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[JITLink][ELF/x86-64] Add support for R_X86_64_GOTPC64 and R_X86_64_GOT64.

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Start adding support for ELF x86-64 large code model, PIC relocations.
This commit is contained in:
Lang Hames 2021-03-21 19:58:08 -07:00
parent 5f6f892eda
commit 15f4aaa81e
8 changed files with 185 additions and 31 deletions
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3
include/llvm/ExecutionEngine/JITLink/ELF_x86_64.h
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@ -26,6 +26,7 @@ enum ELFX86RelocationKind : Edge::Kind {
Pointer64,
Pointer64Anon,
PCRel32,
PCRel64,
PCRel32Minus1,
PCRel32Minus2,
PCRel32Minus4,
@ -35,6 +36,8 @@ enum ELFX86RelocationKind : Edge::Kind {
PCRel32Minus4Anon,
PCRel32GOTLoad,
PCRel32GOT,
PCRel64GOT,
GOT64,
PCRel32TLV,
Delta32,
Delta64,

2
include/llvm/ExecutionEngine/JITLink/JITLink.h
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@ -674,7 +674,7 @@ public:
assert((First || !Last) && "Last can not be null if start is non-null");
return Last;
}
bool isEmpty() const {
bool empty() const {
assert((First || !Last) && "Last can not be null if start is non-null");
return !First;
}

12
lib/ExecutionEngine/JITLink/DefineExternalSectionStartAndEndSymbols.h
View File

@ -40,18 +40,24 @@ public:
: F(std::move(F)) {}
Error operator()(LinkGraph &G) {
for (auto *Sym : G.external_symbols()) {
// This pass will affect the external symbols set, so copy them out into a
// vector and iterate over that.
std::vector<Symbol *> Externals(G.external_symbols().begin(),
G.external_symbols().end());
for (auto *Sym : Externals) {
SectionRangeSymbolDesc D = F(G, *Sym);
if (D.Sec) {
auto &SR = getSectionRange(*D.Sec);
if (D.IsStart) {
if (SR.isEmpty())
if (SR.empty())
G.makeAbsolute(*Sym, 0);
else
G.makeDefined(*Sym, *SR.getFirstBlock(), 0, 0, Linkage::Strong,
Scope::Local, false);
} else {
if (SR.isEmpty())
if (SR.empty())
G.makeAbsolute(*Sym, 0);
else
G.makeDefined(*Sym, *SR.getLastBlock(),

107
lib/ExecutionEngine/JITLink/ELF_x86_64.cpp
View File

@ -40,7 +40,8 @@ public:
PerGraphGOTAndPLTStubsBuilder_ELF_x86_64>::PerGraphGOTAndPLTStubsBuilder;
bool isGOTEdgeToFix(Edge &E) const {
return E.getKind() == PCRel32GOT || E.getKind() == PCRel32GOTLoad;
return E.getKind() == PCRel32GOT || E.getKind() == PCRel32GOTLoad ||
E.getKind() == PCRel64GOT || E.getKind() == GOT64;
}
Symbol &createGOTEntry(Symbol &Target) {
@ -51,14 +52,25 @@ public:
}
void fixGOTEdge(Edge &E, Symbol &GOTEntry) {
assert((E.getKind() == PCRel32GOT || E.getKind() == PCRel32GOTLoad) &&
"Not a GOT edge?");
// If this is a PCRel32GOT then change it to an ordinary PCRel32. If it is
// a PCRel32GOTLoad then leave it as-is for now. We will use the kind to
// check for GOT optimization opportunities in the
// If this is a PCRel32GOT/PCRel64GOT then change it to an ordinary
// PCRel32/PCRel64. If it is a PCRel32GOTLoad then leave it as-is for now:
// We will use the kind to check for GOT optimization opportunities in the
// optimizeMachO_x86_64_GOTAndStubs pass below.
if (E.getKind() == PCRel32GOT)
// If it's a GOT64 leave it as is.
switch (E.getKind()) {
case PCRel32GOT:
E.setKind(PCRel32);
break;
case PCRel64GOT:
E.setKind(PCRel64);
break;
case GOT64:
break;
case PCRel32GOTLoad:
break;
default:
llvm_unreachable("Unexpected GOT edge kind");
}
E.setTarget(GOTEntry);
// Leave the edge addend as-is.
@ -117,7 +129,8 @@ private:
Section *StubsSection = nullptr;
};
StringRef ELFGOTSectionName = "$__GOT";
constexpr StringRef ELFGOTSectionName = "$__GOT";
constexpr StringRef ELFGOTSymbolName = "_GLOBAL_OFFSET_TABLE_";
const char *const DwarfSectionNames[] = {
#define HANDLE_DWARF_SECTION(ENUM_NAME, ELF_NAME, CMDLINE_NAME, OPTION) \
@ -245,6 +258,7 @@ private:
case ELF::R_X86_64_PC32:
return ELF_x86_64_Edges::ELFX86RelocationKind::PCRel32;
case ELF::R_X86_64_PC64:
case ELF::R_X86_64_GOTPC64:
return ELF_x86_64_Edges::ELFX86RelocationKind::Delta64;
case ELF::R_X86_64_64:
return ELF_x86_64_Edges::ELFX86RelocationKind::Pointer64;
@ -252,6 +266,10 @@ private:
case ELF::R_X86_64_GOTPCRELX:
case ELF::R_X86_64_REX_GOTPCRELX:
return ELF_x86_64_Edges::ELFX86RelocationKind::PCRel32GOTLoad;
case ELF::R_X86_64_GOTPCREL64:
return ELF_x86_64_Edges::ELFX86RelocationKind::PCRel64GOT;
case ELF::R_X86_64_GOT64:
return ELF_x86_64_Edges::ELFX86RelocationKind::GOT64;
case ELF::R_X86_64_PLT32:
return ELF_x86_64_Edges::ELFX86RelocationKind::Branch32;
}
@ -699,9 +717,57 @@ public:
ELFJITLinker_x86_64(std::unique_ptr<JITLinkContext> Ctx,
std::unique_ptr<LinkGraph> G,
PassConfiguration PassConfig)
: JITLinker(std::move(Ctx), std::move(G), std::move(PassConfig)) {}
: JITLinker(std::move(Ctx), std::move(G), std::move(PassConfig)) {
getPassConfig().PostAllocationPasses.push_back(
[this](LinkGraph &G) { return getOrCreateGOTSymbol(G); });
}
private:
Symbol *GOTSymbol = nullptr;
Error getOrCreateGOTSymbol(LinkGraph &G) {
Section *GOTSection = nullptr;
auto DefineExternalGOTSymbolIfPresent =
createDefineExternalSectionStartAndEndSymbolsPass(
[&](LinkGraph &LG, Symbol &Sym) -> SectionRangeSymbolDesc {
if (Sym.getName() == ELFGOTSymbolName)
if ((GOTSection = G.findSectionByName(ELFGOTSectionName))) {
GOTSymbol = &Sym;
return {*GOTSection, true};
}
return {};
});
// Try to attach _GLOBAL_OFFSET_TABLE_ to the GOT if it's defined as an
// external.
if (auto Err = DefineExternalGOTSymbolIfPresent(G))
return Err;
// If there's a GOT section but we didn't find an external GOT symbol...
if (GOTSection && !GOTSymbol) {
// Check for an existing defined symbol.
for (auto *Sym : GOTSection->symbols())
if (Sym->getName() == ELFGOTSymbolName) {
GOTSymbol = Sym;
return Error::success();
}
// If there's no defined symbol then create one.
SectionRange SR(*GOTSection);
if (SR.empty())
GOTSymbol = &G.addAbsoluteSymbol(ELFGOTSymbolName, 0, 0,
Linkage::Strong, Scope::Local, true);
else
GOTSymbol =
&G.addDefinedSymbol(*SR.getFirstBlock(), 0, ELFGOTSymbolName, 0,
Linkage::Strong, Scope::Local, false, true);
}
return Error::success();
}
Error applyFixup(LinkGraph &G, Block &B, const Edge &E,
char *BlockWorkingMem) const {
using namespace ELF_x86_64_Edges;
@ -720,6 +786,11 @@ private:
return makeTargetOutOfRangeError(G, B, E);
break;
}
case ELFX86RelocationKind::PCRel64: {
int64_t Value = E.getTarget().getAddress() + E.getAddend() - FixupAddress;
*(little64_t *)FixupPtr = Value;
break;
}
case ELFX86RelocationKind::Pointer64: {
int64_t Value = E.getTarget().getAddress() + E.getAddend();
*(ulittle64_t *)FixupPtr = Value;
@ -751,6 +822,13 @@ private:
*(little64_t *)FixupPtr = Value;
break;
}
case ELFX86RelocationKind::GOT64: {
assert(GOTSymbol && "No GOT section symbol");
int64_t Value =
E.getTarget().getAddress() - GOTSymbol->getAddress() + E.getAddend();
*(little64_t *)FixupPtr = Value;
break;
}
default:
LLVM_DEBUG({
dbgs() << "Bad edge: " << getELFX86RelocationKindName(E.getKind())
@ -793,9 +871,6 @@ identifyELFSectionStartAndEndSymbols(LinkGraph &G, Symbol &Sym) {
if (auto *Sec =
G.findSectionByName(SymName.drop_front(EndSymbolPrefix.size())))
return {*Sec, false};
} else if (SymName == "_GLOBAL_OFFSET_TABLE_") {
if (auto *GOTSec = G.findSectionByName(ELFGOTSectionName))
return {*GOTSec, true};
}
return {};
}
@ -822,13 +897,13 @@ void link_ELF_x86_64(std::unique_ptr<LinkGraph> G,
Config.PostPrunePasses.push_back(
PerGraphGOTAndPLTStubsBuilder_ELF_x86_64::asPass);
// Add GOT/Stubs optimizer pass.
Config.PreFixupPasses.push_back(optimizeELF_x86_64_GOTAndStubs);
// Resolve any external section start / end symbols.
Config.PreFixupPasses.push_back(
Config.PostAllocationPasses.push_back(
createDefineExternalSectionStartAndEndSymbolsPass(
identifyELFSectionStartAndEndSymbols));
// Add GOT/Stubs optimizer pass.
Config.PreFixupPasses.push_back(optimizeELF_x86_64_GOTAndStubs);
}
if (auto Err = Ctx->modifyPassConfig(*G, Config))

6
lib/ExecutionEngine/JITLink/JITLinkGeneric.h
View File

@ -51,6 +51,12 @@ protected:
using SegmentLayoutMap = DenseMap<unsigned, SegmentLayout>;
// Returns the PassConfiguration for this instance. This can be used by
// JITLinkerBase implementations to add late passes that reference their
// own data structures (e.g. for ELF implementations to locate / construct
// a GOT start symbol prior to fixup).
PassConfiguration &getPassConfig() { return Passes; }
// Phase 1:
// 1.1: Run pre-prune passes
// 1.2: Prune graph

58
test/ExecutionEngine/JITLink/X86/ELF_x86-64_large_pic_relocations.s Normal file
View File

@ -0,0 +1,58 @@
# RUN: rm -rf %t && mkdir -p %t
# RUN: llvm-mc -triple=x86_64-unknown-linux -position-independent -filetype=obj \
# RUN: -large-code-model -o %t/elf_lg_pic_reloc.o %s
# RUN: llvm-jitlink -noexec -slab-allocate 100Kb -slab-address 0xfff00000 \
# RUN: -check %s %t/elf_lg_pic_reloc.o
#
# Test ELF large/PIC relocations.
.text
.file "testcase.c"
# Empty main entry point.
.globl main
.p2align 4, 0x90
.type main,@function
main:
retq
.size main, .-main
# Test R_X86_64_GOTPC64 handling. We want to check that the offset of the
# operand is the 64-bit delta to the start of the GOT.
# jitlink-check: decode_operand(test_gotpc64, 1) = \
# jitlink-check: _GLOBAL_OFFSET_TABLE_ - test_lg_pic_GOT
# jitlink-check: decode_operand(test_got64, 1) = \
# jitlink-check: got_addr(elf_lg_pic_reloc.o, named_data) - \
# jitlink-check: _GLOBAL_OFFSET_TABLE_
.globl test_lg_pic_GOT
.p2align 4, 0x90
.type test_lg_pic_GOT,@function
test_lg_pic_GOT:
.L0$pb:
leaq .L0$pb(%rip), %rax
.globl test_gotpc64
test_gotpc64:
movabsq $_GLOBAL_OFFSET_TABLE_-.L0$pb, %rcx
.size test_gotpc64, .-test_gotpc64
addq %rax, %rcx
.globl test_got64
test_got64:
movabsq $named_data@GOT, %rax
.size test_got64, .-test_got64
.size test_lg_pic_GOT, .-test_lg_pic_GOT
.data
.type named_data,@object
.p2align 3
named_data:
.quad 42
.size named_data, 8
.ident "clang version 10.0.0-4ubuntu1 "
.section ".note.GNU-stack","",@progbits
.addrsig

23
test/ExecutionEngine/JITLink/X86/ELF_x86-64_relocations.s → test/ExecutionEngine/JITLink/X86/ELF_x86-64_small_pic_relocations.s
View File

@ -1,12 +1,13 @@
# RUN: rm -rf %t && mkdir -p %t
# RUN: llvm-mc -triple=x86_64-unknown-linux -position-independent -filetype=obj -o %t/elf_reloc.o %s
# RUN: llvm-mc -triple=x86_64-unknown-linux -position-independent -filetype=obj \
# RUN: -o %t/elf_sm_pic_reloc.o %s
# RUN: llvm-jitlink -noexec -slab-allocate 100Kb -slab-address 0xfff00000 \
# RUN: -define-abs external_data=0x1 \
# RUN: -define-abs extern_in_range32=0xffe00000 \
# RUN: -define-abs extern_out_of_range32=0x7fff00000000 \
# RUN: -check %s %t/elf_reloc.o
# RUN: -check %s %t/elf_sm_pic_reloc.o
#
# Test standard ELF relocations.
# Test ELF small/PIC relocations.
.text
.file "testcase.c"
@ -55,7 +56,8 @@ test_call_local:
# resolution, the target turns out to be in-range from the callsite and so the
# edge is relaxed in post-allocation optimization.
#
# jitlink-check: decode_operand(test_call_extern, 0) = extern_in_range32 - next_pc(test_call_extern)
# jitlink-check: decode_operand(test_call_extern, 0) = \
# jitlink-check: extern_in_range32 - next_pc(test_call_extern)
.globl test_call_extern
.p2align 4, 0x90
.type test_call_extern,@function
@ -70,8 +72,10 @@ test_call_extern:
# entry.
#
# jitlink-check: decode_operand(test_call_extern_plt, 0) = \
# jitlink-check: stub_addr(elf_reloc.o, extern_out_of_range32) - next_pc(test_call_extern_plt)
# jitlink-check: *{8}(got_addr(elf_reloc.o, extern_out_of_range32)) = extern_out_of_range32
# jitlink-check: stub_addr(elf_sm_pic_reloc.o, extern_out_of_range32) - \
# jitlink-check: next_pc(test_call_extern_plt)
# jitlink-check: *{8}(got_addr(elf_sm_pic_reloc.o, extern_out_of_range32)) = \
# jitlink-check: extern_out_of_range32
.globl test_call_extern_plt
.p2align 4, 0x90
.type test_call_extern_plt,@function
@ -82,8 +86,9 @@ test_call_extern_plt:
# Test GOTPCREL handling. We want to check both the offset to the GOT entry and its
# contents.
# jitlink-check: decode_operand(test_gotpcrel, 4) = got_addr(elf_reloc.o, named_data) - next_pc(test_gotpcrel)
# jitlink-check: *{8}(got_addr(elf_reloc.o, named_data)) = named_data
# jitlink-check: decode_operand(test_gotpcrel, 4) = \
# jitlink-check: got_addr(elf_sm_pic_reloc.o, named_data) - next_pc(test_gotpcrel)
# jitlink-check: *{8}(got_addr(elf_sm_pic_reloc.o, named_data)) = named_data
.globl test_gotpcrel
.p2align 4, 0x90
@ -96,7 +101,7 @@ test_gotpcrel:
# Test REX_GOTPCRELX handling. We want to check both the offset to the GOT entry and its
# contents.
# jitlink-check: decode_operand(test_rex_gotpcrelx, 4) = \
# jitlink-check: got_addr(elf_reloc.o, external_data) - next_pc(test_rex_gotpcrelx)
# jitlink-check: got_addr(elf_sm_pic_reloc.o, external_data) - next_pc(test_rex_gotpcrelx)
.globl test_rex_gotpcrelx
.p2align 4, 0x90

5
tools/llvm-jitlink/llvm-jitlink-elf.cpp
View File

@ -133,8 +133,9 @@ Error registerELFGraphInfo(Session &S, LinkGraph &G) {
else
return TS.takeError();
SectionContainsContent = true;
} else if (Sym->hasName()) {
dbgs() << "Symbol: " << Sym->getName() << "\n";
}
if (Sym->hasName()) {
if (Sym->isSymbolZeroFill()) {
S.SymbolInfos[Sym->getName()] = {Sym->getSize(), Sym->getAddress()};
SectionContainsZeroFill = true;