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// Copyright 2016 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "base/trace_event/category_registry.h"
#include <string.h>
#include <type_traits>
#include "base/atomicops.h"
#include "base/debug/leak_annotations.h"
#include "base/logging.h"
#include "base/third_party/dynamic_annotations/dynamic_annotations.h"
#include "base/trace_event/trace_category.h"
namespace base {
namespace trace_event {
namespace {
constexpr size_t kMaxCategories = 200;
const int kNumBuiltinCategories = 4;
// |g_categories| might end up causing creating dynamic initializers if not POD.
static_assert(std::is_pod<TraceCategory>::value, "TraceCategory must be POD");
// These entries must be kept consistent with the kCategory* consts below.
TraceCategory g_categories[kMaxCategories] = {
{0, 0, "tracing categories exhausted; must increase kMaxCategories"},
{0, 0, "tracing already shutdown"}, // See kCategoryAlreadyShutdown below.
{0, 0, "__metadata"}, // See kCategoryMetadata below.
{0, 0, "toplevel"}, // Warmup the toplevel category.
};
base::subtle::AtomicWord g_category_index = kNumBuiltinCategories;
bool IsValidCategoryPtr(const TraceCategory* category) {
// If any of these are hit, something has cached a corrupt category pointer.
uintptr_t ptr = reinterpret_cast<uintptr_t>(category);
return ptr % sizeof(void*) == 0 &&
ptr >= reinterpret_cast<uintptr_t>(&g_categories[0]) &&
ptr <= reinterpret_cast<uintptr_t>(&g_categories[kMaxCategories - 1]);
}
} // namespace
// static
TraceCategory* const CategoryRegistry::kCategoryExhausted = &g_categories[0];
TraceCategory* const CategoryRegistry::kCategoryAlreadyShutdown =
&g_categories[1];
TraceCategory* const CategoryRegistry::kCategoryMetadata = &g_categories[2];
// static
void CategoryRegistry::Initialize() {
// Trace is enabled or disabled on one thread while other threads are
// accessing the enabled flag. We don't care whether edge-case events are
// traced or not, so we allow races on the enabled flag to keep the trace
// macros fast.
for (size_t i = 0; i < kMaxCategories; ++i) {
ANNOTATE_BENIGN_RACE(g_categories[i].state_ptr(),
"trace_event category enabled");
// If this DCHECK is hit in a test it means that ResetForTesting() is not
// called and the categories state leaks between test fixtures.
DCHECK(!g_categories[i].is_enabled());
}
}
// static
void CategoryRegistry::ResetForTesting() {
// reset_for_testing clears up only the enabled state and filters. The
// categories themselves cannot be cleared up because the static pointers
// injected by the macros still point to them and cannot be reset.
for (size_t i = 0; i < kMaxCategories; ++i)
g_categories[i].reset_for_testing();
}
// static
TraceCategory* CategoryRegistry::GetCategoryByName(const char* category_name) {
DCHECK(!strchr(category_name, '"'))
<< "Category names may not contain double quote";
// The g_categories is append only, avoid using a lock for the fast path.
size_t category_index = base::subtle::Acquire_Load(&g_category_index);
// Search for pre-existing category group.
for (size_t i = 0; i < category_index; ++i) {
if (strcmp(g_categories[i].name(), category_name) == 0) {
return &g_categories[i];
}
}
return nullptr;
}
bool CategoryRegistry::GetOrCreateCategoryLocked(
const char* category_name,
CategoryInitializerFn category_initializer_fn,
TraceCategory** category) {
// This is the slow path: the lock is not held in the fastpath
// (GetCategoryByName), so more than one thread could have reached here trying
// to add the same category.
*category = GetCategoryByName(category_name);
if (*category)
return false;
// Create a new category.
size_t category_index = base::subtle::Acquire_Load(&g_category_index);
if (category_index >= kMaxCategories) {
NOTREACHED() << "must increase kMaxCategories";
*category = kCategoryExhausted;
return false;
}
// TODO(primiano): this strdup should be removed. The only documented reason
// for it was TraceWatchEvent, which is gone. However, something might have
// ended up relying on this. Needs some auditing before removal.
const char* category_name_copy = strdup(category_name);
ANNOTATE_LEAKING_OBJECT_PTR(category_name_copy);
*category = &g_categories[category_index];
DCHECK(!(*category)->is_valid());
DCHECK(!(*category)->is_enabled());
(*category)->set_name(category_name_copy);
category_initializer_fn(*category);
// Update the max index now.
base::subtle::Release_Store(&g_category_index, category_index + 1);
return true;
}
// static
const TraceCategory* CategoryRegistry::GetCategoryByStatePtr(
const uint8_t* category_state) {
const TraceCategory* category = TraceCategory::FromStatePtr(category_state);
DCHECK(IsValidCategoryPtr(category));
return category;
}
// static
bool CategoryRegistry::IsBuiltinCategory(const TraceCategory* category) {
DCHECK(IsValidCategoryPtr(category));
return category < &g_categories[kNumBuiltinCategories];
}
// static
CategoryRegistry::Range CategoryRegistry::GetAllCategories() {
// The |g_categories| array is append only. We have to only guarantee to
// not return an index to a category which is being initialized by
// GetOrCreateCategoryByName().
size_t category_index = base::subtle::Acquire_Load(&g_category_index);
return CategoryRegistry::Range(&g_categories[0],
&g_categories[category_index]);
}
} // namespace trace_event
} // namespace base
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