Where does kernel stores it's registers while performing a context switch?

Where does kernel stores it's registers while performing a context switch?

[Ketan Singh]

I want to know where the kernel stores it's registers while performing
a context switch on x86 architecture. In ARM I can see  struct
cpu_context_save in arch/arm/include/asm/thread_info.h but what about
x86/x86_64?

Where does kernel stores it's registers while performing a context switch?

[Thibaut SAUTEREAU]

On Sat, Oct 07, 2017 at 07:22:49PM +0530, Ketan Singh wrote:
> I want to know where the kernel stores it's registers while performing
> a context switch on x86 architecture. In ARM I can see  struct
> cpu_context_save in arch/arm/include/asm/thread_info.h but what about
> x86/x86_64?

Are you talking about context switches between two different threads? If
so, on x86, EIP and other CPU registers are saved onto the kernel stack
of the thread, then ESP is saved in the thread_struct structure which is
itself included in task_struct. The kernel function that handles that is
switch_to(), you might want to take a look at it.

If you were talking about switches between kernel and user modes, on x86
it is managed like interrupts, on x86_64 you should read about the task
state segment (TSS).

Hope this helps,


Thibaut