[edk2-devel] [RFT PATCH v3 3/5] UefiCpuPkg/CpuExceptionHandlerLib: Make runtime fixups XCODE-only

[Ard Biesheuvel]

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 at kernel.org>
---
 UefiCpuPkg/Library/CpuExceptionHandlerLib/DxeCpuExceptionHandlerLib.inf                                    |  5 ++++-
 UefiCpuPkg/Library/CpuExceptionHandlerLib/PeiCpuExceptionHandlerLib.inf                                    |  4 +++-
 UefiCpuPkg/Library/CpuExceptionHandlerLib/SmmCpuExceptionHandlerLib.inf                                    |  4 +++-
 UefiCpuPkg/Library/CpuExceptionHandlerLib/X64/{Xcode5ExceptionHandlerAsm.nasm => ExceptionHandlerAsm.nasm} | 10 ++++++++++
 4 files changed, 20 insertions(+), 3 deletions(-)

diff --git a/UefiCpuPkg/Library/CpuExceptionHandlerLib/DxeCpuExceptionHandlerLib.inf b/UefiCpuPkg/Library/CpuExceptionHandlerLib/DxeCpuExceptionHandlerLib.inf
index d0f82095cf926e99..ee9df805c05df4f7 100644
--- a/UefiCpuPkg/Library/CpuExceptionHandlerLib/DxeCpuExceptionHandlerLib.inf
+++ b/UefiCpuPkg/Library/CpuExceptionHandlerLib/DxeCpuExceptionHandlerLib.inf
@@ -28,7 +28,7 @@ [Sources.Ia32]
   Ia32/ArchInterruptDefs.h
 
 [Sources.X64]
-  X64/Xcode5ExceptionHandlerAsm.nasm
+  X64/ExceptionHandlerAsm.nasm
   X64/ArchExceptionHandler.c
   X64/ArchInterruptDefs.h
 
@@ -61,3 +61,6 @@ [LibraryClasses]
   MemoryAllocationLib
   DebugLib
   CcExitLib
+
+[BuildOptions]
+  XCODE:*_*_X64_PP_FLAGS = -DNO_ABSOLUTE_RELOCS_IN_TEXT
diff --git a/UefiCpuPkg/Library/CpuExceptionHandlerLib/PeiCpuExceptionHandlerLib.inf b/UefiCpuPkg/Library/CpuExceptionHandlerLib/PeiCpuExceptionHandlerLib.inf
index 5339f8e604045801..83970c54712f22a2 100644
--- a/UefiCpuPkg/Library/CpuExceptionHandlerLib/PeiCpuExceptionHandlerLib.inf
+++ b/UefiCpuPkg/Library/CpuExceptionHandlerLib/PeiCpuExceptionHandlerLib.inf
@@ -28,7 +28,7 @@ [Sources.Ia32]
   Ia32/ArchInterruptDefs.h
 
 [Sources.X64]
-  X64/Xcode5ExceptionHandlerAsm.nasm
+  X64/ExceptionHandlerAsm.nasm
   X64/ArchExceptionHandler.c
   X64/ArchInterruptDefs.h
 
@@ -62,3 +62,5 @@ [Pcd]
 [FeaturePcd]
   gUefiCpuPkgTokenSpaceGuid.PcdCpuSmmStackGuard                    ## CONSUMES
 
+[BuildOptions]
+  XCODE:*_*_X64_PP_FLAGS = -DNO_ABSOLUTE_RELOCS_IN_TEXT
diff --git a/UefiCpuPkg/Library/CpuExceptionHandlerLib/SmmCpuExceptionHandlerLib.inf b/UefiCpuPkg/Library/CpuExceptionHandlerLib/SmmCpuExceptionHandlerLib.inf
index 8f8a5dab79303f87..acd2936aef4490a5 100644
--- a/UefiCpuPkg/Library/CpuExceptionHandlerLib/SmmCpuExceptionHandlerLib.inf
+++ b/UefiCpuPkg/Library/CpuExceptionHandlerLib/SmmCpuExceptionHandlerLib.inf
@@ -28,7 +28,7 @@ [Sources.Ia32]
   Ia32/ArchInterruptDefs.h
 
 [Sources.X64]
-  X64/Xcode5ExceptionHandlerAsm.nasm
+  X64/ExceptionHandlerAsm.nasm
   X64/ArchExceptionHandler.c
   X64/ArchInterruptDefs.h
 
@@ -61,3 +61,5 @@ [Pcd]
 [FeaturePcd]
   gUefiCpuPkgTokenSpaceGuid.PcdCpuSmmStackGuard                    ## CONSUMES
 
+[BuildOptions]
+  XCODE:*_*_X64_PP_FLAGS = -DNO_ABSOLUTE_RELOCS_IN_TEXT
diff --git a/UefiCpuPkg/Library/CpuExceptionHandlerLib/X64/Xcode5ExceptionHandlerAsm.nasm b/UefiCpuPkg/Library/CpuExceptionHandlerLib/X64/ExceptionHandlerAsm.nasm
similarity index 95%
rename from UefiCpuPkg/Library/CpuExceptionHandlerLib/X64/Xcode5ExceptionHandlerAsm.nasm
rename to UefiCpuPkg/Library/CpuExceptionHandlerLib/X64/ExceptionHandlerAsm.nasm
index 957478574253e619..3823656ea7d4c3b8 100644
--- a/UefiCpuPkg/Library/CpuExceptionHandlerLib/X64/Xcode5ExceptionHandlerAsm.nasm
+++ b/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
 
-- 
2.39.2



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