Re: [PATCH v2] BaseTools/GenFw: Disable support for R_X86_64_32S

Re: [PATCH v2] BaseTools/GenFw: Disable support for R_X86_64_32S

[Gao, Liming]

Reviewed-by: Liming Gao <liming.gao@intel.com>

>-----Original Message-----
>From: Zenith432 [mailto:zenith432@users.sourceforge.net]
>Sent: Tuesday, July 10, 2018 4:51 PM
>To: edk2-devel@lists.01.org
>Cc: Gao, Liming <liming.gao@intel.com>
>Subject: [PATCH v2] BaseTools/GenFw: Disable support for R_X86_64_32S
>
>
>REF:https://bugzilla.tianocore.org/show_bug.cgi?id=999
>
>Cc: Liming Gao <liming.gao@intel.com>
>Contributed-under: TianoCore Contribution Agreement 1.1
>Signed-off-by: Zenith432 <zenith432@users.sourceforge.net>
>---
> BaseTools/Source/C/GenFw/Elf64Convert.c | 23
>++++++++++++++++++++++-
> 1 file changed, 22 insertions(+), 1 deletion(-)
>
>diff --git a/BaseTools/Source/C/GenFw/Elf64Convert.c
>b/BaseTools/Source/C/GenFw/Elf64Convert.c
>index 4636cfee..e42cc3f7 100644
>--- a/BaseTools/Source/C/GenFw/Elf64Convert.c
>+++ b/BaseTools/Source/C/GenFw/Elf64Convert.c
>@@ -993,7 +993,28 @@ WriteRelocations64 (
>                 + (Rel->r_offset - SecShdr->sh_addr)),
>                 EFI_IMAGE_REL_BASED_DIR64);
>               break;
>-            case R_X86_64_32S:
>+            //
>+            // R_X86_64_32 and R_X86_64_32S are ELF64 relocations emitted
>when using
>+            //   the SYSV X64 ABI small non-position-independent code model.
>+            //   R_X86_64_32 is used for unsigned 32-bit immediates with a 32-bit
>operand
>+            //   size.  The value is either not extended, or zero-extended to 64 bits.
>+            //   R_X86_64_32S is used for either signed 32-bit non-rip-relative
>displacements
>+            //   or signed 32-bit immediates with a 64-bit operand size.  The value is
>+            //   sign-extended to 64 bits.
>+            //   EFI_IMAGE_REL_BASED_HIGHLOW is a PE relocation that uses 32-
>bit arithmetic
>+            //   for rebasing an image.
>+            //   EFI PE binaries declare themselves
>EFI_IMAGE_FILE_LARGE_ADDRESS_AWARE and
>+            //   may load above 2GB.  If an EFI PE binary with a converted
>R_X86_64_32S
>+            //   relocation is loaded above 2GB, the value will get sign-extended to
>the
>+            //   negative part of the 64-bit address space.  The negative part of the
>64-bit
>+            //   address space is unmapped, so accessing such an address page-
>faults.
>+            //   In order to support R_X86_64_32S, it is necessary to unset
>+            //   EFI_IMAGE_FILE_LARGE_ADDRESS_AWARE, and the EFI PE loader
>must implement
>+            //   this flag and abstain from loading such a PE binary above 2GB.
>+            //   Since this feature is not supported, support for R_X86_64_32S (and
>hence
>+            //   the small non-position-independent code model) is disabled.
>+            //
>+            // case R_X86_64_32S:
>             case R_X86_64_32:
>               VerboseMsg ("EFI_IMAGE_REL_BASED_HIGHLOW Offset: 0x%08X",
>                 mCoffSectionsOffset[RelShdr->sh_info] + (Rel->r_offset - SecShdr-
>>sh_addr));
>--
>2.17.1