1//===-- xray_init.cc --------------------------------------------*- C++ -*-===//
2//
3//                     The LLVM Compiler Infrastructure
4//
5// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9//
10// This file is a part of XRay, a dynamic runtime instrumentation system.
11//
12// XRay initialisation logic.
13//===----------------------------------------------------------------------===//
14
15#include <fcntl.h>
16#include <strings.h>
17#include <unistd.h>
18
19#include "sanitizer_common/sanitizer_common.h"
20#include "xray_defs.h"
21#include "xray_flags.h"
22#include "xray_interface_internal.h"
23
24extern "C" {
25void __xray_init();
26extern const XRaySledEntry __start_xray_instr_map[] __attribute__((weak));
27extern const XRaySledEntry __stop_xray_instr_map[] __attribute__((weak));
28extern const XRayFunctionSledIndex __start_xray_fn_idx[] __attribute__((weak));
29extern const XRayFunctionSledIndex __stop_xray_fn_idx[] __attribute__((weak));
30
31#if SANITIZER_MAC
32// HACK: This is a temporary workaround to make XRay build on
33// Darwin, but it will probably not work at runtime.
34const XRaySledEntry __start_xray_instr_map[] = {};
35extern const XRaySledEntry __stop_xray_instr_map[] = {};
36extern const XRayFunctionSledIndex __start_xray_fn_idx[] = {};
37extern const XRayFunctionSledIndex __stop_xray_fn_idx[] = {};
38#endif
39}
40
41using namespace __xray;
42
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.
47//
48// FIXME: Support DSO instrumentation maps too. The current solution only works
49// for statically linked executables.
50atomic_uint8_t XRayInitialized{0};
51
52// This should always be updated before XRayInitialized is updated.
53SpinMutex XRayInstrMapMutex;
54XRaySledMap XRayInstrMap;
55
56// Global flag to determine whether the flags have been initialized.
57atomic_uint8_t XRayFlagsInitialized{0};
58
59// A mutex to allow only one thread to initialize the XRay data structures.
60SpinMutex XRayInitMutex;
61
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.
64void __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))
68    return;
69
70  // XRAY is not compatible with PaX MPROTECT
71  CheckMPROTECT();
72
73  if (!atomic_load(&XRayFlagsInitialized, memory_order_acquire)) {
74    initializeFlags();
75    atomic_store(&XRayFlagsInitialized, true, memory_order_release);
76  }
77
78  if (__start_xray_instr_map == nullptr) {
79    if (Verbosity())
80      Report("XRay instrumentation map missing. Not initializing XRay.\n");
81    return;
82  }
83
84  {
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;
90  }
91  atomic_store(&XRayInitialized, true, memory_order_release);
92
93#ifndef XRAY_NO_PREINIT
94  if (flags()->patch_premain)
95    __xray_patch();
96#endif
97}
98
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;
109#else
110// If we cannot use the .preinit_array section, we should instead use dynamic
111// initialisation.
112__attribute__ ((constructor (0)))
113static void __local_xray_dyninit() {
114  __xray_init();
115}
116#endif
117