1 //===-- sanitizer_coverage_fuchsia.cc -------------------------------------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // Sanitizer Coverage Controller for Trace PC Guard, Fuchsia-specific version.
12 // This Fuchsia-specific implementation uses the same basic scheme and the
13 // same simple '.sancov' file format as the generic implementation. The
14 // difference is that we just produce a single blob of output for the whole
15 // program, not a separate one per DSO. We do not sort the PC table and do
16 // not prune the zeros, so the resulting file is always as large as it
17 // would be to report 100% coverage. Implicit tracing information about
18 // the address ranges of DSOs allows offline tools to split the one big
19 // blob into separate files that the 'sancov' tool can understand.
21 // Unlike the traditional implementation that uses an atexit hook to write
22 // out data files at the end, the results on Fuchsia do not go into a file
23 // per se. The 'coverage_dir' option is ignored. Instead, they are stored
24 // directly into a shared memory object (a Zircon VMO). At exit, that VMO
25 // is handed over to a system service that's responsible for getting the
26 // data out to somewhere that it can be fed into the sancov tool (where and
27 // how is not our problem).
29 #include "sanitizer_platform.h"
31 #include "sanitizer_atomic.h"
32 #include "sanitizer_common.h"
33 #include "sanitizer_internal_defs.h"
34 #include "sanitizer_symbolizer_fuchsia.h"
36 #include <zircon/process.h>
37 #include <zircon/sanitizer.h>
38 #include <zircon/syscalls.h>
40 using namespace __sanitizer; // NOLINT
45 // TODO(mcgrathr): Move the constant into a header shared with other impls.
46 constexpr u64 Magic64 = 0xC0BFFFFFFFFFFF64ULL;
47 static_assert(SANITIZER_WORDSIZE == 64, "Fuchsia is always LP64");
49 constexpr const char kSancovSinkName[] = "sancov";
51 // Collects trace-pc guard coverage.
52 // This class relies on zero-initialization.
53 class TracePcGuardController final {
55 // For each PC location being tracked, there is a u32 reserved in global
56 // data called the "guard". At startup, we assign each guard slot a
57 // unique index into the big results array. Later during runtime, the
58 // first call to TracePcGuard (below) will store the corresponding PC at
59 // that index in the array. (Each later call with the same guard slot is
60 // presumed to be from the same PC.) Then it clears the guard slot back
61 // to zero, which tells the compiler not to bother calling in again. At
62 // the end of the run, we have a big array where each element is either
63 // zero or is a tracked PC location that was hit in the trace.
65 // This is called from global constructors. Each translation unit has a
66 // contiguous array of guard slots, and a constructor that calls here
67 // with the bounds of its array. Those constructors are allowed to call
68 // here more than once for the same array. Usually all of these
69 // constructors run in the initial thread, but it's possible that a
70 // dlopen call on a secondary thread will run constructors that get here.
71 void InitTracePcGuard(u32 *start, u32 *end) {
72 if (end > start && *start == 0 && common_flags()->coverage) {
73 // Complete the setup before filling in any guards with indices.
74 // This avoids the possibility of code called from Setup reentering
76 u32 idx = Setup(end - start);
77 for (u32 *p = start; p < end; ++p) {
83 void TracePcGuard(u32 *guard, uptr pc) {
84 atomic_uint32_t *guard_ptr = reinterpret_cast<atomic_uint32_t *>(guard);
85 u32 idx = atomic_exchange(guard_ptr, 0, memory_order_relaxed);
86 if (idx > 0) array_[idx] = pc;
90 BlockingMutexLock locked(&setup_lock_);
92 CHECK_NE(vmo_, ZX_HANDLE_INVALID);
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;
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);
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;
117 BlockingMutex setup_lock_ = BlockingMutex(LINKER_INITIALIZED);
118 uptr *array_ = nullptr;
120 zx_handle_t vmo_ = {};
121 char vmo_name_[ZX_MAX_NAME_LEN] = {};
123 size_t DataSize() const { return next_index_ * sizeof(uintptr_t); }
125 u32 Setup(u32 num_guards) {
126 BlockingMutexLock locked(&setup_lock_);
127 DCHECK(common_flags()->coverage);
129 if (next_index_ == 0) {
130 CHECK_EQ(vmo_, ZX_HANDLE_INVALID);
131 CHECK_EQ(array_, nullptr);
133 // The first sample goes at [1] to reserve [0] for the magic number.
134 next_index_ = 1 + num_guards;
136 zx_status_t status = _zx_vmo_create(DataSize(), 0, &vmo_);
137 CHECK_EQ(status, ZX_OK);
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,
142 _zx_object_set_property(vmo_, ZX_PROP_NAME, vmo_name_,
143 internal_strlen(vmo_name_));
145 // Map the largest possible view we might need into the VMO. Later
146 // we might need to increase the VMO's size before we can use larger
147 // indices, but we'll never move the mapping address so we don't have
148 // any multi-thread synchronization issues with that.
151 _zx_vmar_map(_zx_vmar_root_self(), ZX_VM_PERM_READ | ZX_VM_PERM_WRITE,
152 0, vmo_, 0, MappingSize, &mapping);
153 CHECK_EQ(status, ZX_OK);
155 // Hereafter other threads are free to start storing into
156 // elements [1, next_index_) of the big array.
157 array_ = reinterpret_cast<uptr *>(mapping);
159 // Store the magic number.
160 // Hereafter, the VMO serves as the contents of the '.sancov' file.
165 // The VMO is already mapped in, but it's not big enough to use the
166 // new indices. So increase the size to cover the new maximum index.
168 CHECK_NE(vmo_, ZX_HANDLE_INVALID);
169 CHECK_NE(array_, nullptr);
171 uint32_t first_index = next_index_;
172 next_index_ += num_guards;
174 zx_status_t status = _zx_vmo_set_size(vmo_, DataSize());
175 CHECK_EQ(status, ZX_OK);
182 static TracePcGuardController pc_guard_controller;
185 } // namespace __sancov
187 namespace __sanitizer {
188 void InitializeCoverage(bool enabled, const char *dir) {
189 CHECK_EQ(enabled, common_flags()->coverage);
190 CHECK_EQ(dir, common_flags()->coverage_dir);
192 static bool coverage_enabled = false;
193 if (!coverage_enabled) {
194 coverage_enabled = enabled;
195 Atexit(__sanitizer_cov_dump);
196 AddDieCallback(__sanitizer_cov_dump);
199 } // namespace __sanitizer
202 SANITIZER_INTERFACE_ATTRIBUTE void __sanitizer_dump_coverage( // NOLINT
203 const uptr *pcs, uptr len) {
207 SANITIZER_INTERFACE_WEAK_DEF(void, __sanitizer_cov_trace_pc_guard, u32 *guard) {
209 __sancov::pc_guard_controller.TracePcGuard(guard, GET_CALLER_PC() - 1);
212 SANITIZER_INTERFACE_WEAK_DEF(void, __sanitizer_cov_trace_pc_guard_init,
213 u32 *start, u32 *end) {
214 if (start == end || *start) return;
215 __sancov::pc_guard_controller.InitTracePcGuard(start, end);
218 SANITIZER_INTERFACE_ATTRIBUTE void __sanitizer_dump_trace_pc_guard_coverage() {
219 __sancov::pc_guard_controller.Dump();
221 SANITIZER_INTERFACE_ATTRIBUTE void __sanitizer_cov_dump() {
222 __sanitizer_dump_trace_pc_guard_coverage();
224 // Default empty implementations (weak). Users should redefine them.
225 SANITIZER_INTERFACE_WEAK_DEF(void, __sanitizer_cov_trace_cmp, void) {}
226 SANITIZER_INTERFACE_WEAK_DEF(void, __sanitizer_cov_trace_cmp1, void) {}
227 SANITIZER_INTERFACE_WEAK_DEF(void, __sanitizer_cov_trace_cmp2, void) {}
228 SANITIZER_INTERFACE_WEAK_DEF(void, __sanitizer_cov_trace_cmp4, void) {}
229 SANITIZER_INTERFACE_WEAK_DEF(void, __sanitizer_cov_trace_cmp8, void) {}
230 SANITIZER_INTERFACE_WEAK_DEF(void, __sanitizer_cov_trace_const_cmp1, void) {}
231 SANITIZER_INTERFACE_WEAK_DEF(void, __sanitizer_cov_trace_const_cmp2, void) {}
232 SANITIZER_INTERFACE_WEAK_DEF(void, __sanitizer_cov_trace_const_cmp4, void) {}
233 SANITIZER_INTERFACE_WEAK_DEF(void, __sanitizer_cov_trace_const_cmp8, void) {}
234 SANITIZER_INTERFACE_WEAK_DEF(void, __sanitizer_cov_trace_switch, void) {}
235 SANITIZER_INTERFACE_WEAK_DEF(void, __sanitizer_cov_trace_div4, void) {}
236 SANITIZER_INTERFACE_WEAK_DEF(void, __sanitizer_cov_trace_div8, void) {}
237 SANITIZER_INTERFACE_WEAK_DEF(void, __sanitizer_cov_trace_gep, void) {}
238 SANITIZER_INTERFACE_WEAK_DEF(void, __sanitizer_cov_trace_pc_indir, void) {}
241 #endif // !SANITIZER_FUCHSIA