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335c1007bf
__ppc_get_timebase_freq() always return 0 when using static linked
glibc.
This is a minimal example.c to reproduce:
/******************************/
#include <inttypes.h>
#include <stdint.h>
#include <stdio.h>
#include <sys/platform/ppc.h>
int main() {
uint64_t freq = __ppc_get_timebase_freq();
printf("Time Base frequency = %"PRIu64" Hz\n", freq);
if (freq == 0)
return -1;
return 0;
}
/******************************/
Compile command: gcc -static example.c
This bug has been reproduced, fixed and tested on all powerpc platforms
(ppc32, ppc64 and ppc64le).
The underlying code of __ppc_get_timebase_freq uses __get_timebase_freq
that has a different implementation for shared and static version of
glibc. In the static version, there is an incorrect sense in the if
check for the fd returned when opening /proc/cpuinfo.
This solution is mostly a cherry-pick from:
commit 4791e4f773d060c1a37b27aac5b03cdfa9327afc
Author: Stan Shebs <stanshebs@google.com>
Date: Fri May 17 12:25:19 2019 -0700
Subject: Fix sense of a test in the static-linking version of ppc get_clockfreq
That is in branch glibc/google/grte/v5-2.27/master and was mentioned for
inclusion on master here:
https://www.sourceware.org/ml/libc-alpha/2019-05/msg00409.html
Adapted from original fix for get_clockfreq. That code was moved to
get_timebase_freq.
Also added a static-build testcase for __ppc_get_timebase_freq since the
underlying function has different implementations for shared and static
build.
[BZ #24640]
* sysdeps/unix/sysv/linux/powerpc/get_timebase_freq.c
[!SHARED] (__get_timebase_freq): Fix sense of a test in the
static-linking version.
* sysdeps/unix/sysv/linux/powerpc/Makefile
(tests-static): Add test-gettimebasefreq-static.
(tests): Likewise.
* sysdeps/unix/sysv/linux/powerpc/test-gettimebasefreq-static.c:
New file.
107 lines
3.3 KiB
C
107 lines
3.3 KiB
C
/* Get the frequency of the time base.
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Copyright (C) 2012-2019 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 <stdint.h>
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#include <string.h>
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#include <libc-internal.h>
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#include <not-cancel.h>
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#include <libc-vdso.h>
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uint64_t
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__get_timebase_freq (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_unlikely (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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weak_alias (__get_timebase_freq, __ppc_get_timebase_freq)
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