[Offload] Implement double free (and other allocation error) reporting

As a first step towards a GPU sanitizer we now can track allocations
and deallocations in order to report double frees, and other problems
during deallocation.

Author: jdoerfert

offload/plugins-nextgen/common/include/ErrorReporting.h

@@ -0,0 +1,200 @@
+//===- ErrorReporting.h - Helper to provide nice error messages ----- c++ -===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef OPENMP_LIBOMPTARGET_PLUGINS_NEXTGEN_COMMON_ERROR_REPORTING_H
+#define OPENMP_LIBOMPTARGET_PLUGINS_NEXTGEN_COMMON_ERROR_REPORTING_H
+
+#include "PluginInterface.h"
+
+#include "llvm/ADT/SmallString.h"
+#include "llvm/ADT/StringRef.h"
+#include "llvm/Support/ErrorHandling.h"
+
+#include <cstdio>
+#include <cstdlib>
+#include <string>
+
+namespace llvm {
+namespace omp {
+namespace target {
+namespace plugin {
+
+class ErrorReporter {
+  /// The banner printed at the beginning of an error report.
+  static constexpr auto ErrorBanner = "OFFLOAD ERROR: ";
+
+  /// Terminal color codes
+  ///
+  /// TODO: determine if the terminal supports colors.
+  ///@{
+  static constexpr auto Green = []() { return "\033[1m\033[32m"; };
+  static constexpr auto Blue = []() { return "\033[1m\033[34m"; };
+  static constexpr auto Red = []() { return "\033[1m\033[31m"; };
+  static constexpr auto Magenta = []() { return "\033[1m\033[35m"; };
+  static constexpr auto Cyan = []() { return "\033[1m\033[36m"; };
+  static constexpr auto Default = []() { return "\033[1m\033[0m"; };
+  ///@}
+
+  /// The size of the getBuffer() buffer.
+  static constexpr unsigned BufferSize = 1024;
+
+  /// Return a buffer of size BufferSize that can be used for formatting.
+  static char *getBuffer() {
+    static char *Buffer = nullptr;
+    if (!Buffer)
+      Buffer = reinterpret_cast<char *>(malloc(BufferSize));
+    return Buffer;
+  }
+
+  /// Return the device id as string, or n/a if not available.
+  static std::string getDeviceIdStr(GenericDeviceTy *Device) {
+    return Device ? std::to_string(Device->getDeviceId()) : "n/a";
+  }
+
+  /// Return a nice name for an TargetAllocTy.
+  static std::string getAllocTyName(TargetAllocTy Kind) {
+    switch (Kind) {
+    case TARGET_ALLOC_DEVICE_NON_BLOCKING:
+    case TARGET_ALLOC_DEFAULT:
+    case TARGET_ALLOC_DEVICE:
+      return "device memory";
+    case TARGET_ALLOC_HOST:
+      return "pinned host memory";
+    case TARGET_ALLOC_SHARED:
+      return "managed memory";
+      break;
+    }
+    llvm_unreachable("Unknown target alloc kind");
+  }
+
+  /// Return a C string after \p Format has been instantiated with \p Args.
+  template <typename... ArgsTy>
+  static const char *getCString(const char *Format, ArgsTy &&...Args) {
+    std::snprintf(getBuffer(), BufferSize, Format,
+                  std::forward<ArgsTy>(Args)...);
+    return getBuffer();
+  }
+
+  /// Print \p Format, instantiated with \p Args to stderr.
+  /// TODO: Allow redirection into a file stream.
+  template <typename... ArgsTy>
+  static void print(const char *Format, ArgsTy &&...Args) {
+    fprintf(stderr, Format, std::forward<ArgsTy>(Args)...);
+  }
+
+  /// Pretty print a stack trace.
+  static void reportStackTrace(StringRef StackTrace) {
+    if (StackTrace.empty())
+      return;
+
+    SmallVector<StringRef> Lines, Parts;
+    StackTrace.split(Lines, "\n", /*MaxSplit=*/-1, /*KeepEmpty=*/false);
+    int Start = Lines.empty() || !Lines[0].contains("PrintStackTrace") ? 0 : 1;
+    for (int I = Start, E = Lines.size(); I < E; ++I) {
+      auto Line = Lines[I];
+      Parts.clear();
+      Line.split(Parts, " ", /*MaxSplit=*/2);
+      if (Parts.size() != 3 || Parts[0].size() < 2 || Parts[0][0] != '#') {
+        print("%s\n", Line.str().c_str());
+        continue;
+      }
+      unsigned FrameIdx = std::stoi(Parts[0].drop_front(1).str());
+      if (Start)
+        FrameIdx -= 1;
+      print("    %s%s%s%u %s%s%s %s\n", Magenta(),
+            Parts[0].take_front().str().c_str(), Green(), FrameIdx, Blue(),
+            Parts[1].str().c_str(), Default(), Parts[2].str().c_str());
+    }
+
+    printf("\n");
+  }
+
+  /// Report an error.
+  static void reportError(const char *Message, StringRef StackTrace) {
+    print("%s%s%s\n%s", Red(), ErrorBanner, Message, Default());
+    reportStackTrace(StackTrace);
+  }
+
+  /// Report information about an allocation associated with \p ATI.
+  static void reportAllocationInfo(AllocationTraceInfoTy *ATI) {
+    if (!ATI)
+      return;
+
+    if (!ATI->DeallocationTrace.empty()) {
+      print("%s%s%s\n%s", Cyan(), "Last deallocation:", Default());
+      reportStackTrace(ATI->DeallocationTrace);
+    }
+
+    if (ATI->HostPtr)
+      print("%sLast allocation of size %lu for host pointer %p:\n%s", Cyan(),
+            ATI->Size, ATI->HostPtr, Default());
+    else
+      print("%sLast allocation of size %lu:\n%s", Cyan(), ATI->Size, Default());
+    reportStackTrace(ATI->AllocationTrace);
+    if (!ATI->LastAllocationInfo)
+      return;
+
+    unsigned I = 0;
+    print("%sPrior allocations with the same base pointer:", Cyan());
+    while (ATI->LastAllocationInfo) {
+      print("\n%s", Default());
+      ATI = ATI->LastAllocationInfo;
+      print("%s #%u Prior deallocation of size %lu:\n%s", Cyan(), I, ATI->Size,
+            Default());
+      reportStackTrace(ATI->DeallocationTrace);
+      if (ATI->HostPtr)
+        print("%s #%u Prior allocation for host pointer %p:\n%s", Cyan(), I,
+              ATI->HostPtr, Default());
+      else
+        print("%s #%u Prior allocation:\n%s", Cyan(), I, Default());
+      reportStackTrace(ATI->AllocationTrace);
+      ++I;
+    }
+  }
+
+public:
+  /// Check if the deallocation of \p DevicePtr is valid given \p ATI. Stores \p
+  /// StackTrace to \p ATI->DeallocationTrace if there was no error.
+  static void checkDeallocation(GenericDeviceTy *Device, void *DevicePtr,
+                                TargetAllocTy Kind, AllocationTraceInfoTy *ATI,
+                                std::string &StackTrace) {
+#define DEALLOCATION_ERROR(Format, ...)                                        \
+  reportError(getCString(Format, __VA_ARGS__), StackTrace);                    \
+  reportAllocationInfo(ATI);                                                   \
+  abort();
+
+    if (!ATI) {
+      DEALLOCATION_ERROR("deallocation of non-allocated %s: %p",
+                         getAllocTyName(Kind).c_str(), DevicePtr);
+    }
+
+    if (!ATI->DeallocationTrace.empty()) {
+      DEALLOCATION_ERROR("double-free of %s: %p", getAllocTyName(Kind).c_str(),
+                         DevicePtr);
+    }
+
+    if (ATI->Kind != Kind) {
+      DEALLOCATION_ERROR("deallocation requires %s but allocation was %s: %p",
+                         getAllocTyName(Kind).c_str(),
+                         getAllocTyName(ATI->Kind).c_str(), DevicePtr);
+    }
+
+    ATI->DeallocationTrace = StackTrace;
+
+#undef DEALLOCATION_ERROR
+  }
+};
+
+} // namespace plugin
+} // namespace target
+} // namespace omp
+} // namespace llvm
+
+#endif // OPENMP_LIBOMPTARGET_PLUGINS_NEXTGEN_COMMON_ERROR_REPORTING_H

offload/plugins-nextgen/common/include/PluginInterface.h

@@ -19,6 +19,7 @@
 #include <shared_mutex>
 #include <vector>
 
+#include "ExclusiveAccess.h"
 #include "Shared/APITypes.h"
 #include "Shared/Debug.h"
 #include "Shared/Environment.h"
@@ -382,6 +383,32 @@ struct GenericKernelTy {
   bool IsBareKernel = false;
 };
 
+/// Information about an allocation, when it has been allocated, and when/if it
+/// has been deallocated, for error reporting purposes.
+struct AllocationTraceInfoTy {
+
+  /// The stack trace of the allocation itself.
+  std::string AllocationTrace;
+
+  /// The stack trace of the deallocation, or empty.
+  std::string DeallocationTrace;
+
+  /// The allocated device pointer.
+  void *DevicePtr = nullptr;
+
+  /// The corresponding host pointer (can be null).
+  void *HostPtr = nullptr;
+
+  /// The size of the allocation.
+  uint64_t Size = 0;
+
+  /// The kind of the allocation.
+  TargetAllocTy Kind = TargetAllocTy::TARGET_ALLOC_DEFAULT;
+
+  /// Information about the last allocation at this address, if any.
+  AllocationTraceInfoTy *LastAllocationInfo = nullptr;
+};
+
 /// Class representing a map of host pinned allocations. We track these pinned
 /// allocations, so memory tranfers invloving these buffers can be optimized.
 class PinnedAllocationMapTy {
@@ -866,6 +893,10 @@ struct GenericDeviceTy : public DeviceAllocatorTy {
   /// Reference to the underlying plugin that created this device.
   GenericPluginTy &Plugin;
 
+  /// Map to record when allocations have been performed, and when they have
+  /// been deallocated, both for error reporting purposes.
+  ProtectedObj<DenseMap<void *, AllocationTraceInfoTy *>> AllocationTraces;
+
 private:
   /// Get and set the stack size and heap size for the device. If not used, the
   /// plugin can implement the setters as no-op and setting the output
@@ -916,6 +947,11 @@ struct GenericDeviceTy : public DeviceAllocatorTy {
   UInt32Envar OMPX_InitialNumStreams;
   UInt32Envar OMPX_InitialNumEvents;
 
+  /// Environment variable to determine if stack traces for allocations and
+  /// deallocations are tracked.
+  BoolEnvar OMPX_TrackAllocationTraces =
+      BoolEnvar("OFFLOAD_TRACK_ALLOCATION_TRACES", false);
+
   /// Array of images loaded into the device. Images are automatically
   /// deallocated by the allocator.
   llvm::SmallVector<DeviceImageTy *> LoadedImages;

offload/plugins-nextgen/common/src/PluginInterface.cpp

@@ -14,6 +14,7 @@
 #include "Shared/Debug.h"
 #include "Shared/Environment.h"
 
+#include "ErrorReporting.h"
 #include "GlobalHandler.h"
 #include "JIT.h"
 #include "Utils/ELF.h"
@@ -30,6 +31,8 @@
 #include "llvm/Support/JSON.h"
 #include "llvm/Support/MathExtras.h"
 #include "llvm/Support/MemoryBuffer.h"
+#include "llvm/Support/Signals.h"
+#include "llvm/Support/raw_ostream.h"
 
 #include <cstdint>
 #include <limits>
@@ -1337,6 +1340,25 @@ Expected<void *> GenericDeviceTy::dataAlloc(int64_t Size, void *HostPtr,
     if (auto Err = PinnedAllocs.registerHostBuffer(Alloc, Alloc, Size))
       return std::move(Err);
 
+  // Keep track of the allocation stack if we track allocation traces.
+  if (OMPX_TrackAllocationTraces) {
+    std::string StackTrace;
+    llvm::raw_string_ostream OS(StackTrace);
+    llvm::sys::PrintStackTrace(OS);
+
+    AllocationTraceInfoTy *ATI = new AllocationTraceInfoTy();
+    ATI->AllocationTrace = std::move(StackTrace);
+    ATI->DevicePtr = Alloc;
+    ATI->HostPtr = HostPtr;
+    ATI->Size = Size;
+    ATI->Kind = Kind;
+
+    auto AllocationTraceMap = AllocationTraces.getExclusiveAccessor();
+    auto *&MapATI = (*AllocationTraceMap)[Alloc];
+    ATI->LastAllocationInfo = MapATI;
+    MapATI = ATI;
+  }
+
   return Alloc;
 }
 
@@ -1345,6 +1367,21 @@ Error GenericDeviceTy::dataDelete(void *TgtPtr, TargetAllocTy Kind) {
   if (Plugin.getRecordReplay().isRecordingOrReplaying())
     return Plugin::success();
 
+  // Keep track of the deallocation stack if we track allocation traces.
+  if (OMPX_TrackAllocationTraces) {
+    AllocationTraceInfoTy *ATI = nullptr;
+    {
+      auto AllocationTraceMap = AllocationTraces.getExclusiveAccessor();
+      ATI = (*AllocationTraceMap)[TgtPtr];
+    }
+
+    std::string StackTrace;
+    llvm::raw_string_ostream OS(StackTrace);
+    llvm::sys::PrintStackTrace(OS);
+
+    ErrorReporter::checkDeallocation(this, TgtPtr, Kind, ATI, StackTrace);
+  }
+
   int Res;
   switch (Kind) {
   case TARGET_ALLOC_DEFAULT:

offload/src/omptarget.cpp

@@ -462,7 +462,9 @@ void targetFreeExplicit(void *DevicePtr, int DeviceNum, int Kind,
     FATAL_MESSAGE(DeviceNum, "%s", toString(DeviceOrErr.takeError()).c_str());
 
   if (DeviceOrErr->deleteData(DevicePtr, Kind) == OFFLOAD_FAIL)
-    FATAL_MESSAGE(DeviceNum, "%s", "Failed to deallocate device ptr");
+    FATAL_MESSAGE(DeviceNum, "%s",
+                  "Failed to deallocate device ptr. Set "
+                  "OFFLOAD_TRACK_ALLOCATION_TRACES=1 to track allocations.");
 
   DP("omp_target_free deallocated device ptr\n");
 }