libc/winsup/cygwin/profil.c

/* profil.c -- win32 profil.c equivalent

   This file is part of Cygwin.

   This software is a copyrighted work licensed under the terms of the
   Cygwin license.  Please consult the file "CYGWIN_LICENSE" for
   details. */

/*
 * This file is taken from Cygwin distribution. Please keep it in sync.
 * The differences should be within __MINGW32__ guard.
 */

#ifndef WIN32_LEAN_AND_MEAN
#define WIN32_LEAN_AND_MEAN
#endif
#include <windows.h>
#include <stdio.h>
#include <sys/cygwin.h>
#include <sys/types.h>
#include <errno.h>
#include <pthread.h>
#include "profil.h"

#define SLEEPTIME (1000 / PROF_HZ)

/* global profinfo for profil() call */
static struct profinfo prof;

/* Get the pc for thread THR */

static size_t
get_thrpc (HANDLE thr)
{
  CONTEXT ctx;
  size_t pc;
  int res;

  res = SuspendThread (thr);
  if (res == -1)
    return (size_t) - 1;
  ctx.ContextFlags = CONTEXT_CONTROL | CONTEXT_INTEGER;
  pc = (size_t) - 1;
  if (GetThreadContext (thr, &ctx)) {
#ifndef _WIN64
    pc = ctx.Eip;
#else
    pc = ctx.Rip;
#endif
  }
  ResumeThread (thr);
  return pc;
}

/* Display cell of profile buffer */
#if 0
static void
print_prof (struct profinfo *p)
{
  printf ("profthr %x\ttarget thr %x\n", p->profthr, p->targthr);
  printf ("pc: %x - %x\n", p->lowpc, p->highpc);
  printf ("scale: %x\n", p->scale);
  return;
}
#endif

/* Every time we wake up sample the main thread's pc to hash into the cell
   in the profile buffer ARG.  Then all other pthreads' pc's are sampled.  */

static void
profthr_byhandle (HANDLE thr)
{
  size_t pc;

  /* Sample the pc of the thread indicated by thr; bail if anything amiss. */
  if (thr == INVALID_HANDLE_VALUE)
    return;
  pc = get_thrpc (thr);
  if (pc == -1)
    return;

  /* Code assumes there's only one profinfo in play: the static prof above. */
  if (pc >= prof.lowpc && pc < prof.highpc)
    {
      size_t idx = PROFIDX (pc, prof.lowpc, prof.scale);
      prof.counter[idx]++;
    }
}

static void CALLBACK
profthr_func (LPVOID arg)
{
  struct profinfo *p = (struct profinfo *) arg;

  for (;;)
    {
      /* Record profiling sample for main thread. */
      profthr_byhandle (p->targthr);

      /* Record profiling samples for other pthreads, if any. */
      cygwin_internal (CW_CYGHEAP_PROFTHR_ALL, profthr_byhandle);

#if 0
      print_prof (p);
#endif
      /* Check quit condition, WAIT_OBJECT_0 or WAIT_TIMEOUT */
      if (WaitForSingleObject (p->quitevt, SLEEPTIME) == WAIT_OBJECT_0)
	return;
    }
}

/* Stop profiling to the profiling buffer pointed to by P. */

static int
profile_off (struct profinfo *p)
{
  if (p->profthr)
    {
      SignalObjectAndWait (p->quitevt, p->profthr, INFINITE, FALSE);
      CloseHandle (p->quitevt);
      CloseHandle (p->profthr);
    }
  if (p->targthr)
    CloseHandle (p->targthr);
  p->targthr = 0;
  return 0;
}

/* Create a timer thread and pass it a pointer P to the profiling buffer. */

static int
profile_on (struct profinfo *p)
{
  DWORD thrid;

  /* get handle for this thread */
  if (!DuplicateHandle (GetCurrentProcess (), GetCurrentThread (),
			GetCurrentProcess (), &p->targthr, 0, FALSE,
			DUPLICATE_SAME_ACCESS))
    {
      p->targthr = 0;
      errno = ESRCH;
      return -1;
    }

  p->quitevt = CreateEvent (NULL, TRUE, FALSE, NULL);

  if (!p->quitevt)
    {
      CloseHandle (p->targthr);
      p->targthr = 0;
      errno = EAGAIN;
      return -1;
    }

  p->profthr = CreateThread (0, 0, (DWORD (WINAPI *)(LPVOID)) profthr_func,
                             (void *) p, 0, &thrid);

  if (!p->profthr)
    {
      CloseHandle (p->targthr);
      CloseHandle (p->quitevt);
      p->targthr = 0;
      errno = EAGAIN;
      return -1;
    }

  /* Set profiler thread priority to highest to be sure that it gets the
     processor as soon it requests it (i.e. when the Sleep terminates) to get
     the next data sample as quickly as possible. */

  SetThreadPriority (p->profthr, THREAD_PRIORITY_TIME_CRITICAL);

  return 0;
}

/*
 * Restart profiling in child after fork.
 *
 * The profiling control info in prof needs to be selectively updated.
 * Items counter, lowpc, highpc, and scale are correct as-is.  But items
 * targthr, profthr, and quitevt need updating because these copied HANDLE
 * values are only valid in parent process.  We also zero out the sample
 * buffer so that samples aren't double-counted if multiple gmon.out files
 * are aggregated.  We calculate buffer's size from other data in prof.
 */
static void
profile_child (void)
{
  /* Bail if this was a fork after profiling turned off or was never on. */
  if (!prof.targthr)
    return;

  /* Figure out how big the sample buffer is and zero it out. */
  size_t size = PROFIDX (prof.highpc, prof.lowpc, prof.scale) << 1;
  memset ((char *) prof.counter, 0, size);

  /* Replace stale HANDLEs in prof and create profiling thread. */
  profile_on (&prof);
}

/*
 * Start or stop profiling.
 *
 * Profiling data goes into the SAMPLES buffer of size SIZE (which is treated
 * as an array of uint16_t of size SIZE/2).
 *
 * Each bin represents a range of pc addresses from OFFSET.  The number
 * of pc addresses in a bin depends on SCALE.  (A scale of 65536 maps
 * each bin to two addresses, A scale of 32768 maps each bin to 4 addresses,
 * a scale of 1 maps each bin to 128k addreses).  Scale may be 1 - 65536,
 * or zero to turn off profiling.
 */
int
profile_ctl (struct profinfo * p, char *samples, size_t size,
	     size_t offset, uint32_t scale)
{
  size_t maxbin;

  if (scale > 65536)
    {
      errno = EINVAL;
      return -1;
    }

  profile_off (p);
  if (scale)
    {
      memset (samples, 0, size);
      memset (p, 0, sizeof *p);
      maxbin = size >> 1;
      prof.counter = (uint16_t *) samples;
      prof.lowpc = offset;
      prof.highpc = PROFADDR (maxbin, offset, scale);
      prof.scale = scale;

      /* Set up callback to restart profiling in child after fork. */
      pthread_atfork (NULL, NULL, profile_child);

      return profile_on (p);
    }
  return 0;
}

/* Equivalent to unix profil()
   Every SLEEPTIME interval, the user's program counter (PC) is examined:
   offset is subtracted and the result is multiplied by scale.
   The word pointed to by this address is incremented.  Buf is unused. */

int
profil (char *samples, size_t size, size_t offset, uint32_t scale)
{
  return profile_ctl (&prof, samples, size, offset, scale);
}