1 //===-- xray_init.cpp -------------------------------------------*- C++ -*-===// 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 // This file is a part of XRay, a dynamic runtime instrumentation system. 10 // 11 // XRay initialisation logic. 12 //===----------------------------------------------------------------------===// 13 14 #include <fcntl.h> 15 #include <strings.h> 16 #include <unistd.h> 17 18 #include "sanitizer_common/sanitizer_common.h" 19 #include "xray_defs.h" 20 #include "xray_flags.h" 21 #include "xray_interface_internal.h" 22 23 extern "C" { 24 void __xray_init(); 25 extern const XRaySledEntry __start_xray_instr_map[] __attribute__((weak)); 26 extern const XRaySledEntry __stop_xray_instr_map[] __attribute__((weak)); 27 extern const XRayFunctionSledIndex __start_xray_fn_idx[] __attribute__((weak)); 28 extern const XRayFunctionSledIndex __stop_xray_fn_idx[] __attribute__((weak)); 29 30 #if SANITIZER_MAC 31 // HACK: This is a temporary workaround to make XRay build on 32 // Darwin, but it will probably not work at runtime. 33 const XRaySledEntry __start_xray_instr_map[] = {}; 34 extern const XRaySledEntry __stop_xray_instr_map[] = {}; 35 extern const XRayFunctionSledIndex __start_xray_fn_idx[] = {}; 36 extern const XRayFunctionSledIndex __stop_xray_fn_idx[] = {}; 37 #endif 38 } 39 40 using namespace __xray; 41 42 // When set to 'true' this means the XRay runtime has been initialised. We use 43 // the weak symbols defined above (__start_xray_inst_map and 44 // __stop_xray_instr_map) to initialise the instrumentation map that XRay uses 45 // for runtime patching/unpatching of instrumentation points. 46 // 47 // FIXME: Support DSO instrumentation maps too. The current solution only works 48 // for statically linked executables. 49 atomic_uint8_t XRayInitialized{0}; 50 51 // This should always be updated before XRayInitialized is updated. 52 SpinMutex XRayInstrMapMutex; 53 XRaySledMap XRayInstrMap; 54 55 // Global flag to determine whether the flags have been initialized. 56 atomic_uint8_t XRayFlagsInitialized{0}; 57 58 // A mutex to allow only one thread to initialize the XRay data structures. 59 SpinMutex XRayInitMutex; 60 61 // __xray_init() will do the actual loading of the current process' memory map 62 // and then proceed to look for the .xray_instr_map section/segment. 63 void __xray_init() XRAY_NEVER_INSTRUMENT { 64 SpinMutexLock Guard(&XRayInitMutex); 65 // Short-circuit if we've already initialized XRay before. 66 if (atomic_load(&XRayInitialized, memory_order_acquire)) 67 return; 68 69 // XRAY is not compatible with PaX MPROTECT 70 CheckMPROTECT(); 71 72 if (!atomic_load(&XRayFlagsInitialized, memory_order_acquire)) { 73 initializeFlags(); 74 atomic_store(&XRayFlagsInitialized, true, memory_order_release); 75 } 76 77 if (__start_xray_instr_map == nullptr) { 78 if (Verbosity()) 79 Report("XRay instrumentation map missing. Not initializing XRay.\n"); 80 return; 81 } 82 83 { 84 SpinMutexLock Guard(&XRayInstrMapMutex); 85 XRayInstrMap.Sleds = __start_xray_instr_map; 86 XRayInstrMap.Entries = __stop_xray_instr_map - __start_xray_instr_map; 87 if (__start_xray_fn_idx != nullptr) { 88 XRayInstrMap.SledsIndex = __start_xray_fn_idx; 89 XRayInstrMap.Functions = __stop_xray_fn_idx - __start_xray_fn_idx; 90 } else { 91 size_t CountFunctions = 0; 92 uint64_t LastFnAddr = 0; 93 94 for (std::size_t I = 0; I < XRayInstrMap.Entries; I++) { 95 const auto &Sled = XRayInstrMap.Sleds[I]; 96 const auto Function = Sled.function(); 97 if (Function != LastFnAddr) { 98 CountFunctions++; 99 LastFnAddr = Function; 100 } 101 } 102 103 XRayInstrMap.Functions = CountFunctions; 104 } 105 } 106 atomic_store(&XRayInitialized, true, memory_order_release); 107 108 #ifndef XRAY_NO_PREINIT 109 if (flags()->patch_premain) 110 __xray_patch(); 111 #endif 112 } 113 114 // FIXME: Make check-xray tests work on FreeBSD without 115 // SANITIZER_CAN_USE_PREINIT_ARRAY. 116 // See sanitizer_internal_defs.h where the macro is defined. 117 // Calling unresolved PLT functions in .preinit_array can lead to deadlock on 118 // FreeBSD but here it seems benign. 119 #if !defined(XRAY_NO_PREINIT) && \ 120 (SANITIZER_CAN_USE_PREINIT_ARRAY || SANITIZER_FREEBSD) 121 // Only add the preinit array initialization if the sanitizers can. 122 __attribute__((section(".preinit_array"), 123 used)) void (*__local_xray_preinit)(void) = __xray_init; 124 #else 125 // If we cannot use the .preinit_array section, we should instead use dynamic 126 // initialisation. 127 __attribute__ ((constructor (0))) 128 static void __local_xray_dyninit() { 129 __xray_init(); 130 } 131 #endif 132