On 12/03/18 13:13, Amaan Cheval wrote:
Hey! Thanks for the guidance!
I did look at cpu_asm.S, but I don't quite get how Interrupt_frame is being
used, where by "used" I mean it in the sense that fields within it are
being set to the actual register values, the way they are with stm/ltm for
the Context_Control structure.
This structure is used as a temporary stack to allow interrupt
processing during a context switch. You find some information about this
here:
https://docs.rtems.org/branches/master/c-user/symmetric_multiprocessing_services.html#thread-dispatch-details
The reason I'm looking for ways in which state values are saved into the
CPU_Interrupt_frame
The interrupt exception prologue saves the volatile context of the
interrupted thread into this structure. I guess this is
https://git.rtems.org/rtems/tree/c/src/lib/libbsp/i386/shared/irq/irq_asm.S
I don't know the i386 BSP well and I am not really interested in this
architecture.
struct is because the comment in
./cpukit/score/cpu/no_cpu/include/rtems/score/cpu.h says:
/**
* @ingroup Management
*
* This defines the set of integer and processor state registers that
must
* be saved during an interrupt. This set does not include any which
are
* in @ref Context_Control.
*/
In cpu_asm.S, _CPU_Context_switch has only this bit that's relevant to
Interrupt_frame:
add sp, r2, #(PER_CPU_INTERRUPT_FRAME_AREA + CPU_INTERRUPT_FRAME_SIZE)
Which is effectively:
sp = GET_SELF_CPU_CONTROL() + Per_CPU_Control.Interrupt_frame +
sizeof(CPU_Interrupt_frame)
If the stack grows downwards, I guess pushing to the stack would write to
the Interrupt_frame?
Yes.
I'll continue looking at it now that I know this is
the correct place to look; perhaps what I'm missing is just how the stack
pointer is used or how interrupts are dispatched?
On ARM, it is in this file:
https://git.rtems.org/rtems/tree/cpukit/score/cpu/arm/arm_exc_interrupt.S
SMP context switch code (which is incomplete for i386)
When you say this, does that mean _CPU_Context_switch's bits with "#ifdef
RTEMS_SMP"
Yes.
or do you mean another function altogether?
No, the non-SMP context switch should work fine.
Sorry if that's a
stupid question; evidently I'm not familiar enough with RTEMS' internals -
it's easy to get lost until you find just the right thread to unwind the
whole thing. :P
P.S. - I'm "amaan" on the #rtems IRC in case you think I've confused myself
and gone down the wrong path, and it'd be quicker to clarify on chat.
On Mon, Mar 12, 2018 at 12:18 PM Sebastian Huber <
sebastian.hu...@embedded-brains.de> wrote:
On 10/03/18 15:11, Amaan Cheval wrote:
CPU_INTERRUPT_FRAME_SIZE needs to also be set to allow the
RTEMS_STATIC_ASSERT
in percpuasm.c to be fulfilled.
The CPU_Interrupt_frame must properly defined. It must be used by the
SMP context switch code (which is incomplete for i386). Please have a
look at the ARM context switch code as an example:
https://git.rtems.org/rtems/tree/cpukit/score/cpu/arm/cpu_asm.S
--
Sebastian Huber, embedded brains GmbH
Address : Dornierstr. 4, D-82178 Puchheim, Germany
Phone : +49 89 189 47 41-16
Fax : +49 89 189 47 41-09
E-Mail : sebastian.hu...@embedded-brains.de
PGP : Public key available on request.
Diese Nachricht ist keine geschäftliche Mitteilung im Sinne des EHUG.
--
Sebastian Huber, embedded brains GmbH
Address : Dornierstr. 4, D-82178 Puchheim, Germany
Phone : +49 89 189 47 41-16
Fax : +49 89 189 47 41-09
E-Mail : sebastian.hu...@embedded-brains.de
PGP : Public key available on request.
Diese Nachricht ist keine geschäftliche Mitteilung im Sinne des EHUG.
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