IgHook_IgHookTrace.cpp

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//<<<<<< INCLUDES                                                       >>>>>>

#include "IgHook_IgHookTrace.h"
#include <cstdio>
#include <cstdlib>
#include <dlfcn.h>
#include <sys/mman.h>
#include <unistd.h>
#if __linux
#  include <execinfo.h>
#  include <sys/syscall.h>
#  include <ucontext.h>
#  if __x86_64__
#    define UNW_LOCAL_ONLY
#    include <libunwind.h>
#  endif
#endif
#if __APPLE__
extern "C" void _sigtramp( void );
#endif

//<<<<<< PRIVATE DEFINES                                                >>>>>>

#if !defined MAP_ANONYMOUS && defined MAP_ANON
#  define MAP_ANONYMOUS MAP_ANON
#endif

//<<<<<< PRIVATE CONSTANTS                                              >>>>>>
//<<<<<< PRIVATE TYPES                                                  >>>>>>
//<<<<<< PRIVATE VARIABLE DEFINITIONS                                   >>>>>>
//<<<<<< PUBLIC VARIABLE DEFINITIONS                                    >>>>>>
//<<<<<< CLASS STRUCTURE INITIALIZATION                                 >>>>>>
//<<<<<< PRIVATE FUNCTION DEFINITIONS                                   >>>>>>

#if 0 && __x86_64__ && __linux
// Linux x86-64 does not use regular call frames, like IA-32 does for
// example, and it would be a very difficult job to decipher the call
// stack.  In order to walk the call stack correctly, we have to use
// the DWARF-2 unwind data.  This alone is incredibly, uselessly slow
// for our purposes.
//
// We avoid using the unwind data by caching frame structures for
// recently seen functions.  This is slow to start with, but very
// quickly gets fast enough for our purposes.  Fortunately the x86-64
// unwind library appears to be robust enough to be called in signal
// handlers (unlike at least some IA-32 versions).
//
// The cache consists of two arrays arranged as an open-addressed
// unprobed hash table.  Hash collisions overwrite the entry with the
// latest data.  We try to avoid making this a problem by using a
// high-quality hash function and pure brute force in the form of a
// large hash table.  A couple of megabytes goes a long way to help!
//
// The first of the cache arrays, of "void *", tracks program counter
// addresses.  A parallel array of "int" tracks the size of the call
// frame at that address.  Given a program counter and the canonical
// frame address (CFA) of the previous (= above) call frame, the new
// frame address is the previous plus the delta.  We find the address
// of the caller just above this new frame address.
//
// We use the cache as long as we can find the addresses there.  When
// we fall off the cache, we resort to the language run time unwinder.

struct IgHookTraceArgs
{
  struct
  {
    void **pc;
    int **frame;
  } cache;
  struct
  {
    void **addresses;
    int top;
    int size;
  } stack;
  void **prevframe;
};

static _Unwind_Reason_Code
GCCBackTrace (_Unwind_Context *context, void *arg)
{
  IgHookTraceArgs *args = (IgHookTraceArgs *) arg;
  if (args->stack.top < 0 || args->stack.top >= args->stack.size)
    return _URC_END_OF_STACK;

  args->stack.addresses [args->stack.top++] = (void *) _Unwind_GetIP (context);
  args->prevframe = (void **) _Unwind_GetCFA (context);
  return _URC_NO_REASON;
}
#endif

//<<<<<< PUBLIC FUNCTION DEFINITIONS                                    >>>>>>
//<<<<<< MEMBER FUNCTION DEFINITIONS                                    >>>>>>

IgHookTraceAlloc::IgHookTraceAlloc( void ) : m_pool( 0 ), m_left( 0 ) {}

void* IgHookTraceAlloc::allocate( size_t bytes ) {
  // The reason for the existence of this class is to allocate
  // memory directly using mmap() so we don't create calls to
  // malloc() and friends.  This is for two reasons: it must be
  // possible to use this in asynchronous signal handlers, and
  // calling malloc() in those is a really bad idea; and this is
  // meant to be used by profiling code and it's nicer to not
  // allocate memory in ways tracked by the profiler.
  if ( m_left < bytes ) {
    size_t psize = getpagesize();
    size_t hunk  = psize * 20;
    if ( hunk < bytes ) hunk = ( hunk + psize - 1 ) & ~( psize - 1 );
    void* addr = mmap( 0, hunk, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0 );
    if ( addr == MAP_FAILED ) return 0;

    m_pool = addr;
    m_left = hunk;
  }

  void* ptr = m_pool;
  m_pool    = (char*)m_pool + bytes;
  m_left -= bytes;
  return ptr;
}

void* IgHookTrace::CounterValue::operator new( size_t n, IgHookTraceAlloc* alloc /* = 0 */ ) {
  return alloc ? alloc->allocate( n ) : ::operator new( n );
}

IgHookTrace::CounterValue::CounterValue( Counter* counter, CounterValue* next /* = 0 */,
                                         unsigned long long value /* = 0 */ )
    : m_counter( counter ), m_next( next ), m_value( value ), m_count( 0 ) {}

IgHookTrace::Counter* IgHookTrace::CounterValue::counter( void ) { return m_counter; }

IgHookTrace::CounterValue* IgHookTrace::CounterValue::next( void ) { return m_next; }

unsigned long long IgHookTrace::CounterValue::value( void ) { return m_value; }

unsigned long long IgHookTrace::CounterValue::count( void ) { return m_count; }

unsigned long long IgHookTrace::CounterValue::tick( void ) {
  ++m_count;
  return ++m_value;
}

unsigned long long IgHookTrace::CounterValue::untick( void ) {
  --m_count;
  return --m_value;
}

unsigned long long IgHookTrace::CounterValue::add( unsigned long long value ) {
  ++m_count;
  return m_value += value;
}

unsigned long long IgHookTrace::CounterValue::sub( unsigned long long value ) {
  --m_count;
  return m_value -= value;
}

unsigned long long IgHookTrace::CounterValue::max( unsigned long long value ) {
  ++m_count;
  if ( m_value < value ) m_value = value;
  return m_value;
}

unsigned long long IgHookTrace::CounterValue::add( CounterValue& x ) {
  m_count += x.m_count;
  m_value += x.m_value;
  return m_value;
}

unsigned long long IgHookTrace::CounterValue::sub( CounterValue& x ) {
  m_count -= x.m_count;
  m_value -= x.m_value;
  return m_value;
}

unsigned long long IgHookTrace::CounterValue::max( CounterValue& x ) {
  m_count += x.m_count;
  if ( m_value < x.m_value ) m_value = x.m_value;
  return m_value;
}

void* IgHookTrace::operator new( size_t n, IgHookTraceAlloc* alloc /* = 0 */ ) {
  return alloc ? alloc->allocate( n ) : ::operator new( n );
}

IgHookTrace::IgHookTrace( IgHookTrace* parent /* = 0 */, void* address /* = 0 */ )
    : m_alloc( parent ? parent->m_alloc : new IgHookTraceAlloc )
    , m_parent( parent )
    , m_next( parent ? parent->m_children : 0 )
    , m_children( 0 )
    , m_address( address )
    , m_counters( 0 ) {
  if ( m_parent ) m_parent->m_children = this;
}

IgHookTrace* IgHookTrace::parent( void ) { return m_parent; }

IgHookTrace* IgHookTrace::next( void ) { return m_next; }

void* IgHookTrace::address( void ) { return m_address; }

bool IgHookTrace::symbol( void* address, const char*& sym, const char*& lib, int& offset, int& liboffset ) {
  sym = lib = 0;
  offset    = 0;
  liboffset = (unsigned long)address;

  Dl_info info;
  if ( dladdr( address, &info ) ) {
    if ( info.dli_fname && info.dli_fname[0] ) lib = info.dli_fname;

    if ( info.dli_fbase ) liboffset = (unsigned long)address - (unsigned long)info.dli_fbase;

    if ( info.dli_saddr ) offset = (unsigned long)address - (unsigned long)info.dli_saddr;

    if ( info.dli_sname && info.dli_sname[0] ) sym = info.dli_sname;

    return true;
  }

  return false;
}

bool IgHookTrace::symbol( const char*& sym, const char*& lib, int& offset, int& liboffset ) {
  return symbol( m_address, sym, lib, offset, liboffset );
}

void* IgHookTrace::tosymbol( void* address ) {
  Dl_info info;
  return ( dladdr( address, &info ) && info.dli_fname && info.dli_fname[0] && info.dli_saddr ) ? info.dli_saddr
                                                                                               : address;
}