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 using namespace __xray;
34 // When set to 'true' this means the XRay runtime has been initialised. We use
35 // the weak symbols defined above (__start_xray_inst_map and
36 // __stop_xray_instr_map) to initialise the instrumentation map that XRay uses
37 // for runtime patching/unpatching of instrumentation points.
39 // FIXME: Support DSO instrumentation maps too. The current solution only works
40 // for statically linked executables.
41 atomic_uint8_t XRayInitialized{0};
43 // This should always be updated before XRayInitialized is updated.
44 SpinMutex XRayInstrMapMutex;
45 XRaySledMap XRayInstrMap;
47 // Global flag to determine whether the flags have been initialized.
48 atomic_uint8_t XRayFlagsInitialized{0};
50 // A mutex to allow only one thread to initialize the XRay data structures.
51 SpinMutex XRayInitMutex;
53 // __xray_init() will do the actual loading of the current process' memory map
54 // and then proceed to look for the .xray_instr_map section/segment.
55 void __xray_init() XRAY_NEVER_INSTRUMENT {
56 SpinMutexLock Guard(&XRayInitMutex);
57 // Short-circuit if we've already initialized XRay before.
58 if (atomic_load(&XRayInitialized, memory_order_acquire))
61 if (!atomic_load(&XRayFlagsInitialized, memory_order_acquire)) {
63 atomic_store(&XRayFlagsInitialized, true, memory_order_release);
66 if (__start_xray_instr_map == nullptr) {
68 Report("XRay instrumentation map missing. Not initializing XRay.\n");
73 SpinMutexLock Guard(&XRayInstrMapMutex);
74 XRayInstrMap.Sleds = __start_xray_instr_map;
75 XRayInstrMap.Entries = __stop_xray_instr_map - __start_xray_instr_map;
76 XRayInstrMap.SledsIndex = __start_xray_fn_idx;
77 XRayInstrMap.Functions = __stop_xray_fn_idx - __start_xray_fn_idx;
79 atomic_store(&XRayInitialized, true, memory_order_release);
81 #ifndef XRAY_NO_PREINIT
82 if (flags()->patch_premain)
87 // FIXME: Make check-xray tests work on FreeBSD without
88 // SANITIZER_CAN_USE_PREINIT_ARRAY.
89 // See sanitizer_internal_defs.h where the macro is defined.
90 // Calling unresolved PLT functions in .preinit_array can lead to deadlock on
91 // FreeBSD but here it seems benign.
92 #if !defined(XRAY_NO_PREINIT) && \
93 (SANITIZER_CAN_USE_PREINIT_ARRAY || SANITIZER_FREEBSD)
94 // Only add the preinit array initialization if the sanitizers can.
95 __attribute__((section(".preinit_array"),
96 used)) void (*__local_xray_preinit)(void) = __xray_init;
98 // If we cannot use the .preinit_array section, we should instead use dynamic
100 static bool UNUSED __local_xray_dyninit = [] {