stap signal && trace point

执行  ./install/bin/staprun ./sigkill.ko   结果发现脚本执行命令刷屏了!!

debug_bin]$ ./install/bin/staprun  ./sigkill.ko  
sig[17] SIGCHLD was sent to sh (pid:15237) by exec:ps -->:15239  uid:0
sig[17] SIGCHLD was sent to python (pid:12444) by exec:sh -->:15237  uid:0
sig[34] 0x22 was sent to wafd (pid:11041) by exec:swapper/0 -->:0  uid:0
sig[17] SIGCHLD was sent to sh (pid:15242) by exec:bp_tool -->:15243  uid:0
sig[17] SIGCHLD was sent to sh (pid:15242) by exec:awk -->:15244  uid:0
sig[17] SIGCHLD was sent to sh (pid:15240) by exec:ps -->:15241  uid:0
sig[17] SIGCHLD was sent to plat_srv (pid:3990) by exec:sh -->:15242  uid:0
sig[17] SIGCHLD was sent to python (pid:12444) by exec:sh -->:15240  uid:0
sig[17] SIGCHLD was sent to sh (pid:15245) by exec:bp_tool -->:15246  uid:0
sig[17] SIGCHLD was sent to sh (pid:15245) by exec:awk -->:15247  uid:0
sig[17] SIGCHLD was sent to plat_srv (pid:3990) by exec:sh -->:15245  uid:0
sig[17] SIGCHLD was sent to sh (pid:15248) by exec:bp_tool -->:15249  uid:0
sig[17] SIGCHLD was sent to sh (pid:15248) by exec:awk -->:15250  uid:0
sig[17] SIGCHLD was sent to plat_srv (pid:3990) by exec:sh -->:15248  uid:0
sig[17] SIGCHLD was sent to sh (pid:15251) by exec:ps -->:15252  uid:0
sig[17] SIGCHLD was sent to python (pid:12444) by exec:sh -->:15251  uid:0
sig[17] SIGCHLD was sent to sh (pid:15166) by exec:awk -->:15168  uid:0
sig[17] SIGCHLD was sent to sh (pid:15166) by exec:top -->:15167  uid:0
sig[17] SIGCHLD was sent to python (pid:7298) by exec:sh -->:15166  uid:0
sig[17] SIGCHLD was sent to sh (pid:15253) by exec:ps -->:15254  uid:0
sig[17] SIGCHLD was sent to sh (pid:15253) by exec:grep -->:15255  uid:0
sig[17] SIGCHLD was sent to sh (pid:15253) by exec:grep -->:15257  uid:0
sig[17] SIGCHLD was sent to sh (pid:15253) by exec:grep -->:15256  uid:0
sig[17] SIGCHLD was sent to python (pid:8626) by exec:sh -->:15253  uid:0
sig[17] SIGCHLD was sent to sh (pid:15258) by exec:cat -->:15264  uid:0
sig[17] SIGCHLD was sent to sh (pid:15258) by exec:head -->:15265  uid:0
sig[17] SIGCHLD was sent to sh (pid:15258) by exec:awk -->:15266  uid:0
sig[17] SIGCHLD was sent to python (pid:7298) by exec:sh -->:15258  uid:0
sig[17] SIGCHLD was sent to sh (pid:15259) by exec:ps -->:15260  uid:0
----------------------
sig[17] SIGCHLD was sent to python (pid:8626) by exec:sh -->:15278 uid:0

sig[17] SIGCHLD was sent to python (pid:6750) by exec:ethtool -->:15283 uid:0
sig[17] SIGCHLD was sent to python (pid:6750) by exec:ethtool -->:15284 uid:0
sig[17] SIGCHLD was sent to python (pid:6750) by exec:ethtool -->:15285 uid:0
sig[17] SIGCHLD was sent to python (pid:6750) by exec:ethtool -->:15286 uid:0
sig[17] SIGCHLD was sent to python (pid:6750) by exec:ethtool -->:15287 uid:0
sig[17] SIGCHLD was sent to python (pid:6750) by exec:ethtool -->:15288 uid:0
sig[17] SIGCHLD was sent to python (pid:6750) by exec:ethtool -->:15291 uid:0
sig[17] SIGCHLD was sent to python (pid:6750) by exec:ethtool -->:15289 uid:0
sig[17] SIGCHLD was sent to python (pid:6750) by exec:ethtool -->:15294 uid:0

 

想不通 为啥 要通过命令来获取信息, netlink 不香么!!

 

顺便看下 trace_event的实现,以kfree_skb为例

TRACE_EVENT(kfree_skb,

    TP_PROTO(struct sk_buff *skb, void *location),

    TP_ARGS(skb, location),

    TP_STRUCT__entry(
        __field(    void *,        skbaddr        )
        __field(    void *,        location    )
        __field(    unsigned short,    protocol    )
    ),

    TP_fast_assign(
        __entry->skbaddr = skb;
        __entry->location = location;
        __entry->protocol = ntohs(skb->protocol);
    ),

    TP_printk("skbaddr=%p protocol=%u location=%p",
        __entry->skbaddr, __entry->protocol, __entry->location)
);

其大概意思是 将当前地址堆栈存在location 变量中;最后输出!!

 来看下 trace_event的第一层展开:

#define TRACE_EVENT(name, proto, args, struct, assign, print)    \
    DECLARE_TRACE(name, PARAMS(proto), PARAMS(args))
#define TRACE_EVENT(name, proto, args, tstruct, assign, print) \
    DECLARE_EVENT_CLASS(name,                                    PARAMS(proto),                                PARAMS(args),                                PARAMS(tstruct),                                PARAMS(assign),                                PARAMS(print));                   DEFINE_EVENT(name, name, PARAMS(proto), PARAMS(args));

 

 根据tracepoint.h文件 主要函数为:DEFINE_EVENT 宏定义

#define DEFINE_EVENT(template, name, proto, args)        \
    DECLARE_TRACE(name, PARAMS(proto), PARAMS(args))

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

 

 

#define __DECLARE_TRACE(name, proto, args, cond, data_proto, data_args)     extern struct tracepoint __tracepoint_##name;            \// tracepoint变量“__tracepoint_##name”本身
    static inline void trace_##name(proto)                \// tracepoint桩函数“trace_##name”的定义
    {                                        if (static_key_false(&__tracepoint_##name.key))                    __DO_TRACE(&__tracepoint_##name,                        TP_PROTO(data_proto),                            TP_ARGS(data_args),                            TP_CONDITION(cond),,);                    if (IS_ENABLED(CONFIG_LOCKDEP) && (cond)) {                    rcu_read_lock_sched_notrace();                        rcu_dereference_sched(__tracepoint_##name.funcs);            rcu_read_unlock_sched_notrace();                }                                }                                    __DECLARE_TRACE_RCU(name, PARAMS(proto), PARAMS(args),                PARAMS(cond), PARAMS(data_proto), PARAMS(data_args))        static inline int                        \// tracepoint的回调函数注册函数"register_trace_##name"
    register_trace_##name(void (*probe)(data_proto), void *data)        {                                        return tracepoint_probe_register(&__tracepoint_##name,                            (void *)probe, data);        }                                    static inline int                            register_trace_prio_##name(void (*probe)(data_proto), void *data,                   int prio)                    {                                        return tracepoint_probe_register_prio(&__tracepoint_##name,                           (void *)probe, data, prio);     }                                    static inline int                        \// tracepoint的回调函数反注册函数"unregister_trace_##name"
    unregister_trace_##name(void (*probe)(data_proto), void *data)        {                                        return tracepoint_probe_unregister(&__tracepoint_##name,                        (void *)probe, data);        }                                    static inline void                            check_trace_callback_type_##name(void (*cb)(data_proto))        {                                    }                                    static inline bool                            trace_##name##_enabled(void)                        {                                        return static_key_false(&__tracepoint_##name.key);        }
//桩函数中,逐个调用回调函数进行执行
#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;                            } whil

 

TRACE_EVENT包含5个参数:(name, proto, args, struct, assign, print)
  前面两个参数:proto, args,是给定义tracepoint使用的。在linux/tracepoint.h中构造tracepoint桩函数、callback regitser/unregister函数,在trace/define_trace.h中定义tracepoint变量。
  后面三个参数:struct, assign, print,是给trace_event使用的。在trace/trace_events.h,构造trace_event的callback函数,注册到tracepoint。

TRACE_EVENT:

  • 创建了一个tracepoint,可以放到kernel代码中;
  • 创建了一个回调函数,可以被上述tracepoint调用
  • 回调函数必须实现以最快的方式将传递给它的数据记录到trace ringbuffer中。
  • 必须创建一个函数能解析从ringbuffer读出的数据,转换成便于用户理解的形式。

在define_trace.h中,宏TRACE_EVENT()第二次的展开:

#undef TRACE_EVENT
#define TRACE_EVENT(name, proto, args, tstruct, assign, print)    \
    DEFINE_TRACE(name)

//重新宏定义展开


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


/*
 * 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;     \// 定义tracepoint变量“__tracepoint_##name”本身
    struct tracepoint __tracepoint_##name                     __attribute__((section("__tracepoints"))) =                     { __tpstrtab_##name, STATIC_KEY_INIT_FALSE, reg, unreg, NULL };\// 将tracepoint变量指针"__tracepoint_ptr_##name"存放到section("__tracepoints_ptrs")
    static struct tracepoint * const __tracepoint_ptr_##name __used         __attribute__((section("__tracepoints_ptrs"))) =                 &__tracepoint_##name;

   在随后的trace_events.h中,宏TRACE_EVENT()又进行了多次的展开。宏定义重复多次定义多次展开

太恶心了 !! 以为很简单 结果一个宏定义都这复杂

 

tracepoint.h  trace_events.h  define_trace.h

 

这几个文件看的有点蒙蔽

下次要是需要写trace_point 在继续研究!! 继续打游戏

参考:Using the TRACE_EVENT() part1

trace point example

stap signal && trace point

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