tracepoint.h

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#ifndef _LINUX_TRACEPOINT_H
#define _LINUX_TRACEPOINT_H

/*
 * Kernel Tracepoint API.
 *
 * See Documentation/trace/tracepoints.txt.
 *
 * (C) Copyright 2008 Mathieu Desnoyers <[email protected]>
 *
 * Heavily inspired from the Linux Kernel Markers.
 *
 * This file is released under the GPLv2.
 * See the file COPYING for more details.
 */

#include <linux/errno.h>
#include <linux/types.h>
#include <linux/rcupdate.h>
#include <linux/static_key.h>

struct module;
struct tracepoint;

struct tracepoint_func {
    void *func;
    void *data;
};

struct tracepoint {
    const char *name;       /* Tracepoint name */
    struct static_key key;
    void (*regfunc)(void);
    void (*unregfunc)(void);
    struct tracepoint_func __rcu *funcs;
};

/*
 * Connect a probe to a tracepoint.
 * Internal API, should not be used directly.
 */
extern int tracepoint_probe_register(const char *name, void *probe, void *data);

/*
 * Disconnect a probe from a tracepoint.
 * Internal API, should not be used directly.
 */
extern int
tracepoint_probe_unregister(const char *name, void *probe, void *data);

extern int tracepoint_probe_register_noupdate(const char *name, void *probe,
                          void *data);
extern int tracepoint_probe_unregister_noupdate(const char *name, void *probe,
                        void *data);
extern void tracepoint_probe_update_all(void);

#ifdef CONFIG_MODULES
struct tp_module {
    struct list_head list;
    unsigned int num_tracepoints;
    struct tracepoint * const *tracepoints_ptrs;
};
#endif /* CONFIG_MODULES */

struct tracepoint_iter {
#ifdef CONFIG_MODULES
    struct tp_module *module;
#endif /* CONFIG_MODULES */
    struct tracepoint * const *tracepoint;
};

extern void tracepoint_iter_start(struct tracepoint_iter *iter);
extern void tracepoint_iter_next(struct tracepoint_iter *iter);
extern void tracepoint_iter_stop(struct tracepoint_iter *iter);
extern void tracepoint_iter_reset(struct tracepoint_iter *iter);

/*
 * tracepoint_synchronize_unregister must be called between the last tracepoint
 * probe unregistration and the end of module exit to make sure there is no
 * caller executing a probe when it is freed.
 */
static inline void tracepoint_synchronize_unregister(void)
{
    synchronize_sched();
}

#define PARAMS(args...) args

#endif /* _LINUX_TRACEPOINT_H */

/*
 * Note: we keep the TRACE_EVENT and DECLARE_TRACE outside the include
 *  file ifdef protection.
 *  This is due to the way trace events work. If a file includes two
 *  trace event headers under one "CREATE_TRACE_POINTS" the first include
 *  will override the TRACE_EVENT and break the second include.
 */

#ifndef DECLARE_TRACE

#define TP_PROTO(args...)   args
#define TP_ARGS(args...)    args
#define TP_CONDITION(args...)   args

#ifdef CONFIG_TRACEPOINTS

/*
 * it_func[0] is never NULL because there is at least one element in the array
 * when the array itself is non NULL.
 *
 * Note, the proto and args passed in includes "__data" as the first parameter.
 * The reason for this is to handle the "void" prototype. If a tracepoint
 * has a "void" prototype, then it is invalid to declare a function
 * as "(void *, void)". The DECLARE_TRACE_NOARGS() will pass in just
 * "void *data", where as the DECLARE_TRACE() will pass in "void *data, proto".
 */
#define __DO_TRACE(tp, proto, args, cond, prercu, postrcu)      \
    do {                                \
        struct tracepoint_func *it_func_ptr;            \
        void *it_func;                      \
        void *__data;                       \
                                    \
        if (!(cond))                        \
            return;                     \
        prercu;                         \
        rcu_read_lock_sched_notrace();              \
        it_func_ptr = rcu_dereference_sched((tp)->funcs);   \
        if (it_func_ptr) {                  \
            do {                        \
                it_func = (it_func_ptr)->func;      \
                __data = (it_func_ptr)->data;       \
                ((void(*)(proto))(it_func))(args);  \
            } while ((++it_func_ptr)->func);        \
        }                           \
        rcu_read_unlock_sched_notrace();            \
        postrcu;                        \
    } while (0)

#ifndef MODULE
#define __DECLARE_TRACE_RCU(name, proto, args, cond, data_proto, data_args) \
    static inline void trace_##name##_rcuidle(proto)        \
    {                               \
        if (static_key_false(&__tracepoint_##name.key))     \
            __DO_TRACE(&__tracepoint_##name,        \
                TP_PROTO(data_proto),           \
                TP_ARGS(data_args),         \
                TP_CONDITION(cond),         \
                rcu_idle_exit(),            \
                rcu_idle_enter());          \
    }
#else
#define __DECLARE_TRACE_RCU(name, proto, args, cond, data_proto, data_args)
#endif

/*
 * Make sure the alignment of the structure in the __tracepoints section will
 * not add unwanted padding between the beginning of the section and the
 * structure. Force alignment to the same alignment as the section start.
 */
#define __DECLARE_TRACE(name, proto, args, cond, data_proto, data_args) \
    extern struct tracepoint __tracepoint_##name;           \
    static inline void trace_##name(proto)              \
    {                               \
        if (static_key_false(&__tracepoint_##name.key))     \
            __DO_TRACE(&__tracepoint_##name,        \
                TP_PROTO(data_proto),           \
                TP_ARGS(data_args),         \
                TP_CONDITION(cond),,);          \
    }                               \
    __DECLARE_TRACE_RCU(name, PARAMS(proto), PARAMS(args),      \
        PARAMS(cond), PARAMS(data_proto), PARAMS(data_args))    \
    static inline int                       \
    register_trace_##name(void (*probe)(data_proto), void *data)    \
    {                               \
        return tracepoint_probe_register(#name, (void *)probe,  \
                         data);         \
    }                               \
    static inline int                       \
    unregister_trace_##name(void (*probe)(data_proto), void *data)  \
    {                               \
        return tracepoint_probe_unregister(#name, (void *)probe, \
                           data);       \
    }                               \
    static inline void                      \
    check_trace_callback_type_##name(void (*cb)(data_proto))    \
    {                               \
    }

/*
 * We have no guarantee that gcc and the linker won't up-align the tracepoint
 * structures, so we create an array of pointers that will be used for iteration
 * on the tracepoints.
 */
#define DEFINE_TRACE_FN(name, reg, unreg)                \
    static const char __tpstrtab_##name[]                \
    __attribute__((section("__tracepoints_strings"))) = #name;   \
    struct tracepoint __tracepoint_##name                \
    __attribute__((section("__tracepoints"))) =          \
        { __tpstrtab_##name, STATIC_KEY_INIT_FALSE, reg, unreg, NULL };\
    static struct tracepoint * const __tracepoint_ptr_##name __used  \
    __attribute__((section("__tracepoints_ptrs"))) =         \
        &__tracepoint_##name;

#define DEFINE_TRACE(name)                      \
    DEFINE_TRACE_FN(name, NULL, NULL);

#define EXPORT_TRACEPOINT_SYMBOL_GPL(name)              \
    EXPORT_SYMBOL_GPL(__tracepoint_##name)
#define EXPORT_TRACEPOINT_SYMBOL(name)                  \
    EXPORT_SYMBOL(__tracepoint_##name)

#else /* !CONFIG_TRACEPOINTS */
#define __DECLARE_TRACE(name, proto, args, cond, data_proto, data_args) \
    static inline void trace_##name(proto)              \
    { }                             \
    static inline void trace_##name##_rcuidle(proto)        \
    { }                             \
    static inline int                       \
    register_trace_##name(void (*probe)(data_proto),        \
                  void *data)               \
    {                               \
        return -ENOSYS;                     \
    }                               \
    static inline int                       \
    unregister_trace_##name(void (*probe)(data_proto),      \
                void *data)             \
    {                               \
        return -ENOSYS;                     \
    }                               \
    static inline void check_trace_callback_type_##name(void (*cb)(data_proto)) \
    {                               \
    }

#define DEFINE_TRACE_FN(name, reg, unreg)
#define DEFINE_TRACE(name)
#define EXPORT_TRACEPOINT_SYMBOL_GPL(name)
#define EXPORT_TRACEPOINT_SYMBOL(name)

#endif /* CONFIG_TRACEPOINTS */

/*
 * The need for the DECLARE_TRACE_NOARGS() is to handle the prototype
 * (void). "void" is a special value in a function prototype and can
 * not be combined with other arguments. Since the DECLARE_TRACE()
 * macro adds a data element at the beginning of the prototype,
 * we need a way to differentiate "(void *data, proto)" from
 * "(void *data, void)". The second prototype is invalid.
 *
 * DECLARE_TRACE_NOARGS() passes "void" as the tracepoint prototype
 * and "void *__data" as the callback prototype.
 *
 * DECLARE_TRACE() passes "proto" as the tracepoint protoype and
 * "void *__data, proto" as the callback prototype.
 */
#define DECLARE_TRACE_NOARGS(name)                  \
        __DECLARE_TRACE(name, void, , 1, void *__data, __data)

#define DECLARE_TRACE(name, proto, args)                \
        __DECLARE_TRACE(name, PARAMS(proto), PARAMS(args), 1,   \
                PARAMS(void *__data, proto),        \
                PARAMS(__data, args))

#define DECLARE_TRACE_CONDITION(name, proto, args, cond)        \
    __DECLARE_TRACE(name, PARAMS(proto), PARAMS(args), PARAMS(cond), \
            PARAMS(void *__data, proto),            \
            PARAMS(__data, args))

#define TRACE_EVENT_FLAGS(event, flag)

#endif /* DECLARE_TRACE */

#ifndef TRACE_EVENT
/*
 * For use with the TRACE_EVENT macro:
 *
 * We define a tracepoint, its arguments, its printk format
 * and its 'fast binay record' layout.
 *
 * Firstly, name your tracepoint via TRACE_EVENT(name : the
 * 'subsystem_event' notation is fine.
 *
 * Think about this whole construct as the
 * 'trace_sched_switch() function' from now on.
 *
 *
 *  TRACE_EVENT(sched_switch,
 *
 *  *
 *  * A function has a regular function arguments
 *  * prototype, declare it via TP_PROTO():
 *  *
 *
 *  TP_PROTO(struct rq *rq, struct task_struct *prev,
 *       struct task_struct *next),
 *
 *  *
 *  * Define the call signature of the 'function'.
 *  * (Design sidenote: we use this instead of a
 *  *  TP_PROTO1/TP_PROTO2/TP_PROTO3 ugliness.)
 *  *
 *
 *  TP_ARGS(rq, prev, next),
 *
 *  *
 *  * Fast binary tracing: define the trace record via
 *  * TP_STRUCT__entry(). You can think about it like a
 *  * regular C structure local variable definition.
 *  *
 *  * This is how the trace record is structured and will
 *  * be saved into the ring buffer. These are the fields
 *  * that will be exposed to user-space in
 *  * /sys/kernel/debug/tracing/events/<*>/format.
 *  *
 *  * The declared 'local variable' is called '__entry'
 *  *
 *  * __field(pid_t, prev_prid) is equivalent to a standard declariton:
 *  *
 *  *   pid_t   prev_pid;
 *  *
 *  * __array(char, prev_comm, TASK_COMM_LEN) is equivalent to:
 *  *
 *  *   char    prev_comm[TASK_COMM_LEN];
 *  *
 *
 *  TP_STRUCT__entry(
 *      __array(    char,   prev_comm,  TASK_COMM_LEN   )
 *      __field(    pid_t,  prev_pid            )
 *      __field(    int,    prev_prio           )
 *      __array(    char,   next_comm,  TASK_COMM_LEN   )
 *      __field(    pid_t,  next_pid            )
 *      __field(    int,    next_prio           )
 *  ),
 *
 *  *
 *  * Assign the entry into the trace record, by embedding
 *  * a full C statement block into TP_fast_assign(). You
 *  * can refer to the trace record as '__entry' -
 *  * otherwise you can put arbitrary C code in here.
 *  *
 *  * Note: this C code will execute every time a trace event
 *  * happens, on an active tracepoint.
 *  *
 *
 *  TP_fast_assign(
 *      memcpy(__entry->next_comm, next->comm, TASK_COMM_LEN);
 *      __entry->prev_pid   = prev->pid;
 *      __entry->prev_prio  = prev->prio;
 *      memcpy(__entry->prev_comm, prev->comm, TASK_COMM_LEN);
 *      __entry->next_pid   = next->pid;
 *      __entry->next_prio  = next->prio;
 *  ),
 *
 *  *
 *  * Formatted output of a trace record via TP_printk().
 *  * This is how the tracepoint will appear under ftrace
 *  * plugins that make use of this tracepoint.
 *  *
 *  * (raw-binary tracing wont actually perform this step.)
 *  *
 *
 *  TP_printk("task %s:%d [%d] ==> %s:%d [%d]",
 *      __entry->prev_comm, __entry->prev_pid, __entry->prev_prio,
 *      __entry->next_comm, __entry->next_pid, __entry->next_prio),
 *
 * );
 *
 * This macro construct is thus used for the regular printk format
 * tracing setup, it is used to construct a function pointer based
 * tracepoint callback (this is used by programmatic plugins and
 * can also by used by generic instrumentation like SystemTap), and
 * it is also used to expose a structured trace record in
 * /sys/kernel/debug/tracing/events/.
 *
 * A set of (un)registration functions can be passed to the variant
 * TRACE_EVENT_FN to perform any (un)registration work.
 */

#define DECLARE_EVENT_CLASS(name, proto, args, tstruct, assign, print)
#define DEFINE_EVENT(template, name, proto, args)       \
    DECLARE_TRACE(name, PARAMS(proto), PARAMS(args))
#define DEFINE_EVENT_PRINT(template, name, proto, args, print)  \
    DECLARE_TRACE(name, PARAMS(proto), PARAMS(args))
#define DEFINE_EVENT_CONDITION(template, name, proto,       \
                   args, cond)          \
    DECLARE_TRACE_CONDITION(name, PARAMS(proto),        \
                PARAMS(args), PARAMS(cond))

#define TRACE_EVENT(name, proto, args, struct, assign, print)   \
    DECLARE_TRACE(name, PARAMS(proto), PARAMS(args))
#define TRACE_EVENT_FN(name, proto, args, struct,       \
        assign, print, reg, unreg)          \
    DECLARE_TRACE(name, PARAMS(proto), PARAMS(args))
#define TRACE_EVENT_CONDITION(name, proto, args, cond,      \
                  struct, assign, print)        \
    DECLARE_TRACE_CONDITION(name, PARAMS(proto),        \
                PARAMS(args), PARAMS(cond))

#define TRACE_EVENT_FLAGS(event, flag)

#endif /* ifdef TRACE_EVENT (see note above) */