kprobe与perf probe使用简单记录

kprobe事件添加格式:

p[:[GRP/]EVENT] [MOD:]SYM[+offs]|MEMADDR [FETCHARGS] --增加探测点
r[:[GRP/]EVENT] [MOD:]SYM[+0] [FETCHARGS] --增加return探测点
-:[GRP/]EVENT --删除探测点

各字段说明:

GRP : Group name. If omitted, use “kprobes” for it. --指定后会在events/kprobes目录下生成对应名字的目录,一般不设
EVENT : Event name. If omitted, the event name is generated?based on SYM+offs or MEMADDR. --指定后会在events/kprobes/目录下生成对应名字的目录
MOD : Module name which has given SYM. --模块名,一般不设
SYM[+offs] : Symbol+offset where the probe is inserted. --指定被探测函数和偏移
MEMADDR : Address where the probe is inserted. --指定被探测的内存绝对地址
FETCHARGS : Arguments. Each probe can have up to 128 args. --指定要获取的参数信息
%REG : Fetch register REG --获取指定寄存器值
@ADDR : Fetch memory at ADDR (ADDR should be in kernel) --获取指定内存地址的值
@SYM[+|-offs] : Fetch memory at SYM +|- offs (SYM should be a data symbol) ?–获取全局变量的值
$stackN : Fetch Nth entry of stack (N >= 0) --获取指定栈空间值,即sp寄存器+N后的位置值
$stack : Fetch stack address. --获取sp寄存器值
$retval : Fetch return value.(*) --获取返回值,仅用于return probe
+|-offs(FETCHARG) : Fetch memory at FETCHARG +|- offs address.(**) --以下可以由于获取指定地址的结构体参数内容,可以设定具体的参数名和偏移地址
NAME=FETCHARG : Set NAME as the argument name of FETCHARG.
FETCHARG:TYPE : Set TYPE as the type of FETCHARG. Currently, basic types (u8/u16/u32/u64/s8/s16/s32/s64), “string” and bit field are supported.

使用例子:
切换目录:
[root@localhost ~]# cd /sys/kernel/debug/tracing
添加返回事件探测点:
[root@localhost tracing]# echo ‘r:myretprobe acl_permission_check ret=$retval’ >> kprobe_events
查看输出格式:
[root@localhost tracing]# cat events/kprobes/myretprobe/format
启用跟踪:
[root@localhost tracing]# echo 1 > events/kprobes/myretprobe/enable
执行相关命令
停止跟踪:
[root@localhost tracing]# echo 0 > events/kprobes/myretprobe/enable
查看结果:
[root@localhost tracing]# cat trace
删除探测点:
[root@localhost tracing]# echo ‘-:myretprobe’ >> kprobe_events

通过以上方法添加事件探测点后,也可以通过perf probe查到相关事件,并可以跟踪和移除该事件:
[root@localhost ~]# perf probe --list
/sys/kernel/debug/tracing/uprobe_events file does not exist - please rebuild kernel with CONFIG_UPROBE_EVENTS.
kprobes:myretprobe (on acl_permission_check%return with ret)
跟踪:
[root@localhost ~]# perf record -e kprobes:myretprobe -aR
获得结果:
[root@localhost ~]# perf script
移除事件:
root@localhost ~]# perf probe -d kprobes:myretprobe

PS:在生产系统中使用perf probe时居然不能添加return探测点(测试系统可以正常添加),原因未知,因此使用了kprobe来增加return探测点,添加后一样可以使用perf record进行跟踪

参考:
https://blog.csdn.net/luckyapple1028/article/details/52972315/
http://www.brendangregg.com/perf.html
man perf-probe

你可能感兴趣的:(linux)