Re: [Bugme-new] [Bug 11110] New: Core dumps do not include writable unmodified MAP_PRIVATE maps

[Andrew Morton <akpm@linux-foundation.org>]

(switched to email.  Please respond via emailed reply-to-all, not via the
bugzilla web interface).

On Thu, 17 Jul 2008 11:57:08 -0700 (PDT) bugme-daemon@bugzilla.kernel.org wrote:

> http://bugzilla.kernel.org/show_bug.cgi?id=11110
> 
>            Summary: Core dumps do not include writable unmodified
>                     MAP_PRIVATE maps
>            Product: Process Management
>            Version: 2.5
>      KernelVersion: 2.6.26
>           Platform: All
>         OS/Version: Linux
>               Tree: Mainline
>             Status: NEW
>           Severity: normal
>           Priority: P1
>          Component: Other
>         AssignedTo: process_other@kernel-bugs.osdl.org
>         ReportedBy: drow@false.org
>                 CC: davem@davemloft.net
> 
> 
> Latest working kernel version: Not sure.
> Earliest failing kernel version: Been failing at least since April 2006. 
> Passed at some point previous to that, probably 2.4.
> Distribution: Debian
> Hardware Environment: x86_64 SMP
> Software Environment: GDB testsuite
> Problem Description:
> 
> The test corefile.exp fails because it maps a file and then core dumps,
> expecting the mapped contents to be in the core dump.  The mapping is made with
> these options:
> 
>   buf2 = (char *) mmap (0, MAPSIZE, PROT_READ | PROT_WRITE, MAP_PRIVATE, fd,
> 0);
> 
> Any page that has been touched will be dumped, any unmodified page will not be.
> 
> I've discussed this with David Miller a couple of times; last time I recall was
> in January 2007.
> 
> Steps to reproduce:
> 
>   Run coremaker from the GDB testsuite (attached).  Load the core file into GDB
> and try to print buf2.
> 

Does anyone recall whether this is deliberate behaviour, or did we just goof?

Thanks.

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