[uClinux-dev] SAVE_STACK_SWITCH in system call.

amit bhor amit_bhor at hotpop.com
Fri Mar 14 16:12:48 EST 2003


On Fri, 14 Mar 2003 11:22:20 -0800 (PST), Deepa Sivasankarane 
<sdeepa69 at yahoo.com> wrote:

>
> Hi,
> This is the extended stack (switch_stack: asm-m68knommu/include/ptrace.h)
> that gets saved, after pt_regs (SAVE_ALL),  before calling signal 
> handlers or  context switching (within system_call handler).

But in the system call , if and when it sleeps , these registers will be 
saved anyways(in SWITCH_TO() ). Like i said, i thought the whole idea was 
to *not save* registers that C functions save. So as long as you dont use 
these registers in your system call handler,there should not be a need to 
save them unless you actually sleep.
 Amit,

> Deepa
> amit bhor <amit_bhor at hotpop.com> wrote:hi,
>
> I was looking through the uClinux m68k code and i see a SAVE_STACK_SWITCH 
> before every system call. I thought the whole idea was to not save the 
> scratch registers (callee saved). Am i right here ? I am looking at 
> TOPDIR/arch/m68knommu/platform/68328/entry.S.
>
> Thanks,
> Amit _______________________________________________
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