dynamic_debug.h

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#ifndef _DYNAMIC_DEBUG_H
#define _DYNAMIC_DEBUG_H

/*
 * An instance of this structure is created in a special
 * ELF section at every dynamic debug callsite.  At runtime,
 * the special section is treated as an array of these.
 */
struct _ddebug {
    /*
     * These fields are used to drive the user interface
     * for selecting and displaying debug callsites.
     */
    const char *modname;
    const char *function;
    const char *filename;
    const char *format;
    unsigned int lineno:18;
    /*
     * The flags field controls the behaviour at the callsite.
     * The bits here are changed dynamically when the user
     * writes commands to <debugfs>/dynamic_debug/control
     */
#define _DPRINTK_FLAGS_NONE 0
#define _DPRINTK_FLAGS_PRINT    (1<<0) /* printk() a message using the format */
#define _DPRINTK_FLAGS_INCL_MODNAME (1<<1)
#define _DPRINTK_FLAGS_INCL_FUNCNAME    (1<<2)
#define _DPRINTK_FLAGS_INCL_LINENO  (1<<3)
#define _DPRINTK_FLAGS_INCL_TID     (1<<4)
#if defined DEBUG
#define _DPRINTK_FLAGS_DEFAULT _DPRINTK_FLAGS_PRINT
#else
#define _DPRINTK_FLAGS_DEFAULT 0
#endif
    unsigned int flags:8;
} __attribute__((aligned(8)));


int ddebug_add_module(struct _ddebug *tab, unsigned int n,
                const char *modname);

#if defined(CONFIG_DYNAMIC_DEBUG)
extern int ddebug_remove_module(const char *mod_name);
extern __printf(2, 3)
int __dynamic_pr_debug(struct _ddebug *descriptor, const char *fmt, ...);

extern int ddebug_dyndbg_module_param_cb(char *param, char *val,
                    const char *modname);

struct device;

extern __printf(3, 4)
int __dynamic_dev_dbg(struct _ddebug *descriptor, const struct device *dev,
              const char *fmt, ...);

struct net_device;

extern __printf(3, 4)
int __dynamic_netdev_dbg(struct _ddebug *descriptor,
             const struct net_device *dev,
             const char *fmt, ...);

#define DEFINE_DYNAMIC_DEBUG_METADATA(name, fmt)        \
    static struct _ddebug  __aligned(8)         \
    __attribute__((section("__verbose"))) name = {      \
        .modname = KBUILD_MODNAME,          \
        .function = __func__,               \
        .filename = __FILE__,               \
        .format = (fmt),                \
        .lineno = __LINE__,             \
        .flags =  _DPRINTK_FLAGS_DEFAULT,       \
    }

#define dynamic_pr_debug(fmt, ...)              \
do {                                \
    DEFINE_DYNAMIC_DEBUG_METADATA(descriptor, fmt);     \
    if (unlikely(descriptor.flags & _DPRINTK_FLAGS_PRINT))  \
        __dynamic_pr_debug(&descriptor, pr_fmt(fmt),    \
                   ##__VA_ARGS__);      \
} while (0)

#define dynamic_dev_dbg(dev, fmt, ...)              \
do {                                \
    DEFINE_DYNAMIC_DEBUG_METADATA(descriptor, fmt);     \
    if (unlikely(descriptor.flags & _DPRINTK_FLAGS_PRINT))  \
        __dynamic_dev_dbg(&descriptor, dev, fmt,    \
                  ##__VA_ARGS__);       \
} while (0)

#define dynamic_netdev_dbg(dev, fmt, ...)           \
do {                                \
    DEFINE_DYNAMIC_DEBUG_METADATA(descriptor, fmt);     \
    if (unlikely(descriptor.flags & _DPRINTK_FLAGS_PRINT))  \
        __dynamic_netdev_dbg(&descriptor, dev, fmt, \
                     ##__VA_ARGS__);        \
} while (0)

#else

#include <linux/string.h>
#include <linux/errno.h>

static inline int ddebug_remove_module(const char *mod)
{
    return 0;
}

static inline int ddebug_dyndbg_module_param_cb(char *param, char *val,
                        const char *modname)
{
    if (strstr(param, "dyndbg")) {
        /* avoid pr_warn(), which wants pr_fmt() fully defined */
        printk(KERN_WARNING "dyndbg param is supported only in "
            "CONFIG_DYNAMIC_DEBUG builds\n");
        return 0; /* allow and ignore */
    }
    return -EINVAL;
}

#define dynamic_pr_debug(fmt, ...)                  \
    do { if (0) printk(KERN_DEBUG pr_fmt(fmt), ##__VA_ARGS__); } while (0)
#define dynamic_dev_dbg(dev, fmt, ...)                  \
    do { if (0) dev_printk(KERN_DEBUG, dev, fmt, ##__VA_ARGS__); } while (0)
#endif

#endif