lib/xray/xray_init.cpp - llvm-project/compiler-rt - Git at Google

 //===-- xray_init.cpp -------------------------------------------*- C++ -*-===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 //
 // This file is a part of XRay, a dynamic runtime instrumentation system.
 //
 // XRay initialisation logic.
 //===----------------------------------------------------------------------===//

 #include <fcntl.h>
 #include <strings.h>
 #include <unistd.h>

 #include "sanitizer_common/sanitizer_common.h"
 #include "xray/xray_interface.h"
 #include "xray_allocator.h"
 #include "xray_defs.h"
 #include "xray_flags.h"
 #include "xray_interface_internal.h"

 extern "C" {
 void __xray_init();
 extern const XRaySledEntry __start_xray_instr_map[] __attribute__((weak));
 extern const XRaySledEntry __stop_xray_instr_map[] __attribute__((weak));
 extern const XRayFunctionSledIndex __start_xray_fn_idx[] __attribute__((weak));
 extern const XRayFunctionSledIndex __stop_xray_fn_idx[] __attribute__((weak));

 #if SANITIZER_APPLE
 // HACK: This is a temporary workaround to make XRay build on
 // Darwin, but it will probably not work at runtime.
 const XRaySledEntry __start_xray_instr_map[] = {};
 extern const XRaySledEntry __stop_xray_instr_map[] = {};
 extern const XRayFunctionSledIndex __start_xray_fn_idx[] = {};
 extern const XRayFunctionSledIndex __stop_xray_fn_idx[] = {};
 #endif
 }

 using namespace __xray;

 // When set to 'true' this means the XRay runtime has been initialised. We use
 // the weak symbols defined above (__start_xray_inst_map and
 // __stop_xray_instr_map) to initialise the instrumentation map that XRay uses
 // for runtime patching/unpatching of instrumentation points.
 atomic_uint8_t XRayInitialized{0};

 // This should always be updated before XRayInitialized is updated.
 SpinMutex XRayInstrMapMutex;

 //  Contains maps for the main executable as well as DSOs.
 XRaySledMap *XRayInstrMaps;

 // Number of binary objects registered.
 atomic_uint32_t XRayNumObjects{0};

 // Global flag to determine whether the flags have been initialized.
 atomic_uint8_t XRayFlagsInitialized{0};

 // A mutex to allow only one thread to initialize the XRay data structures.
 SpinMutex XRayInitMutex;

 // Registers XRay sleds and trampolines coming from the main executable or one
 // of the linked DSOs.
 // Returns the object ID if registration is successful, -1 otherwise.
 int32_t
 __xray_register_sleds(const XRaySledEntry *SledsBegin,
                       const XRaySledEntry *SledsEnd,
                       const XRayFunctionSledIndex *FnIndexBegin,
                       const XRayFunctionSledIndex *FnIndexEnd, bool FromDSO,
                       XRayTrampolines Trampolines) XRAY_NEVER_INSTRUMENT {
   if (!SledsBegin || !SledsEnd) {
     Report("Invalid XRay sleds.\n");
     return -1;
   }
   XRaySledMap SledMap;
   SledMap.FromDSO = FromDSO;
   SledMap.Loaded = true;
   SledMap.Trampolines = Trampolines;
   SledMap.Sleds = SledsBegin;
   SledMap.Entries = SledsEnd - SledsBegin;
   if (FnIndexBegin != nullptr) {
     SledMap.SledsIndex = FnIndexBegin;
     SledMap.Functions = FnIndexEnd - FnIndexBegin;
   } else {
     size_t CountFunctions = 0;
     uint64_t LastFnAddr = 0;

     for (std::size_t I = 0; I < SledMap.Entries; I++) {
       const auto &Sled = SledMap.Sleds[I];
       const auto Function = Sled.function();
       if (Function != LastFnAddr) {
         CountFunctions++;
         LastFnAddr = Function;
       }
     }
     SledMap.SledsIndex = nullptr;
     SledMap.Functions = CountFunctions;
   }
   if (SledMap.Functions >= XRayMaxFunctions) {
     Report("Too many functions! Maximum is %ld\n", XRayMaxFunctions);
     return -1;
   }

   if (Verbosity())
     Report("Registering %d new functions!\n", (int)SledMap.Functions);

   {
     SpinMutexLock Guard(&XRayInstrMapMutex);
     auto Idx = atomic_fetch_add(&XRayNumObjects, 1, memory_order_acq_rel);
     if (Idx >= XRayMaxObjects) {
       Report("Too many objects registered! Maximum is %ld\n", XRayMaxObjects);
       return -1;
     }
     XRayInstrMaps[Idx] = std::move(SledMap);
     return Idx;
   }
 }

 // __xray_init() will do the actual loading of the current process' memory map
 // and then proceed to look for the .xray_instr_map section/segment.
 void __xray_init() XRAY_NEVER_INSTRUMENT {
   SpinMutexLock Guard(&XRayInitMutex);
   // Short-circuit if we've already initialized XRay before.
   if (atomic_load(&XRayInitialized, memory_order_acquire))
     return;

   // XRAY is not compatible with PaX MPROTECT
   CheckMPROTECT();

   if (!atomic_load(&XRayFlagsInitialized, memory_order_acquire)) {
     initializeFlags();
     atomic_store(&XRayFlagsInitialized, true, memory_order_release);
   }

   if (__start_xray_instr_map == nullptr) {
     if (Verbosity())
       Report("XRay instrumentation map missing. Not initializing XRay.\n");
     return;
   }

   atomic_store(&XRayNumObjects, 0, memory_order_release);

   // Pre-allocation takes up approx. 5kB for XRayMaxObjects=64.
   XRayInstrMaps = allocateBuffer<XRaySledMap>(XRayMaxObjects);

   int MainBinaryId =
       __xray_register_sleds(__start_xray_instr_map, __stop_xray_instr_map,
                             __start_xray_fn_idx, __stop_xray_fn_idx, false, {});

   // The executable should always get ID 0.
   if (MainBinaryId != 0) {
     Report("Registering XRay sleds failed.\n");
     return;
   }

   atomic_store(&XRayInitialized, true, memory_order_release);

 #ifndef XRAY_NO_PREINIT
   if (flags()->patch_premain)
     __xray_patch();
 #endif
 }

 // Registers XRay sleds and trampolines of an instrumented DSO.
 // Returns the object ID if registration is successful, -1 otherwise.
 //
 // Default visibility is hidden, so we have to explicitly make it visible to
 // DSO.
 SANITIZER_INTERFACE_ATTRIBUTE int32_t __xray_register_dso(
     const XRaySledEntry *SledsBegin, const XRaySledEntry *SledsEnd,
     const XRayFunctionSledIndex *FnIndexBegin,
     const XRayFunctionSledIndex *FnIndexEnd,
     XRayTrampolines Trampolines) XRAY_NEVER_INSTRUMENT {
   // Make sure XRay has been initialized in the main executable.
   __xray_init();

   if (__xray_num_objects() == 0) {
     if (Verbosity())
       Report("No XRay instrumentation map in main executable. Not initializing "
              "XRay for DSO.\n");
     return -1;
   }

   // Register sleds in global map.
   int ObjId = __xray_register_sleds(SledsBegin, SledsEnd, FnIndexBegin,
                                     FnIndexEnd, true, Trampolines);

 #ifndef XRAY_NO_PREINIT
   if (ObjId >= 0 && flags()->patch_premain)
     __xray_patch_object(ObjId);
 #endif

   return ObjId;
 }

 // Deregisters a DSO from the main XRay runtime.
 // Called from the DSO-local runtime when the library is unloaded (e.g. if
 // dlclose is called).
 // Returns true if the object ID is valid and the DSO was successfully
 // deregistered.
 SANITIZER_INTERFACE_ATTRIBUTE bool
 __xray_deregister_dso(int32_t ObjId) XRAY_NEVER_INSTRUMENT {

   if (!atomic_load(&XRayInitialized, memory_order_acquire)) {
     if (Verbosity())
       Report("XRay has not been initialized. Cannot deregister DSO.\n");
     return false;
   }

   if (ObjId <= 0 || static_cast<uint32_t>(ObjId) >= __xray_num_objects()) {
     if (Verbosity())
       Report("Can't deregister object with ID %d: ID is invalid.\n", ObjId);
     return false;
   }

   {
     SpinMutexLock Guard(&XRayInstrMapMutex);
     auto &Entry = XRayInstrMaps[ObjId];
     if (!Entry.FromDSO) {
       if (Verbosity())
         Report("Can't deregister object with ID %d: object does not correspond "
                "to a shared library.\n",
                ObjId);
       return false;
     }
     if (!Entry.Loaded) {
       if (Verbosity())
         Report("Can't deregister object with ID %d: object is not loaded.\n",
                ObjId);
       return true;
     }
     // Mark DSO as unloaded. No need to unpatch.
     Entry.Loaded = false;
   }

   if (Verbosity())
     Report("Deregistered object with ID %d.\n", ObjId);

   return true;
 }

 // FIXME: Make check-xray tests work on FreeBSD without
 // SANITIZER_CAN_USE_PREINIT_ARRAY.
 // See sanitizer_internal_defs.h where the macro is defined.
 // Calling unresolved PLT functions in .preinit_array can lead to deadlock on
 // FreeBSD but here it seems benign.
 #if !defined(XRAY_NO_PREINIT) &&                                               \
     (SANITIZER_CAN_USE_PREINIT_ARRAY || SANITIZER_FREEBSD)
 // Only add the preinit array initialization if the sanitizers can.
 __attribute__((section(".preinit_array"),
                used)) void (*__local_xray_preinit)(void) = __xray_init;
 #else
 // If we cannot use the .preinit_array section, we should instead use dynamic
 // initialisation.
 __attribute__ ((constructor (0)))
 static void __local_xray_dyninit() {
   __xray_init();
 }
 #endif
	//===-- xray_init.cpp -------------------------------------------- C++ --===//
	//
	// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
	// See https://llvm.org/LICENSE.txt for license information.
	// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
	//
	//===----------------------------------------------------------------------===//
	//
	// This file is a part of XRay, a dynamic runtime instrumentation system.
	//
	// XRay initialisation logic.
	//===----------------------------------------------------------------------===//

	#include <fcntl.h>
	#include <strings.h>
	#include <unistd.h>

	#include "sanitizer_common/sanitizer_common.h"
	#include "xray/xray_interface.h"
	#include "xray_allocator.h"
	#include "xray_defs.h"
	#include "xray_flags.h"
	#include "xray_interface_internal.h"

	extern "C" {
	void __xray_init();
	extern const XRaySledEntry __start_xray_instr_map[] __attribute__((weak));
	extern const XRaySledEntry __stop_xray_instr_map[] __attribute__((weak));
	extern const XRayFunctionSledIndex __start_xray_fn_idx[] __attribute__((weak));
	extern const XRayFunctionSledIndex __stop_xray_fn_idx[] __attribute__((weak));

	#if SANITIZER_APPLE
	// HACK: This is a temporary workaround to make XRay build on
	// Darwin, but it will probably not work at runtime.
	const XRaySledEntry __start_xray_instr_map[] = {};
	extern const XRaySledEntry __stop_xray_instr_map[] = {};
	extern const XRayFunctionSledIndex __start_xray_fn_idx[] = {};
	extern const XRayFunctionSledIndex __stop_xray_fn_idx[] = {};
	#endif
	}

	using namespace __xray;

	// When set to 'true' this means the XRay runtime has been initialised. We use
	// the weak symbols defined above (__start_xray_inst_map and
	// __stop_xray_instr_map) to initialise the instrumentation map that XRay uses
	// for runtime patching/unpatching of instrumentation points.
	atomic_uint8_t XRayInitialized{0};

	// This should always be updated before XRayInitialized is updated.
	SpinMutex XRayInstrMapMutex;

	// Contains maps for the main executable as well as DSOs.
	XRaySledMap *XRayInstrMaps;

	// Number of binary objects registered.
	atomic_uint32_t XRayNumObjects{0};

	// Global flag to determine whether the flags have been initialized.
	atomic_uint8_t XRayFlagsInitialized{0};

	// A mutex to allow only one thread to initialize the XRay data structures.
	SpinMutex XRayInitMutex;

	// Registers XRay sleds and trampolines coming from the main executable or one
	// of the linked DSOs.
	// Returns the object ID if registration is successful, -1 otherwise.
	int32_t
	__xray_register_sleds(const XRaySledEntry *SledsBegin,
	const XRaySledEntry *SledsEnd,
	const XRayFunctionSledIndex *FnIndexBegin,
	const XRayFunctionSledIndex *FnIndexEnd, bool FromDSO,
	XRayTrampolines Trampolines) XRAY_NEVER_INSTRUMENT {
	if (!SledsBegin \|\| !SledsEnd) {
	Report("Invalid XRay sleds.\n");
	return -1;
	}
	XRaySledMap SledMap;
	SledMap.FromDSO = FromDSO;
	SledMap.Loaded = true;
	SledMap.Trampolines = Trampolines;
	SledMap.Sleds = SledsBegin;
	SledMap.Entries = SledsEnd - SledsBegin;
	if (FnIndexBegin != nullptr) {
	SledMap.SledsIndex = FnIndexBegin;
	SledMap.Functions = FnIndexEnd - FnIndexBegin;
	} else {
	size_t CountFunctions = 0;
	uint64_t LastFnAddr = 0;

	for (std::size_t I = 0; I < SledMap.Entries; I++) {
	const auto &Sled = SledMap.Sleds[I];
	const auto Function = Sled.function();
	if (Function != LastFnAddr) {
	CountFunctions++;
	LastFnAddr = Function;
	}
	}
	SledMap.SledsIndex = nullptr;
	SledMap.Functions = CountFunctions;
	}
	if (SledMap.Functions >= XRayMaxFunctions) {
	Report("Too many functions! Maximum is %ld\n", XRayMaxFunctions);
	return -1;
	}

	if (Verbosity())
	Report("Registering %d new functions!\n", (int)SledMap.Functions);

	{
	SpinMutexLock Guard(&XRayInstrMapMutex);
	auto Idx = atomic_fetch_add(&XRayNumObjects, 1, memory_order_acq_rel);
	if (Idx >= XRayMaxObjects) {
	Report("Too many objects registered! Maximum is %ld\n", XRayMaxObjects);
	return -1;
	}
	XRayInstrMaps[Idx] = std::move(SledMap);
	return Idx;
	}
	}

	// __xray_init() will do the actual loading of the current process' memory map
	// and then proceed to look for the .xray_instr_map section/segment.
	void __xray_init() XRAY_NEVER_INSTRUMENT {
	SpinMutexLock Guard(&XRayInitMutex);
	// Short-circuit if we've already initialized XRay before.
	if (atomic_load(&XRayInitialized, memory_order_acquire))
	return;

	// XRAY is not compatible with PaX MPROTECT
	CheckMPROTECT();

	if (!atomic_load(&XRayFlagsInitialized, memory_order_acquire)) {
	initializeFlags();
	atomic_store(&XRayFlagsInitialized, true, memory_order_release);
	}

	if (__start_xray_instr_map == nullptr) {
	if (Verbosity())
	Report("XRay instrumentation map missing. Not initializing XRay.\n");
	return;
	}

	atomic_store(&XRayNumObjects, 0, memory_order_release);

	// Pre-allocation takes up approx. 5kB for XRayMaxObjects=64.
	XRayInstrMaps = allocateBuffer<XRaySledMap>(XRayMaxObjects);

	int MainBinaryId =
	__xray_register_sleds(__start_xray_instr_map, __stop_xray_instr_map,
	__start_xray_fn_idx, __stop_xray_fn_idx, false, {});

	// The executable should always get ID 0.
	if (MainBinaryId != 0) {
	Report("Registering XRay sleds failed.\n");
	return;
	}

	atomic_store(&XRayInitialized, true, memory_order_release);

	#ifndef XRAY_NO_PREINIT
	if (flags()->patch_premain)
	__xray_patch();
	#endif
	}

	// Registers XRay sleds and trampolines of an instrumented DSO.
	// Returns the object ID if registration is successful, -1 otherwise.
	//
	// Default visibility is hidden, so we have to explicitly make it visible to
	// DSO.
	SANITIZER_INTERFACE_ATTRIBUTE int32_t __xray_register_dso(
	const XRaySledEntry SledsBegin, const XRaySledEntry SledsEnd,
	const XRayFunctionSledIndex *FnIndexBegin,
	const XRayFunctionSledIndex *FnIndexEnd,
	XRayTrampolines Trampolines) XRAY_NEVER_INSTRUMENT {
	// Make sure XRay has been initialized in the main executable.
	__xray_init();

	if (__xray_num_objects() == 0) {
	if (Verbosity())
	Report("No XRay instrumentation map in main executable. Not initializing "
	"XRay for DSO.\n");
	return -1;
	}

	// Register sleds in global map.
	int ObjId = __xray_register_sleds(SledsBegin, SledsEnd, FnIndexBegin,
	FnIndexEnd, true, Trampolines);

	#ifndef XRAY_NO_PREINIT
	if (ObjId >= 0 && flags()->patch_premain)
	__xray_patch_object(ObjId);
	#endif

	return ObjId;
	}

	// Deregisters a DSO from the main XRay runtime.
	// Called from the DSO-local runtime when the library is unloaded (e.g. if
	// dlclose is called).
	// Returns true if the object ID is valid and the DSO was successfully
	// deregistered.
	SANITIZER_INTERFACE_ATTRIBUTE bool
	__xray_deregister_dso(int32_t ObjId) XRAY_NEVER_INSTRUMENT {

	if (!atomic_load(&XRayInitialized, memory_order_acquire)) {
	if (Verbosity())
	Report("XRay has not been initialized. Cannot deregister DSO.\n");
	return false;
	}

	if (ObjId <= 0 \|\| static_cast<uint32_t>(ObjId) >= __xray_num_objects()) {
	if (Verbosity())
	Report("Can't deregister object with ID %d: ID is invalid.\n", ObjId);
	return false;
	}

	{
	SpinMutexLock Guard(&XRayInstrMapMutex);
	auto &Entry = XRayInstrMaps[ObjId];
	if (!Entry.FromDSO) {
	if (Verbosity())
	Report("Can't deregister object with ID %d: object does not correspond "
	"to a shared library.\n",
	ObjId);
	return false;
	}
	if (!Entry.Loaded) {
	if (Verbosity())
	Report("Can't deregister object with ID %d: object is not loaded.\n",
	ObjId);
	return true;
	}
	// Mark DSO as unloaded. No need to unpatch.
	Entry.Loaded = false;
	}

	if (Verbosity())
	Report("Deregistered object with ID %d.\n", ObjId);

	return true;
	}

	// FIXME: Make check-xray tests work on FreeBSD without
	// SANITIZER_CAN_USE_PREINIT_ARRAY.
	// See sanitizer_internal_defs.h where the macro is defined.
	// Calling unresolved PLT functions in .preinit_array can lead to deadlock on
	// FreeBSD but here it seems benign.
	#if !defined(XRAY_NO_PREINIT) && \
	(SANITIZER_CAN_USE_PREINIT_ARRAY \|\| SANITIZER_FREEBSD)
	// Only add the preinit array initialization if the sanitizers can.
	__attribute__((section(".preinit_array"),
	used)) void (*__local_xray_preinit)(void) = __xray_init;
	#else
	// If we cannot use the .preinit_array section, we should instead use dynamic
	// initialisation.
	__attribute__ ((constructor (0)))
	static void __local_xray_dyninit() {
	__xray_init();
	}
	#endif