我想在x86系统中禁用FPU/MMX/SSE指令，并将为“设备不可用”异常实现一个处理程序。我参考了控制寄存器wiki页面；似乎我必须在cr0寄存器中设置一些标志。如何在cr0中设置这些标志以及在启动时做这项工作？
管理FPU状态的Linux内核代码可以在arch/x86/nernel/traps.c，do_device_not_available（）。默认情况下，Linux内核为所有进程禁用FPU，并在首次访问时启用它。这允许内核减少不使用FPU的进程的上下文切换开销。然而，这也意味着在启动时设置一次TS是不够的；您必须更改管理TS标志的Linux内核代码才能保持这种状态。
通过在do_device_not_available（）中添加禁用标志的早期检查，并发出信号或采取其他操作，可以禁用对FPU的访问。请注意，如果在进程首次使用该特定CPU上的FPU之后再执行此操作，则FPU可能会在一段时间内保持可用，直到FPU寄存器上下文切换，并且FPU被重新禁用。如果您希望避免这种情况，则必须使用stts（）显式重新禁用FPU。
请注意，由于Linux ABI假设您有一个FPU（模拟FPU或硬件FPU，如果两者都没有，内核将不会启动），这可能会在应用程序中导致意外行为。此外，任何使用FPU的内部内核代码（不确定是否有）也可能会中断。执行此操作的风险自负。
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