Ubuntu 11.10 (Oneiric) 上如何编译带 utrace 补丁的内核

首先准备 linux 内核编译环境：

  1. sudo apt-get install fakeroot build-essential crash kexec-tools makedumpfile kernel-wedge kernel-package
  2. sudo apt-get build-dep linux
  3. sudo apt-get install git-core libncurses5 libncurses5-dev libelf-dev asciidoc binutils-dev

检出带有 utrace 补丁的官方内核代码，并生成对应 Ubuntu 当前版本内核（3.0）的补丁：

  1. git clone https://github.com/utrace/linux.git utrace-linux-git
  2. cd utrace-linux-git/
  3. git checkout -b utrace-3.0 origin/utrace-3.0
  4. git diff v3.0 > /tmp/utrace.patch

获得 Ubuntu 定制内核代码，并打上 utrace 补丁：

  1. sudo apt-get install linux-source
  2. tar xjf /usr/src/linux-source-3.0.0.tar.bz2
  3. cd linux-source-3.0.0/
  4. patch -p1 < /tmp/utrace.patch

输出为：

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patching file Documentation/DocBook/Makefile
patching file Documentation/DocBook/utrace.tmpl
patching file arch/x86/kernel/ptrace.c
patching file fs/proc/array.c
patching file include/linux/ptrace.h
patching file include/linux/sched.h
Hunk #1 succeeded at 187 (offset 3 lines).
Hunk #2 succeeded at 206 (offset 3 lines).
Hunk #3 succeeded at 1415 with fuzz 2 (offset 7 lines).
patching file include/linux/signal.h
patching file include/linux/tracehook.h
patching file include/linux/utrace.h
patching file init/Kconfig
Hunk #1 succeeded at 388 (offset 16 lines).
patching file kernel/Makefile
patching file kernel/fork.c
Hunk #1 FAILED at 168.
Hunk #2 succeeded at 1098 (offset 3 lines).
1 out of 2 hunks FAILED -- saving rejects to file kernel/fork.c.rej
patching file kernel/ptrace.c
patching file kernel/sched.c
patching file kernel/signal.c
Hunk #4 succeeded at 1993 (offset -2 lines).
Hunk #5 succeeded at 2017 (offset -2 lines).
Hunk #6 succeeded at 2124 (offset -2 lines).
Hunk #7 succeeded at 2132 (offset -2 lines).
patching file kernel/utrace.c

注意 kernel/fork.c 的补丁失败了，看看 kernel/fork.c.rej ：

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--- kernel/fork.c
+++ kernel/fork.c
@@ -168,6 +168,7 @@
    free_thread_info(tsk->stack);
    rt_mutex_debug_task_free(tsk);
    ftrace_graph_exit_task(tsk);
+   tracehook_free_task(tsk);
    free_task_struct(tsk);
 }
 EXPORT_SYMBOL(free_task);

修改 kernel/fork.c ，在 free_task 函数的 ftrace_graph_exit_task(tsk); 之后手工加上这行 tracehook_free_task 调用即可。

编译新的内核，使用当前系统内核的配置参数作为基准，开启 utrace 补丁提供的 CONFIG_UTRACE 功能即可：

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cp /boot/config-$(uname -r) .config
make oldconfig

出现如下提示时回答 y： Infrastructure for tracing and debugging user processes (UTRACE) [N/y/?] (NEW)

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make-kpkg clean
export CONCURRENCY_LEVEL=9

这里指定编译内核时的并发任务数，设置为核数+1即可

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fakeroot make-kpkg --initrd --append-to-version=-utrace binary-arch

编译完成后，在 linux-source-3.0.0/ 的上级目录会生成 linux-headers/image/debug-symbol 的 deb 安装包，直接用 sudo dpkg -i *.deb 安装即可。重启后选择新内核进入即可用 SystemTap 进行用户态程序跟踪。

参考资料