> On Wed, 7 Nov 2007 14:47:22 -0800 David Brown <[email protected]> wrote:
> compat_sys_times() has bogus return until jiffies is >= 0. I discovered
> this running LTP within 5 minutes of booting.
>
> The return result
>
> return compat_jiffies_to_clock_t(jiffies);
>
> will return '-1' to user space and set the negated clock_t value to errno.
>
> I'm not sure what the correct fix for this is. I can come up with a patch
> if anyone has ideas on how to fix it.
>
> At minimum, perhaps it should return a sane errno value.
RETURN VALUE
times() returns the number of clock ticks that have elapsed since an
arbitrary point in the past. For Linux 2.4 and earlier this point is
the moment the system was booted. Since Linux 2.6, this point is
(2^32/HZ) - 300 (i.e., about 429 million) seconds before system boot
time. The return value may overflow the possible range of type
clock_t. On error, (clock_t) -1 is returned, and errno is set appro-
priately.
Perhaps this is a bug in glibc: it is interpreting the times() return value
in the same way as other syscalls.
It would have been sensible for us to add INITIAL_JIFFIES to the value
instead of exposing this kernel-only detail to the world, although the
problem will of course reoccur once jiffies hits 0x80000000. Unfortunately
we've even gone and enshrined this bogon in the manpage.
Proposed fix:
- return compat_jiffies_to_clock_t(jiffies);
+ return compat_jiffies_to_clock_t((jiffies + INITIAL_JIFFIES) &
+ 0x7fffffff);
?
-
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