1 //===-- xray_init.cc --------------------------------------------*- C++ -*-===//
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 // This file is a part of XRay, a dynamic runtime instrumentation system.
12 // XRay initialisation logic.
13 //===----------------------------------------------------------------------===//
19 #include "sanitizer_common/sanitizer_common.h"
20 #include "xray_defs.h"
21 #include "xray_flags.h"
22 #include "xray_interface_internal.h"
26 extern const XRaySledEntry __start_xray_instr_map[] __attribute__((weak));
27 extern const XRaySledEntry __stop_xray_instr_map[] __attribute__((weak));
28 extern const XRayFunctionSledIndex __start_xray_fn_idx[] __attribute__((weak));
29 extern const XRayFunctionSledIndex __stop_xray_fn_idx[] __attribute__((weak));
32 // HACK: This is a temporary workaround to make XRay build on
33 // Darwin, but it will probably not work at runtime.
34 const XRaySledEntry __start_xray_instr_map[] = {};
35 extern const XRaySledEntry __stop_xray_instr_map[] = {};
36 extern const XRayFunctionSledIndex __start_xray_fn_idx[] = {};
37 extern const XRayFunctionSledIndex __stop_xray_fn_idx[] = {};
41 using namespace __xray;
43 // When set to 'true' this means the XRay runtime has been initialised. We use
44 // the weak symbols defined above (__start_xray_inst_map and
45 // __stop_xray_instr_map) to initialise the instrumentation map that XRay uses
46 // for runtime patching/unpatching of instrumentation points.
48 // FIXME: Support DSO instrumentation maps too. The current solution only works
49 // for statically linked executables.
50 atomic_uint8_t XRayInitialized{0};
52 // This should always be updated before XRayInitialized is updated.
53 SpinMutex XRayInstrMapMutex;
54 XRaySledMap XRayInstrMap;
56 // Global flag to determine whether the flags have been initialized.
57 atomic_uint8_t XRayFlagsInitialized{0};
59 // A mutex to allow only one thread to initialize the XRay data structures.
60 SpinMutex XRayInitMutex;
62 // __xray_init() will do the actual loading of the current process' memory map
63 // and then proceed to look for the .xray_instr_map section/segment.
64 void __xray_init() XRAY_NEVER_INSTRUMENT {
65 SpinMutexLock Guard(&XRayInitMutex);
66 // Short-circuit if we've already initialized XRay before.
67 if (atomic_load(&XRayInitialized, memory_order_acquire))
70 // XRAY is not compatible with PaX MPROTECT
73 if (!atomic_load(&XRayFlagsInitialized, memory_order_acquire)) {
75 atomic_store(&XRayFlagsInitialized, true, memory_order_release);
78 if (__start_xray_instr_map == nullptr) {
80 Report("XRay instrumentation map missing. Not initializing XRay.\n");
85 SpinMutexLock Guard(&XRayInstrMapMutex);
86 XRayInstrMap.Sleds = __start_xray_instr_map;
87 XRayInstrMap.Entries = __stop_xray_instr_map - __start_xray_instr_map;
88 XRayInstrMap.SledsIndex = __start_xray_fn_idx;
89 XRayInstrMap.Functions = __stop_xray_fn_idx - __start_xray_fn_idx;
91 atomic_store(&XRayInitialized, true, memory_order_release);
93 #ifndef XRAY_NO_PREINIT
94 if (flags()->patch_premain)
99 // FIXME: Make check-xray tests work on FreeBSD without
100 // SANITIZER_CAN_USE_PREINIT_ARRAY.
101 // See sanitizer_internal_defs.h where the macro is defined.
102 // Calling unresolved PLT functions in .preinit_array can lead to deadlock on
103 // FreeBSD but here it seems benign.
104 #if !defined(XRAY_NO_PREINIT) && \
105 (SANITIZER_CAN_USE_PREINIT_ARRAY || SANITIZER_FREEBSD)
106 // Only add the preinit array initialization if the sanitizers can.
107 __attribute__((section(".preinit_array"),
108 used)) void (*__local_xray_preinit)(void) = __xray_init;
110 // If we cannot use the .preinit_array section, we should instead use dynamic
112 __attribute__ ((constructor (0)))
113 static void __local_xray_dyninit() {