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Implement the -dynamic-linker option. 

With this dynamic executables can be executed with just ./t instead of
/lib64/ld-2.20.so ./t

llvm-svn: 247446
This commit is contained in:
Rafael Espindola 2015-09-11 18:49:42 +00:00
parent b67dbced9c
commit 7010776db7
5 changed files with 106 additions and 12 deletions
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1
lld/ELF/Config.h
View File

@ -17,6 +17,7 @@ namespace elf2 {
struct Configuration {
llvm::StringRef OutputFile;
llvm::StringRef DynamicLinker;
};
extern Configuration *Config;

4
lld/ELF/Driver.cpp
View File

@ -68,6 +68,10 @@ void LinkerDriver::link(ArrayRef<const char *> ArgsArr) {
if (Config->OutputFile.empty())
error("-o must be specified.");
// Handle -dynamic-linker
if (auto *Arg = Args.getLastArg(OPT_dynamic_linker))
Config->DynamicLinker = Arg->getValue();
// Create a list of input files.
std::vector<MemoryBufferRef> Inputs;

3
lld/ELF/Options.td
View File

@ -6,3 +6,6 @@ include "llvm/Option/OptParser.td"
def output : Separate<["-"], "o">, MetaVarName<"<path>">,
HelpText<"Path to file to write output">;
def dynamic_linker : Separate<["-"], "dynamic-linker">,
HelpText<"Which dynamic linker to use">;

55
lld/ELF/Writer.cpp
View File

@ -110,6 +110,20 @@ private:
};
namespace {
template <bool Is64Bits>
class InterpSection final : public OutputSectionBase<Is64Bits> {
public:
InterpSection()
: OutputSectionBase<Is64Bits>(".interp", SHT_PROGBITS, SHF_ALLOC) {
this->Header.sh_size = Config->DynamicLinker.size() + 1;
this->Header.sh_addralign = 1;
}
void writeTo(uint8_t *Buf) override {
memcpy(Buf, Config->DynamicLinker.data(), Config->DynamicLinker.size());
}
};
template <bool Is64Bits>
class StringTableSection final : public OutputSectionBase<Is64Bits> {
public:
@ -169,7 +183,7 @@ public:
void writeTo(uint8_t *Buf) override;
const SymbolTable &getSymTable() { return Table; }
const SymbolTable &getSymTable() const { return Table; }
void addSymbol(StringRef Name) {
StrTabSec.add(Name);
@ -280,6 +294,10 @@ private:
void openFile(StringRef OutputPath);
void writeHeader();
void writeSections();
bool needsInterpSection() const {
return !SymTabSec.getSymTable().getSharedFiles().empty() &&
!Config->DynamicLinker.empty();
}
std::unique_ptr<llvm::FileOutputBuffer> Buffer;
llvm::SpecificBumpPtrAllocator<OutputSection<ELFT>> CAlloc;
@ -299,6 +317,8 @@ private:
DynamicSection<ELFT> DynamicSec;
InterpSection<ELFT::Is64Bits> InterpSec;
OutputSection<ELFT> *BSSSec = nullptr;
};
} // anonymous namespace
@ -611,6 +631,8 @@ template <class ELFT> void Writer<ELFT>::createSections() {
OutputSections.push_back(&StrTabSec);
if (!SharedFiles.empty()) {
if (needsInterpSection())
OutputSections.push_back(&InterpSec);
OutputSections.push_back(&DynSymSec);
OutputSections.push_back(&DynamicSec);
OutputSections.push_back(&DynStrSec);
@ -642,6 +664,11 @@ template <class ELFT> void Writer<ELFT>::assignAddresses() {
VA = RoundUpToAlignment(VA, PageSize);
NumPhdrs = 0;
// Add a PHDR for PT_INTERP.
if (needsInterpSection())
++NumPhdrs;
// Add a PHDR for the elf header and program headers. Some dynamic linkers
// (musl at least) require them to be covered by a PT_LOAD.
++NumPhdrs;
@ -692,6 +719,18 @@ static uint32_t convertSectionFlagsToPHDRFlags(uint64_t Flags) {
return Ret;
}
template <class ELFT>
static void setValuesFromSection(typename ELFFile<ELFT>::Elf_Phdr &P,
OutputSectionBase<ELFT::Is64Bits> &S) {
P.p_flags = convertSectionFlagsToPHDRFlags(S.getFlags());
P.p_offset = S.getFileOff();
P.p_vaddr = S.getVA();
P.p_paddr = P.p_vaddr;
P.p_filesz = S.getSize();
P.p_memsz = P.p_filesz;
P.p_align = S.getAlign();
}
template <class ELFT> void Writer<ELFT>::writeHeader() {
uint8_t *Buf = Buffer->getBufferStart();
auto *EHdr = reinterpret_cast<Elf_Ehdr *>(Buf);
@ -726,6 +765,12 @@ template <class ELFT> void Writer<ELFT>::writeHeader() {
EHdr->e_shstrndx = StrTabSec.getSectionIndex();
auto PHdrs = reinterpret_cast<Elf_Phdr *>(Buf + EHdr->e_phoff);
if (needsInterpSection()) {
PHdrs->p_type = PT_INTERP;
setValuesFromSection<ELFT>(*PHdrs, InterpSec);
++PHdrs;
}
PHdrs->p_type = PT_LOAD;
PHdrs->p_flags = PF_R;
PHdrs->p_offset = 0;
@ -752,13 +797,7 @@ template <class ELFT> void Writer<ELFT>::writeHeader() {
if (HasDynamicSegment) {
PHdrs->p_type = PT_DYNAMIC;
PHdrs->p_flags = convertSectionFlagsToPHDRFlags(DynamicSec.getFlags());
PHdrs->p_offset = DynamicSec.getFileOff();
PHdrs->p_vaddr = DynamicSec.getVA();
PHdrs->p_paddr = PHdrs->p_vaddr;
PHdrs->p_filesz = DynamicSec.getSize();
PHdrs->p_memsz = DynamicSec.getSize();
PHdrs->p_align = DynamicSec.getAlign();
setValuesFromSection<ELFT>(*PHdrs, DynamicSec);
}
auto SHdrs = reinterpret_cast<Elf_Shdr *>(Buf + EHdr->e_shoff);

55
lld/test/elf2/shared.s
View File

@ -1,20 +1,43 @@
// RUN: llvm-mc -filetype=obj -triple=i686-unknown-linux %s -o %t.o
// RUN: lld -flavor gnu2 %t.o %p/Inputs/i686-simple-library.so -o %t
// RUN: llvm-readobj --program-headers --dynamic-table -t -s -dyn-symbols %t | FileCheck %s
// RUN: lld -flavor gnu2 -dynamic-linker /lib64/ld-linux-x86-64.so.2 %t.o %p/Inputs/i686-simple-library.so -o %t
// RUN: llvm-readobj --program-headers --dynamic-table -t -s -dyn-symbols -section-data %t | FileCheck %s
// REQUIRES: x86
// CHECK: Name: .interp
// CHECK-NEXT: Type: SHT_PROGBITS
// CHECK-NEXT: Flags [
// CHECK-NEXT: SHF_ALLOC
// CHECK-NEXT: ]
// CHECK-NEXT: Address: [[INTERPADDR:.*]]
// CHECK-NEXT: Offset: [[INTERPOFFSET:.*]]
// CHECK-NEXT: Size: [[INTERPSIZE:.*]]
// CHECK-NEXT: Link: 0
// CHECK-NEXT: Info: 0
// CHECK-NEXT: AddressAlignment: 1
// CHECK-NEXT: EntrySize: 0
// CHECK-NEXT: SectionData (
// CHECK-NEXT: 0000: 2F6C6962 36342F6C 642D6C69 6E75782D |/lib64/ld-linux-|
// CHECK-NEXT: 0010: 7838362D 36342E73 6F2E3200 |x86-64.so.2.|
// CHECK-NEXT: )
// CHECK-NEXT: }
// CHECK: Name: .dynsym
// CHECK-NEXT: Type: SHT_DYNSYM
// CHECK-NEXT: Flags [
// CHECK-NEXT: SHF_ALLOC
// CHECK-NEXT: ]
// CHECK-NEXT: Address: [[DYNSYMADDR:.*]]
// CHECK-NEXT: Offset: 0x2000
// CHECK-NEXT: Offset: 0x3000
// CHECK-NEXT: Size: 48
// CHECK-NEXT: Link: [[DYNSTR:.*]]
// CHECK-NEXT: Info: 1
// CHECK-NEXT: AddressAlignment: 4
// CHECK-NEXT: EntrySize: 16
// CHECK-NEXT: SectionData (
// CHECK-NEXT: 0000:
// CHECK-NEXT: 0010:
// CHECK-NEXT: 0020:
// CHECK-NEXT: )
// CHECK-NEXT: }
// CHECK: Name: .dynamic
@ -30,6 +53,11 @@
// CHECK-NEXT: Info: 0
// CHECK-NEXT: AddressAlignment: [[ALIGN:.*]]
// CHECK-NEXT: EntrySize: 8
// CHECK-NEXT: SectionData (
// CHECK-NEXT: 0000:
// CHECK-NEXT: 0010:
// CHECK-NEXT: 0020:
// CHECK-NEXT: )
// CHECK-NEXT: }
// CHECK: Index: [[DYNSTR]]
@ -45,6 +73,13 @@
// CHECK-NEXT: Info: 0
// CHECK-NEXT: AddressAlignment: 1
// CHECK-NEXT: EntrySize: 0
// CHECK-NEXT: SectionData (
// CHECK-NEXT: 0000:
// CHECK-NEXT: 0010:
// CHECK-NEXT: 0020:
// CHECK-NEXT: 0030:
// CHECK-NEXT: 0040:
// CHECK-NEXT: )
// CHECK-NEXT: }
@ -117,7 +152,19 @@
// CHECK-NEXT: 0x00000000 NULL 0x0
// CHECK-NEXT: ]
// CHECK: ProgramHeader {
// CHECK: ProgramHeaders [
// CHECK-NEXT: ProgramHeader {
// CHECK-NEXT: Type: PT_INTERP
// CHECK-NEXT: Offset: [[INTERPOFFSET]]
// CHECK-NEXT: VirtualAddress: [[INTERPADDR]]
// CHECK-NEXT: PhysicalAddress: [[INTERPADDR]]
// CHECK-NEXT: FileSize: [[INTERPSIZE]]
// CHECK-NEXT: MemSize: [[INTERPSIZE]]
// CHECK-NEXT: Flags [
// CHECK-NEXT: PF_R
// CHECK-NEXT: ]
// CHECK-NEXT: Alignment: 1
// CHECK-NEXT: }
// CHECK: Type: PT_DYNAMIC
// CHECK-NEXT: Offset: [[OFFSET]]
// CHECK-NEXT: VirtualAddress: [[ADDR]]