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BZ #16418: Fix powerpc get_clockfreq raciness

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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.
This commit is contained in:
Adhemerval Zanella 2014-11-24 16:18:26 -05:00
parent 191220b306
commit 6b2ba95b6b
3 changed files with 76 additions and 80 deletions
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6
ChangeLog
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@ -1,3 +1,9 @@
2015-01-21 Adhemerval Zanella <azanella@linux.vnet.ibm.com>
[BZ #16418]
* sysdeps/unix/sysv/linux/powerpc/get_clockfreq.c (__get_clockfreq):
Make code racy and cancel safe.
2015-01-21 Carlos O'Donell <carlos@redhat.com>
* sysdeps/arm/unwind-resume.h: Fix copyright year.

18
NEWS
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@ -10,15 +10,15 @@ Version 2.21
* The following bugs are resolved with this release:
6652, 10672, 12674, 12847, 12926, 13862, 14132, 14138, 14171, 14498,
15215, 15884, 16009, 16191, 16469, 16617, 16619, 16657, 16740, 16857,
17192, 17266, 17273, 17344, 17363, 17370, 17371, 17411, 17460, 17475,
17485, 17501, 17506, 17508, 17522, 17555, 17570, 17571, 17572, 17573,
17574, 17582, 17583, 17584, 17585, 17589, 17594, 17601, 17608, 17616,
17625, 17630, 17633, 17634, 17635, 17647, 17653, 17657, 17658, 17664,
17665, 17668, 17682, 17702, 17717, 17719, 17722, 17723, 17724, 17725,
17732, 17733, 17744, 17745, 17746, 17747, 17748, 17775, 17777, 17780,
17781, 17782, 17791, 17793, 17796, 17797, 17803, 17806, 17834, 17844,
17848
15215, 15884, 16009, 16418, 16191, 16469, 16617, 16619, 16657, 16740,
16857, 17192, 17266, 17273, 17344, 17363, 17370, 17371, 17411, 17460,
17475, 17485, 17501, 17506, 17508, 17522, 17555, 17570, 17571, 17572,
17573, 17574, 17582, 17583, 17584, 17585, 17589, 17594, 17601, 17608,
17616, 17625, 17630, 17633, 17634, 17635, 17647, 17653, 17657, 17658,
17664, 17665, 17668, 17682, 17702, 17717, 17719, 17722, 17723, 17724,
17725, 17732, 17733, 17744, 17745, 17746, 17747, 17748, 17775, 17777,
17780, 17781, 17782, 17791, 17793, 17796, 17797, 17803, 17806, 17834,
17844, 17848
* A new semaphore algorithm has been implemented in generic C code for all
machines. Previous custom assembly implementations of semaphore were

132
sysdeps/unix/sysv/linux/powerpc/get_clockfreq.c
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@ -24,95 +24,85 @@
#include <libc-internal.h>
#include <sysdep.h>
#include <bits/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. */
static hp_timing_t timebase_freq;
hp_timing_t result = 0L;
int fd = __open_nocancel ("/proc/cpuinfo", O_RDONLY);
if (__glibc_likely (fd != -1))
return result;
/* If this function was called before, we know the result. */
if (timebase_freq != 0)
return timebase_freq;
/* 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;
/* 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, uint64_t, 0);
if (INTERNAL_SYSCALL_ERROR_P (timebase_freq, err)
&& INTERNAL_SYSCALL_ERRNO (timebase_freq, err) == ENOSYS)
#endif
n = __read_nocancel (fd, buf, sizeof (buf));
if (n == sizeof (buf))
{
int fd = __open ("/proc/cpuinfo", O_RDONLY);
if (__glibc_likely (fd != -1))
/* 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)
{
/* 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;
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);
n = __read (fd, buf, sizeof (buf));
if (n == sizeof (buf))
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')
{
/* 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)
if (*mhz >= '0' && *mhz <= '9')
{
memcpy (buf, buf + half_buf, half_buf);
n = __read (fd, buf + half_buf, half_buf);
result *= 10;
result += *mhz - '0';
}
if (n >= 0)
n += half_buf;
++mhz;
}
if (__builtin_expect (n, 1) > 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;
}
}
timebase_freq = result;
}
__close (fd);
}
}
#endif
return timebase_freq;
return result;
}