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

Andrew Morton
2008-07-17T20:23:17Z

(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.