你可以设置一些寄存器，并发出一个系统调用指令(或中断)，并由陷阱处理程序直接调用内核代码。
You set some registers and issue a system call instruction (or an interrupt) and have the kernel code called directly from the trap handler.
Oprofile是一种细粒度的工具，可以为指令集或者为函数、系统调用或中断处理例程收集采样。
OProfile is fine-grained and can collect samples for a set of instructions, or for function, system call, or interrupt handlers.
此时write系统调用会被进程接收到的SIGBUS信号中断，因为当前进程访问了非法内存地址。
Your write system call will be interrupted by the bus error signal SIGBUS, because you performed a bad memory access.
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