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]!
   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

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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()

>    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
>
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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
> >
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