[PATCH] ArmPlatformPkg/PrePeiCore: seed temporary stack before entering PEI core

[Ard Biesheuvel <ard.biesheuvel@linaro.org>]

DEBUG builds of PEI code will print a diagnostic message regarding
the utilization of temporary RAM before switching to permanent RAM.
For example,

  Total temporary memory:    16352 bytes.
    temporary memory stack ever used:       4820 bytes.
    temporary memory heap used for HobList: 4720 bytes.

Tracking stack utilization like this requires the stack to be seeded
with a known magic value, and this needs to occur before entering C
code, given that it uses the stack. Currently, only Nt32Pkg appears
to implement this feature, but it is useful nonetheless, so let's
wire it up for PrePeiCore.

Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
---
 ArmPlatformPkg/PrePeiCore/AArch64/PrePeiCoreEntryPoint.S |  7 +++++++
 ArmPlatformPkg/PrePeiCore/Arm/PrePeiCoreEntryPoint.S     | 10 ++++++++++
 ArmPlatformPkg/PrePeiCore/Arm/PrePeiCoreEntryPoint.asm   | 10 ++++++++++
 3 files changed, 27 insertions(+)

diff --git a/ArmPlatformPkg/PrePeiCore/AArch64/PrePeiCoreEntryPoint.S b/ArmPlatformPkg/PrePeiCore/AArch64/PrePeiCoreEntryPoint.S
index aab5edab0c42..7a33e2754869 100644
--- a/ArmPlatformPkg/PrePeiCore/AArch64/PrePeiCoreEntryPoint.S
+++ b/ArmPlatformPkg/PrePeiCore/AArch64/PrePeiCoreEntryPoint.S
@@ -13,6 +13,8 @@
 
 #include <AsmMacroIoLibV8.h>
 
+#define INIT_CAR_VALUE      0x5AA55AA55AA55AA5
+
 ASM_FUNC(_ModuleEntryPoint)
   // Do early platform specific actions
   bl    ASM_PFX(ArmPlatformPeiBootAction)
@@ -84,4 +86,9 @@ _PrepareArguments:
 
 _SetupPrimaryCoreStack:
   mov   sp, x1
+  MOV64 (x8, FixedPcdGet64(PcdCPUCoresStackBase))
+  MOV64 (x9, INIT_CAR_VALUE)
+0:stp   x9, x9, [x8], #16
+  cmp   x8, x1
+  b.lt  0b
   b     _PrepareArguments
diff --git a/ArmPlatformPkg/PrePeiCore/Arm/PrePeiCoreEntryPoint.S b/ArmPlatformPkg/PrePeiCore/Arm/PrePeiCoreEntryPoint.S
index 14344425ad4c..7342e49bea59 100644
--- a/ArmPlatformPkg/PrePeiCore/Arm/PrePeiCoreEntryPoint.S
+++ b/ArmPlatformPkg/PrePeiCore/Arm/PrePeiCoreEntryPoint.S
@@ -13,6 +13,8 @@
 
 #include <AsmMacroIoLib.h>
 
+#define INIT_CAR_VALUE      0x5AA55AA5
+
 ASM_FUNC(_ModuleEntryPoint)
   // Do early platform specific actions
   bl    ASM_PFX(ArmPlatformPeiBootAction)
@@ -65,6 +67,14 @@ _PrepareArguments:
 
 _SetupPrimaryCoreStack:
   mov   sp, r1
+  MOV32 (r8, FixedPcdGet64(PcdCPUCoresStackBase))
+  MOV32 (r9, INIT_CAR_VALUE)
+  mov   r10, r9
+  mov   r11, r9
+  mov   r12, r9
+0:stm   r8!, {r9-r12}
+  cmp   r8, r1
+  blt   0b
   b     _PrepareArguments
 
 _NeverReturn:
diff --git a/ArmPlatformPkg/PrePeiCore/Arm/PrePeiCoreEntryPoint.asm b/ArmPlatformPkg/PrePeiCore/Arm/PrePeiCoreEntryPoint.asm
index abea675828df..7455de8aa66e 100644
--- a/ArmPlatformPkg/PrePeiCore/Arm/PrePeiCoreEntryPoint.asm
+++ b/ArmPlatformPkg/PrePeiCore/Arm/PrePeiCoreEntryPoint.asm
@@ -13,6 +13,8 @@
 
 #include <AutoGen.h>
 
+#define INIT_CAR_VALUE      0x5AA55AA5
+
   INCLUDE AsmMacroIoLib.inc
 
   IMPORT  CEntryPoint
@@ -79,6 +81,14 @@ _PrepareArguments
 
 _SetupPrimaryCoreStack
   mov   sp, r1
+  mov32 r8, FixedPcdGet64(PcdCPUCoresStackBase)
+  mov32 r9, INIT_CAR_VALUE
+  mov   r10, r9
+  mov   r11, r9
+  mov   r12, r9
+0:stm   r8!, {r9-r12}
+  cmp   r8, r1
+  blt   0b
   b     _PrepareArguments
 
 _NeverReturn
-- 
2.11.0