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 the kernel and applications. It's similar to Linux Systemtap and Solaris Dtrace.
ktap has 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.
- a simple but powerful scripting language
- register based interpreter (heavily optimized) in Linux kernel
- small and lightweight
- not depend on the gcc toolchain for each script run
- easy to use in embedded environments without debugging info
- support for tracepoint, kprobe, uprobe, function trace, timer, and more
- supported in x86, arm, ppc, mips
- safety in sandbox
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Clone ktap from github
$ git clone http://github.com/ktap/ktap.git -
Compiling ktap
$ cd ktap $ make #generate ktapvm kernel module and ktap binary -
Load ktapvm kernel module(make sure debugfs mounted)
$ make load #need to be root or have sudo access -
Running ktap
$ ./ktap samples/helloworld.kp
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simplest one-liner command to enable all tracepoints
ktap -e "trace *:* { print(argstr) }" -
syscall tracing on target process
ktap -e "trace syscalls:* { print(argstr) }" -- ls -
ftrace(kernel newer than 3.3, and must compiled with CONFIG_FUNCTION_TRACER)
ktap -e "trace ftrace:function { print(argstr) }" ktap -e "trace ftrace:function /ip==mutex*/ { print(argstr) }" -
simple syscall tracing
trace syscalls:* { print(cpu, pid, execname, argstr) } -
syscall tracing in histogram style
var s = {} trace syscalls:sys_enter_* { s[probename] += 1 } trace_end { print_hist(s) } -
kprobe tracing
trace probe:do_sys_open dfd=%di fname=%dx flags=%cx mode=+4($stack) { print("entry:", execname, argstr) } trace probe:do_sys_open%return fd=$retval { print("exit:", execname, argstr) } -
uprobe tracing
trace probe:/lib/libc.so.6:malloc { print("entry:", execname, argstr) } trace probe:/lib/libc.so.6:malloc%return { print("exit:", execname, argstr) } -
stapsdt tracing (userspace static marker)
trace sdt:/lib64/libc.so.6:lll_futex_wake { print("lll_futex_wake", execname, argstr) } or: #trace all static mark in libc trace sdt:/lib64/libc.so.6:* { print(execname, argstr) } -
timer
tick-1ms { printf("time fired on one cpu\n"); } profile-2s { printf("time fired on every cpu\n"); } -
FFI (Call kernel function from ktap script, need to compile with FFI=1)
ffi.cdef[[ int printk(char *fmt, ...); ]] ffi.C.printk("This message is called from ktap ffi\n")
More examples can be found at samples directory.
ktap@freelists.org
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http://www.freelists.org/list/ktap
ktap is licensed under GPL v2
Copyright (C) 2012-2016, Huawei Technologies. All rights reserved.
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.
More info can be found at [documentation][tutorial] [tutorial]: http://www.ktap.org/doc/tutorial.html