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    SubjectRe: [PATCH] core_pattern: Add ability for core_pattern to parse arguments when pattern is a pipe
    On Thu, 26 Jul 2007 15:36:24 -0400 Will Woods <wwoods@redhat.com> wrote:

    > On Thu, 2007-07-26 at 11:48 -0700, Andrew Morton wrote:
    > > On Thu, 26 Jul 2007 13:40:19 -0400 Neil Horman <nhorman@tuxdriver.com> wrote:
    > >
    > > > Currently, core dumps can be redirected to a pipe by placing the
    > > > following string template in /proc/sys/kernel/core_pattern:
    > > > |<path/to/application>
    > > > This patch extends this ability, allowing the core_pattern to contain arguments
    > > > to be passed as an argv array to the userspace helper application. It also add
    > > > a format specifier, %c, which allows the RLIM_CORE value of the crashing
    > > > application to be passed on the command line, since RLIMIT_CORE is reduced to
    > > > zero when execing the userspace helper
    > >
    > > This all seems to be getting a bit nutty. Who needs this feature
    > > and what will they do with it, etc?
    >
    > We're using it for doing a system-wide crash dump handler. Currently
    > Ubuntu's using it with their Apport tool[1] for this purpose; I'm
    > adapting that for Fedora.

    Can you please copy the relevant Ubuntu people on the patches then? It
    would be valuable to get their input on the proposal.

    > The Ubuntu approach requires a kernel patch that adds a bunch of process
    > information (process pid, RLIMIT_CORE, etc) to the environment of the
    > crash handler[2]. Most of that information can instead be parsed out of
    > the ELF headers - which is what I wrote code to do[3]. The problem that
    > remains is determining the value of RLIMIT_CORE. (This is used to
    > determine whether the user wants a normal corefile, thus retaining
    > normal core dump behavior).
    >
    > As I understand it, getrlimit() won't return the correct values while
    > dumping to a pipe. So we need to pass the original RLIMIT_CORE to the
    > userspace helper somehow. It seems sensible to pass arguments to a
    > userspace program by using argv[]. So there we are.

    yup. The changelog should clearly document this new kernel/userspace
    interface, please. Things like what the argv format will be, which args
    are optional, etc.

    > There's probably many other uses for this stuff but that's the specific
    > one we're targeting. Does that make sense? If there's an easier way to
    > get the original RLIMIT_CORE from inside the crash handler, I'd love to
    > hear it.
    >

    I'm still emerging from the "what the heck is this" state ;)

    You need to tell us these things...
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