compiler-rt/lib/xray/xray_init.cpp

   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/xray_interface.h"
  20 #include "xray_allocator.h"
  21 #include "xray_defs.h"
  22 #include "xray_flags.h"
  23 #include "xray_interface_internal.h"
  24
  25 extern "C" {
  26 void __xray_init();
  27 extern const XRaySledEntry __start_xray_instr_map[] __attribute__((weak));
  28 extern const XRaySledEntry __stop_xray_instr_map[] __attribute__((weak));
  29 extern const XRayFunctionSledIndex __start_xray_fn_idx[] __attribute__((weak));
  30 extern const XRayFunctionSledIndex __stop_xray_fn_idx[] __attribute__((weak));
  31
  32 #if SANITIZER_APPLE
  33 // HACK: This is a temporary workaround to make XRay build on
  34 // Darwin, but it will probably not work at runtime.
  35 const XRaySledEntry __start_xray_instr_map[] = {};
  36 extern const XRaySledEntry __stop_xray_instr_map[] = {};
  37 extern const XRayFunctionSledIndex __start_xray_fn_idx[] = {};
  38 extern const XRayFunctionSledIndex __stop_xray_fn_idx[] = {};
  39 #endif
  40 }
  41
  42 using namespace __xray;
  43
  44 // When set to 'true' this means the XRay runtime has been initialised. We use
  45 // the weak symbols defined above (__start_xray_inst_map and
  46 // __stop_xray_instr_map) to initialise the instrumentation map that XRay uses
  47 // for runtime patching/unpatching of instrumentation points.
  48 atomic_uint8_t XRayInitialized{0};
  49
  50 // This should always be updated before XRayInitialized is updated.
  51 SpinMutex XRayInstrMapMutex;
  52
  53 //  Contains maps for the main executable as well as DSOs.
  54 XRaySledMap *XRayInstrMaps;
  55
  56 // Number of binary objects registered.
  57 atomic_uint32_t XRayNumObjects{0};
  58
  59 // Global flag to determine whether the flags have been initialized.
  60 atomic_uint8_t XRayFlagsInitialized{0};
  61
  62 // A mutex to allow only one thread to initialize the XRay data structures.
  63 SpinMutex XRayInitMutex;
  64
  65 // Registers XRay sleds and trampolines coming from the main executable or one
  66 // of the linked DSOs.
  67 // Returns the object ID if registration is successful, -1 otherwise.
  68 int32_t
  69 __xray_register_sleds(const XRaySledEntry *SledsBegin,
  70                       const XRaySledEntry *SledsEnd,
  71                       const XRayFunctionSledIndex *FnIndexBegin,
  72                       const XRayFunctionSledIndex *FnIndexEnd, bool FromDSO,
  73                       XRayTrampolines Trampolines) XRAY_NEVER_INSTRUMENT {
  74   if (!SledsBegin || !SledsEnd) {
  75     Report("Invalid XRay sleds.\n");
  76     return -1;
  77   }
  78   XRaySledMap SledMap;
  79   SledMap.FromDSO = FromDSO;
  80   SledMap.Loaded = true;
  81   SledMap.Trampolines = Trampolines;
  82   SledMap.Sleds = SledsBegin;
  83   SledMap.Entries = SledsEnd - SledsBegin;
  84   if (FnIndexBegin != nullptr) {
  85     SledMap.SledsIndex = FnIndexBegin;
  86     SledMap.Functions = FnIndexEnd - FnIndexBegin;
  87   } else {
  88     size_t CountFunctions = 0;
  89     uint64_t LastFnAddr = 0;
  90
  91     for (std::size_t I = 0; I < SledMap.Entries; I++) {
  92       const auto &Sled = SledMap.Sleds[I];
  93       const auto Function = Sled.function();
  94       if (Function != LastFnAddr) {
  95         CountFunctions++;
  96         LastFnAddr = Function;
  97       }
  98     }
  99     SledMap.SledsIndex = nullptr;
 100     SledMap.Functions = CountFunctions;
 101   }
 102   if (SledMap.Functions >= XRayMaxFunctions) {
 103     Report("Too many functions! Maximum is %ld\n", XRayMaxFunctions);
 104     return -1;
 105   }
 106
 107   if (Verbosity())
 108     Report("Registering %d new functions!\n", SledMap.Functions);
 109
 110   {
 111     SpinMutexLock Guard(&XRayInstrMapMutex);
 112     auto Idx = atomic_fetch_add(&XRayNumObjects, 1, memory_order_acq_rel);
 113     if (Idx >= XRayMaxObjects) {
 114       Report("Too many objects registered! Maximum is %ld\n", XRayMaxObjects);
 115       return -1;
 116     }
 117     XRayInstrMaps[Idx] = std::move(SledMap);
 118     return Idx;
 119   }
 120 }
 121
 122 // __xray_init() will do the actual loading of the current process' memory map
 123 // and then proceed to look for the .xray_instr_map section/segment.
 124 void __xray_init() XRAY_NEVER_INSTRUMENT {
 125   SpinMutexLock Guard(&XRayInitMutex);
 126   // Short-circuit if we've already initialized XRay before.
 127   if (atomic_load(&XRayInitialized, memory_order_acquire))
 128     return;
 129
 130   // XRAY is not compatible with PaX MPROTECT
 131   CheckMPROTECT();
 132
 133   if (!atomic_load(&XRayFlagsInitialized, memory_order_acquire)) {
 134     initializeFlags();
 135     atomic_store(&XRayFlagsInitialized, true, memory_order_release);
 136   }
 137
 138   if (__start_xray_instr_map == nullptr) {
 139     if (Verbosity())
 140       Report("XRay instrumentation map missing. Not initializing XRay.\n");
 141     return;
 142   }
 143
 144   atomic_store(&XRayNumObjects, 0, memory_order_release);
 145
 146   // Pre-allocation takes up approx. 5kB for XRayMaxObjects=64.
 147   XRayInstrMaps = allocateBuffer<XRaySledMap>(XRayMaxObjects);
 148
 149   int MainBinaryId =
 150       __xray_register_sleds(__start_xray_instr_map, __stop_xray_instr_map,
 151                             __start_xray_fn_idx, __stop_xray_fn_idx, false, {});
 152
 153   // The executable should always get ID 0.
 154   if (MainBinaryId != 0) {
 155     Report("Registering XRay sleds failed.\n");
 156     return;
 157   }
 158
 159   atomic_store(&XRayInitialized, true, memory_order_release);
 160
 161 #ifndef XRAY_NO_PREINIT
 162   if (flags()->patch_premain)
 163     __xray_patch();
 164 #endif
 165 }
 166
 167 // Registers XRay sleds and trampolines of an instrumented DSO.
 168 // Returns the object ID if registration is successful, -1 otherwise.
 169 //
 170 // Default visibility is hidden, so we have to explicitly make it visible to
 171 // DSO.
 172 SANITIZER_INTERFACE_ATTRIBUTE int32_t __xray_register_dso(
 173     const XRaySledEntry *SledsBegin, const XRaySledEntry *SledsEnd,
 174     const XRayFunctionSledIndex *FnIndexBegin,
 175     const XRayFunctionSledIndex *FnIndexEnd,
 176     XRayTrampolines Trampolines) XRAY_NEVER_INSTRUMENT {
 177   // Make sure XRay has been initialized in the main executable.
 178   __xray_init();
 179
 180   if (__xray_num_objects() == 0) {
 181     if (Verbosity())
 182       Report("No XRay instrumentation map in main executable. Not initializing "
 183              "XRay for DSO.\n");
 184     return -1;
 185   }
 186
 187   // Register sleds in global map.
 188   int ObjId = __xray_register_sleds(SledsBegin, SledsEnd, FnIndexBegin,
 189                                     FnIndexEnd, true, Trampolines);
 190
 191 #ifndef XRAY_NO_PREINIT
 192   if (ObjId >= 0 && flags()->patch_premain)
 193     __xray_patch_object(ObjId);
 194 #endif
 195
 196   return ObjId;
 197 }
 198
 199 // Deregisters a DSO from the main XRay runtime.
 200 // Called from the DSO-local runtime when the library is unloaded (e.g. if
 201 // dlclose is called).
 202 // Returns true if the object ID is valid and the DSO was successfully
 203 // deregistered.
 204 SANITIZER_INTERFACE_ATTRIBUTE bool
 205 __xray_deregister_dso(int32_t ObjId) XRAY_NEVER_INSTRUMENT {
 206
 207   if (!atomic_load(&XRayInitialized, memory_order_acquire)) {
 208     if (Verbosity())
 209       Report("XRay has not been initialized. Cannot deregister DSO.\n");
 210     return false;
 211   }
 212
 213   if (ObjId <= 0 || static_cast<uint32_t>(ObjId) >= __xray_num_objects()) {
 214     if (Verbosity())
 215       Report("Can't deregister object with ID %d: ID is invalid.\n", ObjId);
 216     return false;
 217   }
 218
 219   {
 220     SpinMutexLock Guard(&XRayInstrMapMutex);
 221     auto &Entry = XRayInstrMaps[ObjId];
 222     if (!Entry.FromDSO) {
 223       if (Verbosity())
 224         Report("Can't deregister object with ID %d: object does not correspond "
 225                "to a shared library.\n",
 226                ObjId);
 227       return false;
 228     }
 229     if (!Entry.Loaded) {
 230       if (Verbosity())
 231         Report("Can't deregister object with ID %d: object is not loaded.\n",
 232                ObjId);
 233       return true;
 234     }
 235     // Mark DSO as unloaded. No need to unpatch.
 236     Entry.Loaded = false;
 237   }
 238
 239   if (Verbosity())
 240     Report("Deregistered object with ID %d.\n", ObjId);
 241
 242   return true;
 243 }
 244
 245 // FIXME: Make check-xray tests work on FreeBSD without
 246 // SANITIZER_CAN_USE_PREINIT_ARRAY.
 247 // See sanitizer_internal_defs.h where the macro is defined.
 248 // Calling unresolved PLT functions in .preinit_array can lead to deadlock on
 249 // FreeBSD but here it seems benign.
 250 #if !defined(XRAY_NO_PREINIT) &&                                               \
 251     (SANITIZER_CAN_USE_PREINIT_ARRAY || SANITIZER_FREEBSD)
 252 // Only add the preinit array initialization if the sanitizers can.
 253 __attribute__((section(".preinit_array"),
 254                used)) void (*__local_xray_preinit)(void) = __xray_init;
 255 #else
 256 // If we cannot use the .preinit_array section, we should instead use dynamic
 257 // initialisation.
 258 __attribute__ ((constructor (0)))
 259 static void __local_xray_dyninit() {
 260   __xray_init();
 261 }
 262 #endif