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From: Andreas Schwab <schwab@suse.de>
To: David Lecomber <david@lecomber.net>
Cc: gdb <gdb@sources.redhat.com>
Subject: Re: Whacky ia64: linux_proc_xfer_partial and lseek vs pread64
References: <1139591736.3780.26.camel@cpc2-oxfd8-0-0-cust771.oxfd.cable.ntl.com>
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Date: Fri, 10 Feb 2006 18:05:00 -0000
In-Reply-To: <1139591736.3780.26.camel@cpc2-oxfd8-0-0-cust771.oxfd.cable.ntl.com> 	(David Lecomber's message of "Fri, 10 Feb 2006 17:15:36 +0000")
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David Lecomber <david@lecomber.net> writes:

> Dear Dan and all,
>
> It's great that these days we use file access to get at the memory via
> the /proc filesystem - but there's an interesting sighting on the ia64
> (suse 9) in linux_proc_xfer_partial.
>
> #ifdef HAVE_PREAD64
>   if (pread64 (fd, readbuf, len, offset) != len)
> #else
>   if (lseek (fd, offset, SEEK_SET) == -1 || read (fd, readbuf, len) !=
> len)
> #endif
>     ret = 0;
>   else
>     ret = len;
>
>
> So, Mr Itanium has pread64, it calls pread64..  it seems to fail
> regularly..  As the strace log shows.

pread and lseek with SEEK_SET do not allow negative offsets.  lseek on
/proc/$$/mem is a special exception.

Andreas.

-- 
Andreas Schwab, SuSE Labs, schwab@suse.de
SuSE Linux Products GmbH, Maxfeldstraße 5, 90409 Nürnberg, Germany
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"And now for something completely different."