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📄 allocator_config.h(2.57 KB)
📄 atomic_helpers.h(4.16 KB)
📄 bytemap.h(992 B)
📄 checksum.cpp(2.52 KB)
📄 checksum.h(1.67 KB)
📄 chunk.h(5.83 KB)
📄 combined.h(40.99 KB)
📄 common.cpp(874 B)
📄 common.h(5.29 KB)
📄 crc32_hw.cpp(656 B)
📄 flags.cpp(2.09 KB)
📄 flags.h(975 B)
📄 flags.inc(2.41 KB)
📄 flags_parser.cpp(4.38 KB)
📄 flags_parser.h(1.23 KB)
📄 fuchsia.cpp(6.04 KB)
📄 fuchsia.h(695 B)
📁 fuzz
📁 include
📄 internal_defs.h(4.61 KB)
📄 linux.cpp(6.1 KB)
📄 linux.h(2.77 KB)
📄 list.h(4.95 KB)
📄 local_cache.h(5.21 KB)
📄 memtag.h(7.21 KB)
📄 mutex.h(1.69 KB)
📄 platform.h(2.03 KB)
📄 primary32.h(18.05 KB)
📄 primary64.h(17.3 KB)
📄 quarantine.h(9.64 KB)
📄 release.cpp(522 B)
📄 release.h(10.27 KB)
📄 report.cpp(6.62 KB)
📄 report.h(1.97 KB)
📄 secondary.h(13.22 KB)
📄 size_class_map.h(9.9 KB)
📄 stack_depot.h(4.47 KB)
📄 stats.h(2.77 KB)
📄 string_utils.cpp(7.93 KB)
📄 string_utils.h(1.05 KB)
📄 tsd.h(1.84 KB)
📄 tsd_exclusive.h(4.03 KB)
📄 tsd_shared.h(5.53 KB)
📄 vector.h(3.07 KB)
📄 wrappers_c.cpp(1.19 KB)
📄 wrappers_c.h(1.46 KB)
📄 wrappers_c.inc(8.6 KB)
📄 wrappers_c_bionic.cpp(2.23 KB)
📄 wrappers_c_checks.h(1.99 KB)
📄 wrappers_cpp.cpp(4.53 KB)

Editing: stack_depot.h

//===-- stack_depot.h -------------------------------------------*- 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 SCUDO_STACK_DEPOT_H_
#define SCUDO_STACK_DEPOT_H_

#include "atomic_helpers.h"
#include "mutex.h"

namespace scudo {

class MurMur2HashBuilder {
  static const u32 M = 0x5bd1e995;
  static const u32 Seed = 0x9747b28c;
  static const u32 R = 24;
  u32 H;

public:
  explicit MurMur2HashBuilder(u32 Init = 0) { H = Seed ^ Init; }
  void add(u32 K) {
    K *= M;
    K ^= K >> R;
    K *= M;
    H *= M;
    H ^= K;
  }
  u32 get() {
    u32 X = H;
    X ^= X >> 13;
    X *= M;
    X ^= X >> 15;
    return X;
  }
};

class StackDepot {
  HybridMutex RingEndMu;
  u32 RingEnd;

// This data structure stores a stack trace for each allocation and
  // deallocation when stack trace recording is enabled, that may be looked up
  // using a hash of the stack trace. The lower bits of the hash are an index
  // into the Tab array, which stores an index into the Ring array where the
  // stack traces are stored. As the name implies, Ring is a ring buffer, so a
  // stack trace may wrap around to the start of the array.
  //
  // Each stack trace in Ring is prefixed by a stack trace marker consisting of
  // a fixed 1 bit in bit 0 (this allows disambiguation between stack frames
  // and stack trace markers in the case where instruction pointers are 4-byte
  // aligned, as they are on arm64), the stack trace hash in bits 1-32, and the
  // size of the stack trace in bits 33-63.
  //
  // The insert() function is potentially racy in its accesses to the Tab and
  // Ring arrays, but find() is resilient to races in the sense that, barring
  // hash collisions, it will either return the correct stack trace or no stack
  // trace at all, even if two instances of insert() raced with one another.
  // This is achieved by re-checking the hash of the stack trace before
  // returning the trace.

#ifdef SCUDO_FUZZ
  // Use smaller table sizes for fuzzing in order to reduce input size.
  static const uptr TabBits = 4;
#else
  static const uptr TabBits = 16;
#endif
  static const uptr TabSize = 1 << TabBits;
  static const uptr TabMask = TabSize - 1;
  atomic_u32 Tab[TabSize];

#ifdef SCUDO_FUZZ
  static const uptr RingBits = 4;
#else
  static const uptr RingBits = 19;
#endif
  static const uptr RingSize = 1 << RingBits;
  static const uptr RingMask = RingSize - 1;
  atomic_u64 Ring[RingSize];

public:
  // Insert hash of the stack trace [Begin, End) into the stack depot, and
  // return the hash.
  u32 insert(uptr *Begin, uptr *End) {
    MurMur2HashBuilder B;
    for (uptr *I = Begin; I != End; ++I)
      B.add(u32(*I) >> 2);
    u32 Hash = B.get();

u32 Pos = Hash & TabMask;
    u32 RingPos = atomic_load_relaxed(&Tab[Pos]);
    u64 Entry = atomic_load_relaxed(&Ring[RingPos]);
    u64 Id = (u64(End - Begin) << 33) | (u64(Hash) << 1) | 1;
    if (Entry == Id)
      return Hash;

ScopedLock Lock(RingEndMu);
    RingPos = RingEnd;
    atomic_store_relaxed(&Tab[Pos], RingPos);
    atomic_store_relaxed(&Ring[RingPos], Id);
    for (uptr *I = Begin; I != End; ++I) {
      RingPos = (RingPos + 1) & RingMask;
      atomic_store_relaxed(&Ring[RingPos], *I);
    }
    RingEnd = (RingPos + 1) & RingMask;
    return Hash;
  }

// Look up a stack trace by hash. Returns true if successful. The trace may be
  // accessed via operator[] passing indexes between *RingPosPtr and
  // *RingPosPtr + *SizePtr.
  bool find(u32 Hash, uptr *RingPosPtr, uptr *SizePtr) const {
    u32 Pos = Hash & TabMask;
    u32 RingPos = atomic_load_relaxed(&Tab[Pos]);
    if (RingPos >= RingSize)
      return false;
    u64 Entry = atomic_load_relaxed(&Ring[RingPos]);
    u64 HashWithTagBit = (u64(Hash) << 1) | 1;
    if ((Entry & 0x1ffffffff) != HashWithTagBit)
      return false;
    u32 Size = u32(Entry >> 33);
    if (Size >= RingSize)
      return false;
    *RingPosPtr = (RingPos + 1) & RingMask;
    *SizePtr = Size;
    MurMur2HashBuilder B;
    for (uptr I = 0; I != Size; ++I) {
      RingPos = (RingPos + 1) & RingMask;
      B.add(u32(atomic_load_relaxed(&Ring[RingPos])) >> 2);
    }
    return B.get() == Hash;
  }

u64 operator[](uptr RingPos) const {
    return atomic_load_relaxed(&Ring[RingPos & RingMask]);
  }
};

} // namespace scudo

#endif // SCUDO_STACK_DEPOT_H_

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Editing: stack_depot.h

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