1 //===-- hwasan_thread_list.h ------------------------------------*- C++ -*-===//
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
7 //===----------------------------------------------------------------------===//
9 // This file is a part of HWAddressSanitizer.
11 //===----------------------------------------------------------------------===//
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.
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.
24 // These constrains guarantee that, given an address A of any element of the
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.
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.
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.
47 #include "hwasan_allocator.h"
48 #include "hwasan_flags.h"
49 #include "hwasan_thread.h"
51 #include "sanitizer_common/sanitizer_placement_new.h"
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)
64 Printf("stack history size too large: %d\n", flags()->stack_history_size);
69 struct ThreadListHead {
72 ThreadListHead() : list_(nullptr) {}
74 void Push(Thread *t) {
86 void Remove(Thread *t) {
87 Thread **cur = &list_;
88 while (*cur != t) cur = &(*cur)->next_;
89 CHECK(*cur && "thread not found");
105 uptr total_stack_size;
108 class HwasanThreadList {
110 HwasanThreadList(uptr storage, uptr size)
111 : free_space_(storage), free_space_end_(storage + size) {
112 // [storage, storage + size) is used as a vector of
113 // thread_alloc_size_-sized, ring_buffer_size_*2-aligned elements.
114 // Each element contains
115 // * a ring buffer at offset 0,
116 // * a Thread object at offset ring_buffer_size_.
117 ring_buffer_size_ = RingBufferSize();
119 RoundUpTo(ring_buffer_size_ + sizeof(Thread), ring_buffer_size_ * 2);
122 Thread *CreateCurrentThread() {
125 SpinMutexLock l(&list_mutex_);
126 t = free_list_.Pop();
128 uptr start = (uptr)t - ring_buffer_size_;
129 internal_memset((void *)start, 0, ring_buffer_size_ + sizeof(Thread));
135 t->Init((uptr)t - ring_buffer_size_, ring_buffer_size_);
140 void DontNeedThread(Thread *t) {
141 uptr start = (uptr)t - ring_buffer_size_;
142 ReleaseMemoryPagesToOS(start, start + thread_alloc_size_);
145 void ReleaseThread(Thread *t) {
146 RemoveThreadStats(t);
148 SpinMutexLock l(&list_mutex_);
149 live_list_.Remove(t);
154 Thread *GetThreadByBufferAddress(uptr p) {
155 return (Thread *)(RoundDownTo(p, ring_buffer_size_ * 2) +
159 uptr MemoryUsedPerThread() {
160 uptr res = sizeof(Thread) + ring_buffer_size_;
161 if (auto sz = flags()->heap_history_size)
162 res += HeapAllocationsRingBuffer::SizeInBytes(sz);
167 void VisitAllLiveThreads(CB cb) {
168 SpinMutexLock l(&list_mutex_);
169 live_list_.ForEach(cb);
172 void AddThreadStats(Thread *t) {
173 SpinMutexLock l(&stats_mutex_);
174 stats_.n_live_threads++;
175 stats_.total_stack_size += t->stack_size();
178 void RemoveThreadStats(Thread *t) {
179 SpinMutexLock l(&stats_mutex_);
180 stats_.n_live_threads--;
181 stats_.total_stack_size -= t->stack_size();
184 ThreadStats GetThreadStats() {
185 SpinMutexLock l(&stats_mutex_);
190 Thread *AllocThread() {
191 uptr align = ring_buffer_size_ * 2;
192 CHECK(IsAligned(free_space_, align));
193 Thread *t = (Thread *)(free_space_ + ring_buffer_size_);
194 free_space_ += thread_alloc_size_;
195 CHECK(free_space_ <= free_space_end_ && "out of thread memory");
200 uptr free_space_end_;
201 uptr ring_buffer_size_;
202 uptr thread_alloc_size_;
204 ThreadListHead free_list_;
205 ThreadListHead live_list_;
206 SpinMutex list_mutex_;
209 SpinMutex stats_mutex_;
212 void InitThreadList(uptr storage, uptr size);
213 HwasanThreadList &hwasanThreadList();