Re: [edk2] [ArmPlatformPkg][Patch] reset x11 before use

[Ard Biesheuvel]

On 16 January 2018 at 21:51, Udit Kumar  wrote:
> This patch reset x11 to zero before using it.
> x11 is marked as caller saved register, therefore before using it
> default (reset) value should be assigned.
>
> If ArmPlatformPeiBootAction function is using x11 then some of
> calculation in this routine may go wrong.
>
> Contributed-under: TianoCore Contribution Agreement 1.1
>
> Signed-off-by: Udit Kumar 
> ---
>  ArmPlatformPkg/PrePi/AArch64/ModuleEntryPoint.S | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/ArmPlatformPkg/PrePi/AArch64/ModuleEntryPoint.S 
> b/ArmPlatformPkg/PrePi/AArch64/ModuleEntryPoint.S
> index a81709d..d391fc1 100644
> --- a/ArmPlatformPkg/PrePi/AArch64/ModuleEntryPoint.S
> +++ b/ArmPlatformPkg/PrePi/AArch64/ModuleEntryPoint.S
> @@ -60,6 +60,7 @@ _SetupStack:
>// Because the 'push' instruction is equivalent to 'stmdb' (decrement 
> before), we need to increment
>// one to the top of the stack. We check if incrementing one does not 
> overflow (case of DRAM at the
>// top of the memory space)
> +  mov x11, 0
>adds  x11, x1, #1
>b.cs  _SetupOverflowStack
>

x11 is used as an output only by the adds instruction, so there is no
point in setting a value first.
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[edk2] [ArmPlatformPkg][Patch] reset x11 before use

[Udit Kumar]

This patch reset x11 to zero before using it.
x11 is marked as caller saved register, therefore before using it
default (reset) value should be assigned.

If ArmPlatformPeiBootAction function is using x11 then some of
calculation in this routine may go wrong.

Contributed-under: TianoCore Contribution Agreement 1.1

Signed-off-by: Udit Kumar 
---
 ArmPlatformPkg/PrePi/AArch64/ModuleEntryPoint.S | 1 +
 1 file changed, 1 insertion(+)

diff --git a/ArmPlatformPkg/PrePi/AArch64/ModuleEntryPoint.S 
b/ArmPlatformPkg/PrePi/AArch64/ModuleEntryPoint.S
index a81709d..d391fc1 100644
--- a/ArmPlatformPkg/PrePi/AArch64/ModuleEntryPoint.S
+++ b/ArmPlatformPkg/PrePi/AArch64/ModuleEntryPoint.S
@@ -60,6 +60,7 @@ _SetupStack:
   // Because the 'push' instruction is equivalent to 'stmdb' (decrement 
before), we need to increment
   // one to the top of the stack. We check if incrementing one does not 
overflow (case of DRAM at the
   // top of the memory space)
+  mov x11, 0
   adds  x11, x1, #1
   b.cs  _SetupOverflowStack
 
-- 
1.9.1

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