[FaultMaps] Add a parser for the __llvm__faultmaps section.

Summary:
The parser is exercised by llvm-objdump using -print-fault-maps.  As is
probably obvious, the code itself was "heavily inspired" by
http://reviews.llvm.org/D10434.

Reviewers: reames, atrick, JosephTremoulet

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D10491

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@240304 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/CodeGen/FaultMaps.h

@@ -12,6 +12,8 @@
 
 #include "llvm/ADT/DenseMap.h"
 #include "llvm/MC/MCSymbol.h"
+#include "llvm/Support/Endian.h"
+#include "llvm/Support/Format.h"
 
 #include <vector>
 #include <map>
@@ -68,6 +70,152 @@ private:
 
   void emitFunctionInfo(const MCSymbol *FnLabel, const FunctionFaultInfos &FFI);
 };
+
+/// A parser for the __llvm_faultmaps section generated by the FaultMaps class
+/// above.  This parser is version locked with with the __llvm_faultmaps section
+/// generated by the version of LLVM that includes it.  No guarantees are made
+/// with respect to forward or backward compatibility.
+class FaultMapParser {
+  typedef uint8_t FaultMapVersionType;
+  static const size_t FaultMapVersionOffset = 0;
+
+  typedef uint8_t Reserved0Type;
+  static const size_t Reserved0Offset =
+      FaultMapVersionOffset + sizeof(FaultMapVersionType);
+
+  typedef uint16_t Reserved1Type;
+  static const size_t Reserved1Offset = Reserved0Offset + sizeof(Reserved0Type);
+
+  typedef uint32_t NumFunctionsType;
+  static const size_t NumFunctionsOffset =
+      Reserved1Offset + sizeof(Reserved1Type);
+
+  static const size_t FunctionInfosOffset =
+      NumFunctionsOffset + sizeof(NumFunctionsType);
+
+  const uint8_t *P;
+  const uint8_t *E;
+
+  template <typename T> static T read(const uint8_t *P, const uint8_t *E) {
+    assert(P + sizeof(T) <= E && "out of bounds read!");
+    return support::endian::read<T, support::little, 1>(P);
+  }
+
+public:
+  class FunctionFaultInfoAccessor {
+    typedef uint32_t FaultKindType;
+    static const size_t FaultKindOffset = 0;
+
+    typedef uint32_t FaultingPCOffsetType;
+    static const size_t FaultingPCOffsetOffset =
+        FaultKindOffset + sizeof(FaultKindType);
+
+    typedef uint32_t HandlerPCOffsetType;
+    static const size_t HandlerPCOffsetOffset =
+        FaultingPCOffsetOffset + sizeof(FaultingPCOffsetType);
+
+    const uint8_t *P;
+    const uint8_t *E;
+
+  public:
+    static const size_t Size =
+        HandlerPCOffsetOffset + sizeof(HandlerPCOffsetType);
+
+    explicit FunctionFaultInfoAccessor(const uint8_t *P, const uint8_t *E)
+        : P(P), E(E) {}
+
+    FaultKindType getFaultKind() const {
+      return read<FaultKindType>(P + FaultKindOffset, E);
+    }
+
+    FaultingPCOffsetType getFaultingPCOffset() const {
+      return read<FaultingPCOffsetType>(P + FaultingPCOffsetOffset, E);
+    }
+
+    HandlerPCOffsetType getHandlerPCOffset() const {
+      return read<HandlerPCOffsetType>(P + HandlerPCOffsetOffset, E);
+    }
+  };
+
+  class FunctionInfoAccessor {
+    typedef uint64_t FunctionAddrType;
+    static const size_t FunctionAddrOffset = 0;
+
+    typedef uint32_t NumFaultingPCsType;
+    static const size_t NumFaultingPCsOffset =
+        FunctionAddrOffset + sizeof(FunctionAddrType);
+
+    typedef uint32_t ReservedType;
+    static const size_t ReservedOffset =
+        NumFaultingPCsOffset + sizeof(NumFaultingPCsType);
+
+    static const size_t FunctionFaultInfosOffset =
+        ReservedOffset + sizeof(ReservedType);
+
+    static const size_t FunctionInfoHeaderSize = FunctionFaultInfosOffset;
+
+    const uint8_t *P;
+    const uint8_t *E;
+
+  public:
+    FunctionInfoAccessor() : P(nullptr), E(nullptr) {}
+
+    explicit FunctionInfoAccessor(const uint8_t *P, const uint8_t *E)
+        : P(P), E(E) {}
+
+    FunctionAddrType getFunctionAddr() const {
+      return read<FunctionAddrType>(P + FunctionAddrOffset, E);
+    }
+
+    NumFaultingPCsType getNumFaultingPCs() const {
+      return read<NumFaultingPCsType>(P + NumFaultingPCsOffset, E);
+    }
+
+    FunctionFaultInfoAccessor getFunctionFaultInfoAt(uint32_t Index) const {
+      assert(Index < getNumFaultingPCs() && "index out of bounds!");
+      const uint8_t *Begin = P + FunctionFaultInfosOffset +
+                             FunctionFaultInfoAccessor::Size * Index;
+      return FunctionFaultInfoAccessor(Begin, E);
+    }
+
+    FunctionInfoAccessor getNextFunctionInfo() const {
+      size_t MySize = FunctionInfoHeaderSize +
+                      getNumFaultingPCs() * FunctionFaultInfoAccessor::Size;
+
+      const uint8_t *Begin = P + MySize;
+      assert(Begin < E && "out of bounds!");
+      return FunctionInfoAccessor(Begin, E);
+    }
+  };
+
+  explicit FaultMapParser(const uint8_t *Begin, const uint8_t *End)
+      : P(Begin), E(End) {}
+
+  FaultMapVersionType getFaultMapVersion() const {
+    auto Version = read<FaultMapVersionType>(P + FaultMapVersionOffset, E);
+    assert(Version == 1 && "only version 1 supported!");
+    return Version;
+  }
+
+  NumFunctionsType getNumFunctions() const {
+    return read<NumFunctionsType>(P + NumFunctionsOffset, E);
+  }
+
+  FunctionInfoAccessor getFirstFunctionInfo() const {
+    const uint8_t *Begin = P + FunctionInfosOffset;
+    return FunctionInfoAccessor(Begin, E);
+  }
+};
+
+raw_ostream &
+operator<<(raw_ostream &OS,
+           const typename FaultMapParser::FunctionFaultInfoAccessor &);
+
+raw_ostream &operator<<(raw_ostream &OS,
+                        const typename FaultMapParser::FunctionInfoAccessor &);
+
+raw_ostream &operator<<(raw_ostream &OS, const FaultMapParser &);
+
 } // namespace llvm
 
 #endif

lib/CodeGen/FaultMaps.cpp

@@ -112,3 +112,40 @@ const char *FaultMaps::faultTypeToString(FaultMaps::FaultKind FT) {
     return "FaultingLoad";
   }
 }
+
+raw_ostream &llvm::
+operator<<(raw_ostream &OS,
+           const typename FaultMapParser::FunctionFaultInfoAccessor &FFI) {
+  OS << "Fault kind: "
+     << FaultMaps::faultTypeToString((FaultMaps::FaultKind)FFI.getFaultKind())
+     << ", faulting PC offset: " << FFI.getFaultingPCOffset()
+     << ", handling PC offset: " << FFI.getHandlerPCOffset();
+  return OS;
+}
+
+raw_ostream &llvm::
+operator<<(raw_ostream &OS,
+           const typename FaultMapParser::FunctionInfoAccessor &FI) {
+  OS << "FunctionAddress: " << format_hex(FI.getFunctionAddr(), 8)
+     << ", NumFaultingPCs: " << FI.getNumFaultingPCs() << "\n";
+  for (unsigned i = 0, e = FI.getNumFaultingPCs(); i != e; ++i)
+    OS << FI.getFunctionFaultInfoAt(i) << "\n";
+  return OS;
+}
+
+raw_ostream &llvm::operator<<(raw_ostream &OS, const FaultMapParser &FMP) {
+  OS << "Version: " << format_hex(FMP.getFaultMapVersion(), 2) << "\n";
+  OS << "NumFunctions: " << FMP.getNumFunctions() << "\n";
+
+  if (FMP.getNumFunctions() == 0)
+    return OS;
+
+  typename FaultMapParser::FunctionInfoAccessor FI;
+
+  for (unsigned i = 0, e = FMP.getNumFunctions(); i != e; ++i) {
+    FI = (i == 0) ? FMP.getFirstFunctionInfo() : FI.getNextFunctionInfo();
+    OS << FI;
+  }
+
+  return OS;
+}

test/CodeGen/X86/implicit-null-check.ll

@@ -1,5 +1,15 @@
 ; RUN: llc -O3 -mtriple=x86_64-apple-macosx -enable-implicit-null-checks < %s | FileCheck %s
 
+; RUN: llc < %s -mtriple=x86_64-apple-macosx -enable-implicit-null-checks \
+; RUN:    | llvm-mc -triple x86_64-apple-macosx -filetype=obj -o - \
+; RUN:    | llvm-objdump -triple x86_64-apple-macosx -fault-map-section - \
+; RUN:    | FileCheck %s -check-prefix OBJDUMP
+
+; RUN: llc < %s -mtriple=x86_64-unknown-linux-gnu -enable-implicit-null-checks \
+; RUN:    | llvm-mc -triple x86_64-unknown-linux-gnu -filetype=obj -o - \
+; RUN:    | llvm-objdump -triple x86_64-unknown-linux-gnu -fault-map-section - \
+; RUN:    | FileCheck %s -check-prefix OBJDUMP
+
 define i32 @imp_null_check_load(i32* %x) {
 ; CHECK-LABEL: _imp_null_check_load:
 ; CHECK: Ltmp1:
@@ -116,3 +126,13 @@ define i32 @imp_null_check_add_result(i32* %x, i32 %p) {
 ; CHECK-NEXT: .long Ltmp1-_imp_null_check_load
 ; Fault[0].HandlerOffset:
 ; CHECK-NEXT: .long Ltmp0-_imp_null_check_load
+
+; OBJDUMP: FaultMap table:
+; OBJDUMP-NEXT: Version: 0x1
+; OBJDUMP-NEXT: NumFunctions: 3
+; OBJDUMP-NEXT: FunctionAddress: 0x000000, NumFaultingPCs: 1
+; OBJDUMP-NEXT: Fault kind: FaultingLoad, faulting PC offset: 0, handling PC offset: 5
+; OBJDUMP-NEXT: FunctionAddress: 0x000000, NumFaultingPCs: 1
+; OBJDUMP-NEXT: Fault kind: FaultingLoad, faulting PC offset: 0, handling PC offset: 7
+; OBJDUMP-NEXT: FunctionAddress: 0x000000, NumFaultingPCs: 1
+; OBJDUMP-NEXT: Fault kind: FaultingLoad, faulting PC offset: 0, handling PC offset: 3

test/MC/X86/faultmap-section-parsing.s

@@ -0,0 +1,29 @@
+// RUN: llvm-mc < %s -triple=x86_64-apple-macosx -filetype=obj -o - | llvm-objdump -fault-map-section - | FileCheck %s
+
+	.section	__LLVM_FAULTMAPS,__llvm_faultmaps
+__LLVM_FaultMaps:
+	.byte	1
+	.byte	0
+	.short	0
+	.long	2
+	.quad	0xFFDEAD
+	.long	1
+	.long	0
+	.long	1
+	.long	100
+	.long	200
+
+	.quad	0xFFDAED
+	.long	1
+	.long	0
+	.long	1
+	.long	400
+	.long	500
+
+// CHECK: FaultMap table:
+// CHECK-NEXT: Version: 0x1
+// CHECK-NEXT: NumFunctions: 2
+// CHECK-NEXT: FunctionAddress: 0xffdead, NumFaultingPCs: 1
+// CHECK-NEXT: Fault kind: FaultingLoad, faulting PC offset: 100, handling PC offset: 200
+// CHECK-NEXT: FunctionAddress: 0xffdaed, NumFaultingPCs: 1
+// CHECK-NEXT: Fault kind: FaultingLoad, faulting PC offset: 400, handling PC offset: 500

tools/llvm-objdump/llvm-objdump.cpp

@@ -17,9 +17,11 @@
 //===----------------------------------------------------------------------===//
 
 #include "llvm-objdump.h"
+#include "llvm/ADT/Optional.h"
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/ADT/StringExtras.h"
 #include "llvm/ADT/Triple.h"
+#include "llvm/CodeGen/FaultMaps.h"
 #include "llvm/MC/MCAsmInfo.h"
 #include "llvm/MC/MCContext.h"
 #include "llvm/MC/MCDisassembler.h"
@@ -153,6 +155,9 @@ cl::opt<bool>
     llvm::PrintImmHex("print-imm-hex",
                       cl::desc("Use hex format for immediate values"));
 
+cl::opt<bool> PrintFaultMaps("fault-map-section",
+                             cl::desc("Display contents of faultmap section"));
+
 static StringRef ToolName;
 static int ReturnValue = EXIT_SUCCESS;
 
@@ -1226,6 +1231,49 @@ void llvm::printWeakBindTable(const ObjectFile *o) {
   }
 }
 
+static void printFaultMaps(const ObjectFile *Obj) {
+  const char *FaultMapSectionName = nullptr;
+
+  if (isa<ELFObjectFileBase>(Obj)) {
+    FaultMapSectionName = ".llvm_faultmaps";
+  } else if (isa<MachOObjectFile>(Obj)) {
+    FaultMapSectionName = "__llvm_faultmaps";
+  } else {
+    errs() << "This operation is only currently supported "
+              "for ELF and Mach-O executable files.\n";
+    return;
+  }
+
+  Optional<object::SectionRef> FaultMapSection;
+
+  for (auto Sec : Obj->sections()) {
+    StringRef Name;
+    Sec.getName(Name);
+    if (Name == FaultMapSectionName) {
+      FaultMapSection = Sec;
+      break;
+    }
+  }
+
+  outs() << "FaultMap table:\n";
+
+  if (!FaultMapSection.hasValue()) {
+    outs() << "<not found>\n";
+    return;
+  }
+
+  StringRef FaultMapContents;
+  if (error(FaultMapSection.getValue().getContents(FaultMapContents))) {
+    errs() << "Could not read the " << FaultMapContents << " section!\n";
+    return;
+  }
+
+  FaultMapParser FMP(FaultMapContents.bytes_begin(),
+                     FaultMapContents.bytes_end());
+
+  outs() << FMP;
+}
+
 static void printPrivateFileHeader(const ObjectFile *o) {
   if (o->isELF()) {
     printELFFileHeader(o);
@@ -1265,6 +1313,8 @@ static void DumpObject(const ObjectFile *o) {
     printLazyBindTable(o);
   if (WeakBind)
     printWeakBindTable(o);
+  if (PrintFaultMaps)
+    printFaultMaps(o);
 }
 
 /// @brief Dump each object file in \a a;
@@ -1362,7 +1412,8 @@ int main(int argc, char **argv) {
       && !(DylibsUsed && MachOOpt)
       && !(DylibId && MachOOpt)
       && !(ObjcMetaData && MachOOpt)
-      && !(DumpSections.size() != 0 && MachOOpt)) {
+      && !(DumpSections.size() != 0 && MachOOpt)
+      && !PrintFaultMaps) {
     cl::PrintHelpMessage();
     return 2;
   }