如何在C中使用寄存器？

Question

Like the CR3 register which is used to point to the page directory. Linux also uses paging and is written in C, but how are these registers used in C (how to select a particular register using C)?

Answer 1

The C language provides no way to access specific processor registers. This is all up to the compiler.

To access specific registers you would have to write at least this part of your code in assembler.

Answer 2

The registers you are talking about are not a property of the language but the property of the hardware on which you run your programs. I believe that you are talking about an x86 type hardware. cr0-4 and orther specific regs are a property of the operating system and are managed by it, including paging table.

So, the language does not provide a way to access those hw-specific registers. The only way is to write an assembly code (hardware-specific) to manipulate them. The only thing which the language provides is the asm() operator which allows to insert assembly code in the program.

Answer 3

Standard C does not provide any facility to directly access processor registers. Some implementations may provide extensions that allow you to embed assembly code in your C code (such as the asm extension provided by gcc).

Generally speaking, if you need direct access to a processor register (or other hardware-specific location), you'd write that routine in assembler and link it into the larger program.