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| -rw-r--r-- | mozglue/baseprofiler/lul/LulMain.h | 378 |
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diff --git a/mozglue/baseprofiler/lul/LulMain.h b/mozglue/baseprofiler/lul/LulMain.h new file mode 100644 index 0000000000..987a878c90 --- /dev/null +++ b/mozglue/baseprofiler/lul/LulMain.h @@ -0,0 +1,378 @@ +/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */ +/* vim: set ts=8 sts=2 et sw=2 tw=80: */ +/* This Source Code Form is subject to the terms of the Mozilla Public + * License, v. 2.0. If a copy of the MPL was not distributed with this + * file, You can obtain one at http://mozilla.org/MPL/2.0/. */ + +#ifndef LulMain_h +#define LulMain_h + +#include "PlatformMacros.h" +#include "mozilla/Atomics.h" +#include "mozilla/MemoryReporting.h" +#include "mozilla/BaseProfilerUtils.h" + +// LUL: A Lightweight Unwind Library. +// This file provides the end-user (external) interface for LUL. + +// Some comments about naming in the implementation. These are safe +// to ignore if you are merely using LUL, but are important if you +// hack on its internals. +// +// Debuginfo readers in general have tended to use the word "address" +// to mean several different things. This sometimes makes them +// difficult to understand and maintain. LUL tries hard to avoid +// using the word "address" and instead uses the following more +// precise terms: +// +// * SVMA ("Stated Virtual Memory Address"): this is an address of a +// symbol (etc) as it is stated in the symbol table, or other +// metadata, of an object. Such values are typically small and +// start from zero or thereabouts, unless the object has been +// prelinked. +// +// * AVMA ("Actual Virtual Memory Address"): this is the address of a +// symbol (etc) in a running process, that is, once the associated +// object has been mapped into a process. Such values are typically +// much larger than SVMAs, since objects can get mapped arbitrarily +// far along the address space. +// +// * "Bias": the difference between AVMA and SVMA for a given symbol +// (specifically, AVMA - SVMA). The bias is always an integral +// number of pages. Once we know the bias for a given object's +// text section (for example), we can compute the AVMAs of all of +// its text symbols by adding the bias to their SVMAs. +// +// * "Image address": typically, to read debuginfo from an object we +// will temporarily mmap in the file so as to read symbol tables +// etc. Addresses in this temporary mapping are called "Image +// addresses". Note that the temporary mapping is entirely +// unrelated to the mappings of the file that the dynamic linker +// must perform merely in order to get the program to run. Hence +// image addresses are unrelated to either SVMAs or AVMAs. + +namespace lul { + +// A machine word plus validity tag. +class TaggedUWord { + public: + // RUNS IN NO-MALLOC CONTEXT + // Construct a valid one. + explicit TaggedUWord(uintptr_t w) : mValue(w), mValid(true) {} + + // RUNS IN NO-MALLOC CONTEXT + // Construct an invalid one. + TaggedUWord() : mValue(0), mValid(false) {} + + // RUNS IN NO-MALLOC CONTEXT + TaggedUWord operator+(TaggedUWord rhs) const { + return (Valid() && rhs.Valid()) ? TaggedUWord(Value() + rhs.Value()) + : TaggedUWord(); + } + + // RUNS IN NO-MALLOC CONTEXT + TaggedUWord operator-(TaggedUWord rhs) const { + return (Valid() && rhs.Valid()) ? TaggedUWord(Value() - rhs.Value()) + : TaggedUWord(); + } + + // RUNS IN NO-MALLOC CONTEXT + TaggedUWord operator&(TaggedUWord rhs) const { + return (Valid() && rhs.Valid()) ? TaggedUWord(Value() & rhs.Value()) + : TaggedUWord(); + } + + // RUNS IN NO-MALLOC CONTEXT + TaggedUWord operator|(TaggedUWord rhs) const { + return (Valid() && rhs.Valid()) ? TaggedUWord(Value() | rhs.Value()) + : TaggedUWord(); + } + + // RUNS IN NO-MALLOC CONTEXT + TaggedUWord CmpGEs(TaggedUWord rhs) const { + if (Valid() && rhs.Valid()) { + intptr_t s1 = (intptr_t)Value(); + intptr_t s2 = (intptr_t)rhs.Value(); + return TaggedUWord(s1 >= s2 ? 1 : 0); + } + return TaggedUWord(); + } + + // RUNS IN NO-MALLOC CONTEXT + TaggedUWord operator<<(TaggedUWord rhs) const { + if (Valid() && rhs.Valid()) { + uintptr_t shift = rhs.Value(); + if (shift < 8 * sizeof(uintptr_t)) return TaggedUWord(Value() << shift); + } + return TaggedUWord(); + } + + // RUNS IN NO-MALLOC CONTEXT + // Is equal? Note: non-validity on either side gives non-equality. + bool operator==(TaggedUWord other) const { + return (mValid && other.Valid()) ? (mValue == other.Value()) : false; + } + + // RUNS IN NO-MALLOC CONTEXT + // Is it word-aligned? + bool IsAligned() const { + return mValid && (mValue & (sizeof(uintptr_t) - 1)) == 0; + } + + // RUNS IN NO-MALLOC CONTEXT + uintptr_t Value() const { return mValue; } + + // RUNS IN NO-MALLOC CONTEXT + bool Valid() const { return mValid; } + + private: + uintptr_t mValue; + bool mValid; +}; + +// The registers, with validity tags, that will be unwound. + +struct UnwindRegs { +#if defined(GP_ARCH_arm) + TaggedUWord r7; + TaggedUWord r11; + TaggedUWord r12; + TaggedUWord r13; + TaggedUWord r14; + TaggedUWord r15; +#elif defined(GP_ARCH_arm64) + TaggedUWord x29; + TaggedUWord x30; + TaggedUWord sp; + TaggedUWord pc; +#elif defined(GP_ARCH_amd64) || defined(GP_ARCH_x86) + TaggedUWord xbp; + TaggedUWord xsp; + TaggedUWord xip; +#elif defined(GP_ARCH_mips64) + TaggedUWord sp; + TaggedUWord fp; + TaggedUWord pc; +#else +# error "Unknown plat" +#endif +}; + +// The maximum number of bytes in a stack snapshot. This value can be increased +// if necessary, but testing showed that 160k is enough to obtain good +// backtraces on x86_64 Linux. Most backtraces fit comfortably into 4-8k of +// stack space, but we do have some very deep stacks occasionally. Please see +// the comments in DoNativeBacktrace as to why it's OK to have this value be so +// large. +static const size_t N_STACK_BYTES = 160 * 1024; + +// The stack chunk image that will be unwound. +struct StackImage { + // [start_avma, +len) specify the address range in the buffer. + // Obviously we require 0 <= len <= N_STACK_BYTES. + uintptr_t mStartAvma; + size_t mLen; + uint8_t mContents[N_STACK_BYTES]; +}; + +// Statistics collection for the unwinder. +template <typename T> +class LULStats { + public: + LULStats() : mContext(0), mCFI(0), mFP(0) {} + + template <typename S> + explicit LULStats(const LULStats<S>& aOther) + : mContext(aOther.mContext), mCFI(aOther.mCFI), mFP(aOther.mFP) {} + + template <typename S> + LULStats<T>& operator=(const LULStats<S>& aOther) { + mContext = aOther.mContext; + mCFI = aOther.mCFI; + mFP = aOther.mFP; + return *this; + } + + template <typename S> + uint32_t operator-(const LULStats<S>& aOther) { + return (mContext - aOther.mContext) + (mCFI - aOther.mCFI) + + (mFP - aOther.mFP); + } + + T mContext; // Number of context frames + T mCFI; // Number of CFI/EXIDX frames + T mFP; // Number of frame-pointer recovered frames +}; + +// The core unwinder library class. Just one of these is needed, and +// it can be shared by multiple unwinder threads. +// +// The library operates in one of two modes. +// +// * Admin mode. The library is this state after creation. In Admin +// mode, no unwinding may be performed. It is however allowable to +// perform administrative tasks -- primarily, loading of unwind info +// -- in this mode. In particular, it is safe for the library to +// perform dynamic memory allocation in this mode. Safe in the +// sense that there is no risk of deadlock against unwinding threads +// that might -- because of where they have been sampled -- hold the +// system's malloc lock. +// +// * Unwind mode. In this mode, calls to ::Unwind may be made, but +// nothing else. ::Unwind guarantees not to make any dynamic memory +// requests, so as to guarantee that the calling thread won't +// deadlock in the case where it already holds the system's malloc lock. +// +// The library is created in Admin mode. After debuginfo is loaded, +// the caller must switch it into Unwind mode by calling +// ::EnableUnwinding. There is no way to switch it back to Admin mode +// after that. To safely switch back to Admin mode would require the +// caller (or other external agent) to guarantee that there are no +// pending ::Unwind calls. + +class PriMap; +class SegArray; +class UniqueStringUniverse; + +class LUL { + public: + // Create; supply a logging sink. Sets the object in Admin mode. + explicit LUL(void (*aLog)(const char*)); + + // Destroy. Caller is responsible for ensuring that no other + // threads are in Unwind calls. All resources are freed and all + // registered unwinder threads are deregistered. Can be called + // either in Admin or Unwind mode. + ~LUL(); + + // Notify the library that unwinding is now allowed and so + // admin-mode calls are no longer allowed. The object is initially + // created in admin mode. The only possible transition is + // admin->unwinding, therefore. + void EnableUnwinding(); + + // Notify of a new r-x mapping, and load the associated unwind info. + // The filename is strdup'd and used for debug printing. If + // aMappedImage is NULL, this function will mmap/munmap the file + // itself, so as to be able to read the unwind info. If + // aMappedImage is non-NULL then it is assumed to point to a + // called-supplied and caller-managed mapped image of the file. + // May only be called in Admin mode. + void NotifyAfterMap(uintptr_t aRXavma, size_t aSize, const char* aFileName, + const void* aMappedImage); + + // In rare cases we know an executable area exists but don't know + // what the associated file is. This call notifies LUL of such + // areas. This is important for correct functioning of stack + // scanning and of the x86-{linux,android} special-case + // __kernel_syscall function handling. + // This must be called only after the code area in + // question really has been mapped. + // May only be called in Admin mode. + void NotifyExecutableArea(uintptr_t aRXavma, size_t aSize); + + // Notify that a mapped area has been unmapped; discard any + // associated unwind info. Acquires mRWlock for writing. Note that + // to avoid segfaulting the stack-scan unwinder, which inspects code + // areas, this must be called before the code area in question is + // really unmapped. Note that, unlike NotifyAfterMap(), this + // function takes the start and end addresses of the range to be + // unmapped, rather than a start and a length parameter. This is so + // as to make it possible to notify an unmap for the entire address + // space using a single call. + // May only be called in Admin mode. + void NotifyBeforeUnmap(uintptr_t aAvmaMin, uintptr_t aAvmaMax); + + // Apply NotifyBeforeUnmap to the entire address space. This causes + // LUL to discard all unwind and executable-area information for the + // entire address space. + // May only be called in Admin mode. + void NotifyBeforeUnmapAll() { NotifyBeforeUnmap(0, UINTPTR_MAX); } + + // Returns the number of mappings currently registered. + // May only be called in Admin mode. + size_t CountMappings(); + + // Unwind |aStackImg| starting with the context in |aStartRegs|. + // Write the number of frames recovered in *aFramesUsed. Put + // the PC values in aFramePCs[0 .. *aFramesUsed-1] and + // the SP values in aFrameSPs[0 .. *aFramesUsed-1]. + // |aFramesAvail| is the size of the two output arrays and hence the + // largest possible value of *aFramesUsed. PC values are always + // valid, and the unwind will stop when the PC becomes invalid, but + // the SP values might be invalid, in which case the value zero will + // be written in the relevant frameSPs[] slot. + // + // This function assumes that the SP values increase as it unwinds + // away from the innermost frame -- that is, that the stack grows + // down. It monitors SP values as it unwinds to check they + // decrease, so as to avoid looping on corrupted stacks. + // + // May only be called in Unwind mode. Multiple threads may unwind + // at once. LUL user is responsible for ensuring that no thread makes + // any Admin calls whilst in Unwind mode. + // MOZ_CRASHes if the calling thread is not registered for unwinding. + // + // The calling thread must previously have been registered via a call to + // RegisterSampledThread. + void Unwind(/*OUT*/ uintptr_t* aFramePCs, + /*OUT*/ uintptr_t* aFrameSPs, + /*OUT*/ size_t* aFramesUsed, + /*OUT*/ size_t* aFramePointerFramesAcquired, size_t aFramesAvail, + UnwindRegs* aStartRegs, StackImage* aStackImg); + + // The logging sink. Call to send debug strings to the caller- + // specified destination. Can only be called by the Admin thread. + void (*mLog)(const char*); + + // Statistics relating to unwinding. These have to be atomic since + // unwinding can occur on different threads simultaneously. + LULStats<mozilla::Atomic<uint32_t>> mStats; + + // Possibly show the statistics. This may not be called from any + // registered sampling thread, since it involves I/O. + void MaybeShowStats(); + + size_t SizeOfIncludingThis(mozilla::MallocSizeOf) const; + + private: + // The statistics counters at the point where they were last printed. + LULStats<uint32_t> mStatsPrevious; + + // Are we in admin mode? Initially |true| but changes to |false| + // once unwinding begins. + bool mAdminMode; + + // The thread ID associated with admin mode. This is the only thread + // that is allowed do perform non-Unwind calls on this object. Conversely, + // no registered Unwinding thread may be the admin thread. This is so + // as to clearly partition the one thread that may do dynamic memory + // allocation from the threads that are being sampled, since the latter + // absolutely may not do dynamic memory allocation. + mozilla::baseprofiler::BaseProfilerThreadId mAdminThreadId; + + // The top level mapping from code address ranges to postprocessed + // unwind info. Basically a sorted array of (addr, len, info) + // records. This field is updated by NotifyAfterMap and NotifyBeforeUnmap. + PriMap* mPriMap; + + // An auxiliary structure that records which address ranges are + // mapped r-x, for the benefit of the stack scanner. + SegArray* mSegArray; + + // A UniqueStringUniverse that holds all the strdup'd strings created + // whilst reading unwind information. This is included so as to make + // it possible to free them in ~LUL. + UniqueStringUniverse* mUSU; +}; + +// Run unit tests on an initialised, loaded-up LUL instance, and print +// summary results on |aLUL|'s logging sink. Also return the number +// of tests run in *aNTests and the number that passed in +// *aNTestsPassed. +void RunLulUnitTests(/*OUT*/ int* aNTests, /*OUT*/ int* aNTestsPassed, + LUL* aLUL); + +} // namespace lul + +#endif // LulMain_h |