ArmPkg/ArmExceptionLib: use static buffer for sp_el0

The exception library is also used in DxeMain before memory services
are available, and AllocatePages() will fail in this case and cause
sp_el0 remains 0. Then if any exception occurs before CpuDxe driver is
loaded, a recursive exception will be trigged by page translation
fault for sp = 0 - 0x130.

Use static buffer instead to fix this issue.

Signed-off-by: Heyi Guo <guoheyi@linux.alibaba.com>
Reviewed-by: Ard Biesheuvel <ard.biesheuvel@arm.com>

1 files changed, 6 insertions, 8 deletions

diff --git a/ArmPkg/Library/ArmExceptionLib/AArch64/AArch64Exception.c b/ArmPkg/Library/ArmExceptionLib/AArch64/AArch64Exception.c
index be1cdcf5eb..514f80a2d4 100644
--- a/ArmPkg/Library/ArmExceptionLib/AArch64/AArch64Exception.c
+++ b/ArmPkg/Library/ArmExceptionLib/AArch64/AArch64Exception.c
@@ -19,7 +19,8 @@ EFI_EXCEPTION_CALLBACK  gDebuggerExceptionHandlers[MAX_AARCH64_EXCEPTION + 1] =
 PHYSICAL_ADDRESS        gExceptionVectorAlignmentMask = ARM_VECTOR_TABLE_ALIGNMENT;

 UINTN                   gDebuggerNoHandlerValue = 0; // todo: define for AArch64

 

-#define EL0_STACK_PAGES   2

+#define EL0_STACK_SIZE  EFI_PAGES_TO_SIZE(2)

+STATIC UINTN mNewStackBase[EL0_STACK_SIZE / sizeof (UINTN)];

 

 VOID

 RegisterEl0Stack (

@@ -31,14 +32,11 @@ RETURN_STATUS ArchVectorConfig(
   )

 {

   UINTN             HcrReg;

-  UINT8             *Stack;

 

-  Stack = AllocatePages (EL0_STACK_PAGES);

-  if (Stack == NULL) {

-    return RETURN_OUT_OF_RESOURCES;

-  }

-

-  RegisterEl0Stack ((UINT8 *)Stack + EFI_PAGES_TO_SIZE (EL0_STACK_PAGES));

+  // Round down sp by 16 bytes alignment

+  RegisterEl0Stack (

+    (VOID *)(((UINTN)mNewStackBase + EL0_STACK_SIZE) & ~0xFUL)

+    );

 

   if (ArmReadCurrentEL() == AARCH64_EL2) {

     HcrReg = ArmReadHcr();