[DWARFDebugLine] Check for (EOF) errors when parsing v5 content descriptors

Summary:
Without that we could be silently reading zeroes, as that's the default
DataExtractor behavior. The entire parse would still most likely fail,
but it would do that with a seemingly unrelated/nonsensical error
message.

Reviewers: dblaikie, probinson, jhenderson

Subscribers: hiraditya, MaskRay, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D77554

Author: labath

llvm/lib/DebugInfo/DWARF/DWARFDebugLine.cpp

@@ -219,21 +219,27 @@ parseV2DirFileTables(const DWARFDataExtractor &DebugLineData,
 static llvm::Expected<ContentDescriptors>
 parseV5EntryFormat(const DWARFDataExtractor &DebugLineData, uint64_t *OffsetPtr,
                    DWARFDebugLine::ContentTypeTracker *ContentTypes) {
+  Error Err = Error::success();
   ContentDescriptors Descriptors;
-  int FormatCount = DebugLineData.getU8(OffsetPtr);
+  int FormatCount = DebugLineData.getU8(OffsetPtr, &Err);
   bool HasPath = false;
-  for (int I = 0; I != FormatCount; ++I) {
+  for (int I = 0; I != FormatCount && !Err; ++I) {
     ContentDescriptor Descriptor;
     Descriptor.Type =
-      dwarf::LineNumberEntryFormat(DebugLineData.getULEB128(OffsetPtr));
-    Descriptor.Form = dwarf::Form(DebugLineData.getULEB128(OffsetPtr));
+        dwarf::LineNumberEntryFormat(DebugLineData.getULEB128(OffsetPtr, &Err));
+    Descriptor.Form = dwarf::Form(DebugLineData.getULEB128(OffsetPtr, &Err));
     if (Descriptor.Type == dwarf::DW_LNCT_path)
       HasPath = true;
     if (ContentTypes)
       ContentTypes->trackContentType(Descriptor.Type);
     Descriptors.push_back(Descriptor);
   }
 
+  if (Err)
+    return createStringError(errc::invalid_argument,
+                             "failed to parse entry content descriptors: %s",
+                             toString(std::move(Err)).c_str());
+
   if (!HasPath)
     return createStringError(errc::invalid_argument,
                              "failed to parse entry content descriptions"

llvm/test/tools/llvm-dwarfdump/X86/debug_line_short_prologue.s

@@ -0,0 +1,68 @@
+## Test cases when we run into the end of section while parsing a line table
+## prologue.
+
+# RUN: llvm-mc -triple x86_64-pc-linux %s -filetype=obj --defsym CASE=0 -o %t0
+# RUN: llvm-dwarfdump -debug-line %t0 2>&1 | FileCheck %s --check-prefixes=ALL,C0
+
+# RUN: llvm-mc -triple x86_64-pc-linux %s -filetype=obj --defsym CASE=1 -o %t1
+# RUN: llvm-dwarfdump -debug-line %t1 2>&1 | FileCheck %s --check-prefixes=ALL,C1
+
+# RUN: llvm-mc -triple x86_64-pc-linux %s -filetype=obj --defsym CASE=2 -o %t2
+# RUN: llvm-dwarfdump -debug-line %t2 2>&1 | FileCheck %s --check-prefixes=ALL,C2
+
+# RUN: llvm-mc -triple x86_64-pc-linux %s -filetype=obj --defsym CASE=3 -o %t3
+# RUN: llvm-dwarfdump -debug-line %t3 2>&1 | FileCheck %s --check-prefixes=ALL,OK
+
+# ALL:      debug_line[0x00000000]
+# C0-NEXT:  warning: parsing line table prologue at 0x00000000 found an invalid directory or file table description at 0x00000027
+# C0-NEXT:  warning: failed to parse entry content descriptors: unexpected end of data at offset 0x27
+# C1-NEXT:  warning: parsing line table prologue at 0x00000000 found an invalid directory or file table description at 0x0000002a
+# C1-NEXT:  warning: failed to parse entry content descriptors: malformed uleb128, extends past end
+# C2-NEXT:  warning: parsing line table prologue at 0x00000000 found an invalid directory or file table description at 0x0000002b
+# C2-NEXT:  warning: failed to parse entry content descriptors: malformed uleb128, extends past end
+# ALL:      include_directories[  0] = "/tmp"
+# OK:       file_names[  0]:
+# OK-NEXT:             name: "foo"
+# OK-NEXT:        dir_index: 0
+
+.section .debug_line,"",@progbits
+.long   .Lend-.Lstart   # Length of Unit
+.Lstart:
+.short  5               # DWARF version number
+.byte   8               # Address Size
+.byte   0               # Segment Selector Size
+.long   .Lprologue_end-.Lprologue_start  # Length of Prologue
+.Lprologue_start:
+.byte   1               # Minimum Instruction Length
+.byte   1               # Maximum Operations per Instruction
+.byte   1               # Default is_stmt
+.byte   -5              # Line Base
+.byte   14              # Line Range
+.byte   13              # Opcode Base
+.byte   0, 1, 1, 1, 1, 0, 0, 0, 1, 0, 0, 1 # Standard Opcode Lengths
+# Directory table format
+.byte   1               # One element per directory entry
+.byte   1               # DW_LNCT_path
+.byte   0x08            # DW_FORM_string
+# Directory table entries
+.byte   1               # 1 directory
+.asciz  "/tmp"
+# File table format
+.if CASE >= 1
+.byte   2               # 2 elements per file entry
+.byte   1               # DW_LNCT_path
+.byte   8               # DW_FORM_string
+.if CASE >= 2
+.byte   2               # DW_LNCT_directory_index
+.if CASE >= 3
+.byte   11              # DW_FORM_data1
+# File table entries
+.byte   1
+.asciz  "foo"
+.byte   0
+.endif
+.endif
+.endif
+
+.Lprologue_end:
+.Lend: