[llvm] r240304 - [FaultMaps] Add a parser for the __llvm__faultmaps section.

Ahmed Bougacha ahmed.bougacha at gmail.com
Mon Jun 22 13:31:31 PDT 2015


Hi Sanjoy,

Seems like this broke my local shared libs build:

Undefined symbols for architecture x86_64:
  "llvm::operator<<(llvm::raw_ostream&, llvm::FaultMapParser const&)",
referenced from:
      printFaultMaps(llvm::object::ObjectFile const*) in llvm-objdump.cpp.o


It's easily fixable by having llvm-objdump link with CodeGen, but I'm
not sure that's reasonable.  Is there a better location for this code?

-Ahmed


On Mon, Jun 22, 2015 at 11:03 AM, Sanjoy Das
<sanjoy at playingwithpointers.com> wrote:
> Author: sanjoy
> Date: Mon Jun 22 13:03:02 2015
> New Revision: 240304
>
> URL: http://llvm.org/viewvc/llvm-project?rev=240304&view=rev
> Log:
> [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
>
> Added:
>     llvm/trunk/test/MC/X86/faultmap-section-parsing.s
> Modified:
>     llvm/trunk/include/llvm/CodeGen/FaultMaps.h
>     llvm/trunk/lib/CodeGen/FaultMaps.cpp
>     llvm/trunk/test/CodeGen/X86/implicit-null-check.ll
>     llvm/trunk/tools/llvm-objdump/llvm-objdump.cpp
>
> Modified: llvm/trunk/include/llvm/CodeGen/FaultMaps.h
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/CodeGen/FaultMaps.h?rev=240304&r1=240303&r2=240304&view=diff
> ==============================================================================
> --- llvm/trunk/include/llvm/CodeGen/FaultMaps.h (original)
> +++ llvm/trunk/include/llvm/CodeGen/FaultMaps.h Mon Jun 22 13:03:02 2015
> @@ -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
>
> Modified: llvm/trunk/lib/CodeGen/FaultMaps.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/FaultMaps.cpp?rev=240304&r1=240303&r2=240304&view=diff
> ==============================================================================
> --- llvm/trunk/lib/CodeGen/FaultMaps.cpp (original)
> +++ llvm/trunk/lib/CodeGen/FaultMaps.cpp Mon Jun 22 13:03:02 2015
> @@ -112,3 +112,40 @@ const char *FaultMaps::faultTypeToString
>      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;
> +}
>
> Modified: llvm/trunk/test/CodeGen/X86/implicit-null-check.ll
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/implicit-null-check.ll?rev=240304&r1=240303&r2=240304&view=diff
> ==============================================================================
> --- llvm/trunk/test/CodeGen/X86/implicit-null-check.ll (original)
> +++ llvm/trunk/test/CodeGen/X86/implicit-null-check.ll Mon Jun 22 13:03:02 2015
> @@ -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(i3
>  ; 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
>
> Added: llvm/trunk/test/MC/X86/faultmap-section-parsing.s
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/MC/X86/faultmap-section-parsing.s?rev=240304&view=auto
> ==============================================================================
> --- llvm/trunk/test/MC/X86/faultmap-section-parsing.s (added)
> +++ llvm/trunk/test/MC/X86/faultmap-section-parsing.s Mon Jun 22 13:03:02 2015
> @@ -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
>
> Modified: llvm/trunk/tools/llvm-objdump/llvm-objdump.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/tools/llvm-objdump/llvm-objdump.cpp?rev=240304&r1=240303&r2=240304&view=diff
> ==============================================================================
> --- llvm/trunk/tools/llvm-objdump/llvm-objdump.cpp (original)
> +++ llvm/trunk/tools/llvm-objdump/llvm-objdump.cpp Mon Jun 22 13:03:02 2015
> @@ -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 Obje
>    }
>  }
>
> +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
>      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;
>    }
>
>
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