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Recommitted 266457 with fix:

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* Do script driven layout only if SECTIONS section exist.

Initial commit message:

[ELF] - Implemented basic location counter support.

This patch implements location counter support. 
It also separates assign addresses for sections to assignAddressesScript() if it scipt exists.

Main testcase is test/ELF/linkerscript-locationcounter.s, It contains some work with location counter. It is basic now.
Implemented location counter assignment and '+' operations.

Patch by myself with LOTS of comments and design suggestions from Rui Ueyama.

Differential revision: http://reviews.llvm.org/D18499

llvm-svn: 266526
This commit is contained in:
George Rimar 2016-04-16 10:10:32 +00:00
parent 357deca829
commit 652852c5c0
8 changed files with 280 additions and 28 deletions
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131
lld/ELF/LinkerScript.cpp
View File

@ -17,20 +17,55 @@
#include "Config.h"
#include "Driver.h"
#include "InputSection.h"
#include "OutputSections.h"
#include "ScriptParser.h"
#include "SymbolTable.h"
#include "llvm/Support/ELF.h"
#include "llvm/Support/FileSystem.h"
#include "llvm/Support/MemoryBuffer.h"
#include "llvm/Support/Path.h"
#include "llvm/Support/StringSaver.h"
using namespace llvm;
using namespace llvm::ELF;
using namespace llvm::object;
using namespace lld;
using namespace lld::elf;
LinkerScript *elf::Script;
static uint64_t getInteger(StringRef S) {
uint64_t V;
if (S.getAsInteger(0, V)) {
error("malformed number: " + S);
return 0;
}
return V;
}
// Evaluates the expression given by list of tokens.
uint64_t LinkerScript::evaluate(std::vector<StringRef> &Tokens,
uint64_t LocCounter) {
uint64_t Result = 0;
for (size_t I = 0, E = Tokens.size(); I < E; ++I) {
// Each second token should be '+' as this is the
// only operator we support now.
if (I % 2 == 1) {
if (Tokens[I] == "+")
continue;
error("error in location counter expression");
return 0;
}
StringRef Tok = Tokens[I];
if (Tok == ".")
Result += LocCounter;
else
Result += getInteger(Tok);
}
return Result;
}
template <class ELFT>
SectionRule *LinkerScript::find(InputSectionBase<ELFT> *S) {
for (SectionRule &R : Sections)
@ -55,6 +90,66 @@ template <class ELFT> bool LinkerScript::shouldKeep(InputSectionBase<ELFT> *S) {
return R && R->Keep;
}
// This method finalizes the Locations list. Adds neccesary locations for
// orphan sections, what prepares it for futher use without
// changes in LinkerScript::assignAddresses().
template <class ELFT>
void LinkerScript::fixupLocations(std::vector<OutputSectionBase<ELFT> *> &S) {
// Orphan sections are sections present in the input files which
// are not explicitly placed into the output file by the linker
// script. We place orphan sections at end of file. Other linkers places
// them using some heuristics as described in
// https://sourceware.org/binutils/docs/ld/Orphan-Sections.html#Orphan-Sections.
for (OutputSectionBase<ELFT> *Sec : S) {
StringRef Name = Sec->getName();
auto I = std::find(SectionOrder.begin(), SectionOrder.end(), Name);
if (I == SectionOrder.end())
Locations.push_back({Command::Section, {}, {Name}});
}
}
template <class ELFT>
void LinkerScript::assignAddresses(std::vector<OutputSectionBase<ELFT> *> &S) {
typedef typename ELFT::uint uintX_t;
Script->fixupLocations(S);
uintX_t ThreadBssOffset = 0;
uintX_t VA =
Out<ELFT>::ElfHeader->getSize() + Out<ELFT>::ProgramHeaders->getSize();
for (LocationNode &Node : Locations) {
if (Node.Type == Command::Expr) {
VA = evaluate(Node.Expr, VA);
continue;
}
auto I =
std::find_if(S.begin(), S.end(), [&](OutputSectionBase<ELFT> *Sec) {
return Sec->getName() == Node.SectionName;
});
if (I == S.end())
continue;
OutputSectionBase<ELFT> *Sec = *I;
uintX_t Align = Sec->getAlign();
if ((Sec->getFlags() & SHF_TLS) && Sec->getType() == SHT_NOBITS) {
uintX_t TVA = VA + ThreadBssOffset;
TVA = alignTo(TVA, Align);
Sec->setVA(TVA);
ThreadBssOffset = TVA - VA + Sec->getSize();
continue;
}
if (Sec->getFlags() & SHF_ALLOC) {
VA = alignTo(VA, Align);
Sec->setVA(VA);
VA += Sec->getSize();
continue;
}
}
}
ArrayRef<uint8_t> LinkerScript::getFiller(StringRef Name) {
auto I = Filler.find(Name);
if (I == Filler.end())
@ -126,6 +221,7 @@ private:
void readSearchDir();
void readSections();
void readLocationCounterValue();
void readOutputSectionDescription();
void readSectionPatterns(StringRef OutSec, bool Keep);
@ -286,9 +382,15 @@ void ScriptParser::readSearchDir() {
}
void ScriptParser::readSections() {
Script->DoLayout = true;
expect("{");
while (!Error && !skip("}"))
readOutputSectionDescription();
while (!Error && !skip("}")) {
StringRef Tok = peek();
if (Tok == ".")
readLocationCounterValue();
else
readOutputSectionDescription();
}
}
void ScriptParser::readSectionPatterns(StringRef OutSec, bool Keep) {
@ -297,9 +399,25 @@ void ScriptParser::readSectionPatterns(StringRef OutSec, bool Keep) {
Script->Sections.emplace_back(OutSec, next(), Keep);
}
void ScriptParser::readLocationCounterValue() {
expect(".");
expect("=");
Script->Locations.push_back({Command::Expr, {}, {}});
LocationNode &Node = Script->Locations.back();
while (!Error) {
StringRef Tok = next();
if (Tok == ";")
break;
Node.Expr.push_back(Tok);
}
if (Node.Expr.empty())
error("error in location counter expression");
}
void ScriptParser::readOutputSectionDescription() {
StringRef OutSec = next();
Script->SectionOrder.push_back(OutSec);
Script->Locations.push_back({Command::Section, {}, {OutSec}});
expect(":");
expect("{");
while (!Error && !skip("}")) {
@ -356,3 +474,12 @@ template bool LinkerScript::shouldKeep(InputSectionBase<ELF32LE> *);
template bool LinkerScript::shouldKeep(InputSectionBase<ELF32BE> *);
template bool LinkerScript::shouldKeep(InputSectionBase<ELF64LE> *);
template bool LinkerScript::shouldKeep(InputSectionBase<ELF64BE> *);
template void
LinkerScript::assignAddresses(std::vector<OutputSectionBase<ELF32LE> *> &);
template void
LinkerScript::assignAddresses(std::vector<OutputSectionBase<ELF32BE> *> &);
template void
LinkerScript::assignAddresses(std::vector<OutputSectionBase<ELF64LE> *> &);
template void
LinkerScript::assignAddresses(std::vector<OutputSectionBase<ELF64BE> *> &);

22
lld/ELF/LinkerScript.h
View File

@ -21,6 +21,7 @@ namespace elf {
class ScriptParser;
template <class ELFT> class InputSectionBase;
template <class ELFT> class OutputSectionBase;
// This class represents each rule in SECTIONS command.
class SectionRule {
@ -40,6 +41,17 @@ private:
StringRef SectionPattern;
};
// This enum represents what we can observe in SECTIONS tag of script:
// Expr is a location counter change, like ". = . + 0x1000"
// Section is a description of output section, like ".data :..."
enum class Command { Expr, Section };
struct LocationNode {
Command Type;
std::vector<StringRef> Expr;
StringRef SectionName;
};
// This is a runner of the linker script.
class LinkerScript {
friend class ScriptParser;
@ -53,9 +65,16 @@ public:
ArrayRef<uint8_t> getFiller(StringRef Name);
template <class ELFT> bool isDiscarded(InputSectionBase<ELFT> *S);
template <class ELFT> bool shouldKeep(InputSectionBase<ELFT> *S);
template <class ELFT>
void assignAddresses(std::vector<OutputSectionBase<ELFT> *> &S);
int compareSections(StringRef A, StringRef B);
bool DoLayout = false;
private:
template <class ELFT>
void fixupLocations(std::vector<OutputSectionBase<ELFT> *> &);
uint64_t evaluate(std::vector<StringRef> &Tokens, uint64_t LocCounter);
template <class ELFT> SectionRule *find(InputSectionBase<ELFT> *S);
// SECTIONS commands.
@ -67,6 +86,9 @@ private:
// Section fill attribute for each section.
llvm::StringMap<std::vector<uint8_t>> Filler;
// Used to assign addresses to sections.
std::vector<LocationNode> Locations;
llvm::BumpPtrAllocator Alloc;
};

13
lld/ELF/Writer.cpp
View File

@ -220,8 +220,12 @@ template <class ELFT> void Writer<ELFT>::run() {
} else {
createPhdrs();
fixHeaders();
fixSectionAlignments();
assignAddresses();
if (Script->DoLayout) {
Script->assignAddresses(OutputSections);
} else {
fixSectionAlignments();
assignAddresses();
}
assignFileOffsets();
setPhdrs();
fixAbsoluteSymbols();
@ -1528,10 +1532,11 @@ template <class ELFT> void Writer<ELFT>::fixSectionAlignments() {
// sections. These are special, we do not include them into output sections
// list, but have them to simplify the code.
template <class ELFT> void Writer<ELFT>::fixHeaders() {
Out<ELFT>::ElfHeader->setVA(Target->getVAStart());
uintX_t BaseVA = Script->DoLayout ? 0 : Target->getVAStart();
Out<ELFT>::ElfHeader->setVA(BaseVA);
Out<ELFT>::ElfHeader->setFileOffset(0);
uintX_t Off = Out<ELFT>::ElfHeader->getSize();
Out<ELFT>::ProgramHeaders->setVA(Off + Target->getVAStart());
Out<ELFT>::ProgramHeaders->setVA(Off + BaseVA);
Out<ELFT>::ProgramHeaders->setFileOffset(Off);
}

8
lld/test/ELF/end.s
View File

@ -36,13 +36,13 @@
// NOBSS-NEXT: SHF_ALLOC
// NOBSS-NEXT: SHF_WRITE
// NOBSS-NEXT: ]
// NOBSS-NEXT: Address: 0x12000
// NOBSS-NEXT: Address: 0x159
// NOBSS-NEXT: Offset:
// NOBSS-NEXT: Size: 2
// NOBSS: ]
// NOBSS: Symbols [
// NOBSS: Name: _end
// NOBSS-NEXT: Value: 0x12002
// NOBSS-NEXT: Value: 0x15B
// NOBSS: ]
// If the layout of the sections is changed, "_end" should point to the end of allocated address space.
@ -60,13 +60,13 @@
// TEXTATEND-NEXT: SHF_ALLOC
// TEXTATEND-NEXT: SHF_EXECINSTR
// TEXTATEND-NEXT: ]
// TEXTATEND-NEXT: Address: 0x12000
// TEXTATEND-NEXT: Address: 0x160
// TEXTATEND-NEXT: Offset:
// TEXTATEND-NEXT: Size: 1
// TEXTATEND: ]
// TEXTATEND: Symbols [
// TEXTATEND: Name: _end
// TEXTATEND-NEXT: Value: 0x12001
// TEXTATEND-NEXT: Value: 0x161
// TEXTATEND: ]
.global _start,_end

74
lld/test/ELF/linkerscript-locationcounter.s Normal file
View File

@ -0,0 +1,74 @@
# REQUIRES: x86
# RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %t
# RUN: echo "SECTIONS { \
# RUN: . = 0x12341; \
# RUN: .data : { *(.data) } \
# RUN: . = . + 0x10000; \
# RUN: .text : { *(.text) } \
# RUN: }" > %t.script
# RUN: ld.lld %t --script %t.script -o %t2
# RUN: llvm-readobj -s %t2 | FileCheck %s
# CHECK: Sections [
# CHECK-NEXT: Section {
# CHECK-NEXT: Index: 0
# CHECK-NEXT: Name: (0)
# CHECK-NEXT: Type: SHT_NULL
# CHECK-NEXT: Flags [
# CHECK-NEXT: ]
# CHECK-NEXT: Address: 0x0
# CHECK-NEXT: Offset: 0x0
# CHECK-NEXT: Size: 0
# CHECK-NEXT: Link: 0
# CHECK-NEXT: Info: 0
# CHECK-NEXT: AddressAlignment: 0
# CHECK-NEXT: EntrySize: 0
# CHECK-NEXT: }
# CHECK-NEXT: Section {
# CHECK-NEXT: Index: 1
# CHECK-NEXT: Name: .data
# CHECK-NEXT: Type: SHT_PROGBITS
# CHECK-NEXT: Flags [
# CHECK-NEXT: SHF_ALLOC
# CHECK-NEXT: SHF_WRITE
# CHECK-NEXT: ]
# CHECK-NEXT: Address: 0x12341
# CHECK-NEXT: Offset: 0x158
# CHECK-NEXT: Size: 8
# CHECK-NEXT: Link: 0
# CHECK-NEXT: Info: 0
# CHECK-NEXT: AddressAlignment: 1
# CHECK-NEXT: EntrySize: 0
# CHECK-NEXT: }
# CHECK-NEXT: Section {
# CHECK-NEXT: Index: 2
# CHECK-NEXT: Name: .text
# CHECK-NEXT: Type: SHT_PROGBITS
# CHECK-NEXT: Flags [
# CHECK-NEXT: SHF_ALLOC
# CHECK-NEXT: SHF_EXECINSTR
# CHECK-NEXT: ]
# CHECK-NEXT: Address: 0x2234C
# CHECK-NEXT: Offset: 0x160
# CHECK-NEXT: Size: 1
# CHECK-NEXT: Link: 0
# CHECK-NEXT: Info: 0
# CHECK-NEXT: AddressAlignment: 4
# CHECK-NEXT: EntrySize: 0
# CHECK-NEXT: }
# RUN: echo "SECTIONS { \
# RUN: . = 0x12Q41; \
# RUN: }" > %t.script
# RUN: not ld.lld %t --script %t.script -o %t2 2>&1 | \
# RUN: FileCheck --check-prefix=NUMERR %s
# NUMERR: malformed number: 0x12Q41
.globl _start;
_start:
nop
.section .data
.quad 0

20
lld/test/ELF/linkerscript-sections-keep.s
View File

@ -12,8 +12,8 @@
# SECGC: Sections:
# SECGC-NEXT: Idx Name Size Address Type
# SECGC-NEXT: 0 00000000 0000000000000000
# SECGC-NEXT: 1 .text 00000007 0000000000011000 TEXT DATA
# SECGC-NEXT: 2 .temp 00000004 0000000000012000 DATA
# SECGC-NEXT: 1 .text 00000007 0000000000000158 TEXT DATA
# SECGC-NEXT: 2 .temp 00000004 000000000000015f DATA
## Now apply KEEP command to preserve the section.
# RUN: echo "SECTIONS { \
@ -26,9 +26,9 @@
# SECNOGC: Sections:
# SECNOGC-NEXT: Idx Name Size Address Type
# SECNOGC-NEXT: 0 00000000 0000000000000000
# SECNOGC-NEXT: 1 .text 00000007 0000000000011000 TEXT DATA
# SECNOGC-NEXT: 2 .keep 00000004 0000000000012000 DATA
# SECNOGC-NEXT: 3 .temp 00000004 0000000000012004 DATA
# SECNOGC-NEXT: 1 .text 00000007 0000000000000158 TEXT DATA
# SECNOGC-NEXT: 2 .keep 00000004 000000000000015f DATA
# SECNOGC-NEXT: 3 .temp 00000004 0000000000000163 DATA
## A section name matches two entries in the SECTIONS directive. The
## first one doesn't have KEEP, the second one does. If section that have
@ -42,9 +42,9 @@
# KEEP-AT-FIRST: Sections:
# KEEP-AT-FIRST-NEXT: Idx Name Size Address Type
# KEEP-AT-FIRST-NEXT: 0 00000000 0000000000000000
# KEEP-AT-FIRST-NEXT: 1 .keep 00000004 0000000000010120 DATA
# KEEP-AT-FIRST-NEXT: 2 .temp 00000004 0000000000010124 DATA
# KEEP-AT-FIRST-NEXT: 3 .text 00000007 0000000000011000 TEXT DATA
# KEEP-AT-FIRST-NEXT: 1 .keep 00000004 0000000000000120 DATA
# KEEP-AT-FIRST-NEXT: 2 .temp 00000004 0000000000000124 DATA
# KEEP-AT-FIRST-NEXT: 3 .text 00000007 0000000000000128 TEXT DATA
# KEEP-AT-FIRST-NEXT: 4 .symtab 00000060 0000000000000000
# KEEP-AT-FIRST-NEXT: 5 .shstrtab 0000002d 0000000000000000
# KEEP-AT-FIRST-NEXT: 6 .strtab 00000012 0000000000000000
@ -63,8 +63,8 @@
# KEEP-AT-SECOND: Sections:
# KEEP-AT-SECOND-NEXT: Idx Name Size Address Type
# KEEP-AT-SECOND-NEXT: 0 00000000 0000000000000000
# KEEP-AT-SECOND-NEXT: 1 .temp 00000004 0000000000010120 DATA
# KEEP-AT-SECOND-NEXT: 2 .text 00000007 0000000000011000 TEXT DATA
# KEEP-AT-SECOND-NEXT: 1 .temp 00000004 0000000000000120 DATA
# KEEP-AT-SECOND-NEXT: 2 .text 00000007 0000000000000124 TEXT DATA
# KEEP-AT-SECOND-NEXT: 3 .symtab 00000048 0000000000000000
# KEEP-AT-SECOND-NEXT: 4 .shstrtab 00000027 0000000000000000
# KEEP-AT-SECOND-NEXT: 5 .strtab 0000000d 0000000000000000

24
lld/test/ELF/linkerscript-va.s Normal file
View File

@ -0,0 +1,24 @@
# REQUIRES: x86
# RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %t
# RUN: echo "SECTIONS {}" > %t.script
# RUN: ld.lld -o %t1 --script %t.script %t
# RUN: llvm-objdump -section-headers %t1 | FileCheck %s
# CHECK: Sections:
# CHECK-NEXT: Idx Name Size Address Type
# CHECK-NEXT: 0 00000000 0000000000000000
# CHECK-NEXT: 1 .foo 00000004 0000000000000120 DATA
# CHECK-NEXT: 2 .boo 00000004 0000000000000124 DATA
# CHECK-NEXT: 3 .text 00000001 0000000000000128 TEXT DATA
.global _start
_start:
nop
.section .foo, "a"
foo:
.long 0
.section .boo, "a"
boo:
.long 0

16
lld/test/ELF/wildcards.s
View File

@ -10,10 +10,10 @@
# SEC-DEFAULT: Sections:
# SEC-DEFAULT-NEXT: Idx Name Size Address Type
# SEC-DEFAULT-NEXT: 0 00000000 0000000000000000
# SEC-DEFAULT-NEXT: 1 .text 00000008 0000000000011000 TEXT DATA
# SEC-DEFAULT-NEXT: 2 .abcd 00000004 0000000000011008 TEXT DATA
# SEC-DEFAULT-NEXT: 3 .ad 00000004 000000000001100c TEXT DATA
# SEC-DEFAULT-NEXT: 4 .ag 00000004 0000000000011010 TEXT DATA
# SEC-DEFAULT-NEXT: 1 .text 00000008 0000000000000120 TEXT DATA
# SEC-DEFAULT-NEXT: 2 .abcd 00000004 0000000000000128 TEXT DATA
# SEC-DEFAULT-NEXT: 3 .ad 00000004 000000000000012c TEXT DATA
# SEC-DEFAULT-NEXT: 4 .ag 00000004 0000000000000130 TEXT DATA
# SEC-DEFAULT-NEXT: 5 .symtab 00000030 0000000000000000
# SEC-DEFAULT-NEXT: 6 .shstrtab 0000002f 0000000000000000
# SEC-DEFAULT-NEXT: 7 .strtab 00000008 0000000000000000
@ -34,9 +34,9 @@
# SEC-ALL: Sections:
# SEC-ALL-NEXT: Idx Name Size Address Type
# SEC-ALL-NEXT: 0 00000000 0000000000000000
# SEC-ALL-NEXT: 1 .text 0000000c 0000000000011000 TEXT DATA
# SEC-ALL-NEXT: 2 .ad 00000004 000000000001100c TEXT DATA
# SEC-ALL-NEXT: 3 .ag 00000004 0000000000011010 TEXT DATA
# SEC-ALL-NEXT: 1 .text 0000000c 0000000000000120 TEXT DATA
# SEC-ALL-NEXT: 2 .ad 00000004 000000000000012c TEXT DATA
# SEC-ALL-NEXT: 3 .ag 00000004 0000000000000130 TEXT DATA
# SEC-ALL-NEXT: 4 .symtab 00000030 0000000000000000
# SEC-ALL-NEXT: 5 .shstrtab 00000029 0000000000000000
# SEC-ALL-NEXT: 6 .strtab 00000008 0000000000000000
@ -50,7 +50,7 @@
# SEC-NO: Sections:
# SEC-NO-NEXT: Idx Name Size Address Type
# SEC-NO-NEXT: 0 00000000 0000000000000000
# SEC-NO-NEXT: 1 .text 00000014 0000000000011000 TEXT DATA
# SEC-NO-NEXT: 1 .text 00000014 0000000000000120 TEXT DATA
# SEC-NO-NEXT: 2 .symtab 00000030 0000000000000000
# SEC-NO-NEXT: 3 .shstrtab 00000021 0000000000000000
# SEC-NO-NEXT: 4 .strtab 00000008 0000000000000000