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+//===-- sanitizer_coverage_fuchsia.cpp ------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// Sanitizer Coverage Controller for Trace PC Guard, Fuchsia-specific version.
+//
+// This Fuchsia-specific implementation uses the same basic scheme and the
+// same simple '.sancov' file format as the generic implementation. The
+// difference is that we just produce a single blob of output for the whole
+// program, not a separate one per DSO. We do not sort the PC table and do
+// not prune the zeros, so the resulting file is always as large as it
+// would be to report 100% coverage. Implicit tracing information about
+// the address ranges of DSOs allows offline tools to split the one big
+// blob into separate files that the 'sancov' tool can understand.
+//
+// Unlike the traditional implementation that uses an atexit hook to write
+// out data files at the end, the results on Fuchsia do not go into a file
+// per se. The 'coverage_dir' option is ignored. Instead, they are stored
+// directly into a shared memory object (a Zircon VMO). At exit, that VMO
+// is handed over to a system service that's responsible for getting the
+// data out to somewhere that it can be fed into the sancov tool (where and
+// how is not our problem).
+
+#include "sanitizer_platform.h"
+#if SANITIZER_FUCHSIA
+#include "sanitizer_atomic.h"
+#include "sanitizer_common.h"
+#include "sanitizer_internal_defs.h"
+#include "sanitizer_symbolizer_fuchsia.h"
+
+#include <zircon/process.h>
+#include <zircon/sanitizer.h>
+#include <zircon/syscalls.h>
+
+using namespace __sanitizer;
+
+namespace __sancov {
+namespace {
+
+// TODO(mcgrathr): Move the constant into a header shared with other impls.
+constexpr u64 Magic64 = 0xC0BFFFFFFFFFFF64ULL;
+static_assert(SANITIZER_WORDSIZE == 64, "Fuchsia is always LP64");
+
+constexpr const char kSancovSinkName[] = "sancov";
+
+// Collects trace-pc guard coverage.
+// This class relies on zero-initialization.
+class TracePcGuardController final {
+ public:
+ // For each PC location being tracked, there is a u32 reserved in global
+ // data called the "guard". At startup, we assign each guard slot a
+ // unique index into the big results array. Later during runtime, the
+ // first call to TracePcGuard (below) will store the corresponding PC at
+ // that index in the array. (Each later call with the same guard slot is
+ // presumed to be from the same PC.) Then it clears the guard slot back
+ // to zero, which tells the compiler not to bother calling in again. At
+ // the end of the run, we have a big array where each element is either
+ // zero or is a tracked PC location that was hit in the trace.
+
+ // This is called from global constructors. Each translation unit has a
+ // contiguous array of guard slots, and a constructor that calls here
+ // with the bounds of its array. Those constructors are allowed to call
+ // here more than once for the same array. Usually all of these
+ // constructors run in the initial thread, but it's possible that a
+ // dlopen call on a secondary thread will run constructors that get here.
+ void InitTracePcGuard(u32 *start, u32 *end) {
+ if (end > start && *start == 0 && common_flags()->coverage) {
+ // Complete the setup before filling in any guards with indices.
+ // This avoids the possibility of code called from Setup reentering
+ // TracePcGuard.
+ u32 idx = Setup(end - start);
+ for (u32 *p = start; p < end; ++p) {
+ *p = idx++;
+ }
+ }
+ }
+
+ void TracePcGuard(u32 *guard, uptr pc) {
+ atomic_uint32_t *guard_ptr = reinterpret_cast<atomic_uint32_t *>(guard);
+ u32 idx = atomic_exchange(guard_ptr, 0, memory_order_relaxed);
+ if (idx > 0) array_[idx] = pc;
+ }
+
+ void Dump() {
+ BlockingMutexLock locked(&setup_lock_);
+ if (array_) {
+ CHECK_NE(vmo_, ZX_HANDLE_INVALID);
+
+ // Publish the VMO to the system, where it can be collected and
+ // analyzed after this process exits. This always consumes the VMO
+ // handle. Any failure is just logged and not indicated to us.
+ __sanitizer_publish_data(kSancovSinkName, vmo_);
+ vmo_ = ZX_HANDLE_INVALID;
+
+ // This will route to __sanitizer_log_write, which will ensure that
+ // information about shared libraries is written out. This message
+ // uses the `dumpfile` symbolizer markup element to highlight the
+ // dump. See the explanation for this in:
+ // https://fuchsia.googlesource.com/zircon/+/master/docs/symbolizer_markup.md
+ Printf("SanitizerCoverage: " FORMAT_DUMPFILE " with up to %u PCs\n",
+ kSancovSinkName, vmo_name_, next_index_ - 1);
+ }
+ }
+
+ private:
+ // We map in the largest possible view into the VMO: one word
+ // for every possible 32-bit index value. This avoids the need
+ // to change the mapping when increasing the size of the VMO.
+ // We can always spare the 32G of address space.
+ static constexpr size_t MappingSize = sizeof(uptr) << 32;
+
+ BlockingMutex setup_lock_ = BlockingMutex(LINKER_INITIALIZED);
+ uptr *array_ = nullptr;
+ u32 next_index_ = 0;
+ zx_handle_t vmo_ = {};
+ char vmo_name_[ZX_MAX_NAME_LEN] = {};
+
+ size_t DataSize() const { return next_index_ * sizeof(uintptr_t); }
+
+ u32 Setup(u32 num_guards) {
+ BlockingMutexLock locked(&setup_lock_);
+ DCHECK(common_flags()->coverage);
+
+ if (next_index_ == 0) {
+ CHECK_EQ(vmo_, ZX_HANDLE_INVALID);
+ CHECK_EQ(array_, nullptr);
+
+ // The first sample goes at [1] to reserve [0] for the magic number.
+ next_index_ = 1 + num_guards;
+
+ zx_status_t status = _zx_vmo_create(DataSize(), ZX_VMO_RESIZABLE, &vmo_);
+ CHECK_EQ(status, ZX_OK);
+
+ // Give the VMO a name including our process KOID so it's easy to spot.
+ internal_snprintf(vmo_name_, sizeof(vmo_name_), "%s.%zu", kSancovSinkName,
+ internal_getpid());
+ _zx_object_set_property(vmo_, ZX_PROP_NAME, vmo_name_,
+ internal_strlen(vmo_name_));
+
+ // Map the largest possible view we might need into the VMO. Later
+ // we might need to increase the VMO's size before we can use larger
+ // indices, but we'll never move the mapping address so we don't have
+ // any multi-thread synchronization issues with that.
+ uintptr_t mapping;
+ status =
+ _zx_vmar_map(_zx_vmar_root_self(), ZX_VM_PERM_READ | ZX_VM_PERM_WRITE,
+ 0, vmo_, 0, MappingSize, &mapping);
+ CHECK_EQ(status, ZX_OK);
+
+ // Hereafter other threads are free to start storing into
+ // elements [1, next_index_) of the big array.
+ array_ = reinterpret_cast<uptr *>(mapping);
+
+ // Store the magic number.
+ // Hereafter, the VMO serves as the contents of the '.sancov' file.
+ array_[0] = Magic64;
+
+ return 1;
+ } else {
+ // The VMO is already mapped in, but it's not big enough to use the
+ // new indices. So increase the size to cover the new maximum index.
+
+ CHECK_NE(vmo_, ZX_HANDLE_INVALID);
+ CHECK_NE(array_, nullptr);
+
+ uint32_t first_index = next_index_;
+ next_index_ += num_guards;
+
+ zx_status_t status = _zx_vmo_set_size(vmo_, DataSize());
+ CHECK_EQ(status, ZX_OK);
+
+ return first_index;
+ }
+ }
+};
+
+static TracePcGuardController pc_guard_controller;
+
+} // namespace
+} // namespace __sancov
+
+namespace __sanitizer {
+void InitializeCoverage(bool enabled, const char *dir) {
+ CHECK_EQ(enabled, common_flags()->coverage);
+ CHECK_EQ(dir, common_flags()->coverage_dir);
+
+ static bool coverage_enabled = false;
+ if (!coverage_enabled) {
+ coverage_enabled = enabled;
+ Atexit(__sanitizer_cov_dump);
+ AddDieCallback(__sanitizer_cov_dump);
+ }
+}
+} // namespace __sanitizer
+
+extern "C" {
+SANITIZER_INTERFACE_ATTRIBUTE void __sanitizer_dump_coverage(const uptr *pcs,
+ uptr len) {
+ UNIMPLEMENTED();
+}
+
+SANITIZER_INTERFACE_WEAK_DEF(void, __sanitizer_cov_trace_pc_guard, u32 *guard) {
+ if (!*guard) return;
+ __sancov::pc_guard_controller.TracePcGuard(guard, GET_CALLER_PC() - 1);
+}
+
+SANITIZER_INTERFACE_WEAK_DEF(void, __sanitizer_cov_trace_pc_guard_init,
+ u32 *start, u32 *end) {
+ if (start == end || *start) return;
+ __sancov::pc_guard_controller.InitTracePcGuard(start, end);
+}
+
+SANITIZER_INTERFACE_ATTRIBUTE void __sanitizer_dump_trace_pc_guard_coverage() {
+ __sancov::pc_guard_controller.Dump();
+}
+SANITIZER_INTERFACE_ATTRIBUTE void __sanitizer_cov_dump() {
+ __sanitizer_dump_trace_pc_guard_coverage();
+}
+// Default empty implementations (weak). Users should redefine them.
+SANITIZER_INTERFACE_WEAK_DEF(void, __sanitizer_cov_trace_cmp, void) {}
+SANITIZER_INTERFACE_WEAK_DEF(void, __sanitizer_cov_trace_cmp1, void) {}
+SANITIZER_INTERFACE_WEAK_DEF(void, __sanitizer_cov_trace_cmp2, void) {}
+SANITIZER_INTERFACE_WEAK_DEF(void, __sanitizer_cov_trace_cmp4, void) {}
+SANITIZER_INTERFACE_WEAK_DEF(void, __sanitizer_cov_trace_cmp8, void) {}
+SANITIZER_INTERFACE_WEAK_DEF(void, __sanitizer_cov_trace_const_cmp1, void) {}
+SANITIZER_INTERFACE_WEAK_DEF(void, __sanitizer_cov_trace_const_cmp2, void) {}
+SANITIZER_INTERFACE_WEAK_DEF(void, __sanitizer_cov_trace_const_cmp4, void) {}
+SANITIZER_INTERFACE_WEAK_DEF(void, __sanitizer_cov_trace_const_cmp8, void) {}
+SANITIZER_INTERFACE_WEAK_DEF(void, __sanitizer_cov_trace_switch, void) {}
+SANITIZER_INTERFACE_WEAK_DEF(void, __sanitizer_cov_trace_div4, void) {}
+SANITIZER_INTERFACE_WEAK_DEF(void, __sanitizer_cov_trace_div8, void) {}
+SANITIZER_INTERFACE_WEAK_DEF(void, __sanitizer_cov_trace_gep, void) {}
+SANITIZER_INTERFACE_WEAK_DEF(void, __sanitizer_cov_trace_pc_indir, void) {}
+} // extern "C"
+
+#endif // !SANITIZER_FUCHSIA