[llvm-dwarfdump] - Teach verifier to report broken DWARF expressions.

Patch improves next things:

* Fixes assert/crash in getOpDesc when giving it a invalid expression op code.
* DWARFExpression::print() called DWARFExpression::Operation::getEndOffset() which
  returned and used uninitialized field EndOffset. Patch fixes that.
* Teaches verifier to verify DW_AT_location and error out on broken expressions.

Differential revision: https://reviews.llvm.org/D39294

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@316756 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 45 insertions, 29 deletions

diff --git a/lib/DebugInfo/DWARF/DWARFExpression.cpp b/lib/DebugInfo/DWARF/DWARFExpression.cpp
index 3417fee14c0..16058e461f4 100644
--- a/lib/DebugInfo/DWARF/DWARFExpression.cpp
+++ b/lib/DebugInfo/DWARF/DWARFExpression.cpp
@@ -104,7 +104,9 @@ static DescVector getDescriptions() {
 static DWARFExpression::Operation::Description getOpDesc(unsigned OpCode) {
   // FIXME: Make this constexpr once all compilers are smart enough to do it.
   static DescVector Descriptions = getDescriptions();
-  assert(OpCode < Descriptions.size());
+  // Handle possible corrupted or unsupported operation.
+  if (OpCode >= Descriptions.size())
+    return {};
   return Descriptions[OpCode];
 }
 
@@ -117,8 +119,10 @@ bool DWARFExpression::Operation::extract(DataExtractor Data, uint16_t Version,
   Opcode = Data.getU8(&Offset);
 
   Desc = getOpDesc(Opcode);
-  if (Desc.Version == Operation::DwarfNA)
+  if (Desc.Version == Operation::DwarfNA) {
+    EndOffset = Offset;
     return false;
+  }
 
   for (unsigned Operand = 0; Operand < 2; ++Operand) {
     unsigned Size = Desc.Op[Operand];
@@ -221,7 +225,7 @@ bool DWARFExpression::Operation::print(raw_ostream &OS,
                                        const MCRegisterInfo *RegInfo,
                                        bool isEH) {
   if (Error) {
-    OS << "decoding error.";
+    OS << "<decoding error>";
     return false;
   }
 
diff --git a/lib/DebugInfo/DWARF/DWARFVerifier.cpp b/lib/DebugInfo/DWARF/DWARFVerifier.cpp
index b10697c9a31..f27c849456b 100644
--- a/lib/DebugInfo/DWARF/DWARFVerifier.cpp
+++ b/lib/DebugInfo/DWARF/DWARFVerifier.cpp
@@ -13,9 +13,11 @@
 #include "llvm/DebugInfo/DWARF/DWARFContext.h"
 #include "llvm/DebugInfo/DWARF/DWARFDebugLine.h"
 #include "llvm/DebugInfo/DWARF/DWARFDie.h"
+#include "llvm/DebugInfo/DWARF/DWARFExpression.h"
 #include "llvm/DebugInfo/DWARF/DWARFFormValue.h"
 #include "llvm/DebugInfo/DWARF/DWARFSection.h"
 #include "llvm/DebugInfo/DWARF/DWARFAcceleratorTable.h"
+#include "llvm/Support/FormatVariadic.h"
 #include "llvm/Support/raw_ostream.h"
 #include <map>
 #include <set>
@@ -377,45 +379,55 @@ unsigned DWARFVerifier::verifyDieRanges(const DWARFDie &Die,
 
 unsigned DWARFVerifier::verifyDebugInfoAttribute(const DWARFDie &Die,
                                                  DWARFAttribute &AttrValue) {
-  const DWARFObject &DObj = DCtx.getDWARFObj();
   unsigned NumErrors = 0;
+  auto ReportError = [&](const Twine &TitleMsg) {
+    ++NumErrors;
+    error() << TitleMsg << '\n';
+    Die.dump(OS, 0, DumpOpts);
+    OS << "\n";
+  };
+
+  const DWARFObject &DObj = DCtx.getDWARFObj();
   const auto Attr = AttrValue.Attr;
   switch (Attr) {
   case DW_AT_ranges:
     // Make sure the offset in the DW_AT_ranges attribute is valid.
     if (auto SectionOffset = AttrValue.Value.getAsSectionOffset()) {
-      if (*SectionOffset >= DObj.getRangeSection().Data.size()) {
-        ++NumErrors;
-        error() << "DW_AT_ranges offset is beyond .debug_ranges "
-                   "bounds:\n";
-        Die.dump(OS, 0, DumpOpts);
-        OS << "\n";
-      }
-    } else {
-      ++NumErrors;
-      error() << "DIE has invalid DW_AT_ranges encoding:\n";
-      Die.dump(OS, 0, DumpOpts);
-      OS << "\n";
+      if (*SectionOffset >= DObj.getRangeSection().Data.size())
+        ReportError("DW_AT_ranges offset is beyond .debug_ranges bounds:");
+      break;
     }
+    ReportError("DIE has invalid DW_AT_ranges encoding:");
     break;
   case DW_AT_stmt_list:
     // Make sure the offset in the DW_AT_stmt_list attribute is valid.
     if (auto SectionOffset = AttrValue.Value.getAsSectionOffset()) {
-      if (*SectionOffset >= DObj.getLineSection().Data.size()) {
-        ++NumErrors;
-        error() << "DW_AT_stmt_list offset is beyond .debug_line "
-                   "bounds: "
-                << format("0x%08" PRIx64, *SectionOffset) << "\n";
-        Die.dump(OS, 0, DumpOpts);
-        OS << "\n";
-      }
-    } else {
-      ++NumErrors;
-      error() << "DIE has invalid DW_AT_stmt_list encoding:\n";
-      Die.dump(OS, 0, DumpOpts);
-      OS << "\n";
+      if (*SectionOffset >= DObj.getLineSection().Data.size())
+        ReportError("DW_AT_stmt_list offset is beyond .debug_line bounds: " +
+                    llvm::formatv("{0:x16}", *SectionOffset));
+      break;
     }
+    ReportError("DIE has invalid DW_AT_stmt_list encoding:");
     break;
+  case DW_AT_location: {
+    Optional<ArrayRef<uint8_t>> Expr = AttrValue.Value.getAsBlock();
+    if (!Expr) {
+      ReportError("DIE has invalid DW_AT_location encoding:");
+      break;
+    }
+
+    DWARFUnit *U = Die.getDwarfUnit();
+    DataExtractor Data(
+        StringRef(reinterpret_cast<const char *>(Expr->data()), Expr->size()),
+        DCtx.isLittleEndian(), 0);
+    DWARFExpression Expression(Data, U->getVersion(), U->getAddressByteSize());
+    bool Error = llvm::any_of(Expression, [](DWARFExpression::Operation &Op) {
+      return Op.isError();
+    });
+    if (Error)
+      ReportError("DIE contains invalid DWARF expression:");
+    break;
+  }
 
   default:
     break;