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

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Message-ID: <18226.38816.486372.52353@cargo.ozlabs.ibm.com>
Date:	Thu, 8 Nov 2007 15:59:12 +1100
From:	Paul Mackerras <paulus@...ba.org>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	lkml@...idb.org, linux-kernel@...r.kernel.org, drepper@...hat.com,
	mtk-manpages@....net
Subject: Re: compat_sys_times() bogus until jiffies >= 0.

Andrew Morton writes:

> "the latter" is what my protopatch does isn't it?  It wraps at 0x7fffffff.
> It appears that glibc treats all of 0x80000000-0xffffffff as an error.

Not on powerpc.  On powerpc the error indication is carried separately
in a condition register bit.  So a force_successful_syscall_return()
call will make glibc automatically do the right thing without any
glibc changes on powerpc.

Wrapping at 0x7fffffff will cause programs to see large negative
deltas between successive calls when the wrap occurs.  I can see that
giving userspace fits. :)

Paul.

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