[edk2-devel] [PATCH v4 2/6] UefiCpuPkg/CpuExceptionHandlerLib: Use single SEC/PEI version

[Ard Biesheuvel]

Currently, we use the non-Xcode5 version of ExceptionHandlerAsm.nasm
only for the SEC and PEI phases, and this version was not compatible
with the XCODE or LLD linkers, which do not permit absolute relocations
in read-only sections.

Given that SEC and PEI code typically executes in place from flash and
does not use page alignment for sections, we can simply emit the code
carrying the absolute symbol references into the .data segment instead.
This works around the linker's objections, and the resulting image will
be mapped executable in its entirety anyway. Since this is only needed
for XCODE, let's make this change conditionally using a preprocessor
macro.

Let's rename the .nasm file to reflect the fact that is used for the
SecPei flavor of this library only, and while at it, remove some
unnecessary absolute references.

Also update the Xcode specific version of this library, and use this
source file instead. This is necesessary, as the Xcode specific version
modifies its own code at runtime, which is not permitted in SEC or PEI.
Note that this also removes CET support from the Xcode5 specific build
of the SEC/PEI version of this library, but this is not needed this
early in any case, and this aligns it with other toolchains, which use
this version of the library, which does not have CET support either.

1. Change for non-XCODE SecPeiCpuExceptionHandlerLib:
. Use SecPeiExceptionHandlerAsm.nasm (renamed from
  ExceptionHandlerAsm.nasm)
. Removed some unnecessary absolute references
  (32 IDT stubs are still in .text.)

2. Change for XCODE SecPeiCpuExceptionHandlerLib:
. Use SecPeiExceptionHandlerAsm.nasm instead of
  Xcode5ExceptionHandlerAsm.nasm
. CET logic is not in SecPeiExceptionHandlerAsm.nasm (but aligns to
  non-XCODE lib instance)
. Fixed a bug that does runtime fixup in TEXT section in SPI flash.
. Emitted the code carrying the absolute symbol references into the
  .data which XCODE or LLD linkers allow.
. Then fixup can be done by other build tools such as GenFv if the code
  runs in SPI flash, or by PE coff loader if the code is loaded to
  memory.

Signed-off-by: Ard Biesheuvel <ardb at kernel.org>
---
 UefiCpuPkg/Library/CpuExceptionHandlerLib/SecPeiCpuExceptionHandlerLib.inf                                 |  4 +++-
 UefiCpuPkg/Library/CpuExceptionHandlerLib/X64/{ExceptionHandlerAsm.nasm => SecPeiExceptionHandlerAsm.nasm} | 12 ++++++++----
 UefiCpuPkg/Library/CpuExceptionHandlerLib/Xcode5SecPeiCpuExceptionHandlerLib.inf                           |  4 +++-
 3 files changed, 14 insertions(+), 6 deletions(-)

diff --git a/UefiCpuPkg/Library/CpuExceptionHandlerLib/SecPeiCpuExceptionHandlerLib.inf b/UefiCpuPkg/Library/CpuExceptionHandlerLib/SecPeiCpuExceptionHandlerLib.inf
index df44371fe018e06d..e7b1144f694183b7 100644
--- a/UefiCpuPkg/Library/CpuExceptionHandlerLib/SecPeiCpuExceptionHandlerLib.inf
+++ b/UefiCpuPkg/Library/CpuExceptionHandlerLib/SecPeiCpuExceptionHandlerLib.inf
@@ -28,7 +28,7 @@ [Sources.Ia32]
   Ia32/ArchInterruptDefs.h
 
 [Sources.X64]
-  X64/ExceptionHandlerAsm.nasm
+  X64/SecPeiExceptionHandlerAsm.nasm
   X64/ArchExceptionHandler.c
   X64/ArchInterruptDefs.h
 
@@ -58,3 +58,5 @@ [Pcd]
 [FeaturePcd]
   gUefiCpuPkgTokenSpaceGuid.PcdCpuSmmStackGuard                    ## CONSUMES
 
+[BuildOptions]
+  XCODE:*_*_X64_NASM_FLAGS = -D NO_ABSOLUTE_RELOCS_IN_TEXT
diff --git a/UefiCpuPkg/Library/CpuExceptionHandlerLib/X64/ExceptionHandlerAsm.nasm b/UefiCpuPkg/Library/CpuExceptionHandlerLib/X64/SecPeiExceptionHandlerAsm.nasm
similarity index 94%
rename from UefiCpuPkg/Library/CpuExceptionHandlerLib/X64/ExceptionHandlerAsm.nasm
rename to UefiCpuPkg/Library/CpuExceptionHandlerLib/X64/SecPeiExceptionHandlerAsm.nasm
index aaf8d622e6f3b8f1..5c7a59c99d3210f1 100644
--- a/UefiCpuPkg/Library/CpuExceptionHandlerLib/X64/ExceptionHandlerAsm.nasm
+++ b/UefiCpuPkg/Library/CpuExceptionHandlerLib/X64/SecPeiExceptionHandlerAsm.nasm
@@ -27,7 +27,9 @@ extern ASM_PFX(CommonExceptionHandler)
 SECTION .data
 
 DEFAULT REL
+%ifndef NO_ABSOLUTE_RELOCS_IN_TEXT
 SECTION .text
+%endif
 
 ALIGN   8
 
@@ -51,6 +53,9 @@ HookAfterStubHeaderBegin:
     push    rax
     mov     rax, HookAfterStubHeaderEnd
     jmp     rax
+
+SECTION .text
+
 HookAfterStubHeaderEnd:
     mov     rax, rsp
     and     sp,  0xfff0        ; make sure 16-byte aligned for exception context
@@ -276,8 +281,7 @@ DrFinish:
     ; and make sure RSP is 16-byte aligned
     ;
     sub     rsp, 4 * 8 + 8
-    mov     rax, ASM_PFX(CommonExceptionHandler)
-    call    rax
+    call    ASM_PFX(CommonExceptionHandler)
     add     rsp, 4 * 8 + 8
 
     cli
@@ -384,10 +388,10 @@ DoIret:
 ; comments here for definition of address map
 global ASM_PFX(AsmGetTemplateAddressMap)
 ASM_PFX(AsmGetTemplateAddressMap):
-    mov     rax, AsmIdtVectorBegin
+    lea     rax, [AsmIdtVectorBegin]
     mov     qword [rcx], rax
     mov     qword [rcx + 0x8],  (AsmIdtVectorEnd - AsmIdtVectorBegin) / 32
-    mov     rax, HookAfterStubHeaderBegin
+    lea     rax, [HookAfterStubHeaderBegin]
     mov     qword [rcx + 0x10], rax
     ret
 
diff --git a/UefiCpuPkg/Library/CpuExceptionHandlerLib/Xcode5SecPeiCpuExceptionHandlerLib.inf b/UefiCpuPkg/Library/CpuExceptionHandlerLib/Xcode5SecPeiCpuExceptionHandlerLib.inf
index 619b39d7f1de9ae3..accc081a95f53453 100644
--- a/UefiCpuPkg/Library/CpuExceptionHandlerLib/Xcode5SecPeiCpuExceptionHandlerLib.inf
+++ b/UefiCpuPkg/Library/CpuExceptionHandlerLib/Xcode5SecPeiCpuExceptionHandlerLib.inf
@@ -33,7 +33,7 @@ [Sources.Ia32]
   Ia32/ArchInterruptDefs.h
 
 [Sources.X64]
-  X64/Xcode5ExceptionHandlerAsm.nasm
+  X64/SecPeiExceptionHandlerAsm.nasm
   X64/ArchExceptionHandler.c
   X64/ArchInterruptDefs.h
 
@@ -63,3 +63,5 @@ [Pcd]
 [FeaturePcd]
   gUefiCpuPkgTokenSpaceGuid.PcdCpuSmmStackGuard                    ## CONSUMES
 
+[BuildOptions]
+  XCODE:*_*_X64_NASM_FLAGS = -D NO_ABSOLUTE_RELOCS_IN_TEXT
-- 
2.39.2



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