[llvm] 70c4930 - [llvm-readobj] [ARMWinEH] Try to resolve label symbols into regular ones
Martin Storsjö via llvm-commits
llvm-commits at lists.llvm.org
Tue May 4 12:39:12 PDT 2021
Author: Martin Storsjö
Date: 2021-05-04T22:22:18+03:00
New Revision: 70c4930637fa9a43eabcbde66e5a74262da1e46c
URL: https://github.com/llvm/llvm-project/commit/70c4930637fa9a43eabcbde66e5a74262da1e46c
DIFF: https://github.com/llvm/llvm-project/commit/70c4930637fa9a43eabcbde66e5a74262da1e46c.diff
LOG: [llvm-readobj] [ARMWinEH] Try to resolve label symbols into regular ones
Unwind info generated by MSVC tends to have relocations pointing at
static "label" symbols like "$LN4" instead of regular ones based on
the actual function's name. Try to resolve such symbols to a non-label
symbol if possible (ideally to an external symbol), to improve
the readability.
Differential Revision: https://reviews.llvm.org/D101567
Added:
llvm/test/tools/llvm-readobj/COFF/arm64-unwind-preferred-symbol.yaml
Modified:
llvm/tools/llvm-readobj/ARMWinEHPrinter.cpp
llvm/tools/llvm-readobj/ARMWinEHPrinter.h
Removed:
################################################################################
diff --git a/llvm/test/tools/llvm-readobj/COFF/arm64-unwind-preferred-symbol.yaml b/llvm/test/tools/llvm-readobj/COFF/arm64-unwind-preferred-symbol.yaml
new file mode 100644
index 000000000000..54dd127fd0d7
--- /dev/null
+++ b/llvm/test/tools/llvm-readobj/COFF/arm64-unwind-preferred-symbol.yaml
@@ -0,0 +1,81 @@
+# Check that we print the external symbol "func", even though the pdata
+# relocation points at the '$LN4' symbol.
+
+# RUN: yaml2obj %s -o %t.obj
+# RUN: llvm-readobj --unwind %t.obj | FileCheck %s
+
+# CHECK: Function: func (0x0)
+
+--- !COFF
+header:
+ Machine: IMAGE_FILE_MACHINE_ARM64
+ Characteristics: [ ]
+sections:
+ - Name: '.text$mn'
+ Characteristics: [ IMAGE_SCN_CNT_CODE, IMAGE_SCN_LNK_COMDAT, IMAGE_SCN_MEM_EXECUTE, IMAGE_SCN_MEM_READ ]
+ Alignment: 8
+ SectionData: FE0F1FF8FF0301D1E003009100000094FF030191FE0741F8C0035FD6
+ Relocations:
+ - VirtualAddress: 12
+ SymbolName: other
+ Type: IMAGE_REL_ARM64_BRANCH26
+ - Name: .pdata
+ Characteristics: [ IMAGE_SCN_CNT_INITIALIZED_DATA, IMAGE_SCN_LNK_COMDAT, IMAGE_SCN_MEM_READ ]
+ Alignment: 4
+ SectionData: 000000001D00A002
+ Relocations:
+ - VirtualAddress: 0
+ SymbolName: '$LN4'
+ Type: IMAGE_REL_ARM64_ADDR32NB
+symbols:
+ - Name: '.text$mn'
+ Value: 0
+ SectionNumber: 1
+ SimpleType: IMAGE_SYM_TYPE_NULL
+ ComplexType: IMAGE_SYM_DTYPE_NULL
+ StorageClass: IMAGE_SYM_CLASS_STATIC
+ SectionDefinition:
+ Length: 28
+ NumberOfRelocations: 1
+ NumberOfLinenumbers: 0
+ CheckSum: 1015150991
+ Number: 0
+ Selection: IMAGE_COMDAT_SELECT_NODUPLICATES
+ - Name: other
+ Value: 0
+ SectionNumber: 0
+ SimpleType: IMAGE_SYM_TYPE_NULL
+ ComplexType: IMAGE_SYM_DTYPE_FUNCTION
+ StorageClass: IMAGE_SYM_CLASS_EXTERNAL
+ - Name: func
+ Value: 0
+ SectionNumber: 1
+ SimpleType: IMAGE_SYM_TYPE_NULL
+ ComplexType: IMAGE_SYM_DTYPE_FUNCTION
+ StorageClass: IMAGE_SYM_CLASS_EXTERNAL
+ - Name: '$LN4'
+ Value: 0
+ SectionNumber: 1
+ SimpleType: IMAGE_SYM_TYPE_NULL
+ ComplexType: IMAGE_SYM_DTYPE_NULL
+ StorageClass: IMAGE_SYM_CLASS_LABEL
+ - Name: .pdata
+ Value: 0
+ SectionNumber: 2
+ SimpleType: IMAGE_SYM_TYPE_NULL
+ ComplexType: IMAGE_SYM_DTYPE_NULL
+ StorageClass: IMAGE_SYM_CLASS_STATIC
+ SectionDefinition:
+ Length: 8
+ NumberOfRelocations: 1
+ NumberOfLinenumbers: 0
+ CheckSum: 3799667335
+ Number: 2
+ Selection: IMAGE_COMDAT_SELECT_ASSOCIATIVE
+ - Name: '$pdata$func'
+ Value: 0
+ SectionNumber: 2
+ SimpleType: IMAGE_SYM_TYPE_NULL
+ ComplexType: IMAGE_SYM_DTYPE_NULL
+ StorageClass: IMAGE_SYM_CLASS_STATIC
+...
diff --git a/llvm/tools/llvm-readobj/ARMWinEHPrinter.cpp b/llvm/tools/llvm-readobj/ARMWinEHPrinter.cpp
index cc9e3d944bbe..99ee639fc45d 100644
--- a/llvm/tools/llvm-readobj/ARMWinEHPrinter.cpp
+++ b/llvm/tools/llvm-readobj/ARMWinEHPrinter.cpp
@@ -238,6 +238,28 @@ ErrorOr<SymbolRef> Decoder::getRelocatedSymbol(const COFFObjectFile &,
return inconvertibleErrorCode();
}
+SymbolRef Decoder::getPreferredSymbol(const COFFObjectFile &COFF,
+ SymbolRef Sym) {
+ // The symbol resolved by getRelocatedSymbol can be any internal
+ // nondescriptive symbol; try to resolve a more descriptive one.
+ COFFSymbolRef CoffSym = COFF.getCOFFSymbol(Sym);
+ if (CoffSym.getStorageClass() != COFF::IMAGE_SYM_CLASS_LABEL)
+ return Sym;
+ for (const auto &S : COFF.symbols()) {
+ COFFSymbolRef CS = COFF.getCOFFSymbol(S);
+ if (CS.getSectionNumber() == CoffSym.getSectionNumber() &&
+ CS.getValue() == CoffSym.getValue()) {
+ if (CS.isExternal())
+ return S;
+ if (CS.getStorageClass() != COFF::IMAGE_SYM_CLASS_LABEL) {
+ Sym = S;
+ CoffSym = CS;
+ }
+ }
+ }
+ return Sym;
+}
+
ErrorOr<SymbolRef> Decoder::getSymbolForLocation(
const COFFObjectFile &COFF, const SectionRef &Section,
uint64_t OffsetInSection, uint64_t ImmediateOffset, uint64_t &SymbolAddress,
@@ -270,6 +292,8 @@ ErrorOr<SymbolRef> Decoder::getSymbolForLocation(
SymbolOffset = 0;
SymOrErr = getSymbol(COFF, SymbolAddress, FunctionOnly);
}
+ if (SymOrErr && FunctionOnly) // Resolve label symbols into function names
+ SymOrErr = getPreferredSymbol(COFF, *SymOrErr);
return SymOrErr;
}
diff --git a/llvm/tools/llvm-readobj/ARMWinEHPrinter.h b/llvm/tools/llvm-readobj/ARMWinEHPrinter.h
index 7870f9790486..efe16850c7fa 100644
--- a/llvm/tools/llvm-readobj/ARMWinEHPrinter.h
+++ b/llvm/tools/llvm-readobj/ARMWinEHPrinter.h
@@ -153,6 +153,9 @@ class Decoder {
uint64_t &SymbolAddress, uint64_t &SymbolOffset,
bool FunctionOnly = false);
+ object::SymbolRef getPreferredSymbol(const object::COFFObjectFile &COFF,
+ object::SymbolRef Sym);
+
bool dumpXDataRecord(const object::COFFObjectFile &COFF,
const object::SectionRef &Section,
uint64_t FunctionAddress, uint64_t VA);
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