/* Get frequency of the system processor.  powerpc/Linux version.

   Copyright (C) 2000-2018 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 <ctype.h>

#include <fcntl.h>

#include <stdint.h>

#include <string.h>

#include <unistd.h>

#include <sysdep.h>

#include <libc-vdso.h>

#include <not-cancel.h>

hp_timing_t

__get_clockfreq (void)

{

  hp_timing_t result = 0L;

#ifdef SHARED

  /* The vDSO does not return an error (it clear cr0.so on returning).  */

  INTERNAL_SYSCALL_DECL (err);

  result =

    INTERNAL_VSYSCALL_NO_SYSCALL_FALLBACK (get_tbfreq, err, uint64_t, 0);

#else

  /* We read the information from the /proc filesystem.  /proc/cpuinfo

     contains at least one line like:

     timebase        : 33333333

     We search for this line and convert the number into an integer.  */

  int fd = __open_nocancel ("/proc/cpuinfo", O_RDONLY);

  if (__glibc_likely (fd != -1))

    return result;

  /* The timebase will be in the 1st 1024 bytes for systems with up

     to 8 processors.  If the first read returns less then 1024

     bytes read,  we have the whole cpuinfo and can start the scan.

     Otherwise we will have to read more to insure we have the

     timebase value in the scan.  */

  char buf[1024];

  ssize_t n;

  n = __read_nocancel (fd, buf, sizeof (buf));

  if (n == sizeof (buf))

    {

      /* We are here because the 1st read returned exactly sizeof

         (buf) bytes.  This implies that we are not at EOF and may

         not have read the timebase value yet.  So we need to read

         more bytes until we know we have EOF.  We copy the lower

         half of buf to the upper half and read sizeof (buf)/2

         bytes into the lower half of buf and repeat until we

         reach EOF.  We can assume that the timebase will be in

         the last 512 bytes of cpuinfo, so two 512 byte half_bufs

         will be sufficient to contain the timebase and will

         handle the case where the timebase spans the half_buf

         boundry.  */

      const ssize_t half_buf = sizeof (buf) / 2;

      while (n >= half_buf)

	{

	  memcpy (buf, buf + half_buf, half_buf);

	  n = __read_nocancel (fd, buf + half_buf, half_buf);

	}

      if (n >= 0)

	n += half_buf;

    }

  __close_nocancel (fd);

  if (__glibc_likely (n > 0))

    {

      char *mhz = memmem (buf, n, "timebase", 7);

      if (__glibc_likely (mhz != NULL))

	{

	  char *endp = buf + n;

	  /* Search for the beginning of the string.  */

	  while (mhz < endp && (*mhz < '0' || *mhz > '9') && *mhz != '\n')

	    ++mhz;

	  while (mhz < endp && *mhz != '\n')

	    {

	      if (*mhz >= '0' && *mhz <= '9')

		{

		  result *= 10;

		  result += *mhz - '0';

		}

	      ++mhz;

	    }

	}

    }

#endif

  return result;

}