eagles125 / ktap

A lightweight script-based dynamic tracing tool for Linux

ktap

A New Scripting Dynamic Tracing Tool For Linux
www.ktap.org

ktap is a new scripting dynamic tracing tool for Linux, it uses a scripting language and lets users trace the Linux kernel dynamically. ktap is designed to give operational insights with interoperability that allows users to tune, troubleshoot and extend kernel and application. It's similar with Linux Systemtap and Solaris Dtrace.

ktap have different design principles from Linux mainstream dynamic tracing language in that it's based on bytecode, so it doesn't depend upon GCC, doesn't require compiling kernel module for each script, safe to use in production environment, fulfilling the embedded ecosystem's tracing needs.

More information can be found at ktap homepage.

Highlights

• simple but powerful scripting language
• register based interpreter (heavily optimized) in Linux kernel
• small and lightweight (6KLOC of interpreter)
• not depend on gcc for each script running
• easy to use in embedded environment without debugging info
• support for tracepoint, kprobe, uprobe, function trace, timer, and more
• supported in x86, arm, ppc, mips
• safety in sandbox

Building & Running

1. Clone ktap from github

    $ git clone http://github.com/ktap/ktap.git
   

2. Compiling ktap

    $ cd ktap
    $ make       #generate ktapvm kernel module and ktap binary
   

3. Load ktapvm kernel module(make sure debugfs mounted)

    $ make load  #need to be root or have sudo access
   

4. Running ktap

    $ ./ktap samples/helloworld.kp
   

Examples

1. simplest one-liner command to enable all tracepoints

    ktap -e "trace *:* { print(argevent) }"
   

2. syscall tracing on target process

    ktap -e "trace syscalls:* { print(argevent) }" -- ls
   

3. ftrace(kernel newer than 3.3, and must compiled with CONFIG_FUNCTION_TRACER)

    ktap -e "trace ftrace:function { print(argevent) }"
   
    ktap -e "trace ftrace:function /ip==mutex*/ { print(argevent) }"
   

4. simple syscall tracing

    trace syscalls:* {
            print(cpu(), pid(), execname(), argevent)
    }
   

5. syscall tracing in histogram style

    var s = {}
   
    trace syscalls:sys_enter_* {
            s[argname] += 1
    }
   
    trace_end {
            histogram(s)
    }
   

6. kprobe tracing

    trace probe:do_sys_open dfd=%di fname=%dx flags=%cx mode=+4($stack) {
            print("entry:", execname(), argevent)
    }
   
    trace probe:do_sys_open%return fd=$retval {
            print("exit:", execname(), argevent)
    }
   

7. uprobe tracing

    trace probe:/lib/libc.so.6:malloc {
            print("entry:", execname(), argevent)
    }
   
    trace probe:/lib/libc.so.6:malloc%return {
            print("exit:", execname(), argevent)
    }
   

8. stapsdt tracing (userspace static marker)

    trace sdt:/lib64/libc.so.6:lll_futex_wake {
            print("lll_futex_wake", execname(), argevent)
    }
   
    or:
   
    #trace all static mark in libc
    trace sdt:/lib64/libc.so.6:* {
            print(execname(), argevent)
    }
   

9. timer

    tick-1ms {
            printf("time fired on one cpu\n");
    }
   
    profile-2s {
            printf("time fired on every cpu\n");
    }
   

10. FFI (Call kernel function from ktap script, need compile with FFI=1)

    cdef[[
            int printk(char *fmt, ...);
    ]]
    
    C.printk("This message is called from ktap ffi\n")
    

More examples can be found at samples directory.

Mailing list

[email protected]
You can subscribe to ktap mailing list at link (subscribe before posting): http://www.freelists.org/list/ktap

Copyright and License

ktap is licensed under GPL v2

Copyright (C) 2012-2013, Jovi Zhangwei [email protected]. All rights reserved.

Contribution

ktap is still under active development, so contributions are welcome. You are encouraged to report bugs, provide feedback, send feature request, or hack on it.

See More

More info can be found at [documentation][tutorial] [tutorial]: http://www.ktap.org/doc/tutorial.html