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    SubjectRe: [RFC] Sectionized printk data
    Em Sun, Feb 10, 2008 at 01:18:18AM +0100, Jan Engelhardt escreveu:
    >
    > On Feb 9 2008 21:54, Arnaldo Carvalho de Melo wrote:
    > >> To drop strings that are only shown once anyway, such as:
    > >>
    > >> static int __init ebtables_init(void)
    > >> {
    > >> int ret;
    > >>
    > >> mutex_lock(&ebt_mutex);
    > >> list_add(&ebt_standard_target.list, &ebt_targets);
    > >> mutex_unlock(&ebt_mutex);
    > >> if ((ret = nf_register_sockopt(&ebt_sockopts)) < 0)
    > >> return ret;
    > >>
    > >> -> printk(KERN_INFO "Ebtables v2.0 registered\n");
    > >> return 0;
    > >> }
    > >>
    > >> >If you say "saving memory" then please let us know with specific examples
    > >> >in what area these savings will really pay off.
    > >
    > >[...]
    > >With a tool like this the advantage is that no source code has to be
    > >changed, strings in __init functions are automagically moved to
    > >.init.data, the disadvantage is that not all strings can be moved to
    > >.init.data as there were (are?) subsystems that keep pointers to the
    > >string passed and another tool would be involved in the build process.
    >
    > There is one corner case to consider:
    >
    >
    > static char abc[] = "foo";
    >
    > int __init init_module(void)
    > {
    > printk(abc);
    > }
    >
    > I am not sure if gcc/ld is smart enough to figure out that abc is
    > only ever used from within an __init function and that it could hence
    > be moved to __initdata.

    The initstr tool mentioned doesn't touches this case, as it doesn't
    searches specific functions such as printk, it looks for strings inside
    __init marked functions. In the above example abc won't be marked as
    __initdata.

    So if there are two places where the same string is used, with one being
    in a __init function one copy goes to .init.data and another to .data.

    - Arnaldo


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