[lld] r306071 - [COFF] Fix SECTION and SECREL relocation handling for absolute symbols
Reid Kleckner via llvm-commits
llvm-commits at lists.llvm.org
Thu Jun 22 16:33:05 PDT 2017
Author: rnk
Date: Thu Jun 22 18:33:04 2017
New Revision: 306071
URL: http://llvm.org/viewvc/llvm-project?rev=306071&view=rev
Log:
[COFF] Fix SECTION and SECREL relocation handling for absolute symbols
Summary:
For SECTION relocations against absolute symbols, MSVC emits the largest
output section index plus one. I've implemented that by threading a
global variable through DefinedAbsolute that is filled in by the Writer.
A more library-oriented approach would be to thread the Writer through
Chunk::writeTo and SectionChunk::applyRel*, but Rui seems to prefer
doing it this way.
MSVC rejects SECREL relocations against absolute symbols, but only when
the relocation is in a real output section. When the relocation is in a
CodeView debug info section destined for the PDB, it seems that this
relocation error is suppressed, and absolute symbols become zeros in the
object file. This is easily implemented by checking the input section
from which we're applying relocations.
This should fix errors about __safe_se_handler_table and
__guard_fids_table when linking the CRT and generating a PDB.
Reviewers: ruiu
Subscribers: aprantl, llvm-commits
Differential Revision: https://reviews.llvm.org/D34541
Added:
lld/trunk/test/COFF/pdb-secrel-absolute.yaml
lld/trunk/test/COFF/secidx-absolute.s
lld/trunk/test/COFF/secrel-absolute.s
Modified:
lld/trunk/COFF/Chunks.cpp
lld/trunk/COFF/Symbols.cpp
lld/trunk/COFF/Symbols.h
lld/trunk/COFF/Writer.cpp
Modified: lld/trunk/COFF/Chunks.cpp
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/COFF/Chunks.cpp?rev=306071&r1=306070&r2=306071&view=diff
==============================================================================
--- lld/trunk/COFF/Chunks.cpp (original)
+++ lld/trunk/COFF/Chunks.cpp Thu Jun 22 18:33:04 2017
@@ -52,6 +52,15 @@ static void add32(uint8_t *P, int32_t V)
static void add64(uint8_t *P, int64_t V) { write64le(P, read64le(P) + V); }
static void or16(uint8_t *P, uint16_t V) { write16le(P, read16le(P) | V); }
+static void applySecRel(const SectionChunk *Sec, uint8_t *Off, Defined *Sym) {
+ // Don't apply section relative relocations to absolute symbols in codeview
+ // debug info sections. MSVC does not treat such relocations as fatal errors,
+ // and they can be found in the standard library for linker-provided symbols
+ // like __guard_fids_table and __safe_se_handler_table.
+ if (!(isa<DefinedAbsolute>(Sym) && Sec->isCodeView()))
+ add32(Off, Sym->getSecrel());
+}
+
void SectionChunk::applyRelX64(uint8_t *Off, uint16_t Type, Defined *Sym,
uint64_t P) const {
uint64_t S = Sym->getRVA();
@@ -66,7 +75,7 @@ void SectionChunk::applyRelX64(uint8_t *
case IMAGE_REL_AMD64_REL32_4: add32(Off, S - P - 8); break;
case IMAGE_REL_AMD64_REL32_5: add32(Off, S - P - 9); break;
case IMAGE_REL_AMD64_SECTION: add16(Off, Sym->getSectionIndex()); break;
- case IMAGE_REL_AMD64_SECREL: add32(Off, Sym->getSecrel()); break;
+ case IMAGE_REL_AMD64_SECREL: applySecRel(this, Off, Sym); break;
default:
fatal("unsupported relocation type 0x" + Twine::utohexstr(Type));
}
@@ -81,7 +90,7 @@ void SectionChunk::applyRelX86(uint8_t *
case IMAGE_REL_I386_DIR32NB: add32(Off, S); break;
case IMAGE_REL_I386_REL32: add32(Off, S - P - 4); break;
case IMAGE_REL_I386_SECTION: add16(Off, Sym->getSectionIndex()); break;
- case IMAGE_REL_I386_SECREL: add32(Off, Sym->getSecrel()); break;
+ case IMAGE_REL_I386_SECREL: applySecRel(this, Off, Sym); break;
default:
fatal("unsupported relocation type 0x" + Twine::utohexstr(Type));
}
@@ -141,7 +150,7 @@ void SectionChunk::applyRelARM(uint8_t *
case IMAGE_REL_ARM_BRANCH20T: applyBranch20T(Off, S - P - 4); break;
case IMAGE_REL_ARM_BRANCH24T: applyBranch24T(Off, S - P - 4); break;
case IMAGE_REL_ARM_BLX23T: applyBranch24T(Off, S - P - 4); break;
- case IMAGE_REL_ARM_SECREL: add32(Off, Sym->getSecrel()); break;
+ case IMAGE_REL_ARM_SECREL: applySecRel(this, Off, Sym); break;
default:
fatal("unsupported relocation type 0x" + Twine::utohexstr(Type));
}
Modified: lld/trunk/COFF/Symbols.cpp
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/COFF/Symbols.cpp?rev=306071&r1=306070&r2=306071&view=diff
==============================================================================
--- lld/trunk/COFF/Symbols.cpp (original)
+++ lld/trunk/COFF/Symbols.cpp Thu Jun 22 18:33:04 2017
@@ -61,6 +61,8 @@ COFFSymbolRef DefinedCOFF::getCOFFSymbol
return COFFSymbolRef(reinterpret_cast<const coff_symbol32 *>(Sym));
}
+uint16_t DefinedAbsolute::OutputSectionIndex = 0;
+
static Chunk *makeImportThunk(DefinedImportData *S, uint16_t Machine) {
if (Machine == AMD64)
return make<ImportThunkChunkX64>(S);
Modified: lld/trunk/COFF/Symbols.h
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/COFF/Symbols.h?rev=306071&r1=306070&r2=306071&view=diff
==============================================================================
--- lld/trunk/COFF/Symbols.h (original)
+++ lld/trunk/COFF/Symbols.h Thu Jun 22 18:33:04 2017
@@ -212,6 +212,11 @@ public:
uint64_t getRVA() { return VA - Config->ImageBase; }
void setVA(uint64_t V) { VA = V; }
+ // The sentinel absolute symbol section index. Section index relocations
+ // against absolute symbols resolve to this 16 bit number, and it is the
+ // largest valid section index plus one. This is written by the Writer.
+ static uint16_t OutputSectionIndex;
+
private:
uint64_t VA;
};
Modified: lld/trunk/COFF/Writer.cpp
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/COFF/Writer.cpp?rev=306071&r1=306070&r2=306071&view=diff
==============================================================================
--- lld/trunk/COFF/Writer.cpp (original)
+++ lld/trunk/COFF/Writer.cpp Thu Jun 22 18:33:04 2017
@@ -219,6 +219,8 @@ uint64_t Defined::getSecrel() {
uint64_t Defined::getSectionIndex() {
if (auto *D = dyn_cast<DefinedRegular>(this))
return D->getChunk()->getOutputSection()->SectionIndex;
+ if (auto *D = dyn_cast<DefinedAbsolute>(this))
+ return DefinedAbsolute::OutputSectionIndex;
fatal("SECTION relocation points to a non-regular symbol: " +
toString(*this));
}
@@ -775,6 +777,10 @@ void Writer::setSectionPermissions() {
// Write section contents to a mmap'ed file.
void Writer::writeSections() {
+ // Record the section index that should be used when resolving a section
+ // relocation against an absolute symbol.
+ DefinedAbsolute::OutputSectionIndex = OutputSections.size() + 1;
+
uint8_t *Buf = Buffer->getBufferStart();
for (OutputSection *Sec : OutputSections) {
uint8_t *SecBuf = Buf + Sec->getFileOff();
Added: lld/trunk/test/COFF/pdb-secrel-absolute.yaml
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/test/COFF/pdb-secrel-absolute.yaml?rev=306071&view=auto
==============================================================================
--- lld/trunk/test/COFF/pdb-secrel-absolute.yaml (added)
+++ lld/trunk/test/COFF/pdb-secrel-absolute.yaml Thu Jun 22 18:33:04 2017
@@ -0,0 +1,84 @@
+# RUN: yaml2obj %s -o %t.obj
+# RUN: lld-link -debug -entry:main -out:%t.exe -pdb:%t.pdb %t.obj
+# RUN: llvm-pdbutil raw -symbols %t.pdb | FileCheck %s
+
+# There is an S_GDATA32 symbol record with .secrel32 and .secidx relocations in
+# it in this debug info. This is similar to the relocations in the loadcfg.obj
+# file in the MSVC CRT. We need to make sure that our relocation logic matches
+# MSVC's for these absolute, linker-provided symbols.
+
+# CHECK: Mod 0000 |
+# CHECK-NEXT: - S_GDATA32 [size = 36] `__guard_fids_table`
+# CHECK-NEXT: type = 0x0022 (unsigned long), addr = 0003:0000
+# CHECK-NEXT: Mod 0001 | `* Linker *`:
+
+--- !COFF
+header:
+ Machine: IMAGE_FILE_MACHINE_AMD64
+ Characteristics: [ ]
+sections:
+ - Name: '.debug$S'
+ Characteristics: [ IMAGE_SCN_CNT_INITIALIZED_DATA, IMAGE_SCN_MEM_DISCARDABLE, IMAGE_SCN_MEM_READ ]
+ Alignment: 1
+ Subsections:
+ - !Symbols
+ Records:
+ - Kind: S_GDATA32
+ DataSym:
+ Type: 34
+ DisplayName: __guard_fids_table
+ - !StringTable
+ Strings:
+ Relocations:
+ - VirtualAddress: 20
+ SymbolName: __guard_fids_table
+ Type: IMAGE_REL_AMD64_SECREL
+ - VirtualAddress: 24
+ SymbolName: __guard_fids_table
+ Type: IMAGE_REL_AMD64_SECTION
+ - Name: '.text$mn'
+ Characteristics: [ IMAGE_SCN_CNT_CODE, IMAGE_SCN_MEM_EXECUTE, IMAGE_SCN_MEM_READ ]
+ Alignment: 16
+ SectionData: 488D0500000000C3
+ Relocations:
+ - VirtualAddress: 3
+ SymbolName: __guard_fids_table
+ Type: IMAGE_REL_AMD64_REL32
+symbols:
+ - Name: '.debug$S'
+ Value: 0
+ SectionNumber: 1
+ SimpleType: IMAGE_SYM_TYPE_NULL
+ ComplexType: IMAGE_SYM_DTYPE_NULL
+ StorageClass: IMAGE_SYM_CLASS_STATIC
+ SectionDefinition:
+ Length: 372
+ NumberOfRelocations: 6
+ NumberOfLinenumbers: 0
+ CheckSum: 0
+ Number: 0
+ - Name: '.text$mn'
+ 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: 1092178131
+ Number: 0
+ - Name: main
+ Value: 0
+ SectionNumber: 2
+ SimpleType: IMAGE_SYM_TYPE_NULL
+ ComplexType: IMAGE_SYM_DTYPE_FUNCTION
+ StorageClass: IMAGE_SYM_CLASS_EXTERNAL
+ - Name: __guard_fids_table
+ Value: 0
+ SectionNumber: 0
+ SimpleType: IMAGE_SYM_TYPE_NULL
+ ComplexType: IMAGE_SYM_DTYPE_NULL
+ StorageClass: IMAGE_SYM_CLASS_EXTERNAL
+...
Added: lld/trunk/test/COFF/secidx-absolute.s
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/test/COFF/secidx-absolute.s?rev=306071&view=auto
==============================================================================
--- lld/trunk/test/COFF/secidx-absolute.s (added)
+++ lld/trunk/test/COFF/secidx-absolute.s Thu Jun 22 18:33:04 2017
@@ -0,0 +1,33 @@
+# RUN: llvm-mc %s -filetype=obj -triple=x86_64-windows-msvc -o %t.obj
+# RUN: lld-link -entry:main -nodefaultlib %t.obj -out:%t.exe
+# RUN: llvm-readobj %t.exe -sections -section-data | FileCheck %s
+
+# Section relocations against absolute symbols resolve to the last real ouput
+# section index plus one.
+
+.text
+.global main
+main:
+ret
+
+.section .rdata,"dr"
+.secidx __guard_fids_table
+
+# CHECK: Sections [
+# CHECK: Section {
+# CHECK: Number: 1
+# CHECK: Name: .rdata (2E 72 64 61 74 61 00 00)
+# CHECK: SectionData (
+# CHECK: 0000: 0300 |..|
+# CHECK: )
+# CHECK: }
+# CHECK: Section {
+# CHECK: Number: 2
+# CHECK: Name: .text (2E 74 65 78 74 00 00 00)
+# CHECK: VirtualSize: 0x1
+# CHECK: SectionData (
+# CHECK: 0000: C3 |.|
+# CHECK: )
+# CHECK: }
+# CHECK-NOT: Section
+# CHECK: ]
Added: lld/trunk/test/COFF/secrel-absolute.s
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/test/COFF/secrel-absolute.s?rev=306071&view=auto
==============================================================================
--- lld/trunk/test/COFF/secrel-absolute.s (added)
+++ lld/trunk/test/COFF/secrel-absolute.s Thu Jun 22 18:33:04 2017
@@ -0,0 +1,14 @@
+# RUN: llvm-mc %s -filetype=obj -triple=x86_64-windows-msvc -o %t.obj
+# RUN: not lld-link -entry:main -nodefaultlib %t.obj -out:%t.exe 2>&1 | FileCheck %s
+
+# secrel relocations against absolute symbols are errors.
+
+# CHECK: SECREL relocation points to a non-regular symbol: __guard_fids_table
+
+.text
+.global main
+main:
+ret
+
+.section .rdata,"dr"
+.secrel32 __guard_fids_table
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