@ -732,7 +732,10 @@
   // FIXME: We don't need AddressSize for split DWARF since relocatable
   // addresses cannot appear there. At the moment DWARFExpression requires it.
   DataExtractor LocData(DObj->getLocDWOSection().Data, isLittleEndian(), 4);
-  LocDWO->parse(LocData);
+  // Use version 4. DWO does not support the DWARF v5 .debug_loclists yet and
+  // that means we are parsing the new style .debug_loc (pre-standatized version
+  // of the .debug_loclists).
+  LocDWO->parse(LocData, 4 /* Version */);
   return LocDWO.get();
 }
 

llvm/lib/DebugInfo/DWARF/DWARFDebugLoc.cpp

diff --git a/llvm/lib/DebugInfo/DWARF/DWARFDebugLoc.cpp b/llvm/lib/DebugInfo/DWARF/DWARFDebugLoc.cpp
index b4bdaaa..044a024 100644
--- a/llvm/lib/DebugInfo/DWARF/DWARFDebugLoc.cpp
+++ b/llvm/lib/DebugInfo/DWARF/DWARFDebugLoc.cpp
@@ -145,7 +145,8 @@
 }
 
 Optional<DWARFDebugLoclists::LocationList>
-DWARFDebugLoclists::parseOneLocationList(DataExtractor Data, unsigned *Offset) {
+DWARFDebugLoclists::parseOneLocationList(DataExtractor Data, unsigned *Offset,
+                                         unsigned Version) {
   LocationList LL;
   LL.Offset = *Offset;
 
@@ -158,7 +159,12 @@
     switch (Kind) {
     case dwarf::DW_LLE_startx_length:
       E.Value0 = Data.getULEB128(Offset);
-      E.Value1 = Data.getU32(Offset);
+      // Pre-DWARF 5 has different interpretation of the length field. We have
+      // to support both pre- and standartized styles for the compatibility.
+      if (Version < 5)
+        E.Value1 = Data.getU32(Offset);
+      else
+        E.Value1 = Data.getULEB128(Offset);
       break;
     case dwarf::DW_LLE_start_length:
       E.Value0 = Data.getAddress(Offset);
@@ -189,13 +195,13 @@
   return LL;
 }
 
-void DWARFDebugLoclists::parse(DataExtractor data) {
+void DWARFDebugLoclists::parse(DataExtractor data, unsigned Version) {
   IsLittleEndian = data.isLittleEndian();
   AddressSize = data.getAddressSize();
 
   uint32_t Offset = 0;
   while (data.isValidOffset(Offset)) {
-    if (auto LL = parseOneLocationList(data, &Offset))
+    if (auto LL = parseOneLocationList(data, &Offset, Version))
       Locations.push_back(std::move(*LL));
     else
       return;

llvm/lib/DebugInfo/DWARF/DWARFDie.cpp

diff --git a/llvm/lib/DebugInfo/DWARF/DWARFDie.cpp b/llvm/lib/DebugInfo/DWARF/DWARFDie.cpp
index 76430b4..31c4cd5 100644
--- a/llvm/lib/DebugInfo/DWARF/DWARFDie.cpp
+++ b/llvm/lib/DebugInfo/DWARF/DWARFDie.cpp
@@ -118,12 +118,20 @@
       return;
     }
 
+    bool UseLocLists = !U->isDWOUnit();
     StringRef LoclistsSectionData =
-        U->isDWOUnit() ? U->getLocSectionData() : Obj.getLoclistsSection().Data;
+        UseLocLists ? Obj.getLoclistsSection().Data : U->getLocSectionData();
+
     if (!LoclistsSectionData.empty()) {
       DataExtractor Data(LoclistsSectionData, Ctx.isLittleEndian(),
                          Obj.getAddressSize());
-      auto LL = DWARFDebugLoclists::parseOneLocationList(Data, &Offset);
+
+      // Old-style location list were used in DWARF v4 (.debug_loc.dwo section).
+      // Modern locations list (.debug_loclists) are used starting from v5.
+      // Ideally we should take the version from the .debug_loclists section
+      // header, but using CU's version for simplicity.
+      auto LL = DWARFDebugLoclists::parseOneLocationList(
+          Data, &Offset, UseLocLists ? U->getVersion() : 4);
 
       uint64_t BaseAddr = 0;
       if (Optional<SectionedAddress> BA = U->getBaseAddress())