[DWARFYAML][debug_ranges] Emit an error message for invalid offset.

[Higuoxing]

Summary

This patch helps make yaml2obj emit an error message when we try to assign an invalid offset to the entry of the 'debug_ranges' section.

[jhenderson]

llvm/lib/ObjectYAML/DWARFEmitter.cpp

134–140

Do you need the new cast? If I've followed it correctly, Offset is a Hex64, so is already a 64-bit number.

138–139

I think this should be " must be greater than or equal to the number of bytes written already (0x"

llvm/test/tools/yaml2obj/ELF/DWARF/debug-ranges.yaml

317

invalid offset to the -> invalid offset to an

337

Let's make this 0x1A to test the edge case (i.e. no off-by-one error).

[Higuoxing]

Address comments.

Thanks for reviewing.

llvm/lib/ObjectYAML/DWARFEmitter.cpp

134–140

Yes, but the compiler complains that 'Use of overloaded operator '<' is ambiguous'. So we have to explicitly cast it to uint64_t.

[jhenderson]

llvm/test/tools/yaml2obj/ELF/DWARF/debug-ranges.yaml

337

Oops, sorry, I failed at hex :-)

I meant 0x1f, i.e. exactly one less than the permitted value!

[Higuoxing]

Update.

llvm/test/tools/yaml2obj/ELF/DWARF/debug-ranges.yaml

337

Never mind :)

[jhenderson]

LGTM, thanks.

llvm/include/llvm/ObjectYAML/DWARFYAML.h

 /// within a range list in the .debug_ranges section.
 struct RangeEntry {
   llvm::yaml::Hex64 LowOffset;
   llvm::yaml::Hex64 HighOffset;
 };
 
 /// Class that describes a single range list inside the .debug_ranges section.
 struct Ranges {
-  llvm::yaml::Hex32 Offset;
+  llvm::yaml::Hex64 Offset;
   llvm::yaml::Hex8 AddrSize;
   std::vector<RangeEntry> Entries;
 };
 
 struct PubEntry {
   llvm::yaml::Hex32 DieOffset;
   llvm::yaml::Hex8 Descriptor;
   StringRef Name;

llvm/lib/ObjectYAML/DWARFEmitter.cpp

 //===----------------------------------------------------------------------===//
 
 #include "llvm/ObjectYAML/DWARFEmitter.h"
 #include "DWARFVisitor.h"
 #include "llvm/ADT/StringMap.h"
 #include "llvm/ADT/StringRef.h"
 #include "llvm/BinaryFormat/Dwarf.h"
 #include "llvm/ObjectYAML/DWARFYAML.h"
+#include "llvm/Support/Errc.h"
 #include "llvm/Support/Error.h"
 #include "llvm/Support/Host.h"
 #include "llvm/Support/LEB128.h"
 #include "llvm/Support/MathExtras.h"
 #include "llvm/Support/MemoryBuffer.h"
 #include "llvm/Support/SwapByteOrder.h"
 #include "llvm/Support/YAMLTraits.h"
 #include "llvm/Support/raw_ostream.h"
for (auto Range : DI.ARanges) {
     ZeroFillBytes(OS, Range.AddrSize * 2);
   }
 
   return Error::success();
 }
 
 Error DWARFYAML::emitDebugRanges(raw_ostream &OS, const DWARFYAML::Data &DI) {
   const size_t RangesOffset = OS.tell();
+  uint64_t EntryIndex = 0;
   for (auto DebugRanges : DI.DebugRanges) {
     const size_t CurrOffset = OS.tell() - RangesOffset;
-    assert(DebugRanges.Offset >= CurrOffset &&
-           "Offset should be greater than or equal to the bytes that we have "
-           "written");
+    if ((uint64_t)DebugRanges.Offset < CurrOffset)
+      return createStringError(errc::invalid_argument,
+                               "'Offset' for 'debug_ranges' with index " +
+                                   Twine(EntryIndex) +
+                                   " must be greater than or equal to the "
+                                   "number of bytes written already (0x" +
+                                   Twine::utohexstr(CurrOffset) + ")");
     if (DebugRanges.Offset > CurrOffset)
       ZeroFillBytes(OS, DebugRanges.Offset - CurrOffset);
     for (auto Entry : DebugRanges.Entries) {
       writeVariableSizedInteger(Entry.LowOffset, DebugRanges.AddrSize, OS,
                                 DI.IsLittleEndian);
       writeVariableSizedInteger(Entry.HighOffset, DebugRanges.AddrSize, OS,
                                 DI.IsLittleEndian);
     }
     ZeroFillBytes(OS, DebugRanges.AddrSize * 2);
+    ++EntryIndex;
   }
 
   return Error::success();
 }
 
 Error DWARFYAML::emitPubSection(raw_ostream &OS,
                                 const DWARFYAML::PubSection &Sect,
                                 bool IsLittleEndian) {

llvm/test/tools/yaml2obj/ELF/DWARF/debug-ranges.yaml

 
 --- !ELF
 FileHeader:
   Class:   ELFCLASS64
   Data:    ELFDATA2LSB
   Type:    ET_EXEC
   Machine: EM_X86_64
 DWARF:
+
+## i) Test that yaml2obj emits an error message if we try to assign an invalid offset to an
+## entry of the '.debug_ranges' section.
+
+# RUN: not yaml2obj --docnum=9 %s -o %t9.o 2>&1 | FileCheck %s --check-prefix=INVALID-OFFSET
+
+# INVALID-OFFSET: yaml2obj: error: 'Offset' for 'debug_ranges' with index 1 must be greater than or equal to the number of bytes written already (0x20)
+
+--- !ELF
+FileHeader:
+  Class:   ELFCLASS64
+  Data:    ELFDATA2LSB
+  Type:    ET_EXEC
+  Machine: EM_X86_64
+DWARF:
+  debug_ranges:
+    - Offset:   0x00
+      AddrSize: 0x08
+      Entries:
+        - LowOffset:  0x01
+          HighOffset: 0x02
+    - Offset:   0x1F ## Must be greater than or equal to 0x20.
+      AddrSize: 0x08
+      Entries:
+        - LowOffset:  0x01
+          HighOffset: 0x02