[PATCH v3] score/aarch64: Align context validation frame

[Gedare Bloom]

On Tue, May 18, 2021 at 3:05 PM Gedare Bloom <gedare at rtems.org> wrote:
>
> On Tue, May 18, 2021 at 2:18 PM Kinsey Moore <kinsey.moore at oarcorp.com> wrote:
> >
> > Looks like this fell through the cracks last month and I totally forgot about it.
> >
> > -----Original Message-----
> > From: Kinsey Moore <kinsey.moore at oarcorp.com>
> > Sent: Tuesday, April 13, 2021 10:15
> > To: devel at rtems.org
> > Cc: Kinsey Moore <kinsey.moore at oarcorp.com>
> > Subject: [PATCH v3] score/aarch64: Align context validation frame
> >
> > Ensure the stack remains aligned by keeping the context frame at a
> > multiple of 16 bytes. This avoids stack alignment exceptions which occur
> > when the stack pointer is not 16 byte aligned.
> > ---
> >  .../cpu/aarch64/aarch64-context-validate.S    | 29 ++++++++++++-------
> >  1 file changed, 18 insertions(+), 11 deletions(-)
> >
> > diff --git a/cpukit/score/cpu/aarch64/aarch64-context-validate.S b/cpukit/score/cpu/aarch64/aarch64-context-validate.S
> > index 57f634934b..1e71bc5b3a 100644
> > --- a/cpukit/score/cpu/aarch64/aarch64-context-validate.S
> > +++ b/cpukit/score/cpu/aarch64/aarch64-context-validate.S
> > @@ -42,7 +42,9 @@
> >
> >  #include <rtems/asm.h>
> >  #include <rtems/score/cpu.h>
> > +#include <rtems/score/basedefs.h>
> >
> > +/* These must be 8 byte aligned to avoid misaligned accesses */
> >  #define FRAME_OFFSET_X4  0x00
> >  #define FRAME_OFFSET_X5  0x08
> >  #define FRAME_OFFSET_X6  0x10
> > @@ -54,18 +56,23 @@
> >  #define FRAME_OFFSET_LR  0x40
> >
> >  #ifdef AARCH64_MULTILIB_VFP
> > -  #define FRAME_OFFSET_V8  0x48
> > -  #define FRAME_OFFSET_V9  0x58
> > -  #define FRAME_OFFSET_V10 0x68
> > -  #define FRAME_OFFSET_V11 0x78
> > -  #define FRAME_OFFSET_V12 0x88
> > -  #define FRAME_OFFSET_V13 0x98
> > -  #define FRAME_OFFSET_V14 0xA8
> > -  #define FRAME_OFFSET_V15 0xB8
> > -
> > -  #define FRAME_SIZE (FRAME_OFFSET_V15 + 0x10)
> > +  /* These must be 16 byte aligned to avoid misaligned accesses */
> > +  #define FRAME_OFFSET_V8  0x50
> > +  #define FRAME_OFFSET_V9  0x60
> > +  #define FRAME_OFFSET_V10 0x70
> > +  #define FRAME_OFFSET_V11 0x80
> > +  #define FRAME_OFFSET_V12 0x90
> > +  #define FRAME_OFFSET_V13 0xA0
> > +  #define FRAME_OFFSET_V14 0xB0
> > +  #define FRAME_OFFSET_V15 0xC0
> > +
>
> These definitions should be consistent with how the Context_Control
> structure gets defined (include/rtems/score/cpu.h). I don't think they
> are consistent in this port?
>
nevermind, I think I may be missing something. but I guess the same
constraint applies to these registers in the context control, it just
happens to work because there are two more variables in the struct
(isr_dispatch_disable and thread_id)? this should be documented  in
cpu.h if it is the case, that these VFP-related registers need to be
aligned to 16 bytes.

> > +  /*
> > +   * Force 16 byte alignment of the frame size to avoid stack pointer alignment
> > +   * exceptions.
> > +   */
> > +  #define FRAME_SIZE RTEMS_ALIGN_UP( FRAME_OFFSET_V15, 16 )
> >  #else
> > -  #define FRAME_SIZE (FRAME_OFFSET_LR + 0x08)
> > +  #define FRAME_SIZE RTEMS_ALIGN_UP( FRAME_OFFSET_LR, 16 )
> >  #endif
> >
> >         .section        .text
> > --
> > 2.20.1
> >
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