Messages in this thread | | | Date | Wed, 2 Jul 2008 13:01:27 +0200 | From | Philippe De Muyter <> | Subject | Re: mmap'ed memory in core files ? |
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[ sorry, reposted to add cc linux1394-devel@lists.sourceforge.net ]
Hi Michael,
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
thanks for the info. I didn't know about /proc/PID/coredump_filter.
that part was promising :
bit 2 Dump file-backed private mappings. bit 3 Dump file-backed shared mappings.
The default value of coredump_filter is 0x3; this reflects traditional Linux behavior and means that only anonymous memory segments are dumped.
Unfortunately, the part that applies to me (I have tested it) is the next one :
Memory-mapped I/O pages such as frame buffer are never dumped, [...], regardless of the coredump_filter value.
Is that a design decision, or a mere finding of the way it is implemented now ?
So, back to my original question :
Can some kind soul provide me some pointers to the way I should modify the kernel to make the inclusion of the video1394 mmapped segment in core files possible ?
best regards
Philippe
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