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llvm-project/bolt/runtime/instr.cpp

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//===- bolt/runtime/instr.cpp ---------------------------------------------===//
//
// 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
//
//===----------------------------------------------------------------------===//
//
// BOLT runtime instrumentation library for x86 Linux. Currently, BOLT does
// not support linking modules with dependencies on one another into the final
// binary (TODO?), which means this library has to be self-contained in a single
// module.
//
// All extern declarations here need to be defined by BOLT itself. Those will be
// undefined symbols that BOLT needs to resolve by emitting these symbols with
// MCStreamer. Currently, Passes/Instrumentation.cpp is the pass responsible
// for defining the symbols here and these two files have a tight coupling: one
// working statically when you run BOLT and another during program runtime when
// you run an instrumented binary. The main goal here is to output an fdata file
// (BOLT profile) with the instrumentation counters inserted by the static pass.
// Counters for indirect calls are an exception, as we can't know them
// statically. These counters are created and managed here. To allow this, we
// need a minimal framework for allocating memory dynamically. We provide this
// with the BumpPtrAllocator class (not LLVM's, but our own version of it).
//
// Since this code is intended to be inserted into any executable, we decided to
// make it standalone and do not depend on any external libraries (i.e. language
// support libraries, such as glibc or stdc++). To allow this, we provide a few
// light implementations of common OS interacting functionalities using direct
// syscall wrappers. Our simple allocator doesn't manage deallocations that
// fragment the memory space, so it's stack based. This is the minimal framework
// provided here to allow processing instrumented counters and writing fdata.
//
// In the C++ idiom used here, we never use or rely on constructors or
// destructors for global objects. That's because those need support from the
// linker in initialization/finalization code, and we want to keep our linker
// very simple. Similarly, we don't create any global objects that are zero
// initialized, since those would need to go .bss, which our simple linker also
// don't support (TODO?).
//
//===----------------------------------------------------------------------===//
#if defined (__x86_64__)
#include "common.h"
// Enables a very verbose logging to stderr useful when debugging
//#define ENABLE_DEBUG
#ifdef ENABLE_DEBUG
#define DEBUG(X) \
{ X; }
#else
#define DEBUG(X) \
{}
#endif
#pragma GCC visibility push(hidden)
extern "C" {
#if defined(__APPLE__)
extern uint64_t* _bolt_instr_locations_getter();
extern uint32_t _bolt_num_counters_getter();
extern uint8_t* _bolt_instr_tables_getter();
extern uint32_t _bolt_instr_num_funcs_getter();
#else
// Main counters inserted by instrumentation, incremented during runtime when
// points of interest (locations) in the program are reached. Those are direct
// calls and direct and indirect branches (local ones). There are also counters
// for basic block execution if they are a spanning tree leaf and need to be
// counted in order to infer the execution count of other edges of the CFG.
extern uint64_t __bolt_instr_locations[];
extern uint32_t __bolt_num_counters;
// Descriptions are serialized metadata about binary functions written by BOLT,
// so we have a minimal understanding about the program structure. For a
// reference on the exact format of this metadata, see *Description structs,
// Location, IntrumentedNode and EntryNode.
// Number of indirect call site descriptions
extern uint32_t __bolt_instr_num_ind_calls;
// Number of indirect call target descriptions
extern uint32_t __bolt_instr_num_ind_targets;
// Number of function descriptions
extern uint32_t __bolt_instr_num_funcs;
// Time to sleep across dumps (when we write the fdata profile to disk)
extern uint32_t __bolt_instr_sleep_time;
// Do not clear counters across dumps, rewrite file with the updated values
extern bool __bolt_instr_no_counters_clear;
// Wait until all forks of instrumented process will finish
extern bool __bolt_instr_wait_forks;
// Filename to dump data to
extern char __bolt_instr_filename[];
// Instumented binary file path
extern char __bolt_instr_binpath[];
// If true, append current PID to the fdata filename when creating it so
// different invocations of the same program can be differentiated.
extern bool __bolt_instr_use_pid;
// Functions that will be used to instrument indirect calls. BOLT static pass
// will identify indirect calls and modify them to load the address in these
// trampolines and call this address instead. BOLT can't use direct calls to
// our handlers because our addresses here are not known at analysis time. We
// only support resolving dependencies from this file to the output of BOLT,
// *not* the other way around.
// TODO: We need better linking support to make that happen.
extern void (*__bolt_ind_call_counter_func_pointer)();
extern void (*__bolt_ind_tailcall_counter_func_pointer)();
// Function pointers to init/fini trampoline routines in the binary, so we can
// resume regular execution of these functions that we hooked
extern void __bolt_start_trampoline();
extern void __bolt_fini_trampoline();
#endif
}
namespace {
/// A simple allocator that mmaps a fixed size region and manages this space
/// in a stack fashion, meaning you always deallocate the last element that
/// was allocated. In practice, we don't need to deallocate individual elements.
/// We monotonically increase our usage and then deallocate everything once we
/// are done processing something.
class BumpPtrAllocator {
/// This is written before each allocation and act as a canary to detect when
/// a bug caused our program to cross allocation boundaries.
struct EntryMetadata {
uint64_t Magic;
uint64_t AllocSize;
};
public:
void *allocate(size_t Size) {
Lock L(M);
if (StackBase == nullptr) {
#if defined(__APPLE__)
int MAP_PRIVATE_MAP_ANONYMOUS = 0x1002;
#else
int MAP_PRIVATE_MAP_ANONYMOUS = 0x22;
#endif
StackBase = reinterpret_cast<uint8_t *>(
__mmap(0, MaxSize, 0x3 /* PROT_READ | PROT_WRITE*/,
Shared ? 0x21 /*MAP_SHARED | MAP_ANONYMOUS*/
: MAP_PRIVATE_MAP_ANONYMOUS /* MAP_PRIVATE | MAP_ANONYMOUS*/,
-1, 0));
StackSize = 0;
}
Size = alignTo(Size + sizeof(EntryMetadata), 16);
uint8_t *AllocAddress = StackBase + StackSize + sizeof(EntryMetadata);
auto *M = reinterpret_cast<EntryMetadata *>(StackBase + StackSize);
M->Magic = Magic;
M->AllocSize = Size;
StackSize += Size;
assert(StackSize < MaxSize, "allocator ran out of memory");
return AllocAddress;
}
#ifdef DEBUG
/// Element-wise deallocation is only used for debugging to catch memory
/// bugs by checking magic bytes. Ordinarily, we reset the allocator once
/// we are done with it. Reset is done with clear(). There's no need
/// to deallocate each element individually.
void deallocate(void *Ptr) {
Lock L(M);
uint8_t MetadataOffset = sizeof(EntryMetadata);
auto *M = reinterpret_cast<EntryMetadata *>(
reinterpret_cast<uint8_t *>(Ptr) - MetadataOffset);
const uint8_t *StackTop = StackBase + StackSize + MetadataOffset;
// Validate size
if (Ptr != StackTop - M->AllocSize) {
// Failed validation, check if it is a pointer returned by operator new []
MetadataOffset +=
sizeof(uint64_t); // Space for number of elements alloc'ed
M = reinterpret_cast<EntryMetadata *>(reinterpret_cast<uint8_t *>(Ptr) -
MetadataOffset);
// Ok, it failed both checks if this assertion fails. Stop the program, we
// have a memory bug.
assert(Ptr == StackTop - M->AllocSize,
"must deallocate the last element alloc'ed");
}
assert(M->Magic == Magic, "allocator magic is corrupt");
StackSize -= M->AllocSize;
}
#else
void deallocate(void *) {}
#endif
void clear() {
Lock L(M);
StackSize = 0;
}
/// Set mmap reservation size (only relevant before first allocation)
void setMaxSize(uint64_t Size) { MaxSize = Size; }
/// Set mmap reservation privacy (only relevant before first allocation)
void setShared(bool S) { Shared = S; }
void destroy() {
if (StackBase == nullptr)
return;
__munmap(StackBase, MaxSize);
}
private:
static constexpr uint64_t Magic = 0x1122334455667788ull;
uint64_t MaxSize = 0xa00000;
uint8_t *StackBase{nullptr};
uint64_t StackSize{0};
bool Shared{false};
Mutex M;
};
/// Used for allocating indirect call instrumentation counters. Initialized by
/// __bolt_instr_setup, our initialization routine.
BumpPtrAllocator GlobalAlloc;
} // anonymous namespace
// User-defined placement new operators. We only use those (as opposed to
// overriding the regular operator new) so we can keep our allocator in the
// stack instead of in a data section (global).
void *operator new(size_t Sz, BumpPtrAllocator &A) { return A.allocate(Sz); }
void *operator new(size_t Sz, BumpPtrAllocator &A, char C) {
auto *Ptr = reinterpret_cast<char *>(A.allocate(Sz));
memSet(Ptr, C, Sz);
return Ptr;
}
void *operator new[](size_t Sz, BumpPtrAllocator &A) {
return A.allocate(Sz);
}
void *operator new[](size_t Sz, BumpPtrAllocator &A, char C) {
auto *Ptr = reinterpret_cast<char *>(A.allocate(Sz));
memSet(Ptr, C, Sz);
return Ptr;
}
// Only called during exception unwinding (useless). We must manually dealloc.
// C++ language weirdness
void operator delete(void *Ptr, BumpPtrAllocator &A) { A.deallocate(Ptr); }
namespace {
// Disable instrumentation optimizations that sacrifice profile accuracy
extern "C" bool __bolt_instr_conservative;
/// Basic key-val atom stored in our hash
struct SimpleHashTableEntryBase {
uint64_t Key;
uint64_t Val;
};
/// This hash table implementation starts by allocating a table of size
/// InitialSize. When conflicts happen in this main table, it resolves
/// them by chaining a new table of size IncSize. It never reallocs as our
/// allocator doesn't support it. The key is intended to be function pointers.
/// There's no clever hash function (it's just x mod size, size being prime).
/// I never tuned the coefficientes in the modular equation (TODO)
/// This is used for indirect calls (each call site has one of this, so it
/// should have a small footprint) and for tallying call counts globally for
/// each target to check if we missed the origin of some calls (this one is a
/// large instantiation of this template, since it is global for all call sites)
template <typename T = SimpleHashTableEntryBase, uint32_t InitialSize = 7,
uint32_t IncSize = 7>
class SimpleHashTable {
public:
using MapEntry = T;
/// Increment by 1 the value of \p Key. If it is not in this table, it will be
/// added to the table and its value set to 1.
void incrementVal(uint64_t Key, BumpPtrAllocator &Alloc) {
++get(Key, Alloc).Val;
}
/// Basic member accessing interface. Here we pass the allocator explicitly to
/// avoid storing a pointer to it as part of this table (remember there is one
/// hash for each indirect call site, so we wan't to minimize our footprint).
MapEntry &get(uint64_t Key, BumpPtrAllocator &Alloc) {
if (!__bolt_instr_conservative) {
TryLock L(M);
if (!L.isLocked())
return NoEntry;
return getOrAllocEntry(Key, Alloc);
}
Lock L(M);
return getOrAllocEntry(Key, Alloc);
}
/// Traverses all elements in the table
template <typename... Args>
void forEachElement(void (*Callback)(MapEntry &, Args...), Args... args) {
if (!TableRoot)
return;
return forEachElement(Callback, InitialSize, TableRoot, args...);
}
void resetCounters();
private:
constexpr static uint64_t VacantMarker = 0;
constexpr static uint64_t FollowUpTableMarker = 0x8000000000000000ull;
MapEntry *TableRoot{nullptr};
MapEntry NoEntry;
Mutex M;
template <typename... Args>
void forEachElement(void (*Callback)(MapEntry &, Args...),
uint32_t NumEntries, MapEntry *Entries, Args... args) {
for (uint32_t I = 0; I < NumEntries; ++I) {
MapEntry &Entry = Entries[I];
if (Entry.Key == VacantMarker)
continue;
if (Entry.Key & FollowUpTableMarker) {
forEachElement(Callback, IncSize,
reinterpret_cast<MapEntry *>(Entry.Key &
~FollowUpTableMarker),
args...);
continue;
}
Callback(Entry, args...);
}
}
MapEntry &firstAllocation(uint64_t Key, BumpPtrAllocator &Alloc) {
TableRoot = new (Alloc, 0) MapEntry[InitialSize];
MapEntry &Entry = TableRoot[Key % InitialSize];
Entry.Key = Key;
return Entry;
}
MapEntry &getEntry(MapEntry *Entries, uint64_t Key, uint64_t Selector,
BumpPtrAllocator &Alloc, int CurLevel) {
const uint32_t NumEntries = CurLevel == 0 ? InitialSize : IncSize;
uint64_t Remainder = Selector / NumEntries;
Selector = Selector % NumEntries;
MapEntry &Entry = Entries[Selector];
// A hit
if (Entry.Key == Key) {
return Entry;
}
// Vacant - add new entry
if (Entry.Key == VacantMarker) {
Entry.Key = Key;
return Entry;
}
// Defer to the next level
if (Entry.Key & FollowUpTableMarker) {
return getEntry(
reinterpret_cast<MapEntry *>(Entry.Key & ~FollowUpTableMarker),
Key, Remainder, Alloc, CurLevel + 1);
}
// Conflict - create the next level
MapEntry *NextLevelTbl = new (Alloc, 0) MapEntry[IncSize];
uint64_t CurEntrySelector = Entry.Key / InitialSize;
for (int I = 0; I < CurLevel; ++I)
CurEntrySelector /= IncSize;
CurEntrySelector = CurEntrySelector % IncSize;
NextLevelTbl[CurEntrySelector] = Entry;
Entry.Key = reinterpret_cast<uint64_t>(NextLevelTbl) | FollowUpTableMarker;
return getEntry(NextLevelTbl, Key, Remainder, Alloc, CurLevel + 1);
}
MapEntry &getOrAllocEntry(uint64_t Key, BumpPtrAllocator &Alloc) {
if (TableRoot)
return getEntry(TableRoot, Key, Key, Alloc, 0);
return firstAllocation(Key, Alloc);
}
};
template <typename T> void resetIndCallCounter(T &Entry) {
Entry.Val = 0;
}
template <typename T, uint32_t X, uint32_t Y>
void SimpleHashTable<T, X, Y>::resetCounters() {
Lock L(M);
forEachElement(resetIndCallCounter);
}
/// Represents a hash table mapping a function target address to its counter.
using IndirectCallHashTable = SimpleHashTable<>;
/// Initialize with number 1 instead of 0 so we don't go into .bss. This is the
/// global array of all hash tables storing indirect call destinations happening
/// during runtime, one table per call site.
IndirectCallHashTable *GlobalIndCallCounters{
reinterpret_cast<IndirectCallHashTable *>(1)};
/// Don't allow reentrancy in the fdata writing phase - only one thread writes
/// it
Mutex *GlobalWriteProfileMutex{reinterpret_cast<Mutex *>(1)};
/// Store number of calls in additional to target address (Key) and frequency
/// as perceived by the basic block counter (Val).
struct CallFlowEntryBase : public SimpleHashTableEntryBase {
uint64_t Calls;
};
using CallFlowHashTableBase = SimpleHashTable<CallFlowEntryBase, 11939, 233>;
/// This is a large table indexing all possible call targets (indirect and
/// direct ones). The goal is to find mismatches between number of calls (for
/// those calls we were able to track) and the entry basic block counter of the
/// callee. In most cases, these two should be equal. If not, there are two
/// possible scenarios here:
///
/// * Entry BB has higher frequency than all known calls to this function.
/// In this case, we have dynamic library code or any uninstrumented code
/// calling this function. We will write the profile for these untracked
/// calls as having source "0 [unknown] 0" in the fdata file.
///
/// * Number of known calls is higher than the frequency of entry BB
/// This only happens when there is no counter for the entry BB / callee
/// function is not simple (in BOLT terms). We don't do anything special
/// here and just ignore those (we still report all calls to the non-simple
/// function, though).
///
class CallFlowHashTable : public CallFlowHashTableBase {
public:
CallFlowHashTable(BumpPtrAllocator &Alloc) : Alloc(Alloc) {}
MapEntry &get(uint64_t Key) { return CallFlowHashTableBase::get(Key, Alloc); }
private:
// Different than the hash table for indirect call targets, we do store the
// allocator here since there is only one call flow hash and space overhead
// is negligible.
BumpPtrAllocator &Alloc;
};
///
/// Description metadata emitted by BOLT to describe the program - refer to
/// Passes/Instrumentation.cpp - Instrumentation::emitTablesAsELFNote()
///
struct Location {
uint32_t FunctionName;
uint32_t Offset;
};
struct CallDescription {
Location From;
uint32_t FromNode;
Location To;
uint32_t Counter;
uint64_t TargetAddress;
};
using IndCallDescription = Location;
struct IndCallTargetDescription {
Location Loc;
uint64_t Address;
};
struct EdgeDescription {
Location From;
uint32_t FromNode;
Location To;
uint32_t ToNode;
uint32_t Counter;
};
struct InstrumentedNode {
uint32_t Node;
uint32_t Counter;
};
struct EntryNode {
uint64_t Node;
uint64_t Address;
};
struct FunctionDescription {
uint32_t NumLeafNodes;
const InstrumentedNode *LeafNodes;
uint32_t NumEdges;
const EdgeDescription *Edges;
uint32_t NumCalls;
const CallDescription *Calls;
uint32_t NumEntryNodes;
const EntryNode *EntryNodes;
/// Constructor will parse the serialized function metadata written by BOLT
FunctionDescription(const uint8_t *FuncDesc);
uint64_t getSize() const {
return 16 + NumLeafNodes * sizeof(InstrumentedNode) +
NumEdges * sizeof(EdgeDescription) +
NumCalls * sizeof(CallDescription) +
NumEntryNodes * sizeof(EntryNode);
}
};
/// The context is created when the fdata profile needs to be written to disk
/// and we need to interpret our runtime counters. It contains pointers to the
/// mmaped binary (only the BOLT written metadata section). Deserialization
/// should be straightforward as most data is POD or an array of POD elements.
/// This metadata is used to reconstruct function CFGs.
struct ProfileWriterContext {
IndCallDescription *IndCallDescriptions;
IndCallTargetDescription *IndCallTargets;
uint8_t *FuncDescriptions;
char *Strings; // String table with function names used in this binary
int FileDesc; // File descriptor for the file on disk backing this
// information in memory via mmap
void *MMapPtr; // The mmap ptr
int MMapSize; // The mmap size
/// Hash table storing all possible call destinations to detect untracked
/// calls and correctly report them as [unknown] in output fdata.
CallFlowHashTable *CallFlowTable;
/// Lookup the sorted indirect call target vector to fetch function name and
/// offset for an arbitrary function pointer.
const IndCallTargetDescription *lookupIndCallTarget(uint64_t Target) const;
};
/// Perform a string comparison and returns zero if Str1 matches Str2. Compares
/// at most Size characters.
int compareStr(const char *Str1, const char *Str2, int Size) {
while (*Str1 == *Str2) {
if (*Str1 == '\0' || --Size == 0)
return 0;
++Str1;
++Str2;
}
return 1;
}
/// Output Location to the fdata file
char *serializeLoc(const ProfileWriterContext &Ctx, char *OutBuf,
const Location Loc, uint32_t BufSize) {
// fdata location format: Type Name Offset
// Type 1 - regular symbol
OutBuf = strCopy(OutBuf, "1 ");
const char *Str = Ctx.Strings + Loc.FunctionName;
uint32_t Size = 25;
while (*Str) {
*OutBuf++ = *Str++;
if (++Size >= BufSize)
break;
}
assert(!*Str, "buffer overflow, function name too large");
*OutBuf++ = ' ';
OutBuf = intToStr(OutBuf, Loc.Offset, 16);
*OutBuf++ = ' ';
return OutBuf;
}
/// Read and deserialize a function description written by BOLT. \p FuncDesc
/// points at the beginning of the function metadata structure in the file.
/// See Instrumentation::emitTablesAsELFNote()
FunctionDescription::FunctionDescription(const uint8_t *FuncDesc) {
NumLeafNodes = *reinterpret_cast<const uint32_t *>(FuncDesc);
DEBUG(reportNumber("NumLeafNodes = ", NumLeafNodes, 10));
LeafNodes = reinterpret_cast<const InstrumentedNode *>(FuncDesc + 4);
NumEdges = *reinterpret_cast<const uint32_t *>(
FuncDesc + 4 + NumLeafNodes * sizeof(InstrumentedNode));
DEBUG(reportNumber("NumEdges = ", NumEdges, 10));
Edges = reinterpret_cast<const EdgeDescription *>(
FuncDesc + 8 + NumLeafNodes * sizeof(InstrumentedNode));
NumCalls = *reinterpret_cast<const uint32_t *>(
FuncDesc + 8 + NumLeafNodes * sizeof(InstrumentedNode) +
NumEdges * sizeof(EdgeDescription));
DEBUG(reportNumber("NumCalls = ", NumCalls, 10));
Calls = reinterpret_cast<const CallDescription *>(
FuncDesc + 12 + NumLeafNodes * sizeof(InstrumentedNode) +
NumEdges * sizeof(EdgeDescription));
NumEntryNodes = *reinterpret_cast<const uint32_t *>(
FuncDesc + 12 + NumLeafNodes * sizeof(InstrumentedNode) +
NumEdges * sizeof(EdgeDescription) + NumCalls * sizeof(CallDescription));
DEBUG(reportNumber("NumEntryNodes = ", NumEntryNodes, 10));
EntryNodes = reinterpret_cast<const EntryNode *>(
FuncDesc + 16 + NumLeafNodes * sizeof(InstrumentedNode) +
NumEdges * sizeof(EdgeDescription) + NumCalls * sizeof(CallDescription));
}
/// Read and mmap descriptions written by BOLT from the executable's notes
/// section
#if defined(HAVE_ELF_H) and !defined(__APPLE__)
void *__attribute__((noinline)) __get_pc() {
return __builtin_extract_return_addr(__builtin_return_address(0));
}
/// Get string with address and parse it to hex pair <StartAddress, EndAddress>
bool parseAddressRange(const char *Str, uint64_t &StartAddress,
uint64_t &EndAddress) {
if (!Str)
return false;
// Parsed string format: <hex1>-<hex2>
StartAddress = hexToLong(Str, '-');
while (*Str && *Str != '-')
++Str;
if (!*Str)
return false;
++Str; // swallow '-'
EndAddress = hexToLong(Str);
return true;
}
/// Get full path to the real binary by getting current virtual address
/// and searching for the appropriate link in address range in
/// /proc/self/map_files
static char *getBinaryPath() {
const uint32_t BufSize = 1024;
const uint32_t NameMax = 4096;
const char DirPath[] = "/proc/self/map_files/";
static char TargetPath[NameMax] = {};
char Buf[BufSize];
if (__bolt_instr_binpath[0] != '\0')
return __bolt_instr_binpath;
if (TargetPath[0] != '\0')
return TargetPath;
unsigned long CurAddr = (unsigned long)__get_pc();
uint64_t FDdir = __open(DirPath,
/*flags=*/0 /*O_RDONLY*/,
/*mode=*/0666);
assert(static_cast<int64_t>(FDdir) >= 0,
"failed to open /proc/self/map_files");
while (long Nread = __getdents(FDdir, (struct dirent *)Buf, BufSize)) {
assert(static_cast<int64_t>(Nread) != -1, "failed to get folder entries");
struct dirent *d;
for (long Bpos = 0; Bpos < Nread; Bpos += d->d_reclen) {
d = (struct dirent *)(Buf + Bpos);
uint64_t StartAddress, EndAddress;
if (!parseAddressRange(d->d_name, StartAddress, EndAddress))
continue;
if (CurAddr < StartAddress || CurAddr > EndAddress)
continue;
char FindBuf[NameMax];
char *C = strCopy(FindBuf, DirPath, NameMax);
C = strCopy(C, d->d_name, NameMax - (C - FindBuf));
*C = '\0';
uint32_t Ret = __readlink(FindBuf, TargetPath, sizeof(TargetPath));
assert(Ret != -1 && Ret != BufSize, "readlink error");
TargetPath[Ret] = '\0';
return TargetPath;
}
}
return nullptr;
}
ProfileWriterContext readDescriptions() {
ProfileWriterContext Result;
char *BinPath = getBinaryPath();
assert(BinPath && BinPath[0] != '\0', "failed to find binary path");
uint64_t FD = __open(BinPath,
/*flags=*/0 /*O_RDONLY*/,
/*mode=*/0666);
assert(static_cast<int64_t>(FD) >= 0, "failed to open binary path");
Result.FileDesc = FD;
// mmap our binary to memory
uint64_t Size = __lseek(FD, 0, 2 /*SEEK_END*/);
uint8_t *BinContents = reinterpret_cast<uint8_t *>(
__mmap(0, Size, 0x1 /* PROT_READ*/, 0x2 /* MAP_PRIVATE*/, FD, 0));
Result.MMapPtr = BinContents;
Result.MMapSize = Size;
Elf64_Ehdr *Hdr = reinterpret_cast<Elf64_Ehdr *>(BinContents);
Elf64_Shdr *Shdr = reinterpret_cast<Elf64_Shdr *>(BinContents + Hdr->e_shoff);
Elf64_Shdr *StringTblHeader = reinterpret_cast<Elf64_Shdr *>(
BinContents + Hdr->e_shoff + Hdr->e_shstrndx * Hdr->e_shentsize);
// Find .bolt.instr.tables with the data we need and set pointers to it
for (int I = 0; I < Hdr->e_shnum; ++I) {
char *SecName = reinterpret_cast<char *>(
BinContents + StringTblHeader->sh_offset + Shdr->sh_name);
if (compareStr(SecName, ".bolt.instr.tables", 64) != 0) {
Shdr = reinterpret_cast<Elf64_Shdr *>(BinContents + Hdr->e_shoff +
(I + 1) * Hdr->e_shentsize);
continue;
}
// Actual contents of the ELF note start after offset 20 decimal:
// Offset 0: Producer name size (4 bytes)
// Offset 4: Contents size (4 bytes)
// Offset 8: Note type (4 bytes)
// Offset 12: Producer name (BOLT\0) (5 bytes + align to 4-byte boundary)
// Offset 20: Contents
uint32_t IndCallDescSize =
*reinterpret_cast<uint32_t *>(BinContents + Shdr->sh_offset + 20);
uint32_t IndCallTargetDescSize = *reinterpret_cast<uint32_t *>(
BinContents + Shdr->sh_offset + 24 + IndCallDescSize);
uint32_t FuncDescSize =
*reinterpret_cast<uint32_t *>(BinContents + Shdr->sh_offset + 28 +
IndCallDescSize + IndCallTargetDescSize);
Result.IndCallDescriptions = reinterpret_cast<IndCallDescription *>(
BinContents + Shdr->sh_offset + 24);
Result.IndCallTargets = reinterpret_cast<IndCallTargetDescription *>(
BinContents + Shdr->sh_offset + 28 + IndCallDescSize);
Result.FuncDescriptions = BinContents + Shdr->sh_offset + 32 +
IndCallDescSize + IndCallTargetDescSize;
Result.Strings = reinterpret_cast<char *>(
BinContents + Shdr->sh_offset + 32 + IndCallDescSize +
IndCallTargetDescSize + FuncDescSize);
return Result;
}
const char ErrMsg[] =
"BOLT instrumentation runtime error: could not find section "
".bolt.instr.tables\n";
reportError(ErrMsg, sizeof(ErrMsg));
return Result;
}
#else
ProfileWriterContext readDescriptions() {
ProfileWriterContext Result;
uint8_t *Tables = _bolt_instr_tables_getter();
uint32_t IndCallDescSize = *reinterpret_cast<uint32_t *>(Tables);
uint32_t IndCallTargetDescSize =
*reinterpret_cast<uint32_t *>(Tables + 4 + IndCallDescSize);
uint32_t FuncDescSize = *reinterpret_cast<uint32_t *>(
Tables + 8 + IndCallDescSize + IndCallTargetDescSize);
Result.IndCallDescriptions =
reinterpret_cast<IndCallDescription *>(Tables + 4);
Result.IndCallTargets = reinterpret_cast<IndCallTargetDescription *>(
Tables + 8 + IndCallDescSize);
Result.FuncDescriptions =
Tables + 12 + IndCallDescSize + IndCallTargetDescSize;
Result.Strings = reinterpret_cast<char *>(
Tables + 12 + IndCallDescSize + IndCallTargetDescSize + FuncDescSize);
return Result;
}
#endif
#if !defined(__APPLE__)
/// Debug by printing overall metadata global numbers to check it is sane
void printStats(const ProfileWriterContext &Ctx) {
char StatMsg[BufSize];
char *StatPtr = StatMsg;
StatPtr =
strCopy(StatPtr,
"\nBOLT INSTRUMENTATION RUNTIME STATISTICS\n\nIndCallDescSize: ");
StatPtr = intToStr(StatPtr,
Ctx.FuncDescriptions -
reinterpret_cast<uint8_t *>(Ctx.IndCallDescriptions),
10);
StatPtr = strCopy(StatPtr, "\nFuncDescSize: ");
StatPtr = intToStr(
StatPtr,
reinterpret_cast<uint8_t *>(Ctx.Strings) - Ctx.FuncDescriptions, 10);
StatPtr = strCopy(StatPtr, "\n__bolt_instr_num_ind_calls: ");
StatPtr = intToStr(StatPtr, __bolt_instr_num_ind_calls, 10);
StatPtr = strCopy(StatPtr, "\n__bolt_instr_num_funcs: ");
StatPtr = intToStr(StatPtr, __bolt_instr_num_funcs, 10);
StatPtr = strCopy(StatPtr, "\n");
__write(2, StatMsg, StatPtr - StatMsg);
}
#endif
/// This is part of a simple CFG representation in memory, where we store
/// a dynamically sized array of input and output edges per node, and store
/// a dynamically sized array of nodes per graph. We also store the spanning
/// tree edges for that CFG in a separate array of nodes in
/// \p SpanningTreeNodes, while the regular nodes live in \p CFGNodes.
struct Edge {
uint32_t Node; // Index in nodes array regarding the destination of this edge
uint32_t ID; // Edge index in an array comprising all edges of the graph
};
/// A regular graph node or a spanning tree node
struct Node {
uint32_t NumInEdges{0}; // Input edge count used to size InEdge
uint32_t NumOutEdges{0}; // Output edge count used to size OutEdges
Edge *InEdges{nullptr}; // Created and managed by \p Graph
Edge *OutEdges{nullptr}; // ditto
};
/// Main class for CFG representation in memory. Manages object creation and
/// destruction, populates an array of CFG nodes as well as corresponding
/// spanning tree nodes.
struct Graph {
uint32_t NumNodes;
Node *CFGNodes;
Node *SpanningTreeNodes;
uint64_t *EdgeFreqs;
uint64_t *CallFreqs;
BumpPtrAllocator &Alloc;
const FunctionDescription &D;
/// Reads a list of edges from function description \p D and builds
/// the graph from it. Allocates several internal dynamic structures that are
/// later destroyed by ~Graph() and uses \p Alloc. D.LeafNodes contain all
/// spanning tree leaf nodes descriptions (their counters). They are the seed
/// used to compute the rest of the missing edge counts in a bottom-up
/// traversal of the spanning tree.
Graph(BumpPtrAllocator &Alloc, const FunctionDescription &D,
const uint64_t *Counters, ProfileWriterContext &Ctx);
~Graph();
void dump() const;
private:
void computeEdgeFrequencies(const uint64_t *Counters,
ProfileWriterContext &Ctx);
void dumpEdgeFreqs() const;
};
Graph::Graph(BumpPtrAllocator &Alloc, const FunctionDescription &D,
const uint64_t *Counters, ProfileWriterContext &Ctx)
: Alloc(Alloc), D(D) {
DEBUG(reportNumber("G = 0x", (uint64_t)this, 16));
// First pass to determine number of nodes
int32_t MaxNodes = -1;
CallFreqs = nullptr;
EdgeFreqs = nullptr;
for (int I = 0; I < D.NumEdges; ++I) {
if (static_cast<int32_t>(D.Edges[I].FromNode) > MaxNodes)
MaxNodes = D.Edges[I].FromNode;
if (static_cast<int32_t>(D.Edges[I].ToNode) > MaxNodes)
MaxNodes = D.Edges[I].ToNode;
}
for (int I = 0; I < D.NumLeafNodes; ++I)
if (static_cast<int32_t>(D.LeafNodes[I].Node) > MaxNodes)
MaxNodes = D.LeafNodes[I].Node;
for (int I = 0; I < D.NumCalls; ++I)
if (static_cast<int32_t>(D.Calls[I].FromNode) > MaxNodes)
MaxNodes = D.Calls[I].FromNode;
// No nodes? Nothing to do
if (MaxNodes < 0) {
DEBUG(report("No nodes!\n"));
CFGNodes = nullptr;
SpanningTreeNodes = nullptr;
NumNodes = 0;
return;
}
++MaxNodes;
DEBUG(reportNumber("NumNodes = ", MaxNodes, 10));
NumNodes = static_cast<uint32_t>(MaxNodes);
// Initial allocations
CFGNodes = new (Alloc) Node[MaxNodes];
DEBUG(reportNumber("G->CFGNodes = 0x", (uint64_t)CFGNodes, 16));
SpanningTreeNodes = new (Alloc) Node[MaxNodes];
DEBUG(reportNumber("G->SpanningTreeNodes = 0x",
(uint64_t)SpanningTreeNodes, 16));
// Figure out how much to allocate to each vector (in/out edge sets)
for (int I = 0; I < D.NumEdges; ++I) {
CFGNodes[D.Edges[I].FromNode].NumOutEdges++;
CFGNodes[D.Edges[I].ToNode].NumInEdges++;
if (D.Edges[I].Counter != 0xffffffff)
continue;
SpanningTreeNodes[D.Edges[I].FromNode].NumOutEdges++;
SpanningTreeNodes[D.Edges[I].ToNode].NumInEdges++;
}
// Allocate in/out edge sets
for (int I = 0; I < MaxNodes; ++I) {
if (CFGNodes[I].NumInEdges > 0)
CFGNodes[I].InEdges = new (Alloc) Edge[CFGNodes[I].NumInEdges];
if (CFGNodes[I].NumOutEdges > 0)
CFGNodes[I].OutEdges = new (Alloc) Edge[CFGNodes[I].NumOutEdges];
if (SpanningTreeNodes[I].NumInEdges > 0)
SpanningTreeNodes[I].InEdges =
new (Alloc) Edge[SpanningTreeNodes[I].NumInEdges];
if (SpanningTreeNodes[I].NumOutEdges > 0)
SpanningTreeNodes[I].OutEdges =
new (Alloc) Edge[SpanningTreeNodes[I].NumOutEdges];
CFGNodes[I].NumInEdges = 0;
CFGNodes[I].NumOutEdges = 0;
SpanningTreeNodes[I].NumInEdges = 0;
SpanningTreeNodes[I].NumOutEdges = 0;
}
// Fill in/out edge sets
for (int I = 0; I < D.NumEdges; ++I) {
const uint32_t Src = D.Edges[I].FromNode;
const uint32_t Dst = D.Edges[I].ToNode;
Edge *E = &CFGNodes[Src].OutEdges[CFGNodes[Src].NumOutEdges++];
E->Node = Dst;
E->ID = I;
E = &CFGNodes[Dst].InEdges[CFGNodes[Dst].NumInEdges++];
E->Node = Src;
E->ID = I;
if (D.Edges[I].Counter != 0xffffffff)
continue;
E = &SpanningTreeNodes[Src]
.OutEdges[SpanningTreeNodes[Src].NumOutEdges++];
E->Node = Dst;
E->ID = I;
E = &SpanningTreeNodes[Dst]
.InEdges[SpanningTreeNodes[Dst].NumInEdges++];
E->Node = Src;
E->ID = I;
}
computeEdgeFrequencies(Counters, Ctx);
}
Graph::~Graph() {
if (CallFreqs)
Alloc.deallocate(CallFreqs);
if (EdgeFreqs)
Alloc.deallocate(EdgeFreqs);
for (int I = NumNodes - 1; I >= 0; --I) {
if (SpanningTreeNodes[I].OutEdges)
Alloc.deallocate(SpanningTreeNodes[I].OutEdges);
if (SpanningTreeNodes[I].InEdges)
Alloc.deallocate(SpanningTreeNodes[I].InEdges);
if (CFGNodes[I].OutEdges)
Alloc.deallocate(CFGNodes[I].OutEdges);
if (CFGNodes[I].InEdges)
Alloc.deallocate(CFGNodes[I].InEdges);
}
if (SpanningTreeNodes)
Alloc.deallocate(SpanningTreeNodes);
if (CFGNodes)
Alloc.deallocate(CFGNodes);
}
void Graph::dump() const {
reportNumber("Dumping graph with number of nodes: ", NumNodes, 10);
report(" Full graph:\n");
for (int I = 0; I < NumNodes; ++I) {
const Node *N = &CFGNodes[I];
reportNumber(" Node #", I, 10);
reportNumber(" InEdges total ", N->NumInEdges, 10);
for (int J = 0; J < N->NumInEdges; ++J)
reportNumber(" ", N->InEdges[J].Node, 10);
reportNumber(" OutEdges total ", N->NumOutEdges, 10);
for (int J = 0; J < N->NumOutEdges; ++J)
reportNumber(" ", N->OutEdges[J].Node, 10);
report("\n");
}
report(" Spanning tree:\n");
for (int I = 0; I < NumNodes; ++I) {
const Node *N = &SpanningTreeNodes[I];
reportNumber(" Node #", I, 10);
reportNumber(" InEdges total ", N->NumInEdges, 10);
for (int J = 0; J < N->NumInEdges; ++J)
reportNumber(" ", N->InEdges[J].Node, 10);
reportNumber(" OutEdges total ", N->NumOutEdges, 10);
for (int J = 0; J < N->NumOutEdges; ++J)
reportNumber(" ", N->OutEdges[J].Node, 10);
report("\n");
}
}
void Graph::dumpEdgeFreqs() const {
reportNumber(
"Dumping edge frequencies for graph with num edges: ", D.NumEdges, 10);
for (int I = 0; I < D.NumEdges; ++I) {
reportNumber("* Src: ", D.Edges[I].FromNode, 10);
reportNumber(" Dst: ", D.Edges[I].ToNode, 10);
reportNumber(" Cnt: ", EdgeFreqs[I], 10);
}
}
/// Auxiliary map structure for fast lookups of which calls map to each node of
/// the function CFG
struct NodeToCallsMap {
struct MapEntry {
uint32_t NumCalls;
uint32_t *Calls;
};
MapEntry *Entries;
BumpPtrAllocator &Alloc;
const uint32_t NumNodes;
NodeToCallsMap(BumpPtrAllocator &Alloc, const FunctionDescription &D,
uint32_t NumNodes)
: Alloc(Alloc), NumNodes(NumNodes) {
Entries = new (Alloc, 0) MapEntry[NumNodes];
for (int I = 0; I < D.NumCalls; ++I) {
DEBUG(reportNumber("Registering call in node ", D.Calls[I].FromNode, 10));
++Entries[D.Calls[I].FromNode].NumCalls;
}
for (int I = 0; I < NumNodes; ++I) {
Entries[I].Calls = Entries[I].NumCalls ? new (Alloc)
uint32_t[Entries[I].NumCalls]
: nullptr;
Entries[I].NumCalls = 0;
}
for (int I = 0; I < D.NumCalls; ++I) {
MapEntry &Entry = Entries[D.Calls[I].FromNode];
Entry.Calls[Entry.NumCalls++] = I;
}
}
/// Set the frequency of all calls in node \p NodeID to Freq. However, if
/// the calls have their own counters and do not depend on the basic block
/// counter, this means they have landing pads and throw exceptions. In this
/// case, set their frequency with their counters and return the maximum
/// value observed in such counters. This will be used as the new frequency
/// at basic block entry. This is used to fix the CFG edge frequencies in the
/// presence of exceptions.
uint64_t visitAllCallsIn(uint32_t NodeID, uint64_t Freq, uint64_t *CallFreqs,
const FunctionDescription &D,
const uint64_t *Counters,
ProfileWriterContext &Ctx) const {
const MapEntry &Entry = Entries[NodeID];
uint64_t MaxValue = 0ull;
for (int I = 0, E = Entry.NumCalls; I != E; ++I) {
const uint32_t CallID = Entry.Calls[I];
DEBUG(reportNumber(" Setting freq for call ID: ", CallID, 10));
const CallDescription &CallDesc = D.Calls[CallID];
if (CallDesc.Counter == 0xffffffff) {
CallFreqs[CallID] = Freq;
DEBUG(reportNumber(" with : ", Freq, 10));
} else {
const uint64_t CounterVal = Counters[CallDesc.Counter];
CallFreqs[CallID] = CounterVal;
MaxValue = CounterVal > MaxValue ? CounterVal : MaxValue;
DEBUG(reportNumber(" with (private counter) : ", CounterVal, 10));
}
DEBUG(reportNumber(" Address: 0x", CallDesc.TargetAddress, 16));
if (CallFreqs[CallID] > 0)
Ctx.CallFlowTable->get(CallDesc.TargetAddress).Calls +=
CallFreqs[CallID];
}
return MaxValue;
}
~NodeToCallsMap() {
for (int I = NumNodes - 1; I >= 0; --I)
if (Entries[I].Calls)
Alloc.deallocate(Entries[I].Calls);
Alloc.deallocate(Entries);
}
};
/// Fill an array with the frequency of each edge in the function represented
/// by G, as well as another array for each call.
void Graph::computeEdgeFrequencies(const uint64_t *Counters,
ProfileWriterContext &Ctx) {
if (NumNodes == 0)
return;
EdgeFreqs = D.NumEdges ? new (Alloc, 0) uint64_t [D.NumEdges] : nullptr;
CallFreqs = D.NumCalls ? new (Alloc, 0) uint64_t [D.NumCalls] : nullptr;
// Setup a lookup for calls present in each node (BB)
NodeToCallsMap *CallMap = new (Alloc) NodeToCallsMap(Alloc, D, NumNodes);
// Perform a bottom-up, BFS traversal of the spanning tree in G. Edges in the
// spanning tree don't have explicit counters. We must infer their value using
// a linear combination of other counters (sum of counters of the outgoing
// edges minus sum of counters of the incoming edges).
uint32_t *Stack = new (Alloc) uint32_t [NumNodes];
uint32_t StackTop = 0;
enum Status : uint8_t { S_NEW = 0, S_VISITING, S_VISITED };
Status *Visited = new (Alloc, 0) Status[NumNodes];
uint64_t *LeafFrequency = new (Alloc, 0) uint64_t[NumNodes];
uint64_t *EntryAddress = new (Alloc, 0) uint64_t[NumNodes];
// Setup a fast lookup for frequency of leaf nodes, which have special
// basic block frequency instrumentation (they are not edge profiled).
for (int I = 0; I < D.NumLeafNodes; ++I) {
LeafFrequency[D.LeafNodes[I].Node] = Counters[D.LeafNodes[I].Counter];
DEBUG({
if (Counters[D.LeafNodes[I].Counter] > 0) {
reportNumber("Leaf Node# ", D.LeafNodes[I].Node, 10);
reportNumber(" Counter: ", Counters[D.LeafNodes[I].Counter], 10);
}
});
}
for (int I = 0; I < D.NumEntryNodes; ++I) {
EntryAddress[D.EntryNodes[I].Node] = D.EntryNodes[I].Address;
DEBUG({
reportNumber("Entry Node# ", D.EntryNodes[I].Node, 10);
reportNumber(" Address: ", D.EntryNodes[I].Address, 16);
});
}
// Add all root nodes to the stack
for (int I = 0; I < NumNodes; ++I)
if (SpanningTreeNodes[I].NumInEdges == 0)
Stack[StackTop++] = I;
// Empty stack?
if (StackTop == 0) {
DEBUG(report("Empty stack!\n"));
Alloc.deallocate(EntryAddress);
Alloc.deallocate(LeafFrequency);
Alloc.deallocate(Visited);
Alloc.deallocate(Stack);
CallMap->~NodeToCallsMap();
Alloc.deallocate(CallMap);
if (CallFreqs)
Alloc.deallocate(CallFreqs);
if (EdgeFreqs)
Alloc.deallocate(EdgeFreqs);
EdgeFreqs = nullptr;
CallFreqs = nullptr;
return;
}
// Add all known edge counts, will infer the rest
for (int I = 0; I < D.NumEdges; ++I) {
const uint32_t C = D.Edges[I].Counter;
if (C == 0xffffffff) // inferred counter - we will compute its value
continue;
EdgeFreqs[I] = Counters[C];
}
while (StackTop > 0) {
const uint32_t Cur = Stack[--StackTop];
DEBUG({
if (Visited[Cur] == S_VISITING)
report("(visiting) ");
else
report("(new) ");
reportNumber("Cur: ", Cur, 10);
});
// This shouldn't happen in a tree
assert(Visited[Cur] != S_VISITED, "should not have visited nodes in stack");
if (Visited[Cur] == S_NEW) {
Visited[Cur] = S_VISITING;
Stack[StackTop++] = Cur;
assert(StackTop <= NumNodes, "stack grew too large");
for (int I = 0, E = SpanningTreeNodes[Cur].NumOutEdges; I < E; ++I) {
const uint32_t Succ = SpanningTreeNodes[Cur].OutEdges[I].Node;
Stack[StackTop++] = Succ;
assert(StackTop <= NumNodes, "stack grew too large");
}
continue;
}
Visited[Cur] = S_VISITED;
// Establish our node frequency based on outgoing edges, which should all be
// resolved by now.
int64_t CurNodeFreq = LeafFrequency[Cur];
// Not a leaf?
if (!CurNodeFreq) {
for (int I = 0, E = CFGNodes[Cur].NumOutEdges; I != E; ++I) {
const uint32_t SuccEdge = CFGNodes[Cur].OutEdges[I].ID;
CurNodeFreq += EdgeFreqs[SuccEdge];
}
}
if (CurNodeFreq < 0)
CurNodeFreq = 0;
const uint64_t CallFreq = CallMap->visitAllCallsIn(
Cur, CurNodeFreq > 0 ? CurNodeFreq : 0, CallFreqs, D, Counters, Ctx);
// Exception handling affected our output flow? Fix with calls info
DEBUG({
if (CallFreq > CurNodeFreq)
report("Bumping node frequency with call info\n");
});
CurNodeFreq = CallFreq > CurNodeFreq ? CallFreq : CurNodeFreq;
if (CurNodeFreq > 0) {
if (uint64_t Addr = EntryAddress[Cur]) {
DEBUG(
reportNumber(" Setting flow at entry point address 0x", Addr, 16));
DEBUG(reportNumber(" with: ", CurNodeFreq, 10));
Ctx.CallFlowTable->get(Addr).Val = CurNodeFreq;
}
}
// No parent? Reached a tree root, limit to call frequency updating.
if (SpanningTreeNodes[Cur].NumInEdges == 0)
continue;
assert(SpanningTreeNodes[Cur].NumInEdges == 1, "must have 1 parent");
const uint32_t Parent = SpanningTreeNodes[Cur].InEdges[0].Node;
const uint32_t ParentEdge = SpanningTreeNodes[Cur].InEdges[0].ID;
// Calculate parent edge freq.
int64_t ParentEdgeFreq = CurNodeFreq;
for (int I = 0, E = CFGNodes[Cur].NumInEdges; I != E; ++I) {
const uint32_t PredEdge = CFGNodes[Cur].InEdges[I].ID;
ParentEdgeFreq -= EdgeFreqs[PredEdge];
}
// Sometimes the conservative CFG that BOLT builds will lead to incorrect
// flow computation. For example, in a BB that transitively calls the exit
// syscall, BOLT will add a fall-through successor even though it should not
// have any successors. So this block execution will likely be wrong. We
// tolerate this imperfection since this case should be quite infrequent.
if (ParentEdgeFreq < 0) {
DEBUG(dumpEdgeFreqs());
DEBUG(report("WARNING: incorrect flow"));
ParentEdgeFreq = 0;
}
DEBUG(reportNumber(" Setting freq for ParentEdge: ", ParentEdge, 10));
DEBUG(reportNumber(" with ParentEdgeFreq: ", ParentEdgeFreq, 10));
EdgeFreqs[ParentEdge] = ParentEdgeFreq;
}
Alloc.deallocate(EntryAddress);
Alloc.deallocate(LeafFrequency);
Alloc.deallocate(Visited);
Alloc.deallocate(Stack);
CallMap->~NodeToCallsMap();
Alloc.deallocate(CallMap);
DEBUG(dumpEdgeFreqs());
}
/// Write to \p FD all of the edge profiles for function \p FuncDesc. Uses
/// \p Alloc to allocate helper dynamic structures used to compute profile for
/// edges that we do not explictly instrument.
const uint8_t *writeFunctionProfile(int FD, ProfileWriterContext &Ctx,
const uint8_t *FuncDesc,
BumpPtrAllocator &Alloc) {
const FunctionDescription F(FuncDesc);
const uint8_t *next = FuncDesc + F.getSize();
#if !defined(__APPLE__)
uint64_t *bolt_instr_locations = __bolt_instr_locations;
#else
uint64_t *bolt_instr_locations = _bolt_instr_locations_getter();
#endif
// Skip funcs we know are cold
#ifndef ENABLE_DEBUG
uint64_t CountersFreq = 0;
for (int I = 0; I < F.NumLeafNodes; ++I)
CountersFreq += bolt_instr_locations[F.LeafNodes[I].Counter];
if (CountersFreq == 0) {
for (int I = 0; I < F.NumEdges; ++I) {
const uint32_t C = F.Edges[I].Counter;
if (C == 0xffffffff)
continue;
CountersFreq += bolt_instr_locations[C];
}
if (CountersFreq == 0) {
for (int I = 0; I < F.NumCalls; ++I) {
const uint32_t C = F.Calls[I].Counter;
if (C == 0xffffffff)
continue;
CountersFreq += bolt_instr_locations[C];
}
if (CountersFreq == 0)
return next;
}
}
#endif
Graph *G = new (Alloc) Graph(Alloc, F, bolt_instr_locations, Ctx);
DEBUG(G->dump());
if (!G->EdgeFreqs && !G->CallFreqs) {
G->~Graph();
Alloc.deallocate(G);
return next;
}
for (int I = 0; I < F.NumEdges; ++I) {
const uint64_t Freq = G->EdgeFreqs[I];
if (Freq == 0)
continue;
const EdgeDescription *Desc = &F.Edges[I];
char LineBuf[BufSize];
char *Ptr = LineBuf;
Ptr = serializeLoc(Ctx, Ptr, Desc->From, BufSize);
Ptr = serializeLoc(Ctx, Ptr, Desc->To, BufSize - (Ptr - LineBuf));
Ptr = strCopy(Ptr, "0 ", BufSize - (Ptr - LineBuf) - 22);
Ptr = intToStr(Ptr, Freq, 10);
*Ptr++ = '\n';
__write(FD, LineBuf, Ptr - LineBuf);
}
for (int I = 0; I < F.NumCalls; ++I) {
const uint64_t Freq = G->CallFreqs[I];
if (Freq == 0)
continue;
char LineBuf[BufSize];
char *Ptr = LineBuf;
const CallDescription *Desc = &F.Calls[I];
Ptr = serializeLoc(Ctx, Ptr, Desc->From, BufSize);
Ptr = serializeLoc(Ctx, Ptr, Desc->To, BufSize - (Ptr - LineBuf));
Ptr = strCopy(Ptr, "0 ", BufSize - (Ptr - LineBuf) - 25);
Ptr = intToStr(Ptr, Freq, 10);
*Ptr++ = '\n';
__write(FD, LineBuf, Ptr - LineBuf);
}
G->~Graph();
Alloc.deallocate(G);
return next;
}
#if !defined(__APPLE__)
const IndCallTargetDescription *
ProfileWriterContext::lookupIndCallTarget(uint64_t Target) const {
uint32_t B = 0;
uint32_t E = __bolt_instr_num_ind_targets;
if (E == 0)
return nullptr;
do {
uint32_t I = (E - B) / 2 + B;
if (IndCallTargets[I].Address == Target)
return &IndCallTargets[I];
if (IndCallTargets[I].Address < Target)
B = I + 1;
else
E = I;
} while (B < E);
return nullptr;
}
/// Write a single indirect call <src, target> pair to the fdata file
void visitIndCallCounter(IndirectCallHashTable::MapEntry &Entry,
int FD, int CallsiteID,
ProfileWriterContext *Ctx) {
if (Entry.Val == 0)
return;
DEBUG(reportNumber("Target func 0x", Entry.Key, 16));
DEBUG(reportNumber("Target freq: ", Entry.Val, 10));
const IndCallDescription *CallsiteDesc =
&Ctx->IndCallDescriptions[CallsiteID];
const IndCallTargetDescription *TargetDesc =
Ctx->lookupIndCallTarget(Entry.Key);
if (!TargetDesc) {
DEBUG(report("Failed to lookup indirect call target\n"));
char LineBuf[BufSize];
char *Ptr = LineBuf;
Ptr = serializeLoc(*Ctx, Ptr, *CallsiteDesc, BufSize);
Ptr = strCopy(Ptr, "0 [unknown] 0 0 ", BufSize - (Ptr - LineBuf) - 40);
Ptr = intToStr(Ptr, Entry.Val, 10);
*Ptr++ = '\n';
__write(FD, LineBuf, Ptr - LineBuf);
return;
}
Ctx->CallFlowTable->get(TargetDesc->Address).Calls += Entry.Val;
char LineBuf[BufSize];
char *Ptr = LineBuf;
Ptr = serializeLoc(*Ctx, Ptr, *CallsiteDesc, BufSize);
Ptr = serializeLoc(*Ctx, Ptr, TargetDesc->Loc, BufSize - (Ptr - LineBuf));
Ptr = strCopy(Ptr, "0 ", BufSize - (Ptr - LineBuf) - 25);
Ptr = intToStr(Ptr, Entry.Val, 10);
*Ptr++ = '\n';
__write(FD, LineBuf, Ptr - LineBuf);
}
/// Write to \p FD all of the indirect call profiles.
void writeIndirectCallProfile(int FD, ProfileWriterContext &Ctx) {
for (int I = 0; I < __bolt_instr_num_ind_calls; ++I) {
DEBUG(reportNumber("IndCallsite #", I, 10));
GlobalIndCallCounters[I].forEachElement(visitIndCallCounter, FD, I, &Ctx);
}
}
/// Check a single call flow for a callee versus all known callers. If there are
/// less callers than what the callee expects, write the difference with source
/// [unknown] in the profile.
void visitCallFlowEntry(CallFlowHashTable::MapEntry &Entry, int FD,
ProfileWriterContext *Ctx) {
DEBUG(reportNumber("Call flow entry address: 0x", Entry.Key, 16));
DEBUG(reportNumber("Calls: ", Entry.Calls, 10));
DEBUG(reportNumber("Reported entry frequency: ", Entry.Val, 10));
DEBUG({
if (Entry.Calls > Entry.Val)
report(" More calls than expected!\n");
});
if (Entry.Val <= Entry.Calls)
return;
DEBUG(reportNumber(
" Balancing calls with traffic: ", Entry.Val - Entry.Calls, 10));
const IndCallTargetDescription *TargetDesc =
Ctx->lookupIndCallTarget(Entry.Key);
if (!TargetDesc) {
// There is probably something wrong with this callee and this should be
// investigated, but I don't want to assert and lose all data collected.
DEBUG(report("WARNING: failed to look up call target!\n"));
return;
}
char LineBuf[BufSize];
char *Ptr = LineBuf;
Ptr = strCopy(Ptr, "0 [unknown] 0 ", BufSize);
Ptr = serializeLoc(*Ctx, Ptr, TargetDesc->Loc, BufSize - (Ptr - LineBuf));
Ptr = strCopy(Ptr, "0 ", BufSize - (Ptr - LineBuf) - 25);
Ptr = intToStr(Ptr, Entry.Val - Entry.Calls, 10);
*Ptr++ = '\n';
__write(FD, LineBuf, Ptr - LineBuf);
}
/// Open fdata file for writing and return a valid file descriptor, aborting
/// program upon failure.
int openProfile() {
// Build the profile name string by appending our PID
char Buf[BufSize];
char *Ptr = Buf;
uint64_t PID = __getpid();
Ptr = strCopy(Buf, __bolt_instr_filename, BufSize);
if (__bolt_instr_use_pid) {
Ptr = strCopy(Ptr, ".", BufSize - (Ptr - Buf + 1));
Ptr = intToStr(Ptr, PID, 10);
Ptr = strCopy(Ptr, ".fdata", BufSize - (Ptr - Buf + 1));
}
*Ptr++ = '\0';
uint64_t FD = __open(Buf,
/*flags=*/0x241 /*O_WRONLY|O_TRUNC|O_CREAT*/,
/*mode=*/0666);
if (static_cast<int64_t>(FD) < 0) {
report("Error while trying to open profile file for writing: ");
report(Buf);
reportNumber("\nFailed with error number: 0x",
0 - static_cast<int64_t>(FD), 16);
__exit(1);
}
return FD;
}
#endif
} // anonymous namespace
#if !defined(__APPLE__)
/// Reset all counters in case you want to start profiling a new phase of your
/// program independently of prior phases.
/// The address of this function is printed by BOLT and this can be called by
/// any attached debugger during runtime. There is a useful oneliner for gdb:
///
/// gdb -p $(pgrep -xo PROCESSNAME) -ex 'p ((void(*)())0xdeadbeef)()' \
/// -ex 'set confirm off' -ex quit
///
/// Where 0xdeadbeef is this function address and PROCESSNAME your binary file
/// name.
extern "C" void __bolt_instr_clear_counters() {
memSet(reinterpret_cast<char *>(__bolt_instr_locations), 0,
__bolt_num_counters * 8);
for (int I = 0; I < __bolt_instr_num_ind_calls; ++I)
GlobalIndCallCounters[I].resetCounters();
}
/// This is the entry point for profile writing.
/// There are three ways of getting here:
///
/// * Program execution ended, finalization methods are running and BOLT
/// hooked into FINI from your binary dynamic section;
/// * You used the sleep timer option and during initialization we forked
/// a separete process that will call this function periodically;
/// * BOLT prints this function address so you can attach a debugger and
/// call this function directly to get your profile written to disk
/// on demand.
///
extern "C" void __attribute((force_align_arg_pointer))
__bolt_instr_data_dump() {
// Already dumping
if (!GlobalWriteProfileMutex->acquire())
return;
BumpPtrAllocator HashAlloc;
HashAlloc.setMaxSize(0x6400000);
ProfileWriterContext Ctx = readDescriptions();
Ctx.CallFlowTable = new (HashAlloc, 0) CallFlowHashTable(HashAlloc);
DEBUG(printStats(Ctx));
int FD = openProfile();
BumpPtrAllocator Alloc;
const uint8_t *FuncDesc = Ctx.FuncDescriptions;
for (int I = 0, E = __bolt_instr_num_funcs; I < E; ++I) {
FuncDesc = writeFunctionProfile(FD, Ctx, FuncDesc, Alloc);
Alloc.clear();
DEBUG(reportNumber("FuncDesc now: ", (uint64_t)FuncDesc, 16));
}
assert(FuncDesc == (void *)Ctx.Strings,
"FuncDesc ptr must be equal to stringtable");
writeIndirectCallProfile(FD, Ctx);
Ctx.CallFlowTable->forEachElement(visitCallFlowEntry, FD, &Ctx);
__fsync(FD);
__close(FD);
__munmap(Ctx.MMapPtr, Ctx.MMapSize);
__close(Ctx.FileDesc);
HashAlloc.destroy();
GlobalWriteProfileMutex->release();
DEBUG(report("Finished writing profile.\n"));
}
/// Event loop for our child process spawned during setup to dump profile data
/// at user-specified intervals
void watchProcess() {
timespec ts, rem;
uint64_t Ellapsed = 0ull;
uint64_t ppid;
if (__bolt_instr_wait_forks) {
// Store parent pgid
ppid = -__getpgid(0);
// And leave parent process group
__setpgid(0, 0);
} else {
// Store parent pid
ppid = __getppid();
if (ppid == 1) {
// Parent already dead
__bolt_instr_data_dump();
goto out;
}
}
ts.tv_sec = 1;
ts.tv_nsec = 0;
while (1) {
__nanosleep(&ts, &rem);
// This means our parent process or all its forks are dead,
// so no need for us to keep dumping.
if (__kill(ppid, 0) < 0) {
if (__bolt_instr_no_counters_clear)
__bolt_instr_data_dump();
break;
}
if (++Ellapsed < __bolt_instr_sleep_time)
continue;
Ellapsed = 0;
__bolt_instr_data_dump();
if (__bolt_instr_no_counters_clear == false)
__bolt_instr_clear_counters();
}
out:;
DEBUG(report("My parent process is dead, bye!\n"));
__exit(0);
}
extern "C" void __bolt_instr_indirect_call();
extern "C" void __bolt_instr_indirect_tailcall();
/// Initialization code
extern "C" void __attribute((force_align_arg_pointer)) __bolt_instr_setup() {
const uint64_t CountersStart =
reinterpret_cast<uint64_t>(&__bolt_instr_locations[0]);
const uint64_t CountersEnd = alignTo(
reinterpret_cast<uint64_t>(&__bolt_instr_locations[__bolt_num_counters]),
0x1000);
DEBUG(reportNumber("replace mmap start: ", CountersStart, 16));
DEBUG(reportNumber("replace mmap stop: ", CountersEnd, 16));
assert (CountersEnd > CountersStart, "no counters");
// Maps our counters to be shared instead of private, so we keep counting for
// forked processes
__mmap(CountersStart, CountersEnd - CountersStart,
0x3 /*PROT_READ|PROT_WRITE*/,
0x31 /*MAP_ANONYMOUS | MAP_SHARED | MAP_FIXED*/, -1, 0);
__bolt_ind_call_counter_func_pointer = __bolt_instr_indirect_call;
__bolt_ind_tailcall_counter_func_pointer = __bolt_instr_indirect_tailcall;
// Conservatively reserve 100MiB shared pages
GlobalAlloc.setMaxSize(0x6400000);
GlobalAlloc.setShared(true);
GlobalWriteProfileMutex = new (GlobalAlloc, 0) Mutex();
if (__bolt_instr_num_ind_calls > 0)
GlobalIndCallCounters =
new (GlobalAlloc, 0) IndirectCallHashTable[__bolt_instr_num_ind_calls];
if (__bolt_instr_sleep_time != 0) {
// Separate instrumented process to the own process group
if (__bolt_instr_wait_forks)
__setpgid(0, 0);
if (long PID = __fork())
return;
watchProcess();
}
}
extern "C" __attribute((force_align_arg_pointer)) void
instrumentIndirectCall(uint64_t Target, uint64_t IndCallID) {
GlobalIndCallCounters[IndCallID].incrementVal(Target, GlobalAlloc);
}
/// We receive as in-stack arguments the identifier of the indirect call site
/// as well as the target address for the call
extern "C" __attribute((naked)) void __bolt_instr_indirect_call()
{
__asm__ __volatile__(SAVE_ALL
"mov 0xa0(%%rsp), %%rdi\n"
"mov 0x98(%%rsp), %%rsi\n"
"call instrumentIndirectCall\n"
RESTORE_ALL
"ret\n"
:::);
}
extern "C" __attribute((naked)) void __bolt_instr_indirect_tailcall()
{
__asm__ __volatile__(SAVE_ALL
"mov 0x98(%%rsp), %%rdi\n"
"mov 0x90(%%rsp), %%rsi\n"
"call instrumentIndirectCall\n"
RESTORE_ALL
"ret\n"
:::);
}
/// This is hooking ELF's entry, it needs to save all machine state.
extern "C" __attribute((naked)) void __bolt_instr_start()
{
__asm__ __volatile__(SAVE_ALL
"call __bolt_instr_setup\n"
RESTORE_ALL
"jmp __bolt_start_trampoline\n"
:::);
}
/// This is hooking into ELF's DT_FINI
extern "C" void __bolt_instr_fini() {
__bolt_fini_trampoline();
if (__bolt_instr_sleep_time == 0)
__bolt_instr_data_dump();
DEBUG(report("Finished.\n"));
}
#endif
#if defined(__APPLE__)
extern "C" void __bolt_instr_data_dump() {
ProfileWriterContext Ctx = readDescriptions();
int FD = 2;
BumpPtrAllocator Alloc;
const uint8_t *FuncDesc = Ctx.FuncDescriptions;
uint32_t bolt_instr_num_funcs = _bolt_instr_num_funcs_getter();
for (int I = 0, E = bolt_instr_num_funcs; I < E; ++I) {
FuncDesc = writeFunctionProfile(FD, Ctx, FuncDesc, Alloc);
Alloc.clear();
DEBUG(reportNumber("FuncDesc now: ", (uint64_t)FuncDesc, 16));
}
assert(FuncDesc == (void *)Ctx.Strings,
"FuncDesc ptr must be equal to stringtable");
}
// On OSX/iOS the final symbol name of an extern "C" function/variable contains
// one extra leading underscore: _bolt_instr_setup -> __bolt_instr_setup.
extern "C"
__attribute__((section("__TEXT,__setup")))
__attribute__((force_align_arg_pointer))
void _bolt_instr_setup() {
__asm__ __volatile__(SAVE_ALL :::);
report("Hello!\n");
__asm__ __volatile__(RESTORE_ALL :::);
}
extern "C"
__attribute__((section("__TEXT,__fini")))
__attribute__((force_align_arg_pointer))
void _bolt_instr_fini() {
report("Bye!\n");
__bolt_instr_data_dump();
}
#endif
#endif
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