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[llvm-readobj/llvm-readelf] - Don't fail to dump the object if .dynsy…
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…m has broken sh_link field.

This is https://bugs.llvm.org/show_bug.cgi?id=42215.

GNU readelf allows to dump the objects in that case,
but llvm-readobj/llvm-readelf reports an error and stops.

The patch fixes that.

Differential revision: https://reviews.llvm.org/D63074

llvm-svn: 362938
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George Rimar committed Jun 10, 2019
1 parent 8cd8c57 commit dd4f253
Showing 6 changed files with 78 additions and 7 deletions.
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60 changes: 60 additions & 0 deletions llvm/test/tools/llvm-readobj/elf-broken-dynsym-link.test
Original file line number Diff line number Diff line change
@@ -0,0 +1,60 @@
## Test that we are able to dump section headers even if the
## .dynsym section's sh_link field is broken.

## Case 1: sh_link is set to 0.
# RUN: yaml2obj %s -o %t1
# RUN: llvm-readobj -S %t1 2>&1 | FileCheck %s --check-prefixes=LLVM,ERR
# RUN: llvm-readelf -S %t1 2>&1 | FileCheck %s --check-prefixes=GNU,ERR

# ERR: warning: invalid sh_type for string table, expected SHT_STRTAB

# LLVM: Name: .dynsym
# LLVM-NEXT: Type: SHT_DYNSYM
# LLVM-NEXT: Flags [
# LLVM-NEXT: SHF_ALLOC
# LLVM-NEXT: ]
# LLVM-NEXT: Address: 0x0
# LLVM-NEXT: Offset: 0x180
# LLVM-NEXT: Size: 24
# LLVM-NEXT: Link: 0

# GNU: Section Headers:
# GNU-NEXT: [Nr] Name Type Address Off Size ES Flg Lk
# GNU-NEXT: [ 0] NULL 0000000000000000 000000 000000 00 0 0
# GNU-NEXT: [ 1] .dynsym DYNSYM 0000000000000000 000180 000018 18 A 0

--- !ELF
FileHeader:
Class: ELFCLASS64
Data: ELFDATA2LSB
Type: ET_DYN
Machine: EM_X86_64
Sections:
- Name: .dynsym
Type: SHT_DYNSYM

## TODO: Remove precompiled input object after fixing yaml2obj.
## See https://bugs.llvm.org/show_bug.cgi?id=42216.

## Case 2: sh_link is set to 255, which is larger than the number of the sections.
# RUN: llvm-readobj -S %p/Inputs/elf-broken-dynsym-link.elf-x86-64 2>&1 \
# RUN: | FileCheck %s --check-prefixes=LLVM2,ERR2
# RUN: llvm-readelf -S %p/Inputs/elf-broken-dynsym-link.elf-x86-64 2>&1 \
# RUN: | FileCheck %s --check-prefixes=GNU2,ERR2

# ERR2: warning: invalid section index

# LLVM2: Name: .dynsym
# LLVM2-NEXT: Type: SHT_DYNSYM
# LLVM2-NEXT: Flags [
# LLVM2-NEXT: SHF_ALLOC
# LLVM2-NEXT: ]
# LLVM2-NEXT: Address: 0x0
# LLVM2-NEXT: Offset: 0x180
# LLVM2-NEXT: Size: 2
# LLVM2-NEXT: Link: 255

# GNU2: Section Headers:
# GNU2-NEXT: [Nr] Name Type Address Off Size ES Flg Lk
# GNU2-NEXT: [ 0] NULL 0000000000000000 000000 000000 00 0 0
# GNU2-NEXT: [ 1] .dynsym DYNSYM 0000000000000000 000180 000002 18 A 255
12 changes: 6 additions & 6 deletions llvm/test/tools/yaml2obj/explicit-dynsym-no-dynstr.yaml
Original file line number Diff line number Diff line change
@@ -2,14 +2,14 @@
## explicitly, but .dynstr is not present.

# RUN: yaml2obj %s -o %t
# RUN: not llvm-readelf --section-headers %t 2>&1 | FileCheck %s
# RUN: llvm-readelf --section-headers %t | FileCheck %s

## TODO: Check that .dynsym has Link field set to 0.
## GNU readelf is able to dump sections headers,
## but llvm-readelf reports an error below too early.
## See https://bugs.llvm.org/show_bug.cgi?id=42215.
## Check that .dynsym has Link field set to 0.

# CHECK: error: invalid sh_type for string table, expected SHT_STRTAB
# CHECK: Section Headers:
# CHECK-NEXT: [Nr] Name Type Address Off Size ES Flg Lk
# CHECK-NEXT: [ 0] NULL 0000000000000000 000000 000000 00 0 0
# CHECK-NEXT: [ 1] .dynsym DYNSYM 0000000000000000 000180 000018 18 A 0

--- !ELF
FileHeader:
6 changes: 5 additions & 1 deletion llvm/tools/llvm-readobj/ELFDumper.cpp
Original file line number Diff line number Diff line change
@@ -1423,7 +1423,11 @@ ELFDumper<ELFT>::ELFDumper(const object::ELFObjectFile<ELFT> *ObjF,
// This is only used (if Elf_Shdr present)for naming section in GNU
// style
DynSymtabName = unwrapOrError(Obj->getSectionName(&Sec));
DynamicStringTable = unwrapOrError(Obj->getStringTableForSymtab(Sec));

if (Expected<StringRef> E = Obj->getStringTableForSymtab(Sec))
DynamicStringTable = *E;
else
warn(E.takeError());
}
break;
case ELF::SHT_SYMTAB_SHNDX:
6 changes: 6 additions & 0 deletions llvm/tools/llvm-readobj/llvm-readobj.cpp
Original file line number Diff line number Diff line change
@@ -378,6 +378,12 @@ void reportWarning(Twine Msg) {
WithColor::warning(errs()) << Msg << "\n";
}

void warn(Error Err) {
handleAllErrors(std::move(Err), [&](const ErrorInfoBase &EI) {
reportWarning(EI.message());
});
}

void error(Error EC) {
if (!EC)
return;
1 change: 1 addition & 0 deletions llvm/tools/llvm-readobj/llvm-readobj.h
Original file line number Diff line number Diff line change
@@ -23,6 +23,7 @@ namespace llvm {
// Various helper functions.
LLVM_ATTRIBUTE_NORETURN void reportError(Twine Msg);
void reportWarning(Twine Msg);
void warn(llvm::Error Err);
void error(std::error_code EC);
void error(llvm::Error EC);
template <typename T> T error(llvm::Expected<T> &&E) {

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