glibc/sysdeps/mach/hurd/profil.c

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/* Low-level statistical profiling support function. Mach/Hurd version.
Copyright (C) 1995-2017 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);
}
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)
/* Fetch PC samples. This function must be very careful not to depend
on Hurd threadvar 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 error_t special_profil_failure;
static volatile int a, b, c;
special_profil_failure = err;
a = 1;
b = 0;
while (1)
c = 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 threadvar
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 threadvar 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>