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    Subject[RFC] Sectionized printk data
    Date
    Hi,

    current approaches to have printk format strings in the corresponding
    data section to the function they appear in look like the following (at
    least what I have seen so far):

    int __init some_function(void)
    {
    static char errmsg[] __initdata = "failure %s in %s\n";

    [...]
    printk(errmsg);
    [...]
    }

    The attached patch allows something along the lines:

    int __init some_function(void)
    {
    [...]
    pr_init(KERN_WARNING "failure %s in %s\n", ...);
    [...]
    }

    Another idea I had was to make printk a macro that figures out the
    section of the surrounding function and then moves the data
    automatically when it is a literal, but I couldn't find mechanisms that
    allow this. Anyone of you got an idea?

    What do you think in general?

    Hannes

    ---
    From: Johannes Weiner <hannes@saeurebad.de>

    Sectionized printk wrappers

    Introduce printk wrappers that place format string literals in init/exit
    data sections.

    Signed-off-by: Johannes Weiner <hannes@saeurebad.de>
    ---
    The place for these wrappers is probably very wrong. Suggestions
    welcome.

    <Imagine diff-stat here>

    diff --git a/include/linux/kernel.h b/include/linux/kernel.h
    index ff356b2..6a1355d 100644
    --- a/include/linux/kernel.h
    +++ b/include/linux/kernel.h
    @@ -192,7 +192,22 @@ static inline int __cold printk(const char *s, ...) { return 0; }
    static inline int log_buf_get_len(void) { return 0; }
    static inline int log_buf_read(int idx) { return 0; }
    static inline int log_buf_copy(char *dest, int idx, int len) { return 0; }
    -#endif
    +
    +/* Sectionized printk constant data */
    +#include <linux/init.h>
    +#define pr_section(sec, fmt, args...) ({ \
    + static const char __fmt[] sec = fmt; \
    + printk(__fmt, ## args); \
    +})
    +#define pr_init(fmt, args) pr_section(__initdata, fmt, ## args)
    +#define pr_exit(fmt, args) pr_section(__exitdata, fmt, ## args)
    +#define pr_devinit(fmt, args) pr_section(__devinitdata, fmt, ## args)
    +#define pr_devexit(fmt, args) pr_section(__devexitdata, fmt, ## args)
    +#define pr_cpuinit(fmt, args) pr_section(__cpuinitdata, fmt, ## args)
    +#define pr_cpuexit(fmt, args) pr_section(__cpuexitdata, fmt, ## args)
    +#define pr_meminit(fmt, args) pr_section(__meminitdata, fmt, ## args)
    +#define pr_memexit(fmt, args) pr_section(__memexitdata, fmt, ## args)
    +#endif /* CONFIG_PRINTK */

    extern void __attribute__((format(printf, 1, 2)))
    early_printk(const char *fmt, ...);

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