Messages in this thread | | | Date | Fri, 23 Sep 2005 17:31:07 +0530 | From | Vivek Goyal <> | Subject | Re: [Fastboot] [PATCH] Kdump(x86): add note type NT_KDUMPINFO tokernelcore dumps |
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On Fri, Sep 23, 2005 at 01:12:23AM -0600, Eric W. Biederman wrote: > Dave Anderson <anderson@redhat.com> writes: > > > So does elf_core_dump() as well, but to gdb it's useless AFAICT... > > We can always post_process things when generating a core dump > if we have enough information. > > > Hey -- I wasn't even aware of the "crashing_cpu" variable. > > That would work just fine. > > > > Still a "panic_task", and perhaps even a "crash_page_size" variable > > would be nice as well. No additional notes required... > > To avoid defining an ABI that we need to maintain there is some > benefit in simply using static variables. But the form of the > information really isn't the concern. > > Where we capture the information and how reliable is that capture > is the concern. > > To capture page size the easiest and most reliable way I can see > to do is to modify vmlinux.lds.S to contain something like: > > _page_shift = PAGE_SHIFT; > Giving you an absolute symbol _page_shift in vmlinux that > contains the value you need, without overhead in the running > kernel.
That's a cool idea. I just tested it.
[vivek@vivegoya linux]$ readelf -s vmlinux | grep __page_shift 28865: 0000000c 0 NOTYPE GLOBAL DEFAULT ABS __page_shift
> > crashing_cpu makes sense to capture in some form, we definitely > need to compute something that will allow us to write to > a per cpu area on an SMP system. > > The big concern at this point is that the code has not undergone > a serious stability audit. So it is the expectation that there > is still code we can remove and modify to increase the likely hood > of getting a crash dump. > > Currently we know that stack overflows sometimes happen and that > they are a source of kernel crashes. It would be good if we could > take a crash dump despite them. To do that requires code more > robust than we have today. Quite likely it means that we will > not be able to reliably capture the task_struct of the crashing cpu. >
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