【OpenHarmony开发】 tracepoint的机制总结

一、tracepoint 的机制

1.1 DECLARE_HOOK 解析

DECLARE_HOOK(vendor_bond_check_dev_link,TP_PROTO(const struct bonding *bond, const struct slave *slave, int *state), TP_ARGS(bond, slave, state));

// 在已经实现如下宏定义的前提下
// CONFIG_TRACEPOINTS 和 CONFIG_VENDOR_HOOKS
#include <trace/hooks/vendor_hooks.h> // 没有的化自行添加
#define DECLARE_HOOK DECLARE_TRACE#include <linux/tracepoint.h>
#define DECLARE_TRACE(name, proto, args) \__DECLARE_TRACE(name, PARAMS(proto), PARAMS(args), \cpu_online(raw_smp_processor_id()), \PARAMS(void *__data, proto))#define PARAMS(args...) args
#define TP_PROTO(args...)   args
#define TP_ARGS(args...)    args

经过转换后

__DECLARE_TRACE(vendor_bond_check_dev_link, PARAMS(const struct bonding *bond, const struct slave *slave, int *state), PARAMS(bond, slave, state), \cpu_online(raw_smp_processor_id()), \PARAMS(void *__data, const struct bonding *bond, const struct slave *slave, int *state))|||||||||||||||\|||/\|/|
__DECLARE_TRACE(vendor_bond_check_dev_link, \PARAMS(const struct bonding *bond, const struct slave *slave, int *state), \PARAMS(bond, slave, state), \cpu_online(raw_smp_processor_id()), \PARAMS(void *__data, const struct bonding *bond, const struct slave *slave, int *state))

进一步解析

#define raw_smp_processor_id() (current_thread_info()->cpu) // 获取运行当前线程的CPUID
#define cpu_online(cpu)     cpumask_test_cpu((cpu), cpu_online_mask) // 测试 CPU 掩码中的 CPU

#define __DECLARE_TRACE(name, proto, args, cond, data_proto)            \extern int __traceiter_##name(data_proto);                          \DECLARE_STATIC_CALL(tp_func_##name, __traceiter_##name);            \extern struct tracepoint __tracepoint_##name;                       \static inline void trace_##name(proto)                              \{                                                                   \if (static_key_false(&__tracepoint_##name.key))                 \__DO_TRACE(name,                                            \TP_ARGS(args),                                          \TP_CONDITION(cond), 0);                                 \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))                                           \static inline int                                                   \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                                                   \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);              \}

转换后结果

__DECLARE_TRACE( \vendor_bond_check_dev_link, \PARAMS(const struct bonding *bond, const struct slave *slave, int *state), \PARAMS(bond, slave, state), \cpu_online(raw_smp_processor_id()), \PARAMS(void *__data, const struct bonding *bond, const struct slave *slave, int *state) \
)|||||||||||||||\|||/\|/|
extern int __traceiter_vendor_bond_check_dev_link(void *__data, const struct bonding *bond, const struct slave *slave, int *state);
DECLARE_STATIC_CALL(tp_func_vendor_bond_check_dev_link, __traceiter_vendor_bond_check_dev_link);
extern struct tracepoint __tracepoint_vendor_bond_check_dev_link;static inline void trace_vendor_bond_check_dev_link(const struct bonding *bond, const struct slave *slave, int *state)
{if (static_key_false(&__tracepoint_vendor_bond_check_dev_link.key))__DO_TRACE(vendor_bond_check_dev_link,TP_ARGS(bond, slave, state),TP_CONDITION(cpu_online(raw_smp_processor_id())), 0);if (IS_ENABLED(CONFIG_LOCKDEP) && (cpu_online(raw_smp_processor_id()))) {rcu_read_lock_sched_notrace();rcu_dereference_sched(__tracepoint_vendor_bond_check_dev_link.funcs);rcu_read_unlock_sched_notrace();}
}__DECLARE_TRACE_RCU( \vendor_bond_check_dev_link, \PARAMS(const struct bonding *bond, const struct slave *slave, int *state), \PARAMS(bond, slave, state), \PARAMS(cpu_online(raw_smp_processor_id()))
)static inline int register_trace_vendor_bond_check_dev_link(void (*probe)(void *__data, const struct bonding *bond, const struct slave *slave, int *state),void *data)
{return tracepoint_probe_register(&__tracepoint_vendor_bond_check_dev_link, (void *)probe, data);
}static inline int register_trace_prio_vendor_bond_check_dev_link(void (*probe)(void *__data, const struct bonding *bond, const struct slave *slave, int *state),void *data, int prio)
{return tracepoint_probe_register_prio(&__tracepoint_vendor_bond_check_dev_link, (void *)probe, data, prio);
}static inline int unregister_trace_vendor_bond_check_dev_link(void (*probe)(void *__data, const struct bonding *bond, const struct slave *slave, int *state),void *data)
{return tracepoint_probe_unregister(&__tracepoint_vendor_bond_check_dev_link, (void *)probe, data);
}static inline void check_trace_callback_type_vendor_bond_check_dev_link(void (*cb)(void *__data, const struct bonding *bond, const struct slave *slave, int *state))
{
}static inline bool trace_vendor_bond_check_dev_link_enabled(void)
{return static_key_false(&__tracepoint_vendor_bond_check_dev_link.key);
}

1.2 DECLARE_STATIC_CALL 解析

#define DECLARE_STATIC_CALL(name, func) \extern struct static_call_key STATIC_CALL_KEY(name); \extern typeof(func) STATIC_CALL_TRAMP(name);#define STATIC_CALL_KEY(name)       __PASTE(STATIC_CALL_KEY_PREFIX, name)
#define __PASTE(a,b) ___PASTE(a,b)
#define ___PASTE(a,b) a##b
#define STATIC_CALL_KEY_PREFIX      __SCK__#define STATIC_CALL_TRAMP(name)     __PASTE(STATIC_CALL_TRAMP_PREFIX, name)
#define STATIC_CALL_TRAMP_PREFIX    __SCT__|||||||||||||||\|||/\|/|
#define DECLARE_STATIC_CALL(name, func) \extern struct static_call_key __SCK__##name; \extern typeof(func) __SCT__##name;

转换后

extern int __traceiter_vendor_bond_check_dev_link(void *__data, const struct bonding *bond, const struct slave *slave, int *state);
DECLARE_STATIC_CALL(tp_func_vendor_bond_check_dev_link, __traceiter_vendor_bond_check_dev_link);|||||||||||||||\|||/\|/|
extern int __traceiter_vendor_bond_check_dev_link(void *__data, const struct bonding *bond, const struct slave *slave, int *state);
extern struct static_call_key __SCK__tp_func_vendor_bond_check_dev_link;
extern typeof(__traceiter_vendor_bond_check_dev_link) __SCT__tp_func_vendor_bond_check_dev_link; // 定义一个和__traceiter_vendor_bond_check_dev_link相同类型的变量

1.3 trace_vendor_bond_check_dev_link 函数解析---执行钩子函数

struct tracepoint {const char *name;struct static_key key;struct static_call_key *static_call_key;void *static_call_tramp;void *iterator;int (*regfunc)(void);void (*unregfunc)(void);struct tracepoint_func __rcu *funcs;
};extern struct tracepoint __tracepoint_vendor_bond_check_dev_link;static inline void trace_vendor_bond_check_dev_link(const struct bonding *bond, const struct slave *slave, int *state)
{// 使用了全局变量__tracepoint_vendor_bond_check_dev_link，必定有地方会初始化了该变量if (static_key_false(&__tracepoint_vendor_bond_check_dev_link.key))__DO_TRACE(vendor_bond_check_dev_link,TP_ARGS(bond, slave, state),TP_CONDITION(cpu_online(raw_smp_processor_id())), 0);if (IS_ENABLED(CONFIG_LOCKDEP) && (cpu_online(raw_smp_processor_id()))) {rcu_read_lock_sched_notrace();rcu_dereference_sched(__tracepoint_vendor_bond_check_dev_link.funcs);rcu_read_unlock_sched_notrace();}
}

1.4 __DECLARE_TRACE_RCU 解析

#define __DECLARE_TRACE_RCU(name, proto, args, cond) \static inline void trace_##name##_rcuidle(proto) \{ \if (static_key_false(&__tracepoint_##name.key)) \__DO_TRACE(name, \TP_ARGS(args), \TP_CONDITION(cond), 1); \}

1.5 register_trace_vendor_bond_check_dev_link 函数介绍---注册钩子函数

static inline int register_trace_vendor_bond_check_dev_link(void (*probe)(void *__data, const struct bonding *bond, const struct slave *slave, int *state),void *data)
{return tracepoint_probe_register(&__tracepoint_vendor_bond_check_dev_link, (void *)probe, data);
}

int tracepoint_probe_register(struct tracepoint *tp, void *probe, void *data)
{return tracepoint_probe_register_prio(tp, probe, data, TRACEPOINT_DEFAULT_PRIO);
}

int tracepoint_probe_register_prio(struct tracepoint *tp, void *probe, void *data, int prio)
{struct tracepoint_func tp_func;int ret;mutex_lock(&tracepoints_mutex);tp_func.func = probe;tp_func.data = data;tp_func.prio = prio;ret = tracepoint_add_func(tp, &tp_func, prio, true); // 整个过程就是显示tp = tp_funcmutex_unlock(&tracepoints_mutex);return ret;
}

static int tracepoint_add_func(struct tracepoint *tp,struct tracepoint_func *func, int prio, bool warn)
{struct tracepoint_func *old, *tp_funcs;int ret;if (tp->regfunc && !static_key_enabled(&tp->key)) {ret = tp->regfunc();if (ret < 0)return ret;}// 核心代码1，拿到钩子列表tp_funcs = rcu_dereference_protected(tp->funcs,lockdep_is_held(&tracepoints_mutex));// 核心代码2，注册新的钩子到列表old = func_add(&tp_funcs, func, prio);if (IS_ERR(old)) {WARN_ON_ONCE(warn && PTR_ERR(old) != -ENOMEM);return PTR_ERR(old);}/** rcu_assign_pointer has as smp_store_release() which makes sure* that the new probe callbacks array is consistent before setting* a pointer to it.  This array is referenced by __DO_TRACE from* include/linux/tracepoint.h using rcu_dereference_sched().*/switch (nr_func_state(tp_funcs)) {case TP_FUNC_1:        /* 0->1 *//** Make sure new static func never uses old data after a* 1->0->1 transition sequence.*/tp_rcu_cond_sync(TP_TRANSITION_SYNC_1_0_1);/* Set static call to first function */tracepoint_update_call(tp, tp_funcs);/* Both iterator and static call handle NULL tp->funcs */rcu_assign_pointer(tp->funcs, tp_funcs);static_key_enable(&tp->key);break;case TP_FUNC_2:        /* 1->2 *//* Set iterator static call */tracepoint_update_call(tp, tp_funcs);/** Iterator callback installed before updating tp->funcs.* Requires ordering between RCU assign/dereference and* static call update/call.*/fallthrough;case TP_FUNC_N:        /* N->N+1 (N>1) */rcu_assign_pointer(tp->funcs, tp_funcs);/** Make sure static func never uses incorrect data after a* N->...->2->1 (N>1) transition sequence.*/if (tp_funcs[0].data != old[0].data)tp_rcu_get_state(TP_TRANSITION_SYNC_N_2_1);break;default:WARN_ON_ONCE(1);break;}release_probes(old);return 0;
}

1.6 unregister_trace_vendor_bond_check_dev_link 函数解析---注销钩子函数

不做介绍了，和 register 类似

二、tracepiont 其他的功能介绍

【待补充】

三、Demo 实例讲解

后面实现用例的时候补充，当前仅介绍官方的 demo

3.1 驱动侧代码实现

#include <trace/hooks/bonding.h>static void vendor_foo(void *data, const struct bonding *bond,const struct slave *slave, int *state)
{pr_info("%s\n", __func__);                                                                                                                                                                                                                                                                            
}static int __init vendor_bond_init(void)
{return register_trace_vendor_bond_check_dev_link(&vendor_foo, NULL);
}static void __exit vendor_bond_exit(void)
{unregister_trace_vendor_bond_check_dev_link(&vendor_foo, NULL);
}module_init(vendor_bond_init);
module_exit(vendor_bond_exit);

3.2 内核侧代码实现

代码合入链接

3.3 测试代码

#include <linux/kernel.h>                                                                                                                                                                                                                                                                                       
#include <linux/module.h>
#include <net/bonding.h>
#include <trace/hooks/bonding.h>static void vendor_bond_check_dev_link(void *data, const struct bonding *bond,const struct slave *slave, int *state)
{pr_info("%s\n", __func__);
}static int __init bondingTestInit(void)
{return register_trace_vendor_bond_check_dev_link(&vendor_bond_check_dev_link, NULL);
}static void __exit bondingTestExit(void)
{printk("bonding test exit\n");unregister_trace_vendor_bond_check_dev_link(&vendor_bond_check_dev_link, NULL);
}/* 模块入口和出口函数 */
module_init(bondingTestInit)
module_exit(bondingTestExit)/* 模块信息 */
MODULE_AUTHOR("Wei Yongjun <[email]weiyongjun1@huawei.com[/email]>");
MODULE_LICENSE("GPL");
MODULE_ESCRIPTION("bondtest driver");

最后

有很多小伙伴不知道学习哪些鸿蒙开发技术？不知道需要重点掌握哪些鸿蒙应用开发知识点？而且学习时频繁踩坑，最终浪费大量时间。所以有一份实用的鸿蒙（HarmonyOS NEXT）资料用来跟着学习是非常有必要的。

鸿蒙HarmonyOS Next全套学习资料←点击领取！（安全链接，放心点击）

这份鸿蒙（HarmonyOS NEXT）资料包含了鸿蒙开发必掌握的核心知识要点，内容包含了（ArkTS、ArkUI开发组件、Stage模型、多端部署、分布式应用开发、音频、视频、WebGL、OpenHarmony多媒体技术、Napi组件、OpenHarmony内核、Harmony南向开发、鸿蒙项目实战等等）鸿蒙（HarmonyOS NEXT）技术知识点。

希望这一份鸿蒙学习资料能够给大家带来帮助，有需要的小伙伴自行领取，限时开源，先到先得~无套路领取！！

鸿蒙（HarmonyOS NEXT）最新学习路线