1 /* 2 * Copyright (C) 2020 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 #ifndef SRC_KALLSYMS_LAZY_KERNEL_SYMBOLIZER_H_ 18 #define SRC_KALLSYMS_LAZY_KERNEL_SYMBOLIZER_H_ 19 20 #include <memory> 21 22 #include "perfetto/ext/base/thread_checker.h" 23 24 namespace perfetto { 25 26 class KernelSymbolMap; 27 28 // This class is a wrapper around KernelSymbolMap. It serves two purposes: 29 // 1. Deals with /proc/kallsyms reads and temporary lowering of kptr_restrict. 30 // KernelSymbolMap is just a parser and doesn't do I/O. 31 // 2. Allows to share the same KernelSymbolMap instance across several clients 32 // and tear it down when tracing stops. 33 // 34 // LazyKernelSymbolizer is owned by the (one) FtraceController. FtraceController 35 // handles LazyKernelSymbolizer pointers to N CpuReader-s (one per CPU). In 36 // this way all CpuReader instances can share the same symbol map instance. 37 // The object being shared is LazyKernelSymbolizer, which is cheap and always 38 // valid. LazyKernelSymbolizer may or may not contain a valid symbol map. 39 class LazyKernelSymbolizer { 40 public: 41 // Constructs an empty instance. Does NOT load any symbols upon construction. 42 // Loading and parsing happens on the first GetOrCreateKernelSymbolMap() call. 43 LazyKernelSymbolizer(); 44 ~LazyKernelSymbolizer(); 45 46 // Returns |instance_|, creating it if doesn't exist or was destroyed. 47 KernelSymbolMap* GetOrCreateKernelSymbolMap(); 48 is_valid()49 bool is_valid() const { return !!symbol_map_; } 50 51 // Destroys the |symbol_map_| freeing up memory. A further call to 52 // GetOrCreateKernelSymbolMap() will create it again. 53 void Destroy(); 54 55 // Exposed for testing. 56 static bool CanReadKernelSymbolAddresses( 57 const char* ksyms_path_for_testing = nullptr); 58 59 private: 60 std::unique_ptr<KernelSymbolMap> symbol_map_; 61 PERFETTO_THREAD_CHECKER(thread_checker_) 62 }; 63 64 } // namespace perfetto 65 66 #endif // SRC_KALLSYMS_LAZY_KERNEL_SYMBOLIZER_H_ 67