From 7f8eb4d2f6033ba83ea914cff465aa5a4c45353a Mon Sep 17 00:00:00 2001
From: Mikhail Krichanov <mikhailkrichanov@gmail.com>
Date: Mon, 9 Sep 2024 11:48:53 +0300
Subject: [PATCH] SysCall: Refactored SysCallReturnToCore handling to fix
 CLANGDWARF NOOPT.

---
 .../Core/Dxe/SysCall/AARCH64/InitializeMsr.c  |  3 +++
 MdeModulePkg/Core/Dxe/SysCall/BootServices.c  |  9 ++++++++
 .../Dxe/SysCall/IA32/CoreBootServices.nasm    | 22 +++++++++----------
 .../Dxe/SysCall/X64/CoreBootServices.nasm     | 16 +++++++++-----
 MdePkg/Include/Uefi/UefiSpec.h                |  2 +-
 5 files changed, 34 insertions(+), 18 deletions(-)

diff --git a/MdeModulePkg/Core/Dxe/SysCall/AARCH64/InitializeMsr.c b/MdeModulePkg/Core/Dxe/SysCall/AARCH64/InitializeMsr.c
index 3ab3bffde7..7d11e063fe 100644
--- a/MdeModulePkg/Core/Dxe/SysCall/AARCH64/InitializeMsr.c
+++ b/MdeModulePkg/Core/Dxe/SysCall/AARCH64/InitializeMsr.c
@@ -45,6 +45,9 @@ SysCallBootService (
   EFI_PHYSICAL_ADDRESS    Physical;
 
   if (Type == SysCallReturnToCore) {
+    //
+    // TODO: Refactoring
+    //
     ReturnToCore (*(EFI_STATUS *)CoreRbp, mCoreSp);
   }
 
diff --git a/MdeModulePkg/Core/Dxe/SysCall/BootServices.c b/MdeModulePkg/Core/Dxe/SysCall/BootServices.c
index fabbb41e5f..aafdf60412 100644
--- a/MdeModulePkg/Core/Dxe/SysCall/BootServices.c
+++ b/MdeModulePkg/Core/Dxe/SysCall/BootServices.c
@@ -65,6 +65,12 @@ CallInstallMultipleProtocolInterfaces (
   IN VOID        *Function
   );
 
+VOID
+EFIAPI
+ReturnToCore (
+  IN EFI_STATUS Status
+  );
+  
 VOID
 EFIAPI
 FreeProtocolsList (
@@ -318,6 +324,9 @@ CallBootService (
   DEBUG ((DEBUG_VERBOSE, "Type: %a\n", SysCallNames[Type]));
 
   switch (Type) {
+    case SysCallReturnToCore:
+      ReturnToCore (CoreRbp->Argument1);
+      break;
     case SysCallLocateProtocol:
       //
       // Argument 1: EFI_GUID  *Protocol
diff --git a/MdeModulePkg/Core/Dxe/SysCall/IA32/CoreBootServices.nasm b/MdeModulePkg/Core/Dxe/SysCall/IA32/CoreBootServices.nasm
index c4d3714f2c..af51544705 100644
--- a/MdeModulePkg/Core/Dxe/SysCall/IA32/CoreBootServices.nasm
+++ b/MdeModulePkg/Core/Dxe/SysCall/IA32/CoreBootServices.nasm
@@ -126,10 +126,6 @@ ASM_PFX(CoreBootServices):
     mov     fs, ax
     mov     gs, ax
 
-    ; Special case for SysCallReturnToCore.
-    cmp     ecx, 0
-    je      coreReturnAddress
-
     ; Prepare CallBootService arguments.
     call ASM_PFX(AllowSupervisorAccessToUserMemory)
     mov     eax, [edx + 4 * 4] ; User Argument 3
@@ -202,19 +198,23 @@ ASM_PFX(CallRing3):
     sti
     sysexit
 
-coreReturnAddress:
+;------------------------------------------------------------------------------
+; VOID
+; EFIAPI
+; ReturnToCore (
+;   IN EFI_STATUS Status
+;   );
+;------------------------------------------------------------------------------
+global ASM_PFX(ReturnToCore)
+ASM_PFX(ReturnToCore):
+    mov     eax, [esp + 4]
+
     mov     esp, [ASM_PFX(CoreEsp)]
     pop     esi
     pop     edi
     pop     ebp
     pop     ebx
 
-    call ASM_PFX(AllowSupervisorAccessToUserMemory)
-    mov     eax, [edx + 2 * 4] ; User Argument 1
-    push    eax
-    call ASM_PFX(ForbidSupervisorAccessToUserMemory)
-    pop     eax
-
     sti
     ret
 
diff --git a/MdeModulePkg/Core/Dxe/SysCall/X64/CoreBootServices.nasm b/MdeModulePkg/Core/Dxe/SysCall/X64/CoreBootServices.nasm
index 3f9f4661ce..9d72b81935 100644
--- a/MdeModulePkg/Core/Dxe/SysCall/X64/CoreBootServices.nasm
+++ b/MdeModulePkg/Core/Dxe/SysCall/X64/CoreBootServices.nasm
@@ -132,10 +132,6 @@ ASM_PFX(CoreBootServices):
     mov     fs, ax
     mov     gs, ax
 
-    ; Special case for SysCallReturnToCore.
-    cmp     r10, 0
-    je      coreReturnAddress
-
     ; Save User Stack pointers and switch to Core SysCall Stack.
     mov     rax, [ASM_PFX(gCoreSysCallStackTop)]
     sub     rax, 8
@@ -228,7 +224,15 @@ ASM_PFX(CallRing3):
     ; Pass control to user image
 o64 sysret
 
-coreReturnAddress:
+;------------------------------------------------------------------------------
+; VOID
+; EFIAPI
+; ReturnToCore (
+;   IN EFI_STATUS Status
+;   );
+;------------------------------------------------------------------------------
+global ASM_PFX(ReturnToCore)
+ASM_PFX(ReturnToCore):
     mov     rsp, [ASM_PFX(CoreRsp)]
     pop     r15
     pop     r14
@@ -239,7 +243,7 @@ coreReturnAddress:
     pop     rbp
     pop     rbx
 
-    mov     rax, rdx
+    mov     rax, rcx
     sti
     ret
 
diff --git a/MdePkg/Include/Uefi/UefiSpec.h b/MdePkg/Include/Uefi/UefiSpec.h
index b6273143eb..26a7fbf235 100644
--- a/MdePkg/Include/Uefi/UefiSpec.h
+++ b/MdePkg/Include/Uefi/UefiSpec.h
@@ -2029,7 +2029,7 @@ typedef enum {
   //
   // BootServices
   //
-  SysCallReturnToCore,     // Must always be zero for CoreBootServices.nasm.
+  SysCallReturnToCore,
   SysCallLocateProtocol,
   SysCallOpenProtocol,
   SysCallInstallMultipleProtocolInterfaces,