libsanitizer/sanitizer_common/sanitizer_stackdepot.cc

   1 //===-- sanitizer_stackdepot.cc -------------------------------------------===//
   2 //
   3 // This file is distributed under the University of Illinois Open Source
   4 // License. See LICENSE.TXT for details.
   5 //
   6 //===----------------------------------------------------------------------===//
   7 //
   8 // This file is shared between AddressSanitizer and ThreadSanitizer
   9 // run-time libraries.
  10 //===----------------------------------------------------------------------===//
  11
  12 #include "sanitizer_stackdepot.h"
  13 #include "sanitizer_common.h"
  14 #include "sanitizer_internal_defs.h"
  15 #include "sanitizer_mutex.h"
  16 #include "sanitizer_atomic.h"
  17
  18 namespace __sanitizer {
  19
  20 const int kTabSize = 1024 * 1024;  // Hash table size.
  21 const int kPartBits = 8;
  22 const int kPartShift = sizeof(u32) * 8 - kPartBits - 1;
  23 const int kPartCount = 1 << kPartBits;  // Number of subparts in the table.
  24 const int kPartSize = kTabSize / kPartCount;
  25 const int kMaxId = 1 << kPartShift;
  26
  27 struct StackDesc {
  28   StackDesc *link;
  29   u32 id;
  30   u32 hash;
  31   uptr size;
  32   uptr stack[1];  // [size]
  33 };
  34
  35 static struct {
  36   StaticSpinMutex mtx;  // Protects alloc of new blocks for region allocator.
  37   atomic_uintptr_t region_pos;  // Region allocator for StackDesc's.
  38   atomic_uintptr_t region_end;
  39   atomic_uintptr_t tab[kTabSize];  // Hash table of StackDesc's.
  40   atomic_uint32_t seq[kPartCount];  // Unique id generators.
  41 } depot;
  42
  43 static u32 hash(const uptr *stack, uptr size) {
  44   // murmur2
  45   const u32 m = 0x5bd1e995;
  46   const u32 seed = 0x9747b28c;
  47   const u32 r = 24;
  48   u32 h = seed ^ (size * sizeof(uptr));
  49   for (uptr i = 0; i < size; i++) {
  50     u32 k = stack[i];
  51     k *= m;
  52     k ^= k >> r;
  53     k *= m;
  54     h *= m;
  55     h ^= k;
  56   }
  57   h ^= h >> 13;
  58   h *= m;
  59   h ^= h >> 15;
  60   return h;
  61 }
  62
  63 static StackDesc *tryallocDesc(uptr memsz) {
  64   // Optimisic lock-free allocation, essentially try to bump the region ptr.
  65   for (;;) {
  66     uptr cmp = atomic_load(&depot.region_pos, memory_order_acquire);
  67     uptr end = atomic_load(&depot.region_end, memory_order_acquire);
  68     if (cmp == 0 || cmp + memsz > end)
  69       return 0;
  70     if (atomic_compare_exchange_weak(
  71         &depot.region_pos, &cmp, cmp + memsz,
  72         memory_order_acquire))
  73       return (StackDesc*)cmp;
  74   }
  75 }
  76
  77 static StackDesc *allocDesc(uptr size) {
  78   // Frist, try to allocate optimisitically.
  79   uptr memsz = sizeof(StackDesc) + (size - 1) * sizeof(uptr);
  80   StackDesc *s = tryallocDesc(memsz);
  81   if (s)
  82     return s;
  83   // If failed, lock, retry and alloc new superblock.
  84   SpinMutexLock l(&depot.mtx);
  85   for (;;) {
  86     s = tryallocDesc(memsz);
  87     if (s)
  88       return s;
  89     atomic_store(&depot.region_pos, 0, memory_order_relaxed);
  90     uptr allocsz = 64 * 1024;
  91     if (allocsz < memsz)
  92       allocsz = memsz;
  93     uptr mem = (uptr)MmapOrDie(allocsz, "stack depot");
  94     atomic_store(&depot.region_end, mem + allocsz, memory_order_release);
  95     atomic_store(&depot.region_pos, mem, memory_order_release);
  96   }
  97 }
  98
  99 static u32 find(StackDesc *s, const uptr *stack, uptr size, u32 hash) {
 100   // Searches linked list s for the stack, returns its id.
 101   for (; s; s = s->link) {
 102     if (s->hash == hash && s->size == size) {
 103       uptr i = 0;
 104       for (; i < size; i++) {
 105         if (stack[i] != s->stack[i])
 106           break;
 107       }
 108       if (i == size)
 109         return s->id;
 110     }
 111   }
 112   return 0;
 113 }
 114
 115 static StackDesc *lock(atomic_uintptr_t *p) {
 116   // Uses the pointer lsb as mutex.
 117   for (int i = 0;; i++) {
 118     uptr cmp = atomic_load(p, memory_order_relaxed);
 119     if ((cmp & 1) == 0
 120         && atomic_compare_exchange_weak(p, &cmp, cmp | 1,
 121                                         memory_order_acquire))
 122       return (StackDesc*)cmp;
 123     if (i < 10)
 124       proc_yield(10);
 125     else
 126       internal_sched_yield();
 127   }
 128 }
 129
 130 static void unlock(atomic_uintptr_t *p, StackDesc *s) {
 131   DCHECK_EQ((uptr)s & 1, 0);
 132   atomic_store(p, (uptr)s, memory_order_release);
 133 }
 134
 135 u32 StackDepotPut(const uptr *stack, uptr size) {
 136   if (stack == 0 || size == 0)
 137     return 0;
 138   uptr h = hash(stack, size);
 139   atomic_uintptr_t *p = &depot.tab[h % kTabSize];
 140   uptr v = atomic_load(p, memory_order_consume);
 141   StackDesc *s = (StackDesc*)(v & ~1);
 142   // First, try to find the existing stack.
 143   u32 id = find(s, stack, size, h);
 144   if (id)
 145     return id;
 146   // If failed, lock, retry and insert new.
 147   StackDesc *s2 = lock(p);
 148   if (s2 != s) {
 149     id = find(s2, stack, size, h);
 150     if (id) {
 151       unlock(p, s2);
 152       return id;
 153     }
 154   }
 155   uptr part = (h % kTabSize) / kPartSize;
 156   id = atomic_fetch_add(&depot.seq[part], 1, memory_order_relaxed) + 1;
 157   CHECK_LT(id, kMaxId);
 158   id |= part << kPartShift;
 159   CHECK_NE(id, 0);
 160   CHECK_EQ(id & (1u << 31), 0);
 161   s = allocDesc(size);
 162   s->id = id;
 163   s->hash = h;
 164   s->size = size;
 165   internal_memcpy(s->stack, stack, size * sizeof(uptr));
 166   s->link = s2;
 167   unlock(p, s);
 168   return id;
 169 }
 170
 171 const uptr *StackDepotGet(u32 id, uptr *size) {
 172   if (id == 0)
 173     return 0;
 174   CHECK_EQ(id & (1u << 31), 0);
 175   // High kPartBits contain part id, so we need to scan at most kPartSize lists.
 176   uptr part = id >> kPartShift;
 177   for (int i = 0; i != kPartSize; i++) {
 178     uptr idx = part * kPartSize + i;
 179     CHECK_LT(idx, kTabSize);
 180     atomic_uintptr_t *p = &depot.tab[idx];
 181     uptr v = atomic_load(p, memory_order_consume);
 182     StackDesc *s = (StackDesc*)(v & ~1);
 183     for (; s; s = s->link) {
 184       if (s->id == id) {
 185         *size = s->size;
 186         return s->stack;
 187       }
 188     }
 189   }
 190   *size = 0;
 191   return 0;
 192 }
 193
 194 }  // namespace __sanitizer