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
39using namespace __sanitizer;
40
41namespace __sancov {
42namespace {
43
44// TODO(mcgrathr): Move the constant into a header shared with other impls.
45constexpr u64 Magic64 = 0xC0BFFFFFFFFFFF64ULL;
46static_assert(SANITIZER_WORDSIZE == 64, "Fuchsia is always LP64");
47
48constexpr const char kSancovSinkName[] = "sancov";
49
50// Collects trace-pc guard coverage.
51// This class relies on zero-initialization.
52class TracePcGuardController final {
53 public:
54  constexpr TracePcGuardController() {}
55
56  // For each PC location being tracked, there is a u32 reserved in global
57  // data called the "guard".  At startup, we assign each guard slot a
58  // unique index into the big results array.  Later during runtime, the
59  // first call to TracePcGuard (below) will store the corresponding PC at
60  // that index in the array.  (Each later call with the same guard slot is
61  // presumed to be from the same PC.)  Then it clears the guard slot back
62  // to zero, which tells the compiler not to bother calling in again.  At
63  // the end of the run, we have a big array where each element is either
64  // zero or is a tracked PC location that was hit in the trace.
65
66  // This is called from global constructors.  Each translation unit has a
67  // contiguous array of guard slots, and a constructor that calls here
68  // with the bounds of its array.  Those constructors are allowed to call
69  // here more than once for the same array.  Usually all of these
70  // constructors run in the initial thread, but it's possible that a
71  // dlopen call on a secondary thread will run constructors that get here.
72  void InitTracePcGuard(u32 *start, u32 *end) {
73    if (end > start && *start == 0 && common_flags()->coverage) {
74      // Complete the setup before filling in any guards with indices.
75      // This avoids the possibility of code called from Setup reentering
76      // TracePcGuard.
77      u32 idx = Setup(end - start);
78      for (u32 *p = start; p < end; ++p) {
79        *p = idx++;
80      }
81    }
82  }
83
84  void TracePcGuard(u32 *guard, uptr pc) {
85    atomic_uint32_t *guard_ptr = reinterpret_cast<atomic_uint32_t *>(guard);
86    u32 idx = atomic_exchange(guard_ptr, 0, memory_order_relaxed);
87    if (idx > 0)
88      array_[idx] = pc;
89  }
90
91  void Dump() {
92    Lock locked(&setup_lock_);
93    if (array_) {
94      CHECK_NE(vmo_, ZX_HANDLE_INVALID);
95
96      // Publish the VMO to the system, where it can be collected and
97      // analyzed after this process exits.  This always consumes the VMO
98      // handle.  Any failure is just logged and not indicated to us.
99      __sanitizer_publish_data(kSancovSinkName, vmo_);
100      vmo_ = ZX_HANDLE_INVALID;
101
102      // This will route to __sanitizer_log_write, which will ensure that
103      // information about shared libraries is written out.  This message
104      // uses the `dumpfile` symbolizer markup element to highlight the
105      // dump.  See the explanation for this in:
106      // https://fuchsia.googlesource.com/zircon/+/master/docs/symbolizer_markup.md
107      Printf("SanitizerCoverage: " FORMAT_DUMPFILE " with up to %u PCs\n",
108             kSancovSinkName, vmo_name_, next_index_ - 1);
109    }
110  }
111
112 private:
113  // We map in the largest possible view into the VMO: one word
114  // for every possible 32-bit index value.  This avoids the need
115  // to change the mapping when increasing the size of the VMO.
116  // We can always spare the 32G of address space.
117  static constexpr size_t MappingSize = sizeof(uptr) << 32;
118
119  Mutex setup_lock_;
120  uptr *array_ = nullptr;
121  u32 next_index_ = 0;
122  zx_handle_t vmo_ = {};
123  char vmo_name_[ZX_MAX_NAME_LEN] = {};
124
125  size_t DataSize() const { return next_index_ * sizeof(uintptr_t); }
126
127  u32 Setup(u32 num_guards) {
128    Lock locked(&setup_lock_);
129    DCHECK(common_flags()->coverage);
130
131    if (next_index_ == 0) {
132      CHECK_EQ(vmo_, ZX_HANDLE_INVALID);
133      CHECK_EQ(array_, nullptr);
134
135      // The first sample goes at [1] to reserve [0] for the magic number.
136      next_index_ = 1 + num_guards;
137
138      zx_status_t status = _zx_vmo_create(DataSize(), ZX_VMO_RESIZABLE, &vmo_);
139      CHECK_EQ(status, ZX_OK);
140
141      // Give the VMO a name including our process KOID so it's easy to spot.
142      internal_snprintf(vmo_name_, sizeof(vmo_name_), "%s.%zu", kSancovSinkName,
143                        internal_getpid());
144      _zx_object_set_property(vmo_, ZX_PROP_NAME, vmo_name_,
145                              internal_strlen(vmo_name_));
146      uint64_t size = DataSize();
147      status = _zx_object_set_property(vmo_, ZX_PROP_VMO_CONTENT_SIZE, &size,
148                                       sizeof(size));
149      CHECK_EQ(status, ZX_OK);
150
151      // Map the largest possible view we might need into the VMO.  Later
152      // we might need to increase the VMO's size before we can use larger
153      // indices, but we'll never move the mapping address so we don't have
154      // any multi-thread synchronization issues with that.
155      uintptr_t mapping;
156      status =
157          _zx_vmar_map(_zx_vmar_root_self(), ZX_VM_PERM_READ | ZX_VM_PERM_WRITE,
158                       0, vmo_, 0, MappingSize, &mapping);
159      CHECK_EQ(status, ZX_OK);
160
161      // Hereafter other threads are free to start storing into
162      // elements [1, next_index_) of the big array.
163      array_ = reinterpret_cast<uptr *>(mapping);
164
165      // Store the magic number.
166      // Hereafter, the VMO serves as the contents of the '.sancov' file.
167      array_[0] = Magic64;
168
169      return 1;
170    } else {
171      // The VMO is already mapped in, but it's not big enough to use the
172      // new indices.  So increase the size to cover the new maximum index.
173
174      CHECK_NE(vmo_, ZX_HANDLE_INVALID);
175      CHECK_NE(array_, nullptr);
176
177      uint32_t first_index = next_index_;
178      next_index_ += num_guards;
179
180      zx_status_t status = _zx_vmo_set_size(vmo_, DataSize());
181      CHECK_EQ(status, ZX_OK);
182      uint64_t size = DataSize();
183      status = _zx_object_set_property(vmo_, ZX_PROP_VMO_CONTENT_SIZE, &size,
184                                       sizeof(size));
185      CHECK_EQ(status, ZX_OK);
186
187      return first_index;
188    }
189  }
190};
191
192static TracePcGuardController pc_guard_controller;
193
194}  // namespace
195}  // namespace __sancov
196
197namespace __sanitizer {
198void InitializeCoverage(bool enabled, const char *dir) {
199  CHECK_EQ(enabled, common_flags()->coverage);
200  CHECK_EQ(dir, common_flags()->coverage_dir);
201
202  static bool coverage_enabled = false;
203  if (!coverage_enabled) {
204    coverage_enabled = enabled;
205    Atexit(__sanitizer_cov_dump);
206    AddDieCallback(__sanitizer_cov_dump);
207  }
208}
209}  // namespace __sanitizer
210
211extern "C" {
212SANITIZER_INTERFACE_ATTRIBUTE void __sanitizer_dump_coverage(const uptr *pcs,
213                                                             uptr len) {
214  UNIMPLEMENTED();
215}
216
217SANITIZER_INTERFACE_WEAK_DEF(void, __sanitizer_cov_trace_pc_guard, u32 *guard) {
218  if (!*guard)
219    return;
220  __sancov::pc_guard_controller.TracePcGuard(guard, GET_CALLER_PC() - 1);
221}
222
223SANITIZER_INTERFACE_WEAK_DEF(void, __sanitizer_cov_trace_pc_guard_init,
224                             u32 *start, u32 *end) {
225  if (start == end || *start)
226    return;
227  __sancov::pc_guard_controller.InitTracePcGuard(start, end);
228}
229
230SANITIZER_INTERFACE_ATTRIBUTE void __sanitizer_dump_trace_pc_guard_coverage() {
231  __sancov::pc_guard_controller.Dump();
232}
233SANITIZER_INTERFACE_ATTRIBUTE void __sanitizer_cov_dump() {
234  __sanitizer_dump_trace_pc_guard_coverage();
235}
236// Default empty implementations (weak). Users should redefine them.
237SANITIZER_INTERFACE_WEAK_DEF(void, __sanitizer_cov_trace_cmp, void) {}
238SANITIZER_INTERFACE_WEAK_DEF(void, __sanitizer_cov_trace_cmp1, void) {}
239SANITIZER_INTERFACE_WEAK_DEF(void, __sanitizer_cov_trace_cmp2, void) {}
240SANITIZER_INTERFACE_WEAK_DEF(void, __sanitizer_cov_trace_cmp4, void) {}
241SANITIZER_INTERFACE_WEAK_DEF(void, __sanitizer_cov_trace_cmp8, void) {}
242SANITIZER_INTERFACE_WEAK_DEF(void, __sanitizer_cov_trace_const_cmp1, void) {}
243SANITIZER_INTERFACE_WEAK_DEF(void, __sanitizer_cov_trace_const_cmp2, void) {}
244SANITIZER_INTERFACE_WEAK_DEF(void, __sanitizer_cov_trace_const_cmp4, void) {}
245SANITIZER_INTERFACE_WEAK_DEF(void, __sanitizer_cov_trace_const_cmp8, void) {}
246SANITIZER_INTERFACE_WEAK_DEF(void, __sanitizer_cov_trace_switch, void) {}
247SANITIZER_INTERFACE_WEAK_DEF(void, __sanitizer_cov_trace_div4, void) {}
248SANITIZER_INTERFACE_WEAK_DEF(void, __sanitizer_cov_trace_div8, void) {}
249SANITIZER_INTERFACE_WEAK_DEF(void, __sanitizer_cov_trace_gep, void) {}
250SANITIZER_INTERFACE_WEAK_DEF(void, __sanitizer_cov_trace_pc_indir, void) {}
251}  // extern "C"
252
253#endif  // !SANITIZER_FUCHSIA
254