Re: [PATCH 2/4] ArmPkg/ArmLib: AARCH64: set frame pointer in cache maintenance routine

[Leif Lindholm <leif.lindholm@linaro.org>]

On Wed, Feb 22, 2017 at 12:56:04PM +0000, Ard Biesheuvel wrote:
> On 22 February 2017 at 09:38, Ard Biesheuvel <ard.biesheuvel@linaro.org> wrote:
> > Stack and unstack the frame pointer according to the AAPCS in
> > AArch64AllDataCachesOperation ().
> >
> > Contributed-under: TianoCore Contribution Agreement 1.0
> > Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> > ---
> >  ArmPkg/Library/ArmLib/AArch64/AArch64Support.S | 4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/ArmPkg/Library/ArmLib/AArch64/AArch64Support.S b/ArmPkg/Library/ArmLib/AArch64/AArch64Support.S
> > index 5cee7c1519c3..c35c05fdf681 100644
> > --- a/ArmPkg/Library/ArmLib/AArch64/AArch64Support.S
> > +++ b/ArmPkg/Library/ArmLib/AArch64/AArch64Support.S
> > @@ -273,7 +273,7 @@ ASM_FUNC(ArmDisableBranchPrediction)
> >  ASM_FUNC(AArch64AllDataCachesOperation)
> >  // We can use regs 0-7 and 9-15 without having to save/restore.
> >  // Save our link register on the stack. - The stack must always be quad-word aligned
> > -  str   x30, [sp, #-16]!
> > +  stp   x29, x30, [sp, #-16]!
> 
> As discussed over IRC, this needs
> 
> mov x29, sp
> 
> appended as well.
> 
> This ensures that this function will show up in a backtrace when an
> exception is taken (and not handled) in the callback invoked by this
> function. Without setting (and preserving) x29, it will still point to
> the caller of AArch64AllDataCachesOperation()

Sounds good.
With that addition:
Reviewed-by: Leif Lindholm <leif.lindholm@linaro.org>

> >    mov   x1, x0                  // Save Function call in x1
> >    mrs   x6, clidr_el1           // Read EL1 CLIDR
> >    and   x3, x6, #0x7000000      // Mask out all but Level of Coherency (LoC)
> > @@ -324,7 +324,7 @@ L_Skip:
> >  L_Finished:
> >    dsb   sy
> >    isb
> > -  ldr   x30, [sp], #0x10
> > +  ldp   x29, x30, [sp], #0x10
> >    ret
> >
> >
> > --
> > 2.7.4
> >