Re: compat_sys_times() bogus until jiffies >= 0.

[David Miller <davem@davemloft.net>]

From: Paul Mackerras <paulus@samba.org>
Date: Thu, 8 Nov 2007 16:15:51 +1100

> David Miller writes:
> 
> > I can't see where x86 is doing this though, so perhaps for x86
> > glibc does make the negative value check.  But I doubt it is
> > checking the range 0x80000000-0xffffffff, otherwise mmap() would
> > be busted.
> 
> At least for the INTERNAL_SYSCALL macro in glibc, the error check is:
> 
> #define INTERNAL_SYSCALL_ERROR_P(val, err) \
>   ((unsigned int) (val) >= 0xfffff001u)
> 
> in sysdeps/unix/sysv/linux/i386/sysdep.h.  Similarly the PSEUDO macro
> in that file does a cmpl $-4095,%eax to test for error.  (There is also
> a PSEUDO_NOERRNO which doesn't test for error.)
> 
> So the convention on (32-bit) x86 is that -4095 .. -1 are error
> values, and other values are successful return values.

Thanks for figuring that out.

Really there is no way to fix sys_times() return values
universally.  Each proposed solution either doesn't fix
the problem, or adds a new failure mode.