ubsan_diag.cpp

//===-- ubsan_diag.cpp ----------------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// Diagnostic reporting for the UBSan runtime.
//
//===----------------------------------------------------------------------===//

#include "ubsan_platform.h"
#if CAN_SANITIZE_UB
#include "ubsan_diag.h"
#include "ubsan_init.h"
#include "ubsan_flags.h"
#include "ubsan_monitor.h"
#include "sanitizer_common/sanitizer_placement_new.h"
#include "sanitizer_common/sanitizer_report_decorator.h"
#include "sanitizer_common/sanitizer_stacktrace.h"
#include "sanitizer_common/sanitizer_stacktrace_printer.h"
#include "sanitizer_common/sanitizer_suppressions.h"
#include "sanitizer_common/sanitizer_symbolizer.h"
#include <stdio.h>

using namespace __ubsan;

// UBSan is combined with runtimes that already provide this functionality
// (e.g., ASan) as well as runtimes that lack it (e.g., scudo). Tried to use
// weak linkage to resolve this issue which is not portable and breaks on
// Windows.
// TODO(yln): This is a temporary workaround. GetStackTrace functions will be
// removed in the future.
void ubsan_GetStackTrace(BufferedStackTrace *stack, uptr max_depth,
                         uptr pc, uptr bp, void *context, bool fast) {
  uptr top = 0;
  uptr bottom = 0;
  if (StackTrace::WillUseFastUnwind(fast)) {
    GetThreadStackTopAndBottom(false, &top, &bottom);
    stack->Unwind(max_depth, pc, bp, nullptr, top, bottom, true);
  } else
    stack->Unwind(max_depth, pc, bp, context, 0, 0, false);
}

static void MaybePrintStackTrace(uptr pc, uptr bp) {
  // We assume that flags are already parsed, as UBSan runtime
  // will definitely be called when we print the first diagnostics message.
  if (!flags()->print_stacktrace)
    return;

  BufferedStackTrace stack;
  ubsan_GetStackTrace(&stack, kStackTraceMax, pc, bp, nullptr,
                common_flags()->fast_unwind_on_fatal);
  stack.Print();
}

static const char *ConvertTypeToString(ErrorType Type) {
  switch (Type) {
#define UBSAN_CHECK(Name, SummaryKind, FSanitizeFlagName)                      \
  case ErrorType::Name:                                                        \
    return SummaryKind;
#include "ubsan_checks.inc"
#undef UBSAN_CHECK
  }
  UNREACHABLE("unknown ErrorType!");
}

static const char *ConvertTypeToFlagName(ErrorType Type) {
  switch (Type) {
#define UBSAN_CHECK(Name, SummaryKind, FSanitizeFlagName)                      \
  case ErrorType::Name:                                                        \
    return FSanitizeFlagName;
#include "ubsan_checks.inc"
#undef UBSAN_CHECK
  }
  UNREACHABLE("unknown ErrorType!");
}

static void MaybeReportErrorSummary(Location Loc, ErrorType Type) {
  if (!common_flags()->print_summary)
    return;
  if (!flags()->report_error_type)
    Type = ErrorType::GenericUB;
  const char *ErrorKind = ConvertTypeToString(Type);
  if (Loc.isSourceLocation()) {
    SourceLocation SLoc = Loc.getSourceLocation();
    if (!SLoc.isInvalid()) {
      AddressInfo AI;
      AI.file = internal_strdup(SLoc.getFilename());
      AI.line = SLoc.getLine();
      AI.column = SLoc.getColumn();
      AI.function = internal_strdup("");  // Avoid printing ?? as function name.
      ReportErrorSummary(ErrorKind, AI, GetSanititizerToolName());
      AI.Clear();
      return;
    }
  } else if (Loc.isSymbolizedStack()) {
    const AddressInfo &AI = Loc.getSymbolizedStack()->info;
    ReportErrorSummary(ErrorKind, AI, GetSanititizerToolName());
    return;
  }
  ReportErrorSummary(ErrorKind, GetSanititizerToolName());
}

namespace {
class Decorator : public SanitizerCommonDecorator {
 public:
  Decorator() : SanitizerCommonDecorator() {}
  const char *Highlight() const { return Green(); }
  const char *Note() const { return Black(); }
};
}

SymbolizedStack *__ubsan::getSymbolizedLocation(uptr PC) {
  InitAsStandaloneIfNecessary();
  return Symbolizer::GetOrInit()->SymbolizePC(PC);
}

Diag &Diag::operator<<(const TypeDescriptor &V) {
  return AddArg(V.getTypeName());
}

Diag &Diag::operator<<(const Value &V) {
  if (V.getType().isSignedIntegerTy())
    AddArg(V.getSIntValue());
  else if (V.getType().isUnsignedIntegerTy())
    AddArg(V.getUIntValue());
  else if (V.getType().isFloatTy())
    AddArg(V.getFloatValue());
  else
    AddArg("<unknown>");
  return *this;
}

/// Hexadecimal printing for numbers too large for Printf to handle directly.
static void RenderHex(InternalScopedString *Buffer, UIntMax Val) {
#if HAVE_INT128_T
  Buffer->append("0x%08x%08x%08x%08x", (unsigned int)(Val >> 96),
                 (unsigned int)(Val >> 64), (unsigned int)(Val >> 32),
                 (unsigned int)(Val));
#else
  UNREACHABLE("long long smaller than 64 bits?");
#endif
}

static void RenderLocation(InternalScopedString *Buffer, Location Loc) {
  switch (Loc.getKind()) {
  case Location::LK_Source: {
    SourceLocation SLoc = Loc.getSourceLocation();
    if (SLoc.isInvalid())
      Buffer->append("<unknown>");
    else
      RenderSourceLocation(Buffer, SLoc.getFilename(), SLoc.getLine(),
                           SLoc.getColumn(), common_flags()->symbolize_vs_style,
                           common_flags()->strip_path_prefix);
    return;
  }
  case Location::LK_Memory:
    Buffer->append("%p", Loc.getMemoryLocation());
    return;
  case Location::LK_Symbolized: {
    const AddressInfo &Info = Loc.getSymbolizedStack()->info;
    if (Info.file)
      RenderSourceLocation(Buffer, Info.file, Info.line, Info.column,
                           common_flags()->symbolize_vs_style,
                           common_flags()->strip_path_prefix);
    else if (Info.module)
      RenderModuleLocation(Buffer, Info.module, Info.module_offset,
                           Info.module_arch, common_flags()->strip_path_prefix);
    else
      Buffer->append("%p", Info.address);
    return;
  }
  case Location::LK_Null:
    Buffer->append("<unknown>");
    return;
  }
}

static void RenderText(InternalScopedString *Buffer, const char *Message,
                       const Diag::Arg *Args) {
  for (const char *Msg = Message; *Msg; ++Msg) {
    if (*Msg != '%') {
      Buffer->append("%c", *Msg);
      continue;
    }
    const Diag::Arg &A = Args[*++Msg - '0'];
    switch (A.Kind) {
    case Diag::AK_String:
      Buffer->append("%s", A.String);
      break;
    case Diag::AK_TypeName: {
      if (SANITIZER_WINDOWS)
        // The Windows implementation demangles names early.
        Buffer->append("'%s'", A.String);
      else
        Buffer->append("'%s'", Symbolizer::GetOrInit()->Demangle(A.String));
      break;
    }
    case Diag::AK_SInt:
      // 'long long' is guaranteed to be at least 64 bits wide.
      if (A.SInt >= INT64_MIN && A.SInt <= INT64_MAX)
        Buffer->append("%lld", (long long)A.SInt);
      else
        RenderHex(Buffer, A.SInt);
      break;
    case Diag::AK_UInt:
      if (A.UInt <= UINT64_MAX)
        Buffer->append("%llu", (unsigned long long)A.UInt);
      else
        RenderHex(Buffer, A.UInt);
      break;
    case Diag::AK_Float: {
      // FIXME: Support floating-point formatting in sanitizer_common's
      //        printf, and stop using snprintf here.
      char FloatBuffer[32];
#if SANITIZER_WINDOWS
      sprintf_s(FloatBuffer, sizeof(FloatBuffer), "%Lg", (long double)A.Float);
#else
      snprintf(FloatBuffer, sizeof(FloatBuffer), "%Lg", (long double)A.Float);
#endif
      Buffer->append("%s", FloatBuffer);
      break;
    }
    case Diag::AK_Pointer:
      Buffer->append("%p", A.Pointer);
      break;
    }
  }
}

/// Find the earliest-starting range in Ranges which ends after Loc.
static Range *upperBound(MemoryLocation Loc, Range *Ranges,
                         unsigned NumRanges) {
  Range *Best = 0;
  for (unsigned I = 0; I != NumRanges; ++I)
    if (Ranges[I].getEnd().getMemoryLocation() > Loc &&
        (!Best ||
         Best->getStart().getMemoryLocation() >
         Ranges[I].getStart().getMemoryLocation()))
      Best = &Ranges[I];
  return Best;
}

static inline uptr subtractNoOverflow(uptr LHS, uptr RHS) {
  return (LHS < RHS) ? 0 : LHS - RHS;
}

static inline uptr addNoOverflow(uptr LHS, uptr RHS) {
  const uptr Limit = (uptr)-1;
  return (LHS > Limit - RHS) ? Limit : LHS + RHS;
}

/// Render a snippet of the address space near a location.
static void PrintMemorySnippet(const Decorator &Decor, MemoryLocation Loc,
                               Range *Ranges, unsigned NumRanges,
                               const Diag::Arg *Args) {
  // Show at least the 8 bytes surrounding Loc.
  const unsigned MinBytesNearLoc = 4;
  MemoryLocation Min = subtractNoOverflow(Loc, MinBytesNearLoc);
  MemoryLocation Max = addNoOverflow(Loc, MinBytesNearLoc);
  MemoryLocation OrigMin = Min;
  for (unsigned I = 0; I < NumRanges; ++I) {
    Min = __sanitizer::Min(Ranges[I].getStart().getMemoryLocation(), Min);
    Max = __sanitizer::Max(Ranges[I].getEnd().getMemoryLocation(), Max);
  }

  // If we have too many interesting bytes, prefer to show bytes after Loc.
  const unsigned BytesToShow = 32;
  if (Max - Min > BytesToShow)
    Min = __sanitizer::Min(Max - BytesToShow, OrigMin);
  Max = addNoOverflow(Min, BytesToShow);

  if (!IsAccessibleMemoryRange(Min, Max - Min)) {
    Printf("<memory cannot be printed>\n");
    return;
  }

  // Emit data.
  InternalScopedString Buffer(1024);
  for (uptr P = Min; P != Max; ++P) {
    unsigned char C = *reinterpret_cast<const unsigned char*>(P);
    Buffer.append("%s%02x", (P % 8 == 0) ? "  " : " ", C);
  }
  Buffer.append("\n");

  // Emit highlights.
  Buffer.append(Decor.Highlight());
  Range *InRange = upperBound(Min, Ranges, NumRanges);
  for (uptr P = Min; P != Max; ++P) {
    char Pad = ' ', Byte = ' ';
    if (InRange && InRange->getEnd().getMemoryLocation() == P)
      InRange = upperBound(P, Ranges, NumRanges);
    if (!InRange && P > Loc)
      break;
    if (InRange && InRange->getStart().getMemoryLocation() < P)
      Pad = '~';
    if (InRange && InRange->getStart().getMemoryLocation() <= P)
      Byte = '~';
    if (P % 8 == 0)
      Buffer.append("%c", Pad);
    Buffer.append("%c", Pad);
    Buffer.append("%c", P == Loc ? '^' : Byte);
    Buffer.append("%c", Byte);
  }
  Buffer.append("%s\n", Decor.Default());

  // Go over the line again, and print names for the ranges.
  InRange = 0;
  unsigned Spaces = 0;
  for (uptr P = Min; P != Max; ++P) {
    if (!InRange || InRange->getEnd().getMemoryLocation() == P)
      InRange = upperBound(P, Ranges, NumRanges);
    if (!InRange)
      break;

    Spaces += (P % 8) == 0 ? 2 : 1;

    if (InRange && InRange->getStart().getMemoryLocation() == P) {
      while (Spaces--)
        Buffer.append(" ");
      RenderText(&Buffer, InRange->getText(), Args);
      Buffer.append("\n");
      // FIXME: We only support naming one range for now!
      break;
    }

    Spaces += 2;
  }

  Printf("%s", Buffer.data());
  // FIXME: Print names for anything we can identify within the line:
  //
  //  * If we can identify the memory itself as belonging to a particular
  //    global, stack variable, or dynamic allocation, then do so.
  //
  //  * If we have a pointer-size, pointer-aligned range highlighted,
  //    determine whether the value of that range is a pointer to an
  //    entity which we can name, and if so, print that name.
  //
  // This needs an external symbolizer, or (preferably) ASan instrumentation.
}

Diag::~Diag() {
  // All diagnostics should be printed under report mutex.
  ScopedReport::CheckLocked();
  Decorator Decor;
  InternalScopedString Buffer(1024);

  // Prepare a report that a monitor process can inspect.
  if (Level == DL_Error) {
    RenderText(&Buffer, Message, Args);
    UndefinedBehaviorReport UBR{ConvertTypeToString(ET), Loc, Buffer};
    Buffer.clear();
  }

  Buffer.append(Decor.Bold());
  RenderLocation(&Buffer, Loc);
  Buffer.append(":");

  switch (Level) {
  case DL_Error:
    Buffer.append("%s runtime error: %s%s", Decor.Warning(), Decor.Default(),
                  Decor.Bold());
    break;

  case DL_Note:
    Buffer.append("%s note: %s", Decor.Note(), Decor.Default());
    break;
  }

  RenderText(&Buffer, Message, Args);

  Buffer.append("%s\n", Decor.Default());
  Printf("%s", Buffer.data());

  if (Loc.isMemoryLocation())
    PrintMemorySnippet(Decor, Loc.getMemoryLocation(), Ranges, NumRanges, Args);
}

ScopedReport::Initializer::Initializer() { InitAsStandaloneIfNecessary(); }

ScopedReport::ScopedReport(ReportOptions Opts, Location SummaryLoc,
                           ErrorType Type)
    : Opts(Opts), SummaryLoc(SummaryLoc), Type(Type) {}

ScopedReport::~ScopedReport() {
  MaybePrintStackTrace(Opts.pc, Opts.bp);
  MaybeReportErrorSummary(SummaryLoc, Type);
  if (flags()->halt_on_error)
    Die();
}

ALIGNED(64) static char suppression_placeholder[sizeof(SuppressionContext)];
static SuppressionContext *suppression_ctx = nullptr;
static const char kVptrCheck[] = "vptr_check";
static const char *kSuppressionTypes[] = {
#define UBSAN_CHECK(Name, SummaryKind, FSanitizeFlagName) FSanitizeFlagName,
#include "ubsan_checks.inc"
#undef UBSAN_CHECK
    kVptrCheck,
};

void __ubsan::InitializeSuppressions() {
  CHECK_EQ(nullptr, suppression_ctx);
  suppression_ctx = new (suppression_placeholder)
      SuppressionContext(kSuppressionTypes, ARRAY_SIZE(kSuppressionTypes));
  suppression_ctx->ParseFromFile(flags()->suppressions);
}

bool __ubsan::IsVptrCheckSuppressed(const char *TypeName) {
  InitAsStandaloneIfNecessary();
  CHECK(suppression_ctx);
  Suppression *s;
  return suppression_ctx->Match(TypeName, kVptrCheck, &s);
}

bool __ubsan::IsPCSuppressed(ErrorType ET, uptr PC, const char *Filename) {
  InitAsStandaloneIfNecessary();
  CHECK(suppression_ctx);
  const char *SuppType = ConvertTypeToFlagName(ET);
  // Fast path: don't symbolize PC if there is no suppressions for given UB
  // type.
  if (!suppression_ctx->HasSuppressionType(SuppType))
    return false;
  Suppression *s = nullptr;
  // Suppress by file name known to runtime.
  if (Filename != nullptr && suppression_ctx->Match(Filename, SuppType, &s))
    return true;
  // Suppress by module name.
  if (const char *Module = Symbolizer::GetOrInit()->GetModuleNameForPc(PC)) {
    if (suppression_ctx->Match(Module, SuppType, &s))
      return true;
  }
  // Suppress by function or source file name from debug info.
  SymbolizedStackHolder Stack(Symbolizer::GetOrInit()->SymbolizePC(PC));
  const AddressInfo &AI = Stack.get()->info;
  return suppression_ctx->Match(AI.function, SuppType, &s) ||
         suppression_ctx->Match(AI.file, SuppType, &s);
}

#endif  // CAN_SANITIZE_UB