linux - 在 linux 内核的上下文中，硬件 "gates"是什么？

Question

In user space, the ioctl system call has the following prototype:

int ioctl(int fd, unsigned long cmd, ...);

The prototype stands out in the list of Unix system calls because of the dots, which usually mark the function as having a variable number ofarguments. In a real system, however, a system call cannot actually have a variable number of arguments. System calls must have a well-defined prototype, because user programs can access them only through hardware "gates".

那么这些硬件门是什么？页码为 135 和 136。

Answer 1

硬件“门”是允许切换到内核上下文的特定指令，通常是让程序向内核请求某些东西。这可能是类似 syscall、sysenter 或 int 0x80 的指令，具体取决于您的系统。

我应该指出，这些在实践中通常不被称为“硬件门”，而是类似“系统调用指令”的东西。