[llvm] a795bd9 - [llvm-objcopy] - Do not crash on object that has relocations but no symbol table.
Georgii Rymar via llvm-commits
llvm-commits at lists.llvm.org
Wed Oct 30 03:22:52 PDT 2019
Author: Georgii Rymar
Date: 2019-10-30T13:17:22+03:00
New Revision: a795bd96454402bbb4f5fcd186d4b112c8010000
URL: https://github.com/llvm/llvm-project/commit/a795bd96454402bbb4f5fcd186d4b112c8010000
DIFF: https://github.com/llvm/llvm-project/commit/a795bd96454402bbb4f5fcd186d4b112c8010000.diff
LOG: [llvm-objcopy] - Do not crash on object that has relocations but no symbol table.
It was revealed by D69260.
Tool crashed when scanned relocations in a object without a symbol table.
This patch teaches it either to handle such objects (when relocations
does not use symbols we do not need a symbol table to proceed)
or to show an appropriate error otherwise.
Differential revision: https://reviews.llvm.org/D69304
Added:
llvm/test/tools/llvm-objcopy/ELF/relocations-no-symtab.test
Modified:
llvm/test/tools/llvm-objcopy/ELF/no-symbol-relocation.test
llvm/tools/llvm-objcopy/ELF/Object.cpp
Removed:
################################################################################
diff --git a/llvm/test/tools/llvm-objcopy/ELF/no-symbol-relocation.test b/llvm/test/tools/llvm-objcopy/ELF/no-symbol-relocation.test
index 91040170d739..eccc48b2134f 100644
--- a/llvm/test/tools/llvm-objcopy/ELF/no-symbol-relocation.test
+++ b/llvm/test/tools/llvm-objcopy/ELF/no-symbol-relocation.test
@@ -1,8 +1,8 @@
-# RUN: yaml2obj %s > %t
-# RUN: llvm-objcopy %t %t2
+# RUN: yaml2obj --docnum=1 %s > %t1
+# RUN: llvm-objcopy %t1 %t2
# RUN: llvm-readobj --relocations %t2 | FileCheck %s
-!ELF
+--- !ELF
FileHeader:
Class: ELFCLASS64
Data: ELFDATA2LSB
@@ -21,11 +21,50 @@ Sections:
Relocations:
- Offset: 0x1000
Type: R_X86_64_RELATIVE
-## TODO: llvm-objcopy crashes without the following line.
-Symbols: []
# CHECK: Relocations [
# CHECK-NEXT: Section (2) .rel.text {
# CHECK-NEXT: 0x1000 R_X86_64_RELATIVE - 0x0
# CHECK-NEXT: }
# CHECK-NEXT:]
+
+## Check we produce a valid output when stripping unneeded symbols from an object that
+## has a symbol table and a relocation with a symbol index of 0.
+
+# RUN: yaml2obj --docnum=2 %s > %t3
+# RUN: llvm-objcopy --strip-unneeded %t3 %t4
+# RUN: llvm-readobj --relocations --sections --symbols %t4 | FileCheck %s --check-prefix=STRIP
+
+# STRIP: Relocations [
+# STRIP-NEXT: Section {{.*}} .rel.text {
+# STRIP-NEXT: 0x1000 R_X86_64_NONE - 0x0
+# STRIP-NEXT: }
+# STRIP-NEXT: ]
+# STRIP-NEXT: Symbols [
+# STRIP-NEXT: Symbol {
+# STRIP-NEXT: Name: (0)
+# STRIP-NEXT: Value: 0x0
+# STRIP-NEXT: Size: 0
+# STRIP-NEXT: Binding: Local (0x0)
+# STRIP-NEXT: Type: None (0x0)
+# STRIP-NEXT: Other: 0
+# STRIP-NEXT: Section: Undefined (0x0)
+# STRIP-NEXT: }
+# STRIP-NEXT: ]
+
+--- !ELF
+FileHeader:
+ Class: ELFCLASS64
+ Data: ELFDATA2LSB
+ Type: ET_REL
+ Machine: EM_X86_64
+Sections:
+ - Name: .text
+ Type: SHT_PROGBITS
+ - Name: .rel.text
+ Type: SHT_REL
+ Info: .text
+ Relocations:
+ - Offset: 0x1000
+ Type: R_X86_64_NONE
+Symbols: []
diff --git a/llvm/test/tools/llvm-objcopy/ELF/relocations-no-symtab.test b/llvm/test/tools/llvm-objcopy/ELF/relocations-no-symtab.test
new file mode 100644
index 000000000000..d627d2d6de1c
--- /dev/null
+++ b/llvm/test/tools/llvm-objcopy/ELF/relocations-no-symtab.test
@@ -0,0 +1,55 @@
+## Check that we can copy an object that has a relocation
+## with a symbol index of 0 even when there is no symbol table.
+
+# RUN: yaml2obj --docnum=1 %s -o %t1
+# RUN: llvm-objcopy %t1 %t2
+# RUN: llvm-readobj --relocations %t2 | FileCheck %s
+
+# CHECK: Relocations [
+# CHECK-NEXT: Section {{.*}} .rel.text {
+# CHECK-NEXT: 0x1000 R_X86_64_RELATIVE - 0x0
+# CHECK-NEXT: }
+# CHECK-NEXT:]
+
+--- !ELF
+FileHeader:
+ Class: ELFCLASS64
+ Data: ELFDATA2LSB
+ Type: ET_REL
+ Machine: EM_X86_64
+Sections:
+ - Name: .text
+ Type: SHT_PROGBITS
+ Flags: [ SHF_ALLOC, SHF_EXECINSTR ]
+ - Name: .rel.text
+ Type: SHT_REL
+ Info: .text
+ Relocations:
+ - Offset: 0x1000
+ Type: R_X86_64_RELATIVE
+
+## Check that we report an error when a relocation refers to a
+## non-zero symbol index but there is no symbol table.
+
+# RUN: yaml2obj --docnum=2 %s -o %t3
+# RUN: not llvm-objcopy %t3 /dev/null 2>&1 | FileCheck %s --check-prefix=ERR
+
+# ERR: error: '.rel.text': relocation references symbol with index 1, but there is no symbol table
+
+--- !ELF
+FileHeader:
+ Class: ELFCLASS64
+ Data: ELFDATA2LSB
+ Type: ET_REL
+ Machine: EM_X86_64
+Sections:
+ - Name: .text
+ Type: SHT_PROGBITS
+ Flags: [ SHF_ALLOC, SHF_EXECINSTR ]
+ - Name: .rel.text
+ Type: SHT_REL
+ Info: .text
+ Relocations:
+ - Offset: 0x1000
+ Symbol: 1
+ Type: R_X86_64_NONE
diff --git a/llvm/tools/llvm-objcopy/ELF/Object.cpp b/llvm/tools/llvm-objcopy/ELF/Object.cpp
index 74145dad6e6b..0fb42e0305f8 100644
--- a/llvm/tools/llvm-objcopy/ELF/Object.cpp
+++ b/llvm/tools/llvm-objcopy/ELF/Object.cpp
@@ -815,7 +815,8 @@ Error RelocationSection::removeSectionReferences(
}
for (const Relocation &R : Relocations) {
- if (!R.RelocSymbol->DefinedIn || !ToRemove(R.RelocSymbol->DefinedIn))
+ if (!R.RelocSymbol || !R.RelocSymbol->DefinedIn ||
+ !ToRemove(R.RelocSymbol->DefinedIn))
continue;
return createStringError(llvm::errc::invalid_argument,
"section '%s' cannot be removed: (%s+0x%" PRIx64
@@ -868,7 +869,8 @@ static void writeRel(const RelRange &Relocations, T *Buf) {
for (const auto &Reloc : Relocations) {
Buf->r_offset = Reloc.Offset;
setAddend(*Buf, Reloc.Addend);
- Buf->setSymbolAndType(Reloc.RelocSymbol->Index, Reloc.Type, false);
+ Buf->setSymbolAndType(Reloc.RelocSymbol ? Reloc.RelocSymbol->Index : 0,
+ Reloc.Type, false);
++Buf;
}
}
@@ -893,7 +895,7 @@ void RelocationSection::accept(MutableSectionVisitor &Visitor) {
Error RelocationSection::removeSymbols(
function_ref<bool(const Symbol &)> ToRemove) {
for (const Relocation &Reloc : Relocations)
- if (ToRemove(*Reloc.RelocSymbol))
+ if (Reloc.RelocSymbol && ToRemove(*Reloc.RelocSymbol))
return createStringError(
llvm::errc::invalid_argument,
"not stripping symbol '%s' because it is named in a relocation",
@@ -903,7 +905,8 @@ Error RelocationSection::removeSymbols(
void RelocationSection::markSymbols() {
for (const Relocation &Reloc : Relocations)
- Reloc.RelocSymbol->Referenced = true;
+ if (Reloc.RelocSymbol)
+ Reloc.RelocSymbol->Referenced = true;
}
void RelocationSection::replaceSectionReferences(
@@ -1418,7 +1421,15 @@ static void initRelocations(RelocationSection *Relocs,
ToAdd.Offset = Rel.r_offset;
getAddend(ToAdd.Addend, Rel);
ToAdd.Type = Rel.getType(false);
- ToAdd.RelocSymbol = SymbolTable->getSymbolByIndex(Rel.getSymbol(false));
+
+ if (uint32_t Sym = Rel.getSymbol(false)) {
+ if (!SymbolTable)
+ error("'" + Relocs->Name +
+ "': relocation references symbol with index " + Twine(Sym) +
+ ", but there is no symbol table");
+ ToAdd.RelocSymbol = SymbolTable->getSymbolByIndex(Sym);
+ }
+
Relocs->addRelocation(ToAdd);
}
}
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