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