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    SubjectRe: [PATCH 3/16] LTTng 0.6.36 for 2.6.18 : Linux Kernel Markers
    * Frank Ch. Eigler ( wrote:
    > One question:
    > > [...]
    > > + /* Markers in modules. */
    > > + list_for_each_entry(mod, &modules, list) {
    > > + if (mod->license_gplok)
    > > + found += marker_set_probe_range(name, format, probe,
    > > + mod->markers, mod->markers+mod->num_markers);
    > > + }
    > > [...]
    > > +EXPORT_SYMBOL(marker_set_probe);
    > Are you sure the license_gplok check is necessary here? We should
    > consider encouraging non-gpl module writers to instrument their code,
    > to give users a slightly better chance of debugging problems.

    Hi Frank,

    I was kind of expecting this question. Well, it turns out that my markers module
    modifies the struct module in module.h to add a few fields. Some drivers that I
    won't name (ok, ok I will : clearcase) have the funny habit of distributing
    their kernel modules as ".ko" files instead of sending a proper ".o" and later
    link it against a wrapper.

    The result is, I must say, quite bad : when I want to add a probe, I iterate on
    each modules, verifying if there are any markers in the object. Things gets
    really messy when the structure is corrupted.

    The simplest way to work around this non-GPL problem is to completely disable
    access to the marker infrastructure to non-GPL modules. I am not against
    instrumentation of binary-only modules, but I don't think it is kernel
    developer's job to support their broken binary blob distribution.

    I thought that we might use the crc checksum as another criterion. As long as
    the machines do not crash when adding markers when such modules are loaded.



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