[JITLink] Refer to FDE's CIE (not the most recent CIE) when parsing eh-frame.

Frame Descriptor Entries (FDEs) have a pointer back to a Common Information
Entry (CIE) that describes how the rest FDE should be parsed. JITLink had been
assuming that FDEs always referred to the most recent CIE encountered, but the
spec allows them to point back to any previously encountered CIE. This patch
fixes JITLink to look up the correct CIE for the FDE.

The testcase is a MachO binary with an FDE that refers to a CIE that is not the
one immediately proceeding it (the layout can be viewed wit
'dwarfdump --eh-frame <testcase>'. This test case had to be a binary as llvm-mc
now sorts FDEs (as of r356216) to ensure FDEs *do* point to the most recent CIE.

llvm-svn: 359105

2 files changed, 27 insertions, 13 deletions

diff --git a/llvm/lib/ExecutionEngine/JITLink/EHFrameSupport.cpp b/llvm/lib/ExecutionEngine/JITLink/EHFrameSupport.cpp
index 6517b3b0d0c..c531df82446 100644
--- a/llvm/lib/ExecutionEngine/JITLink/EHFrameSupport.cpp
+++ b/llvm/lib/ExecutionEngine/JITLink/EHFrameSupport.cpp
@@ -163,8 +163,7 @@ Error EHFrameParser::processCIE() {
 
   LLVM_DEBUG(dbgs() << "  Record is CIE\n");
 
-  /// Reset state for the new CIE.
-  LSDAFieldPresent = false;
+  CIEInformation CIEInfo(*CurRecordAtom);
 
   uint8_t Version = 0;
   if (auto Err = EHFrameReader.readInteger(Version))
@@ -219,7 +218,7 @@ Error EHFrameParser::processCIE() {
   while (uint8_t Field = *NextField++) {
     switch (Field) {
     case 'L': {
-      LSDAFieldPresent = true;
+      CIEInfo.FDEsHaveLSDAField = true;
       uint8_t LSDAPointerEncoding;
       if (auto Err = EHFrameReader.readInteger(LSDAPointerEncoding))
         return Err;
@@ -268,6 +267,10 @@ Error EHFrameParser::processCIE() {
     return make_error<JITLinkError>("Read past the end of the augmentation "
                                     "data while parsing fields");
 
+  assert(!CIEInfos.count(CurRecordAtom->getAddress()) &&
+         "Multiple CIEs recorded at the same address?");
+  CIEInfos[CurRecordAtom->getAddress()] = std::move(CIEInfo);
+
   return Error::success();
 }
 
@@ -280,14 +283,18 @@ Error EHFrameParser::processFDE(JITTargetAddress CIEPointerAddress,
            << format("0x%016" PRIx64, CIEPointerAddress - CIEPointer) << "\n";
   });
 
-  auto CIEAtom = G.findAtomByAddress(CIEPointerAddress - CIEPointer);
-  if (!CIEAtom)
-    return CIEAtom.takeError();
+  auto CIEInfoItr = CIEInfos.find(CIEPointerAddress - CIEPointer);
+  if (CIEInfoItr == CIEInfos.end())
+    return make_error<JITLinkError>(
+        "FDE at " + formatv("{0:x16}", CurRecordAtom->getAddress()) +
+        " points to non-existant CIE at " +
+        formatv("{0:x16}", CIEPointerAddress - CIEPointer));
+  auto &CIEInfo = CIEInfoItr->second;
 
   // The CIEPointer looks good. Add a relocation.
   CurRecordAtom->addEdge(FDEToCIERelocKind,
                          CIEPointerAddress - CurRecordAtom->getAddress(),
-                         *CIEAtom, 0);
+                         *CIEInfo.CIEAtom, 0);
 
   // Read and sanity check the PC-start pointer and size.
   JITTargetAddress PCBeginAddress = EHFrameAddress + EHFrameReader.getOffset();
@@ -329,15 +336,15 @@ Error EHFrameParser::processFDE(JITTargetAddress CIEPointerAddress,
   if (auto Err = EHFrameReader.skip(G.getPointerSize()))
     return Err;
 
-  if (LSDAFieldPresent) {
+  if (CIEInfo.FDEsHaveLSDAField) {
     uint64_t AugmentationDataSize;
     if (auto Err = EHFrameReader.readULEB128(AugmentationDataSize))
       return Err;
     if (AugmentationDataSize != G.getPointerSize())
-      return make_error<JITLinkError>("Unexpected FDE augmentation data size "
-                                      "(expected " +
-                                      Twine(G.getPointerSize()) + ", got " +
-                                      Twine(AugmentationDataSize) + ")");
+      return make_error<JITLinkError>(
+          "Unexpected FDE augmentation data size (expected " +
+          Twine(G.getPointerSize()) + ", got " + Twine(AugmentationDataSize) +
+          ") for FDE at " + formatv("{0:x16}", CurRecordAtom->getAddress()));
     JITTargetAddress LSDAAddress = EHFrameAddress + EHFrameReader.getOffset();
     auto LSDADelta = readAbsolutePointer();
     if (!LSDADelta)
diff --git a/llvm/lib/ExecutionEngine/JITLink/EHFrameSupportImpl.h b/llvm/lib/ExecutionEngine/JITLink/EHFrameSupportImpl.h
index 78be89cfca9..d679edef7ea 100644
--- a/llvm/lib/ExecutionEngine/JITLink/EHFrameSupportImpl.h
+++ b/llvm/lib/ExecutionEngine/JITLink/EHFrameSupportImpl.h
@@ -44,13 +44,20 @@ private:
   Error processCIE();
   Error processFDE(JITTargetAddress CIEPointerAddress, uint32_t CIEPointer);
 
+  struct CIEInformation {
+    CIEInformation() = default;
+    CIEInformation(DefinedAtom &CIEAtom) : CIEAtom(&CIEAtom) {}
+    DefinedAtom *CIEAtom = nullptr;
+    bool FDEsHaveLSDAField = false;
+  };
+
   AtomGraph &G;
   Section &EHFrameSection;
   StringRef EHFrameContent;
   JITTargetAddress EHFrameAddress;
   BinaryStreamReader EHFrameReader;
   DefinedAtom *CurRecordAtom = nullptr;
-  bool LSDAFieldPresent = false;
+  DenseMap<JITTargetAddress, CIEInformation> CIEInfos;
   Edge::Kind FDEToCIERelocKind;
   Edge::Kind FDEToTargetRelocKind;
 };