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    SubjectRe: mmap'ed memory in core files ?
    On Tue, Jul 1, 2008 at 11:44 PM, Bron Gondwana <brong@fastmail.fm> wrote:
    > On Tue, Jul 01, 2008 at 08:16:11PM +0200, Michael Kerrisk wrote:
    >> On 7/1/08, Philippe De Muyter <phdm@macqel.be> 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:
    >> http://www.kernel.org/doc/man-pages/online/pages/man5/core.5.html
    >
    > 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.

    Do you have a ssimple example program for this?

    --
    Michael Kerrisk
    Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
    man-pages online: http://www.kernel.org/doc/man-pages/online_pages.html
    Found a bug? http://www.kernel.org/doc/man-pages/reporting_bugs.html


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