How To Create a kernel thread

最新推荐文章于 2023-11-27 17:42:31 发布

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最新推荐文章于 2023-11-27 17:42:31 发布

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文章标签： kernel Linux Thread

本文链接：https://blog.youkuaiyun.com/u011673554/article/details/50806684

本文深入探讨了Linux内核中kernel_thread()函数的核心作用，特别是CLONE_VM和CLONE_UNTRACED标志如何优化内存管理和安全追踪。通过分析函数内部逻辑，解释了新内核线程如何初始化栈帧并执行用户定义的函数。

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kernel_thread() --> 
    do_fork(flags|CLONE_VM|CLONE_UNTRACED, 0, pregs, 0, NULL, NULL);

The CLONE_VM flag avoids the duplication of the page tables of the calling process: this duplication would be a waste of time and memory, because the new kernel thread will not access the User Mode address space anyway.
The CLONE_UNTRACED flag ensures that no process will be able to trace the new kernel thread, even if the calling process is being traced.

The kernel_thread() function builds up the Kernel Mode Stack area ,so that:
• The ebx and edx registers will be set by copy_thread() to the values of the parameters fn and arg, respectively.
• The eip register will be set to the address of the following assembly language fragment:

movl %edx,%eax
pushl %edx
call *%ebx
pushl %eax
call do_exit

Therefore, the new kernel thread starts by executing the fn(arg) function. If this function terminates, the kernel thread executes the _exit() system call passing to it the return value of fn().

From：《Understanding The Linux Kernel》3rd Edition.