How Kernel stack is used in case of different processor mode in ARM architecture?

[Arun KS]

Hello Rahul,

On Tue, Mar 25, 2014 at 6:29 AM, Rahul Garg <rahul.lnmiit at gmail.com> wrote:
> As I understand every process have a user stack and kernel stack.
True.

> Apart from that there is a stack for every mode in ARM achitecture. So
This is wrong.
Only irq, abort and undefined modes have stacks in linux. That too is
very limited, 3 bytes per mode per cpu.
Have a look at arch/arm/kernel/irq.c
struct stack {
        u32 irq[3];
        u32 abt[3];
        u32 und[3];
} ____cacheline_aligned;

kernel runs in SVC mode and the stack used belong to the kernel stack
of the current task.
Even irq, abort and undefined exception handlers use kernel stack of
current task. All the exception
handlers switch to SVC mode at a very early stage and use kernel
stack. Those 3 bytes are used
as stack just during the transition phase(for example transition from
irq to svc mode during and interrupt).

Thanks,
Arun
> I want to know How different stack and stack pointer works in ARM
> modes? Also when this kernel stack associated with the process will be
> used ?
>
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