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6b2ba95b6b
This patch fix powerpc __get_clockfreq racy and cancel-safe issues by dropping internal static cache and by using nocancel file operations. The vDSO failure check is also removed, since kernel code does not return an error (it cleans cr0.so bit on function return) and the static code (to read value /proc) now uses non-cancellable calls.
109 lines
3.4 KiB
C
109 lines
3.4 KiB
C
/* Get frequency of the system processor. powerpc/Linux version.
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Copyright (C) 2000-2015 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<http://www.gnu.org/licenses/>. */
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#include <ctype.h>
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#include <fcntl.h>
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#include <stdint.h>
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#include <string.h>
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#include <unistd.h>
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#include <libc-internal.h>
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#include <sysdep.h>
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#include <bits/libc-vdso.h>
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#include <not-cancel.h>
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hp_timing_t
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__get_clockfreq (void)
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{
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hp_timing_t result = 0L;
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#ifdef SHARED
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/* The vDSO does not return an error (it clear cr0.so on returning). */
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INTERNAL_SYSCALL_DECL (err);
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result =
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INTERNAL_VSYSCALL_NO_SYSCALL_FALLBACK (get_tbfreq, err, uint64_t, 0);
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#else
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/* We read the information from the /proc filesystem. /proc/cpuinfo
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contains at least one line like:
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timebase : 33333333
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We search for this line and convert the number into an integer. */
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int fd = __open_nocancel ("/proc/cpuinfo", O_RDONLY);
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if (__glibc_likely (fd != -1))
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return result;
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/* The timebase will be in the 1st 1024 bytes for systems with up
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to 8 processors. If the first read returns less then 1024
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bytes read, we have the whole cpuinfo and can start the scan.
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Otherwise we will have to read more to insure we have the
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timebase value in the scan. */
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char buf[1024];
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ssize_t n;
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n = __read_nocancel (fd, buf, sizeof (buf));
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if (n == sizeof (buf))
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{
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/* We are here because the 1st read returned exactly sizeof
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(buf) bytes. This implies that we are not at EOF and may
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not have read the timebase value yet. So we need to read
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more bytes until we know we have EOF. We copy the lower
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half of buf to the upper half and read sizeof (buf)/2
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bytes into the lower half of buf and repeat until we
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reach EOF. We can assume that the timebase will be in
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the last 512 bytes of cpuinfo, so two 512 byte half_bufs
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will be sufficient to contain the timebase and will
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handle the case where the timebase spans the half_buf
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boundry. */
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const ssize_t half_buf = sizeof (buf) / 2;
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while (n >= half_buf)
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{
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memcpy (buf, buf + half_buf, half_buf);
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n = __read_nocancel (fd, buf + half_buf, half_buf);
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}
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if (n >= 0)
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n += half_buf;
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}
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__close_nocancel (fd);
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if (__glibc_likely (n > 0))
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{
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char *mhz = memmem (buf, n, "timebase", 7);
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if (__glibc_likely (mhz != NULL))
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{
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char *endp = buf + n;
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/* Search for the beginning of the string. */
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while (mhz < endp && (*mhz < '0' || *mhz > '9') && *mhz != '\n')
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++mhz;
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while (mhz < endp && *mhz != '\n')
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{
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if (*mhz >= '0' && *mhz <= '9')
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{
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result *= 10;
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result += *mhz - '0';
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}
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++mhz;
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}
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}
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}
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#endif
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return result;
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}
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