libsanitizer/hwasan/hwasan_thread_list.h

   1 //===-- hwasan_thread_list.h ------------------------------------*- C++ -*-===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8 //
   9 // This file is a part of HWAddressSanitizer.
  10 //
  11 //===----------------------------------------------------------------------===//
  12
  13 // HwasanThreadList is a registry for live threads, as well as an allocator for
  14 // HwasanThread objects and their stack history ring buffers. There are
  15 // constraints on memory layout of the shadow region and CompactRingBuffer that
  16 // are part of the ABI contract between compiler-rt and llvm.
  17 //
  18 // * Start of the shadow memory region is aligned to 2**kShadowBaseAlignment.
  19 // * All stack ring buffers are located within (2**kShadowBaseAlignment)
  20 // sized region below and adjacent to the shadow region.
  21 // * Each ring buffer has a size of (2**N)*4096 where N is in [0, 8), and is
  22 // aligned to twice its size. The value of N can be different for each buffer.
  23 //
  24 // These constrains guarantee that, given an address A of any element of the
  25 // ring buffer,
  26 //     A_next = (A + sizeof(uptr)) & ~((1 << (N + 13)) - 1)
  27 //   is the address of the next element of that ring buffer (with wrap-around).
  28 // And, with K = kShadowBaseAlignment,
  29 //     S = (A | ((1 << K) - 1)) + 1
  30 //   (align up to kShadowBaseAlignment) is the start of the shadow region.
  31 //
  32 // These calculations are used in compiler instrumentation to update the ring
  33 // buffer and obtain the base address of shadow using only two inputs: address
  34 // of the current element of the ring buffer, and N (i.e. size of the ring
  35 // buffer). Since the value of N is very limited, we pack both inputs into a
  36 // single thread-local word as
  37 //   (1 << (N + 56)) | A
  38 // See the implementation of class CompactRingBuffer, which is what is stored in
  39 // said thread-local word.
  40 //
  41 // Note the unusual way of aligning up the address of the shadow:
  42 //   (A | ((1 << K) - 1)) + 1
  43 // It is only correct if A is not already equal to the shadow base address, but
  44 // it saves 2 instructions on AArch64.
  45
  46 #include "hwasan.h"
  47 #include "hwasan_allocator.h"
  48 #include "hwasan_flags.h"
  49 #include "hwasan_thread.h"
  50
  51 #include "sanitizer_common/sanitizer_placement_new.h"
  52
  53 namespace __hwasan {
  54
  55 static uptr RingBufferSize() {
  56   uptr desired_bytes = flags()->stack_history_size * sizeof(uptr);
  57   // FIXME: increase the limit to 8 once this bug is fixed:
  58   // https://bugs.llvm.org/show_bug.cgi?id=39030
  59   for (int shift = 1; shift < 7; ++shift) {
  60     uptr size = 4096 * (1ULL << shift);
  61     if (size >= desired_bytes)
  62       return size;
  63   }
  64   Printf("stack history size too large: %d\n", flags()->stack_history_size);
  65   CHECK(0);
  66   return 0;
  67 }
  68
  69 struct ThreadStats {
  70   uptr n_live_threads;
  71   uptr total_stack_size;
  72 };
  73
  74 class HwasanThreadList {
  75  public:
  76   HwasanThreadList(uptr storage, uptr size)
  77       : free_space_(storage), free_space_end_(storage + size) {
  78     // [storage, storage + size) is used as a vector of
  79     // thread_alloc_size_-sized, ring_buffer_size_*2-aligned elements.
  80     // Each element contains
  81     // * a ring buffer at offset 0,
  82     // * a Thread object at offset ring_buffer_size_.
  83     ring_buffer_size_ = RingBufferSize();
  84     thread_alloc_size_ =
  85         RoundUpTo(ring_buffer_size_ + sizeof(Thread), ring_buffer_size_ * 2);
  86   }
  87
  88   Thread *CreateCurrentThread(const Thread::InitState *state = nullptr) {
  89     Thread *t = nullptr;
  90     {
  91       SpinMutexLock l(&free_list_mutex_);
  92       if (!free_list_.empty()) {
  93         t = free_list_.back();
  94         free_list_.pop_back();
  95       }
  96     }
  97     if (t) {
  98       uptr start = (uptr)t - ring_buffer_size_;
  99       internal_memset((void *)start, 0, ring_buffer_size_ + sizeof(Thread));
 100     } else {
 101       t = AllocThread();
 102     }
 103     {
 104       SpinMutexLock l(&live_list_mutex_);
 105       live_list_.push_back(t);
 106     }
 107     t->Init((uptr)t - ring_buffer_size_, ring_buffer_size_, state);
 108     AddThreadStats(t);
 109     return t;
 110   }
 111
 112   void DontNeedThread(Thread *t) {
 113     uptr start = (uptr)t - ring_buffer_size_;
 114     ReleaseMemoryPagesToOS(start, start + thread_alloc_size_);
 115   }
 116
 117   void RemoveThreadFromLiveList(Thread *t) {
 118     SpinMutexLock l(&live_list_mutex_);
 119     for (Thread *&t2 : live_list_)
 120       if (t2 == t) {
 121         // To remove t2, copy the last element of the list in t2's position, and
 122         // pop_back(). This works even if t2 is itself the last element.
 123         t2 = live_list_.back();
 124         live_list_.pop_back();
 125         return;
 126       }
 127     CHECK(0 && "thread not found in live list");
 128   }
 129
 130   void ReleaseThread(Thread *t) {
 131     RemoveThreadStats(t);
 132     t->Destroy();
 133     DontNeedThread(t);
 134     RemoveThreadFromLiveList(t);
 135     SpinMutexLock l(&free_list_mutex_);
 136     free_list_.push_back(t);
 137   }
 138
 139   Thread *GetThreadByBufferAddress(uptr p) {
 140     return (Thread *)(RoundDownTo(p, ring_buffer_size_ * 2) +
 141                       ring_buffer_size_);
 142   }
 143
 144   uptr MemoryUsedPerThread() {
 145     uptr res = sizeof(Thread) + ring_buffer_size_;
 146     if (auto sz = flags()->heap_history_size)
 147       res += HeapAllocationsRingBuffer::SizeInBytes(sz);
 148     return res;
 149   }
 150
 151   template <class CB>
 152   void VisitAllLiveThreads(CB cb) {
 153     SpinMutexLock l(&live_list_mutex_);
 154     for (Thread *t : live_list_) cb(t);
 155   }
 156
 157   void AddThreadStats(Thread *t) {
 158     SpinMutexLock l(&stats_mutex_);
 159     stats_.n_live_threads++;
 160     stats_.total_stack_size += t->stack_size();
 161   }
 162
 163   void RemoveThreadStats(Thread *t) {
 164     SpinMutexLock l(&stats_mutex_);
 165     stats_.n_live_threads--;
 166     stats_.total_stack_size -= t->stack_size();
 167   }
 168
 169   ThreadStats GetThreadStats() {
 170     SpinMutexLock l(&stats_mutex_);
 171     return stats_;
 172   }
 173
 174   uptr GetRingBufferSize() const { return ring_buffer_size_; }
 175
 176  private:
 177   Thread *AllocThread() {
 178     SpinMutexLock l(&free_space_mutex_);
 179     uptr align = ring_buffer_size_ * 2;
 180     CHECK(IsAligned(free_space_, align));
 181     Thread *t = (Thread *)(free_space_ + ring_buffer_size_);
 182     free_space_ += thread_alloc_size_;
 183     CHECK(free_space_ <= free_space_end_ && "out of thread memory");
 184     return t;
 185   }
 186
 187   SpinMutex free_space_mutex_;
 188   uptr free_space_;
 189   uptr free_space_end_;
 190   uptr ring_buffer_size_;
 191   uptr thread_alloc_size_;
 192
 193   SpinMutex free_list_mutex_;
 194   InternalMmapVector<Thread *> free_list_;
 195   SpinMutex live_list_mutex_;
 196   InternalMmapVector<Thread *> live_list_;
 197
 198   ThreadStats stats_;
 199   SpinMutex stats_mutex_;
 200 };
 201
 202 void InitThreadList(uptr storage, uptr size);
 203 HwasanThreadList &hwasanThreadList();
 204
 205 } // namespace __hwasan