Some edk2 modules generate X86 machine code at module execution time by: - compiling "template" code with NASM at module build time,
- linking the object code into the module, - and patching the immediate (constant) operands of some instructions when the module is executed. Add a helper function to BaseLib so that the C code performing the patching is easier to read and maintain. The implementation in this patch is taken mainly from Mike Kinney's mailing list message at <E92EE9817A31E24EB0585FDF735412F5B895C360@ORSMSX113.amr.corp.intel.com">http://mid.mail-archive.com/E92EE9817A31E24EB0585FDF735412F5B895C360@ORSMSX113.amr.corp.intel.com>. Cc: Ard Biesheuvel <ard.biesheu...@linaro.org> Cc: Eric Dong <eric.d...@intel.com> Cc: Jiewen Yao <jiewen....@intel.com> Cc: Leif Lindholm <leif.lindh...@linaro.org> Cc: Liming Gao <liming....@intel.com> Cc: Michael D Kinney <michael.d.kin...@intel.com> Cc: Ruiyu Ni <ruiyu...@intel.com> Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=866 Contributed-under: TianoCore Contribution Agreement 1.1 Signed-off-by: Laszlo Ersek <ler...@redhat.com> --- MdePkg/Library/BaseLib/BaseLib.inf | 2 + MdePkg/Include/Library/BaseLib.h | 42 +++++++++ MdePkg/Library/BaseLib/X86PatchInstruction.c | 89 ++++++++++++++++++++ 3 files changed, 133 insertions(+) diff --git a/MdePkg/Library/BaseLib/BaseLib.inf b/MdePkg/Library/BaseLib/BaseLib.inf index fbfb0063b75f..4353e242f458 100644 --- a/MdePkg/Library/BaseLib/BaseLib.inf +++ b/MdePkg/Library/BaseLib/BaseLib.inf @@ -431,6 +431,7 @@ [Sources.Ia32] X86DisablePaging64.c X86DisablePaging32.c X86RdRand.c + X86PatchInstruction.c [Sources.X64] X64/Thunk16.nasm @@ -757,6 +758,7 @@ [Sources.X64] X86DisablePaging64.c X86DisablePaging32.c X86RdRand.c + X86PatchInstruction.c X64/GccInline.c | GCC X64/Thunk16.S | XCODE X64/SwitchStack.nasm| GCC diff --git a/MdePkg/Include/Library/BaseLib.h b/MdePkg/Include/Library/BaseLib.h index e4455e71d5c3..0dcb394c9280 100644 --- a/MdePkg/Include/Library/BaseLib.h +++ b/MdePkg/Include/Library/BaseLib.h @@ -9068,5 +9068,47 @@ AsmWriteTr ( IN UINT16 Selector ); +/** + Patch the immediate operand of an IA32 or X64 instruction such that the byte, + word, dword or qword operand is encoded at the end of the instruction's + binary representation. + + This function should be used to update object code that was compiled with + NASM from assembly source code. Example: + + NASM source code: + + mov eax, strict dword 0 ; the imm32 zero operand will be patched + ASM_PFX(gPatchCr3): + mov cr3, eax + + C source code: + + extern UINT8 gPatchCr3; + PatchInstructionX86 (&gPatchCr3, AsmReadCr3 (), 4); + + @param[out] InstructionEnd Pointer to the byte one past the instruction to + patch. The immediate operand to patch is expected + to comprise the trailing bytes of the + instruction. If InstructionEnd is closer to + address 0 than ValueSize permits, then ASSERT(). + + @param[in] PatchValue The constant to write to the immediate operand. + The caller is responsible for ensuring that + PatchValue can be represented in the byte, word, + dword or qword operand (as indicated through + ValueSize); otherwise ASSERT(). + + @param[in] ValueSize The size of the operand in bytes; must be 1, 2, + 4, or 8. ASSERT() otherwise. +**/ +VOID +EFIAPI +PatchInstructionX86 ( + OUT VOID *InstructionEnd, + IN UINT64 PatchValue, + IN UINTN ValueSize + ); + #endif // defined (MDE_CPU_IA32) || defined (MDE_CPU_X64) #endif // !defined (__BASE_LIB__) diff --git a/MdePkg/Library/BaseLib/X86PatchInstruction.c b/MdePkg/Library/BaseLib/X86PatchInstruction.c new file mode 100644 index 000000000000..82c86244c9c0 --- /dev/null +++ b/MdePkg/Library/BaseLib/X86PatchInstruction.c @@ -0,0 +1,89 @@ +/** @file + IA-32/x64 PatchInstructionX86() + + Copyright (C) 2018, Intel Corporation. All rights reserved.<BR> + Copyright (C) 2018, Red Hat, Inc. + + This program and the accompanying materials are licensed and made available + under the terms and conditions of the BSD License which accompanies this + distribution. The full text of the license may be found at + http://opensource.org/licenses/bsd-license.php. + + THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS, WITHOUT + WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED. +**/ + +#include "BaseLibInternals.h" + +/** + Patch the immediate operand of an IA32 or X64 instruction such that the byte, + word, dword or qword operand is encoded at the end of the instruction's + binary representation. + + This function should be used to update object code that was compiled with + NASM from assembly source code. Example: + + NASM source code: + + mov eax, strict dword 0 ; the imm32 zero operand will be patched + ASM_PFX(gPatchCr3): + mov cr3, eax + + C source code: + + extern UINT8 gPatchCr3; + PatchInstructionX86 (&gPatchCr3, AsmReadCr3 (), 4); + + @param[out] InstructionEnd Pointer to the byte one past the instruction to + patch. The immediate operand to patch is expected + to comprise the trailing bytes of the + instruction. If InstructionEnd is closer to + address 0 than ValueSize permits, then ASSERT(). + + @param[in] PatchValue The constant to write to the immediate operand. + The caller is responsible for ensuring that + PatchValue can be represented in the byte, word, + dword or qword operand (as indicated through + ValueSize); otherwise ASSERT(). + + @param[in] ValueSize The size of the operand in bytes; must be 1, 2, + 4, or 8. ASSERT() otherwise. +**/ +VOID +EFIAPI +PatchInstructionX86 ( + OUT VOID *InstructionEnd, + IN UINT64 PatchValue, + IN UINTN ValueSize + ) +{ + // + // The equality ((UINTN)InstructionEnd == ValueSize) would assume a zero-size + // instruction at address 0; forbid it. + // + ASSERT ((UINTN)InstructionEnd > ValueSize); + + switch (ValueSize) { + case 1: + ASSERT (PatchValue <= MAX_UINT8); + *((UINT8 *)InstructionEnd - 1) = (UINT8)PatchValue; + break; + + case 2: + ASSERT (PatchValue <= MAX_UINT16); + WriteUnaligned16 ((UINT16 *)InstructionEnd - 1, (UINT16)PatchValue); + break; + + case 4: + ASSERT (PatchValue <= MAX_UINT32); + WriteUnaligned32 ((UINT32 *)InstructionEnd - 1, (UINT32)PatchValue); + break; + + case 8: + WriteUnaligned64 ((UINT64 *)InstructionEnd - 1, PatchValue); + break; + + default: + ASSERT (FALSE); + } +} -- 2.14.1.3.gb7cf6e02401b _______________________________________________ edk2-devel mailing list edk2-devel@lists.01.org https://lists.01.org/mailman/listinfo/edk2-devel
