UefiCpuPkg/CpuExceptionHandlerLib: Make runtime fixups XCODE-only

The CPU exception handler library code was rewritten at some point to
populate the vector code templates with absolute references at runtime,
given that the XCODE linker does not permit absolute references in
executable code when creating PIE executables.

This is rather unfortunate, as this prevents us from using strict
permissions on the memory mappings, given that the .text section needs
to be writable at runtime for this arrangement to work.

So let's make this hack XCODE-only, by setting a preprocessor #define
from the command line when using the XCODE toolchain, and only including
the runtime fixup code when the macro is defined.

While at it, rename the Xcode5ExceptionHandlerAsm.nasm source file and
drop the Xcode5 prefix: this code is used by other toolchains too.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Reviewed-by: Ray Ni <ray.ni@intel.com>

UefiCpuPkg/Library/CpuExceptionHandlerLib/DxeCpuExceptionHandlerLib.inf

@@ -28,7 +28,7 @@
   Ia32/ArchInterruptDefs.h
 
 [Sources.X64]
-  X64/Xcode5ExceptionHandlerAsm.nasm
+  X64/ExceptionHandlerAsm.nasm
   X64/ArchExceptionHandler.c
   X64/ArchInterruptDefs.h
 
@@ -61,3 +61,6 @@
   MemoryAllocationLib
   DebugLib
   CcExitLib
+
+[BuildOptions]
+  XCODE:*_*_X64_NASM_FLAGS = -D NO_ABSOLUTE_RELOCS_IN_TEXT

UefiCpuPkg/Library/CpuExceptionHandlerLib/SmmCpuExceptionHandlerLib.inf

@@ -28,7 +28,7 @@
   Ia32/ArchInterruptDefs.h
 
 [Sources.X64]
-  X64/Xcode5ExceptionHandlerAsm.nasm
+  X64/ExceptionHandlerAsm.nasm
   X64/ArchExceptionHandler.c
   X64/ArchInterruptDefs.h
 
@@ -61,3 +61,5 @@
 [FeaturePcd]
   gUefiCpuPkgTokenSpaceGuid.PcdCpuSmmStackGuard                    ## CONSUMES
 
+[BuildOptions]
+  XCODE:*_*_X64_NASM_FLAGS = -D NO_ABSOLUTE_RELOCS_IN_TEXT

UefiCpuPkg/Library/CpuExceptionHandlerLib/X64/ExceptionHandlerAsm.nasm

@@ -59,7 +59,11 @@ AsmIdtVectorBegin:
 %rep  256
     push    strict dword %[Vector] ; This instruction pushes sign-extended 8-byte value on stack
     push    rax
+%ifdef NO_ABSOLUTE_RELOCS_IN_TEXT
     mov     rax, strict qword 0    ; mov     rax, ASM_PFX(CommonInterruptEntry)
+%else
+    mov     rax, ASM_PFX(CommonInterruptEntry)
+%endif
     jmp     rax
 %assign Vector Vector+1
 %endrep
@@ -69,8 +73,12 @@ HookAfterStubHeaderBegin:
     push    strict dword 0      ; 0 will be fixed
 VectorNum:
     push    rax
+%ifdef NO_ABSOLUTE_RELOCS_IN_TEXT
     mov     rax, strict qword 0 ;     mov     rax, HookAfterStubHeaderEnd
 JmpAbsoluteAddress:
+%else
+    mov     rax, HookAfterStubHeaderEnd
+%endif
     jmp     rax
 HookAfterStubHeaderEnd:
     mov     rax, rsp
@@ -457,6 +465,7 @@ ASM_PFX(AsmGetTemplateAddressMap):
     lea     rax, [HookAfterStubHeaderBegin]
     mov     qword [rcx + 0x10], rax
 
+%ifdef NO_ABSOLUTE_RELOCS_IN_TEXT
 ; Fix up CommonInterruptEntry address
     lea    rax, [ASM_PFX(CommonInterruptEntry)]
     lea    rcx, [AsmIdtVectorBegin]
@@ -468,6 +477,7 @@ ASM_PFX(AsmGetTemplateAddressMap):
     lea    rax, [HookAfterStubHeaderEnd]
     lea    rcx, [JmpAbsoluteAddress]
     mov    qword [rcx - 8], rax
+%endif
 
     ret