2.5-18.1

sysdeps/unix/sysv/linux/powerpc/get_clockfreq.c

@@ -0,0 +1,117 @@
+/* Get frequency of the system processor.  powerpc/Linux version.
+   Copyright (C) 2000, 2001, 2005 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, write to the Free
+   Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
+   02111-1307 USA.  */
+
+#include <ctype.h>
+#include <fcntl.h>
+#include <string.h>
+#include <unistd.h>
+#include <libc-internal.h>
+#include <sysdep.h>
+#include <bits/libc-vdso.h>
+
+hp_timing_t
+__get_clockfreq (void)
+{
+  /* 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.  */
+  static hp_timing_t timebase_freq;
+  hp_timing_t result = 0L;
+
+  /* If this function was called before, we know the result.  */
+  if (timebase_freq != 0)
+    return timebase_freq;
+
+  /* If we can use the vDSO to obtain the timebase even better.  */
+#ifdef SHARED
+  INTERNAL_SYSCALL_DECL (err);
+  timebase_freq = INTERNAL_VSYSCALL_NO_SYSCALL_FALLBACK (get_tbfreq, err, 0);
+  if (INTERNAL_SYSCALL_ERROR_P (timebase_freq, err)
+      && INTERNAL_SYSCALL_ERRNO (timebase_freq, err) == ENOSYS)
+#endif
+    {
+      int fd = open ("/proc/cpuinfo", O_RDONLY);
+
+      if (__builtin_expect (fd != -1, 1))
+	{
+	  /* 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 (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 (fd, buf + half_buf, half_buf);
+		}
+	      if (n >= 0)
+		n += half_buf;
+	    }
+
+	  if (__builtin_expect (n, 1) > 0)
+	    {
+	      char *mhz = memmem (buf, n, "timebase", 7);
+
+	      if (__builtin_expect (mhz != NULL, 1))
+		{
+		  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;
+		    }
+		}
+	      timebase_freq = result;
+	    }
+	  close (fd);
+	}
+    }
+
+  return timebase_freq;
+}