/* Low-level statistical profiling support function.  Mach/Hurd version.

   Copyright (C) 1995-2018 Free Software Foundation, Inc.

   This file is part of the GNU C Library.

   The GNU C Library is free software; you can redistribute it and/or

   modify it under the terms of the GNU Lesser General Public

   License as published by the Free Software Foundation; either

   version 2.1 of the License, or (at your option) any later version.

   The GNU C Library is distributed in the hope that it will be useful,

   but WITHOUT ANY WARRANTY; without even the implied warranty of

   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public

   License along with the GNU C Library; if not, see

   <http://www.gnu.org/licenses/>.  */

#include <sys/types.h>

#include <unistd.h>

#include <errno.h>

#include <hurd.h>

#include <mach/mach4.h>

#include <mach/pc_sample.h>

#include <cthreads.h>

#include <assert.h>

#include <libc-internal.h>

#define MAX_PC_SAMPLES	512	/* XXX ought to be exported in kernel hdr */

static thread_t profile_thread = MACH_PORT_NULL;

static u_short *samples;

static size_t maxsamples;

static size_t pc_offset;

static size_t sample_scale;

static sampled_pc_seqno_t seqno;

static spin_lock_t lock = SPIN_LOCK_INITIALIZER;

static mach_msg_timeout_t collector_timeout; /* ms between collections.  */

static int profile_tick;

/* Reply port used by profiler thread */

static mach_port_t profil_reply_port = MACH_PORT_NULL;

/* Forwards */

static kern_return_t profil_task_get_sampled_pcs (mach_port_t,

						  sampled_pc_seqno_t *,

						  sampled_pc_array_t,

						  mach_msg_type_number_t *);

static void fetch_samples (void);

static void profile_waiter (void);

/* Enable statistical profiling, writing samples of the PC into at most

   SIZE bytes of SAMPLE_BUFFER; every processor clock tick while profiling

   is enabled, the system examines the user PC and increments

   SAMPLE_BUFFER[((PC - OFFSET) / 2) * SCALE / 65536].  If SCALE is zero,

   disable profiling.  Returns zero on success, -1 on error.  */

static error_t

update_waiter (u_short *sample_buffer, size_t size, size_t offset, u_int scale)

{

  error_t err;

  if (profile_thread == MACH_PORT_NULL)

    {

      if (profil_reply_port == MACH_PORT_NULL)

	profil_reply_port = __mach_reply_port ();

      /* Set up the profiling collector thread.  */

      err = __thread_create (__mach_task_self (), &profile_thread);

      if (! err)

	err = __mach_setup_thread (__mach_task_self (), profile_thread,

				   &profile_waiter, NULL, NULL);

      if (! err)

	err = __mach_setup_tls(profile_thread);

    }

  else

    err = 0;

  if (! err)

    {

      err = __task_enable_pc_sampling (__mach_task_self (), &profile_tick,

				       SAMPLED_PC_PERIODIC);

      if (!err && sample_scale == 0)

	/* Profiling was not turned on, so the collector thread was

	   suspended.  Resume it.  */

	err = __thread_resume (profile_thread);

      if (! err)

	{

	  samples = sample_buffer;

	  maxsamples = size / sizeof *sample_buffer;

	  pc_offset = offset;

	  sample_scale = scale;

	  /* Calculate a good period for the collector thread.  From TICK

	     and the kernel buffer size we get the length of time it takes

	     to fill the buffer; translate that to milliseconds for

	     mach_msg, and chop it in half for general lag factor.  */

	  collector_timeout = MAX_PC_SAMPLES * profile_tick / 1000 / 2;

	}

    }

  return err;

}

int

__profile_frequency (void)

{

  return 1000000 / profile_tick;

}

libc_hidden_def (__profile_frequency)

int

__profil (u_short *sample_buffer, size_t size, size_t offset, u_int scale)

{

  error_t err;

  __spin_lock (&lock);

  if (scale == 0)

    {

      /* Disable profiling.  */

      int count;

      if (profile_thread != MACH_PORT_NULL)

	__thread_suspend (profile_thread);

      /* Fetch the last set of samples */

      if (sample_scale)

	fetch_samples ();

      err = __task_disable_pc_sampling (__mach_task_self (), &count);

      sample_scale = 0;

      seqno = 0;

    }

  else

    err = update_waiter (sample_buffer, size, offset, scale);

  __spin_unlock (&lock);

  return err ? __hurd_fail (err) : 0;

}

weak_alias (__profil, profil)

static volatile error_t special_profil_failure;

/* Fetch PC samples.  This function must be very careful not to depend

   on Hurd TLS variables.  We arrange that by using a special

   stub arranged for at the end of this file. */

static void

fetch_samples (void)

{

  sampled_pc_t pc_samples[MAX_PC_SAMPLES];

  mach_msg_type_number_t nsamples, i;

  error_t err;

  nsamples = MAX_PC_SAMPLES;

  err = profil_task_get_sampled_pcs (__mach_task_self (), &seqno,

				     pc_samples, &nsamples);

  if (err)

    {

      static volatile int a, b;

      special_profil_failure = err;

      a = 1;

      b = 0;

      while (1)

	a = a / b;

    }

  for (i = 0; i < nsamples; ++i)

    {

      /* Do arithmetic in long long to avoid overflow problems. */

      long long pc_difference = pc_samples[i].pc - pc_offset;

      size_t idx = ((pc_difference / 2) * sample_scale) / 65536;

      if (idx < maxsamples)

	++samples[idx];

    }

}

/* This function must be very careful not to depend on Hurd TLS

   variables.  We arrange that by using special stubs arranged for at the

   end of this file. */

static void

profile_waiter (void)

{

  mach_msg_header_t msg;

  mach_port_t timeout_reply_port;

  timeout_reply_port = __mach_reply_port ();

  while (1)

    {

      __spin_lock (&lock);

      fetch_samples ();

      __spin_unlock (&lock);

      __mach_msg (&msg, MACH_RCV_MSG|MACH_RCV_TIMEOUT, 0, sizeof msg,

		  timeout_reply_port, collector_timeout, MACH_PORT_NULL);

    }

}

/* Fork interaction */

/* Before fork, lock the interlock so that we are in a clean state. */

static void

fork_profil_prepare (void)

{

  __spin_lock (&lock);

}

text_set_element (_hurd_fork_prepare_hook, fork_profil_prepare);

/* In the parent, unlock the interlock once fork is complete. */

static void

fork_profil_parent (void)

{

  __spin_unlock (&lock);

}

text_set_element (_hurd_fork_parent_hook, fork_profil_parent);

/* In the child, unlock the interlock, and start a profiling thread up

   if necessary. */

static void

fork_profil_child (void)

{

  u_short *sb;

  size_t n, o, ss;

  error_t err;

  __spin_unlock (&lock);

  if (profile_thread != MACH_PORT_NULL)

    {

      __mach_port_deallocate (__mach_task_self (), profile_thread);

      profile_thread = MACH_PORT_NULL;

    }

  sb = samples;

  samples = NULL;

  n = maxsamples;

  maxsamples = 0;

  o = pc_offset;

  pc_offset = 0;

  ss = sample_scale;

  sample_scale = 0;

  if (ss != 0)

    {

      err = update_waiter (sb, n * sizeof *sb, o, ss);

      assert_perror (err);

    }

}

text_set_element (_hurd_fork_child_hook, fork_profil_child);

/* Special RPC stubs for profile_waiter are made by including the normal

   source code, with special CPP state to prevent it from doing the

   usual thing. */

/* Include these first; then our #define's will take full effect, not

   being overridden. */

#include <mach/mig_support.h>

/* This need not do anything; it is always associated with errors, which

   are fatal in profile_waiter anyhow. */

#define __mig_put_reply_port(foo)

/* Use our static variable instead of the usual TLS mechanism for

   this. */

#define __mig_get_reply_port() profil_reply_port

/* Make the functions show up as static */

#define mig_external static

/* Turn off the attempt to generate ld aliasing records. */

#undef weak_alias

#define weak_alias(a,b)

/* And change their names to avoid confusing disasters. */

#define __vm_deallocate_rpc profil_vm_deallocate

#define __task_get_sampled_pcs profil_task_get_sampled_pcs

/* And include the source code */

#include <../mach/RPC_task_get_sampled_pcs.c>