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[LLD][COFF] Support marking sections as x86_64 code in ARM64EC object files (#135280)

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On ARM64EC, the `IMAGE_SCN_GPREL` flag is repurposed to indicate that
section code is x86_64. This enables embedding x86_64 code within
ARM64EC object files. MSVC uses this for export thunks in .exp files.
This commit is contained in:
Jacek Caban 2025-04-11 16:13:46 +02:00 committed by GitHub
parent cd85f5dbdf
commit f8f01b5eeb
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3 changed files with 54 additions and 2 deletions
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10
lld/COFF/Chunks.cpp
View File

@ -61,6 +61,16 @@ SectionChunk::SectionChunk(ObjFile *f, const coff_section *h, Kind k)
live = true; live = true;
} }
MachineTypes SectionChunk::getMachine() const {
MachineTypes machine = file->getMachineType();
// On ARM64EC, the IMAGE_SCN_GPREL flag is repurposed to indicate that section
// code is x86_64. This enables embedding x86_64 code within ARM64EC object
// files. MSVC uses this for export thunks in .exp files.
if (isArm64EC(machine) && (header->Characteristics & IMAGE_SCN_GPREL))
machine = AMD64;
return machine;
}
// SectionChunk is one of the most frequently allocated classes, so it is // SectionChunk is one of the most frequently allocated classes, so it is
// important to keep it as compact as possible. As of this writing, the number // important to keep it as compact as possible. As of this writing, the number
// below is the size of this class on x64 platforms. // below is the size of this class on x64 platforms.

3
lld/COFF/Chunks.h
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@ -253,8 +253,7 @@ public:
size_t getSize() const { return header->SizeOfRawData; } size_t getSize() const { return header->SizeOfRawData; }
ArrayRef<uint8_t> getContents() const; ArrayRef<uint8_t> getContents() const;
void writeTo(uint8_t *buf) const; void writeTo(uint8_t *buf) const;
MachineTypes getMachine() const;
MachineTypes getMachine() const { return file->getMachineType(); }
// Defend against unsorted relocations. This may be overly conservative. // Defend against unsorted relocations. This may be overly conservative.
void sortRelocations(); void sortRelocations();

43
lld/test/COFF/arm64ec-x86-sec.yaml Normal file
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@ -0,0 +1,43 @@
# REQUIRES: aarch64, x86
# RUN: yaml2obj %s -o %t.obj
# RUN: llvm-mc -filetype=obj -triple=arm64ec-windows %S/Inputs/loadconfig-arm64ec.s -o %t-loadcfg.obj
# RUN: lld-link -machine:arm64ec -dll -noentry %t.obj %t-loadcfg.obj -out:%t.dll
# RUN: llvm-objdump -d %t.dll | FileCheck %s
# CHECK: Disassembly of section .text:
# CHECK-EMPTY:
# CHECK-NEXT: 0000000180001000 <.text>:
# CHECK-NEXT: 180001000: d503201f nop
# CHECK-NEXT: 180001004: d65f03c0 ret
# CHECK-NEXT: ...
# CHECK-NEXT: 180002000: e9 ff ef ff ff jmp 0x180001004 <.text+0x4>
# CHECK-NEXT: 180002005: c3 retq
# CHECK-NEXT: 180002006: cc int3
--- !COFF
header:
Machine: IMAGE_FILE_MACHINE_ARM64EC
Characteristics: [ ]
sections:
- Name: .text
Characteristics: [ IMAGE_SCN_CNT_CODE, IMAGE_SCN_MEM_EXECUTE, IMAGE_SCN_MEM_READ ]
Alignment: 4
SectionData: 1F2003D5C0035FD6
SizeOfRawData: 8
- Name: .text
Characteristics: [ IMAGE_SCN_CNT_CODE, IMAGE_SCN_GPREL, IMAGE_SCN_MEM_EXECUTE, IMAGE_SCN_MEM_READ ]
Alignment: 16
SectionData: E900000000C3CC
SizeOfRawData: 7
Relocations:
- VirtualAddress: 1
SymbolName: func
Type: IMAGE_REL_ARM64_PAGEBASE_REL21 # interpreted as IMAGE_REL_AMD64_REL32
symbols:
- Name: func
Value: 4
SectionNumber: 1
SimpleType: IMAGE_SYM_TYPE_NULL
ComplexType: IMAGE_SYM_DTYPE_NULL
StorageClass: IMAGE_SYM_CLASS_EXTERNAL