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Revert r362743 "Revert "Revert "Reland D61583 [ELF] Error on relocations to STT_SECTION symbols if the sections were discarded""" 

(In effect, reverting "[ELF] Error on relocations to STT_SECTION symbols if the sections were discarded".)

It caused debug info problems in LibreOffice [1] and Chromium/V8 [2].
Reverting until those can be fixed.

It also reverts r362497 "STT_SECTION symbol should be defined" on .eh_frame, .debug*, .zdebug* and .gcc_except_table"
which was landed as a follow-up to the above.

> With -r or --emit-relocs, we warn `STT_SECTION symbol should be defined`
> on relocations to discarded section symbol. This was added as an error
> in rLLD319404, but was not so effective before D61583 (it turned the
> error to a warning).
>
> Relocations from .eh_frame .debug* .zdebug* .gcc_except_table to
> discarded .text are very common and somewhat expected. Don't warn/error
> on them. As a reference, ld.bfd has a similar logic in
> _bfd_elf_default_action_discarded() to allow these cases.
>
> Delete invalid-undef-section-symbol.test because what it intended to
> check is now covered by the updated comdat-discarded-reloc.s
>
> Delete relocatable-eh-frame.s because we allow relocations from
> .eh_frame as a special case now.

And finally it reverts r362218 "[ELF] Replace a dead test in getSymVA() with assert()"
as that also depended on the main change reverted here.

> Symbols relative to discarded comdat sections are Undefined instead of
> Defined now (after D59649 and D61583). The `== &InputSection::Discarded`
> test becomes dead. I cannot find a test related to this behavior.

 [1] http://lists.llvm.org/pipermail/llvm-commits/Week-of-Mon-20190603/659848.html
 [2] https://bugs.chromium.org/p/chromium/issues/detail?id=978067

llvm-svn: 364321
This commit is contained in:
Hans Wennborg 2019-06-25 14:58:46 +00:00
parent e98f8cf78f
commit 36c23cad15
12 changed files with 75 additions and 150 deletions
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5
lld/ELF/DWARF.cpp
View File

@ -93,11 +93,8 @@ LLDDwarfObj<ELFT>::findAux(const InputSectionBase &Sec, uint64_t Pos,
uint32_t SecIndex = File->getSectionIndex(Sym);
// Broken debug info can point to a non-Defined symbol.
Symbol &S = File->getRelocTargetSym(Rel);
auto *DR = dyn_cast<Defined>(&S);
auto *DR = dyn_cast<Defined>(&File->getRelocTargetSym(Rel));
if (!DR) {
if (S.isSection())
return None;
RelType Type = Rel.getType(Config->IsMips64EL);
if (Type != Target->NoneRel)
error(toString(File) + ": relocation " + lld::toString(Type) + " at 0x" +

3
lld/ELF/InputFiles.cpp
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@ -1080,9 +1080,6 @@ template <class ELFT> void ObjFile<ELFT>::initializeSymbols() {
if (ESym.st_shndx == SHN_UNDEF)
this->Symbols[I] = make<Undefined>(this, Name, Binding, StOther, Type);
else if (Sec == &InputSection::Discarded)
this->Symbols[I] = make<Undefined>(this, Name, Binding, StOther, Type,
/*DiscardedSecIdx=*/SecIdx);
else
this->Symbols[I] =
make<Defined>(this, Name, Binding, StOther, Type, Value, Size, Sec);

20
lld/ELF/InputSection.cpp
View File

@ -412,8 +412,7 @@ void InputSection::copyRelocations(uint8_t *Buf, ArrayRef<RelTy> Rels) {
for (const RelTy &Rel : Rels) {
RelType Type = Rel.getType(Config->IsMips64EL);
const ObjFile<ELFT> *File = getFile<ELFT>();
Symbol &Sym = File->getRelocTargetSym(Rel);
Symbol &Sym = getFile<ELFT>()->getRelocTargetSym(Rel);
auto *P = reinterpret_cast<typename ELFT::Rela *>(Buf);
Buf += sizeof(RelTy);
@ -436,23 +435,10 @@ void InputSection::copyRelocations(uint8_t *Buf, ArrayRef<RelTy> Rels) {
// .eh_frame is horribly special and can reference discarded sections. To
// avoid having to parse and recreate .eh_frame, we just replace any
// relocation in it pointing to discarded sections with R_*_NONE, which
// hopefully creates a frame that is ignored at runtime. Also, don't warn
// on .gcc_except_table and debug sections.
//
// See the comment in maybeReportUndefined for PPC64 .toc .
// hopefully creates a frame that is ignored at runtime.
auto *D = dyn_cast<Defined>(&Sym);
if (!D) {
if (!Sec->Name.startswith(".debug") &&
!Sec->Name.startswith(".zdebug") && Sec->Name != ".eh_frame" &&
Sec->Name != ".gcc_except_table" && Sec->Name != ".toc") {
uint32_t SecIdx = cast<Undefined>(Sym).DiscardedSecIdx;
Elf_Shdr_Impl<ELFT> Sec =
CHECK(File->getObj().sections(), File)[SecIdx];
warn("relocation refers to a discarded section: " +
CHECK(File->getObj().getSectionName(&Sec), File) +
"\n>>> referenced by " + getObjMsg(P->r_offset));
}
P->setSymbolAndType(0, 0, false);
error("STT_SECTION symbol should be defined");
continue;
}
SectionBase *Section = D->Section->Repl;

14
lld/ELF/Relocations.cpp
View File

@ -653,17 +653,9 @@ static std::string maybeReportDiscarded(Undefined &Sym) {
return "";
ArrayRef<Elf_Shdr_Impl<ELFT>> ObjSections =
CHECK(File->getObj().sections(), File);
std::string Msg;
if (Sym.Type == ELF::STT_SECTION) {
Msg = "relocation refers to a discarded section: ";
Msg += CHECK(
File->getObj().getSectionName(&ObjSections[Sym.DiscardedSecIdx]), File);
} else {
Msg = "relocation refers to a symbol in a discarded section: " +
toString(Sym);
}
Msg += "\n>>> defined in " + toString(File);
std::string Msg =
"relocation refers to a symbol in a discarded section: " + toString(Sym) +
"\n>>> defined in " + toString(File);
Elf_Shdr_Impl<ELFT> ELFSec = ObjSections[Sym.DiscardedSecIdx - 1];
if (ELFSec.sh_type != SHT_GROUP)

8
lld/ELF/Symbols.cpp
View File

@ -48,11 +48,17 @@ static uint64_t getSymVA(const Symbol &Sym, int64_t &Addend) {
auto &D = cast<Defined>(Sym);
SectionBase *IS = D.Section;
// According to the ELF spec reference to a local symbol from outside
// the group are not allowed. Unfortunately .eh_frame breaks that rule
// and must be treated specially. For now we just replace the symbol with
// 0.
if (IS == &InputSection::Discarded)
return 0;
// This is an absolute symbol.
if (!IS)
return D.Value;
assert(IS != &InputSection::Discarded);
IS = IS->Repl;
uint64_t Offset = D.Value;

12
lld/test/ELF/Inputs/comdat-discarded-reloc.s
View File

@ -1,8 +1,6 @@
.global bar, _start
.section .text.bar1,"aG",@progbits,group,comdat
.section .text.foo,"aG",@progbits,group,comdat
.section .text
_start:
.quad .text.foo
.quad bar
.section .text.bar2
.global bar
bar:
.quad .text.bar1

12
lld/test/ELF/comdat-discarded-error.s
View File

@ -5,7 +5,7 @@
# RUN: echo '.section .text.foo,"axG",@progbits,foo,comdat; .globl bar; bar:' |\
# RUN: llvm-mc -filetype=obj -triple=x86_64 - -o %t3.o
# RUN: not ld.lld %t2.o %t3.o %t1.o -o /dev/null 2>&1 | FileCheck %s
# RUN: not ld.lld %t1.o %t2.o %t3.o -o /dev/null 2>&1 | FileCheck %s
# CHECK: error: relocation refers to a symbol in a discarded section: bar
# CHECK-NEXT: >>> defined in {{.*}}3.o
@ -13,16 +13,6 @@
# CHECK-NEXT: >>> prevailing definition is in {{.*}}2.o
# CHECK-NEXT: >>> referenced by {{.*}}1.o:(.text+0x1)
# CHECK: error: relocation refers to a discarded section: .text.foo
# CHECK-NEXT: >>> defined in {{.*}}1.o
# CHECK-NEXT: >>> section group signature: foo
# CHECK-NEXT: >>> prevailing definition is in {{.*}}2.o
# CHECK-NEXT: >>> referenced by {{.*}}1.o:(.data+0x0)
.globl _start
_start:
jmp bar
.section .text.foo,"axG",@progbits,foo,comdat
.data
.quad .text.foo

63
lld/test/ELF/comdat-discarded-gdb-index.s
View File

@ -1,63 +0,0 @@
# REQUIRES: x86
# RUN: llvm-mc -filetype=obj -triple=x86_64 %s -o %t.o
# RUN: ld.lld --gdb-index %t.o %t.o -o %t
## .debug_info has a relocation to .text.foo . The second %t.o is discarded.
## Check we don't error on the relocation.
# CHECK: .rela.debug_info {
# CHECK-NEXT: 0xC R_X86_64_64 .text.foo 0x0
.section .text.foo,"axG",@progbits,foo,comdat
.globl foo
.Lfunc_begin0:
foo:
ret
.Lfunc_end0:
.section .debug_abbrev,"",@progbits
.byte 1 # Abbreviation Code
.byte 17 # DW_TAG_compile_unit
.byte 1 # DW_CHILDREN_yes
.byte 17 # DW_AT_low_pc
.byte 1 # DW_FORM_addr
.byte 18 # DW_AT_high_pc
.byte 6 # DW_FORM_data4
.ascii "\264B" # DW_AT_GNU_pubnames
.byte 25 # DW_FORM_flag_present
.byte 0 # EOM(1)
.byte 0 # EOM(2)
.byte 2 # Abbreviation Code
.byte 46 # DW_TAG_subprogram
.byte 0 # DW_CHILDREN_no
.byte 3 # DW_AT_name
.byte 8 # DW_FORM_string
.byte 0 # EOM(1)
.byte 0 # EOM(2)
.byte 0
.section .debug_info,"",@progbits
.Lcu_begin0:
.long .Lcu_end0 - .Lcu_begin0 - 4
.short 4 # DWARF version number
.long 0 # Offset Into Abbrev. Section
.byte 4 # Address Size
.Ldie0:
.byte 1 # Abbrev [1] DW_TAG_compile_unit
.quad .Lfunc_begin0 # DW_AT_low_pc
.long .Lfunc_end0 - .Lfunc_begin0 # DW_AT_high_pc
.byte 2 # Abbrev [2] DW_TAG_subprogram
.asciz "foo" # DW_AT_name
.byte 0
.Lcu_end0:
.section .debug_gnu_pubnames,"",@progbits
.long .LpubNames_end0 - .LpubNames_begin0
.LpubNames_begin0:
.short 2 # Version
.long .Lcu_begin0 # CU Offset
.long .Lcu_end0 - .Lcu_begin0
.long .Ldie0 - .Lcu_begin0
.byte 48 # Attributes: FUNCTION, EXTERNAL
.asciz "foo" # External Name
.long 0
.LpubNames_end0:

39
lld/test/ELF/comdat-discarded-reloc.s
View File

@ -1,42 +1,17 @@
# REQUIRES: x86
# RUN: llvm-mc -filetype=obj -triple=x86_64-pc-linux %s -o %t.o
# RUN: llvm-mc -filetype=obj -triple=x86_64-pc-linux %p/Inputs/comdat-discarded-reloc.s -o %t2.o
# RUN: ld.lld -gc-sections --noinhibit-exec %t2.o %t.o -o /dev/null
# RUN: ld.lld -r %t2.o %t.o -o %t 2>&1 | FileCheck --check-prefix=WARN %s
# RUN: llvm-readobj -r %t | FileCheck --check-prefix=RELOC %s
# RUN: ld.lld -gc-sections %t.o %t2.o -o %t
## ELF spec doesn't allow a relocation to point to a deduplicated
## COMDAT section. Unfortunately this happens in practice (e.g. .eh_frame)
## Test case checks we do not crash.
# WARN: warning: relocation refers to a discarded section: .text.bar1
# WARN-NEXT: >>> referenced by {{.*}}.o:(.rela.text.bar2+0x0)
# WARN-NOT: warning
.global bar, _start
# RELOC: .rela.eh_frame {
# RELOC-NEXT: R_X86_64_NONE
# RELOC-NEXT: }
# RELOC-NEXT: .rela.debug_foo {
# RELOC-NEXT: R_X86_64_NONE
# RELOC-NEXT: }
# RELOC-NEXT: .rela.gcc_except_table {
# RELOC-NEXT: R_X86_64_NONE
# RELOC-NEXT: }
.section .text.foo,"aG",@progbits,group,comdat
.section .text.bar1,"aG",@progbits,group,comdat
## .text.bar1 in this file is discarded. Warn on the relocation.
.section .text.bar2,"ax"
.globl bar
bar:
.quad .text.bar1
## Don't warn on .eh_frame, .debug*, .zdebug*, or .gcc_except_table
.section .eh_frame,"a"
.quad .text.bar1
.section .debug_foo
.quad .text.bar1
.section .gcc_except_table,"a"
.quad .text.bar1
.section .text
_start:
.quad .text.foo
.quad bar

4
lld/test/ELF/comdat.s
View File

@ -1,7 +1,7 @@
// REQUIRES: x86
// RUN: llvm-mc -filetype=obj -triple=x86_64-pc-linux %s -o %t.o
// RUN: llvm-mc -filetype=obj -triple=x86_64-pc-linux %p/Inputs/comdat.s -o %t2.o
// RUN: ld.lld -shared %t.o %t2.o -o %t
// RUN: ld.lld -shared %t.o %t.o %t2.o -o %t
// RUN: llvm-objdump -d %t | FileCheck %s
// RUN: llvm-readobj -S --symbols %t | FileCheck --check-prefix=READ %s
@ -31,7 +31,9 @@ foo:
// CHECK-EMPTY:
// CHECK-NEXT: bar:
// 0x1000 - 0x1001 - 5 = -6
// 0 - 0x1006 - 5 = -4107
// CHECK-NEXT: 1001: {{.*}} callq -6
// CHECK-NEXT: 1006: {{.*}} callq -4107
.section .text3,"axG",@progbits,zed,comdat,unique,0

26
lld/test/ELF/invalid-undef-section-symbol.test Normal file
View File

@ -0,0 +1,26 @@
# RUN: yaml2obj %s -o %t.o
# RUN: not ld.lld -r %t.o -o /dev/null 2>&1 | FileCheck %s
# We used to crash at this.
# CHECK: STT_SECTION symbol should be defined
--- !ELF
FileHeader:
Class: ELFCLASS64
Data: ELFDATA2LSB
Type: ET_REL
Machine: EM_X86_64
Sections:
- Name: .text
Type: SHT_PROGBITS
- Name: .rela.text
Type: SHT_RELA
AddressAlign: 0x0000000000000008
Info: .text
Relocations:
- Offset: 0x0000000000000000
Symbol: .text
Type: R_X86_64_NONE
Symbols:
- Name: .text
Type: STT_SECTION

19
lld/test/ELF/relocatable-eh-frame.s Normal file
View File

@ -0,0 +1,19 @@
# REQUIRES: x86
# RUN: llvm-mc -filetype=obj -triple=x86_64-pc-linux %s -o %t.o
# RUN: ld.lld -r %t.o %t.o -o %t
# RUN: llvm-readobj -r %t | FileCheck %s
# RUN: ld.lld %t -o %t.so -shared
# RUN: llvm-objdump -h %t.so | FileCheck --check-prefix=DSO %s
# DSO: .eh_frame 00000034
# CHECK: Relocations [
# CHECK-NEXT: Section ({{.*}}) .rela.eh_frame {
# CHECK-NEXT: 0x20 R_X86_64_PC32 .foo 0x0
# CHECK-NEXT: 0x50 R_X86_64_NONE - 0x0
# CHECK-NEXT: }
# CHECK-NEXT: ]
.section .foo,"aG",@progbits,bar,comdat
.cfi_startproc
.cfi_endproc