libsanitizer/sanitizer_common/sanitizer_coverage_fuchsia.cpp

   1 //===-- sanitizer_coverage_fuchsia.cpp ------------------------------------===//
   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 // Sanitizer Coverage Controller for Trace PC Guard, Fuchsia-specific version.
  10 //
  11 // This Fuchsia-specific implementation uses the same basic scheme and the
  12 // same simple '.sancov' file format as the generic implementation.  The
  13 // difference is that we just produce a single blob of output for the whole
  14 // program, not a separate one per DSO.  We do not sort the PC table and do
  15 // not prune the zeros, so the resulting file is always as large as it
  16 // would be to report 100% coverage.  Implicit tracing information about
  17 // the address ranges of DSOs allows offline tools to split the one big
  18 // blob into separate files that the 'sancov' tool can understand.
  19 //
  20 // Unlike the traditional implementation that uses an atexit hook to write
  21 // out data files at the end, the results on Fuchsia do not go into a file
  22 // per se.  The 'coverage_dir' option is ignored.  Instead, they are stored
  23 // directly into a shared memory object (a Zircon VMO).  At exit, that VMO
  24 // is handed over to a system service that's responsible for getting the
  25 // data out to somewhere that it can be fed into the sancov tool (where and
  26 // how is not our problem).
  27
  28 #include "sanitizer_platform.h"
  29 #if SANITIZER_FUCHSIA
  30 #include <zircon/process.h>
  31 #include <zircon/sanitizer.h>
  32 #include <zircon/syscalls.h>
  33
  34 #include "sanitizer_atomic.h"
  35 #include "sanitizer_common.h"
  36 #include "sanitizer_internal_defs.h"
  37 #include "sanitizer_symbolizer_fuchsia.h"
  38
  39 using namespace __sanitizer;
  40
  41 namespace __sancov {
  42 namespace {
  43
  44 // TODO(mcgrathr): Move the constant into a header shared with other impls.
  45 constexpr u64 Magic64 = 0xC0BFFFFFFFFFFF64ULL;
  46 static_assert(SANITIZER_WORDSIZE == 64, "Fuchsia is always LP64");
  47
  48 constexpr const char kSancovSinkName[] = "sancov";
  49
  50 // Collects trace-pc guard coverage.
  51 // This class relies on zero-initialization.
  52 class TracePcGuardController final {
  53  public:
  54   // For each PC location being tracked, there is a u32 reserved in global
  55   // data called the "guard".  At startup, we assign each guard slot a
  56   // unique index into the big results array.  Later during runtime, the
  57   // first call to TracePcGuard (below) will store the corresponding PC at
  58   // that index in the array.  (Each later call with the same guard slot is
  59   // presumed to be from the same PC.)  Then it clears the guard slot back
  60   // to zero, which tells the compiler not to bother calling in again.  At
  61   // the end of the run, we have a big array where each element is either
  62   // zero or is a tracked PC location that was hit in the trace.
  63
  64   // This is called from global constructors.  Each translation unit has a
  65   // contiguous array of guard slots, and a constructor that calls here
  66   // with the bounds of its array.  Those constructors are allowed to call
  67   // here more than once for the same array.  Usually all of these
  68   // constructors run in the initial thread, but it's possible that a
  69   // dlopen call on a secondary thread will run constructors that get here.
  70   void InitTracePcGuard(u32 *start, u32 *end) {
  71     if (end > start && *start == 0 && common_flags()->coverage) {
  72       // Complete the setup before filling in any guards with indices.
  73       // This avoids the possibility of code called from Setup reentering
  74       // TracePcGuard.
  75       u32 idx = Setup(end - start);
  76       for (u32 *p = start; p < end; ++p) {
  77         *p = idx++;
  78       }
  79     }
  80   }
  81
  82   void TracePcGuard(u32 *guard, uptr pc) {
  83     atomic_uint32_t *guard_ptr = reinterpret_cast<atomic_uint32_t *>(guard);
  84     u32 idx = atomic_exchange(guard_ptr, 0, memory_order_relaxed);
  85     if (idx > 0)
  86       array_[idx] = pc;
  87   }
  88
  89   void Dump() {
  90     BlockingMutexLock locked(&setup_lock_);
  91     if (array_) {
  92       CHECK_NE(vmo_, ZX_HANDLE_INVALID);
  93
  94       // Publish the VMO to the system, where it can be collected and
  95       // analyzed after this process exits.  This always consumes the VMO
  96       // handle.  Any failure is just logged and not indicated to us.
  97       __sanitizer_publish_data(kSancovSinkName, vmo_);
  98       vmo_ = ZX_HANDLE_INVALID;
  99
 100       // This will route to __sanitizer_log_write, which will ensure that
 101       // information about shared libraries is written out.  This message
 102       // uses the `dumpfile` symbolizer markup element to highlight the
 103       // dump.  See the explanation for this in:
 104       // https://fuchsia.googlesource.com/zircon/+/master/docs/symbolizer_markup.md
 105       Printf("SanitizerCoverage: " FORMAT_DUMPFILE " with up to %u PCs\n",
 106              kSancovSinkName, vmo_name_, next_index_ - 1);
 107     }
 108   }
 109
 110  private:
 111   // We map in the largest possible view into the VMO: one word
 112   // for every possible 32-bit index value.  This avoids the need
 113   // to change the mapping when increasing the size of the VMO.
 114   // We can always spare the 32G of address space.
 115   static constexpr size_t MappingSize = sizeof(uptr) << 32;
 116
 117   BlockingMutex setup_lock_ = BlockingMutex(LINKER_INITIALIZED);
 118   uptr *array_ = nullptr;
 119   u32 next_index_ = 0;
 120   zx_handle_t vmo_ = {};
 121   char vmo_name_[ZX_MAX_NAME_LEN] = {};
 122
 123   size_t DataSize() const { return next_index_ * sizeof(uintptr_t); }
 124
 125   u32 Setup(u32 num_guards) {
 126     BlockingMutexLock locked(&setup_lock_);
 127     DCHECK(common_flags()->coverage);
 128
 129     if (next_index_ == 0) {
 130       CHECK_EQ(vmo_, ZX_HANDLE_INVALID);
 131       CHECK_EQ(array_, nullptr);
 132
 133       // The first sample goes at [1] to reserve [0] for the magic number.
 134       next_index_ = 1 + num_guards;
 135
 136       zx_status_t status = _zx_vmo_create(DataSize(), ZX_VMO_RESIZABLE, &vmo_);
 137       CHECK_EQ(status, ZX_OK);
 138
 139       // Give the VMO a name including our process KOID so it's easy to spot.
 140       internal_snprintf(vmo_name_, sizeof(vmo_name_), "%s.%zu", kSancovSinkName,
 141                         internal_getpid());
 142       _zx_object_set_property(vmo_, ZX_PROP_NAME, vmo_name_,
 143                               internal_strlen(vmo_name_));
 144       uint64_t size = DataSize();
 145       status = _zx_object_set_property(vmo_, ZX_PROP_VMO_CONTENT_SIZE, &size,
 146                                        sizeof(size));
 147       CHECK_EQ(status, ZX_OK);
 148
 149       // Map the largest possible view we might need into the VMO.  Later
 150       // we might need to increase the VMO's size before we can use larger
 151       // indices, but we'll never move the mapping address so we don't have
 152       // any multi-thread synchronization issues with that.
 153       uintptr_t mapping;
 154       status =
 155           _zx_vmar_map(_zx_vmar_root_self(), ZX_VM_PERM_READ | ZX_VM_PERM_WRITE,
 156                        0, vmo_, 0, MappingSize, &mapping);
 157       CHECK_EQ(status, ZX_OK);
 158
 159       // Hereafter other threads are free to start storing into
 160       // elements [1, next_index_) of the big array.
 161       array_ = reinterpret_cast<uptr *>(mapping);
 162
 163       // Store the magic number.
 164       // Hereafter, the VMO serves as the contents of the '.sancov' file.
 165       array_[0] = Magic64;
 166
 167       return 1;
 168     } else {
 169       // The VMO is already mapped in, but it's not big enough to use the
 170       // new indices.  So increase the size to cover the new maximum index.
 171
 172       CHECK_NE(vmo_, ZX_HANDLE_INVALID);
 173       CHECK_NE(array_, nullptr);
 174
 175       uint32_t first_index = next_index_;
 176       next_index_ += num_guards;
 177
 178       zx_status_t status = _zx_vmo_set_size(vmo_, DataSize());
 179       CHECK_EQ(status, ZX_OK);
 180       uint64_t size = DataSize();
 181       status = _zx_object_set_property(vmo_, ZX_PROP_VMO_CONTENT_SIZE, &size,
 182                                        sizeof(size));
 183       CHECK_EQ(status, ZX_OK);
 184
 185       return first_index;
 186     }
 187   }
 188 };
 189
 190 static TracePcGuardController pc_guard_controller;
 191
 192 }  // namespace
 193 }  // namespace __sancov
 194
 195 namespace __sanitizer {
 196 void InitializeCoverage(bool enabled, const char *dir) {
 197   CHECK_EQ(enabled, common_flags()->coverage);
 198   CHECK_EQ(dir, common_flags()->coverage_dir);
 199
 200   static bool coverage_enabled = false;
 201   if (!coverage_enabled) {
 202     coverage_enabled = enabled;
 203     Atexit(__sanitizer_cov_dump);
 204     AddDieCallback(__sanitizer_cov_dump);
 205   }
 206 }
 207 }  // namespace __sanitizer
 208
 209 extern "C" {
 210 SANITIZER_INTERFACE_ATTRIBUTE void __sanitizer_dump_coverage(const uptr *pcs,
 211                                                              uptr len) {
 212   UNIMPLEMENTED();
 213 }
 214
 215 SANITIZER_INTERFACE_WEAK_DEF(void, __sanitizer_cov_trace_pc_guard, u32 *guard) {
 216   if (!*guard)
 217     return;
 218   __sancov::pc_guard_controller.TracePcGuard(guard, GET_CALLER_PC() - 1);
 219 }
 220
 221 SANITIZER_INTERFACE_WEAK_DEF(void, __sanitizer_cov_trace_pc_guard_init,
 222                              u32 *start, u32 *end) {
 223   if (start == end || *start)
 224     return;
 225   __sancov::pc_guard_controller.InitTracePcGuard(start, end);
 226 }
 227
 228 SANITIZER_INTERFACE_ATTRIBUTE void __sanitizer_dump_trace_pc_guard_coverage() {
 229   __sancov::pc_guard_controller.Dump();
 230 }
 231 SANITIZER_INTERFACE_ATTRIBUTE void __sanitizer_cov_dump() {
 232   __sanitizer_dump_trace_pc_guard_coverage();
 233 }
 234 // Default empty implementations (weak). Users should redefine them.
 235 SANITIZER_INTERFACE_WEAK_DEF(void, __sanitizer_cov_trace_cmp, void) {}
 236 SANITIZER_INTERFACE_WEAK_DEF(void, __sanitizer_cov_trace_cmp1, void) {}
 237 SANITIZER_INTERFACE_WEAK_DEF(void, __sanitizer_cov_trace_cmp2, void) {}
 238 SANITIZER_INTERFACE_WEAK_DEF(void, __sanitizer_cov_trace_cmp4, void) {}
 239 SANITIZER_INTERFACE_WEAK_DEF(void, __sanitizer_cov_trace_cmp8, void) {}
 240 SANITIZER_INTERFACE_WEAK_DEF(void, __sanitizer_cov_trace_const_cmp1, void) {}
 241 SANITIZER_INTERFACE_WEAK_DEF(void, __sanitizer_cov_trace_const_cmp2, void) {}
 242 SANITIZER_INTERFACE_WEAK_DEF(void, __sanitizer_cov_trace_const_cmp4, void) {}
 243 SANITIZER_INTERFACE_WEAK_DEF(void, __sanitizer_cov_trace_const_cmp8, void) {}
 244 SANITIZER_INTERFACE_WEAK_DEF(void, __sanitizer_cov_trace_switch, void) {}
 245 SANITIZER_INTERFACE_WEAK_DEF(void, __sanitizer_cov_trace_div4, void) {}
 246 SANITIZER_INTERFACE_WEAK_DEF(void, __sanitizer_cov_trace_div8, void) {}
 247 SANITIZER_INTERFACE_WEAK_DEF(void, __sanitizer_cov_trace_gep, void) {}
 248 SANITIZER_INTERFACE_WEAK_DEF(void, __sanitizer_cov_trace_pc_indir, void) {}
 249 }  // extern "C"
 250
 251 #endif  // !SANITIZER_FUCHSIA