From 684d6fdee208a1fa12e9cbe0a45f3c5b4b575ad7 Mon Sep 17 00:00:00 2001
From: James Henderson <james.henderson@sony.com>
Date: Tue, 25 Feb 2020 16:07:16 +0000
Subject: [PATCH] [DebugInfo] Add check for .debug_line
 minimum_instruction_length of 0

If the minimum_instruction_length of a debug line program is 0, no
address advancing via special opcodes, DW_LNS_const_add_pc, and
DW_LNS_advance_pc can occur, since the minimum_instruction_length is
used in a multiplication. This patch adds a warning reporting when this
issue occurs.

Reviewed by: probinson

Differential Revision: https://reviews.llvm.org/D75189
---
 llvm/lib/DebugInfo/DWARF/DWARFDebugLine.cpp        |  8 +++++
 .../DebugInfo/DWARF/DWARFDebugLineTest.cpp         | 35 ++++++++++++++++++++++
 2 files changed, 43 insertions(+)

diff --git a/llvm/lib/DebugInfo/DWARF/DWARFDebugLine.cpp b/llvm/lib/DebugInfo/DWARF/DWARFDebugLine.cpp
index ff23f61..6638474 100644
--- a/llvm/lib/DebugInfo/DWARF/DWARFDebugLine.cpp
+++ b/llvm/lib/DebugInfo/DWARF/DWARFDebugLine.cpp
@@ -592,6 +592,14 @@ uint64_t DWARFDebugLine::ParsingState::advanceAddr(uint64_t OperationAdvance,
         ", which is unsupported. Assuming a value of 1 instead",
         LineTableOffset, OpcodeName.data(), OpcodeOffset,
         LineTable->Prologue.MaxOpsPerInst));
+  if (ReportAdvanceAddrProblem && LineTable->Prologue.MinInstLength == 0)
+    ErrorHandler(
+        createStringError(errc::invalid_argument,
+                          "line table program at offset 0x%8.8" PRIx64
+                          " contains a %s opcode at offset 0x%8.8" PRIx64
+                          ", but the prologue minimum_instruction_length value "
+                          "is 0, which prevents any address advancing",
+                          LineTableOffset, OpcodeName.data(), OpcodeOffset));
   ReportAdvanceAddrProblem = false;
   uint64_t AddrOffset = OperationAdvance * LineTable->Prologue.MinInstLength;
   Row.Address.Address += AddrOffset;
diff --git a/llvm/unittests/DebugInfo/DWARF/DWARFDebugLineTest.cpp b/llvm/unittests/DebugInfo/DWARF/DWARFDebugLineTest.cpp
index 5585a59..2ffad82 100644
--- a/llvm/unittests/DebugInfo/DWARF/DWARFDebugLineTest.cpp
+++ b/llvm/unittests/DebugInfo/DWARF/DWARFDebugLineTest.cpp
@@ -1001,6 +1001,41 @@ INSTANTIATE_TEST_CASE_P(
     Values(std::make_tuple(0, true),       // Test zero value (error).
            std::make_tuple(14, false)), ); // Test non-zero value (no error).
 
+struct BadMinInstLenFixture : TestWithParam<std::tuple<uint8_t, bool>>,
+                              AdjustAddressFixtureBase {
+  void SetUp() override {
+    std::tie(MinInstLength, IsErrorExpected) = GetParam();
+  }
+
+  uint64_t editPrologue(LineTable &LT) override {
+    DWARFDebugLine::Prologue Prologue = LT.createBasicPrologue();
+    Prologue.MinInstLength = MinInstLength;
+    LT.setPrologue(Prologue);
+    return Prologue.TotalLength + Prologue.sizeofTotalLength();
+  }
+
+  uint64_t getAdjustedAddr(uint64_t Base, uint64_t ConstIncr,
+                           uint64_t SpecialIncr,
+                           uint64_t AdvanceIncr) override {
+    return MinInstLength != 0 ? AdjustAddressFixtureBase::getAdjustedAddr(
+                                    Base, ConstIncr, SpecialIncr, AdvanceIncr)
+                              : Base;
+  }
+
+  uint8_t MinInstLength;
+};
+
+TEST_P(BadMinInstLenFixture, MinInstLengthProblemsReportedCorrectly) {
+  runTest(/*CheckAdvancePC=*/true,
+          "but the prologue minimum_instruction_length value is 0, which "
+          "prevents any address advancing");
+}
+
+INSTANTIATE_TEST_CASE_P(
+    BadMinInstLenParams, BadMinInstLenFixture,
+    Values(std::make_tuple(0, true),      // Test zero value (error).
+           std::make_tuple(1, false)), ); // Test non-zero value (no error).
+
 TEST_F(DebugLineBasicFixture, ParserParsesCorrectly) {
   if (!setupGenerator())
     return;
-- 
2.7.4