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    SubjectRe: mmap'ed memory in core files ?
    On Tue, Jul 01, 2008 at 08:16:11PM +0200, Michael Kerrisk wrote:
    > On 7/1/08, Philippe De Muyter <> wrote:
    > > Hello everybody,
    > >
    > > I develop video acquisition software using the video1394 interface.
    > > The images grabbed by the camera and iee1394 bus are kept in kernel
    > > memory and made available to the user program through a mmap call done
    > > in the libdc1394 library :
    > >
    > > dma_ring_buffer= mmap(0, vmmap.nb_buffers * vmmap.buf_size,
    > > PROT_READ|PROT_WRITE,MAP_SHARED, craw->capture.dma_fd, 0);
    > >
    > > Sometimes, my program crashes and produces a core file :) It seems to
    > > me that the core file does not contain the mmap'ed memory and hence
    > > I cannot replay my program with the same image for debugging purpose.
    > >
    > > Is it possible to configure the kernel through /proc, or through the mmap
    > > system call to have that mmapped segment in the core file, or do I need
    > > to modify the kernel itself to obtain the behaviour I want ? If I
    > > need to modify the kernel, can some kind soul provide me some pointers ?
    > Have a look at the section "Controlling which mappings are written to
    > the core dump" in a recent core.5 man page:

    Interesting (and somewhat off topic to your conversation here) - it
    appears that when dumping mappings, the kernel ignores the maximum
    core size set with "limit".

    This is particularly interesting on a 64 bit kernel where a bug in
    your code causes you to try to read something about 2Gb into your
    alleged mmaped file (actual size ~500 bytes) and the segfault causes
    a coredump.


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