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PECOFF: Fix base relocation for ImageBase. 

This is yet another edge case of base relocation for symbols. Absolute
symbols are in general not target of base relocation because absolute
atom is a way to point to a specific memory location. In r229816, I
removed entries for absolute atoms from the base relocation table
(so that they won't be fixed by the loader).

However, there was one exception -- ImageBase. ImageBase points to the
start address of the current image in memory. That needs to be fixed up
at load time. This patch is to treat the symbol in a special manner.

llvm-svn: 229961
This commit is contained in:
Rui Ueyama 2015-02-20 03:35:59 +00:00
parent ad6eb127c9
commit 11f42aa285
3 changed files with 27 additions and 4 deletions
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8
lld/lib/ReaderWriter/PECOFF/WriterPECOFF.cpp
View File

@ -784,7 +784,13 @@ void AtomChunk::addBaseRelocations(BaseRelocationList &relocSites) const {
for (const Reference *ref : *atom) {
if (ref->kindNamespace() != Reference::KindNamespace::COFF)
continue;
if (isa<AbsoluteAtom>(ref->target()))
// An absolute symbol points to a fixed location in memory. Their
// address should not be fixed at load time. One exception is ImageBase
// because that's relative to run-time image base address.
if (auto *abs = dyn_cast<AbsoluteAtom>(ref->target()))
if (!abs->name().equals("__ImageBase") &&
!abs->name().equals("___ImageBase"))
continue;
uint64_t address = layout->_virtualAddr + ref->offsetInAtom();

11
lld/test/pecoff/Inputs/basereloc.obj.yaml
View File

@ -6,7 +6,7 @@ sections:
- Name: .text
Characteristics: [ IMAGE_SCN_CNT_CODE, IMAGE_SCN_MEM_EXECUTE, IMAGE_SCN_MEM_READ ]
Alignment: 4
SectionData: B800000000506800000000680000000050E80000000050E800000000
SectionData: B800000000506800000000680000000050E80000000050E80000000050E800000000
Relocations:
- VirtualAddress: 0
SymbolName: abs_symbol
@ -23,6 +23,9 @@ sections:
- VirtualAddress: 24
SymbolName: _ExitProcess@4
Type: IMAGE_REL_I386_REL32
- VirtualAddress: 30
SymbolName: ___ImageBase
Type: IMAGE_REL_I386_DIR32
- Name: .data
Characteristics: [ IMAGE_SCN_CNT_INITIALIZED_DATA, IMAGE_SCN_MEM_READ, IMAGE_SCN_MEM_WRITE ]
Alignment: 4
@ -117,4 +120,10 @@ symbols:
SimpleType: IMAGE_SYM_TYPE_NULL
ComplexType: IMAGE_SYM_DTYPE_NULL
StorageClass: IMAGE_SYM_CLASS_EXTERNAL
- Name: ___ImageBase
Value: 0
SectionNumber: 0
SimpleType: IMAGE_SYM_TYPE_NULL
ComplexType: IMAGE_SYM_DTYPE_NULL
StorageClass: IMAGE_SYM_CLASS_EXTERNAL
...

12
lld/test/pecoff/base-reloc.test
View File

@ -17,6 +17,14 @@ BASEREL-NEXT: Entry {
BASEREL-NEXT: Type: HIGHLOW
BASEREL-NEXT: Address: 0x200C
BASEREL-NEXT: }
BASEREL-NEXT: Entry {
BASEREL-NEXT: Type: HIGHLOW
BASEREL-NEXT: Address: 0x201E
BASEREL-NEXT: }
BASEREL-NEXT: Entry {
BASEREL-NEXT: Type: ABSOLUTE
BASEREL-NEXT: Address: 0x2000
BASEREL-NEXT: }
BASEREL-NEXT: ]
NOBASEREL: BaseReloc [
@ -37,9 +45,9 @@ BASEREL-HEADER-NOT: IMAGE_FILE_RELOCS_STRIPPED
NOBASEREL-HEADER: IMAGE_FILE_RELOCS_STRIPPED
BASEREL-HEADER: BaseRelocationTableRVA: 0x3000
BASEREL-HEADER: BaseRelocationTableSize: 0xC
BASEREL-HEADER: BaseRelocationTableSize: 0x10
BASEREL-HEADER: Name: .reloc (2E 72 65 6C 6F 63 00 00)
BASEREL-HEADER-NEXT: VirtualSize: 0xC
BASEREL-HEADER-NEXT: VirtualSize: 0x10
BASEREL-HEADER-NEXT: VirtualAddress: 0x3000
BASEREL-HEADER-NEXT: RawDataSize: 512
BASEREL-HEADER-NEXT: PointerToRawData: 0x600