[lld] r282429 - [ELF] - Linkerscript: implemented BYTE/SHORT/LONG/QUAD commands.
George Rimar via llvm-commits
llvm-commits at lists.llvm.org
Mon Sep 26 12:22:51 PDT 2016
Author: grimar
Date: Mon Sep 26 14:22:50 2016
New Revision: 282429
URL: http://llvm.org/viewvc/llvm-project?rev=282429&view=rev
Log:
[ELF] - Linkerscript: implemented BYTE/SHORT/LONG/QUAD commands.
The BYTE, SHORT, LONG, and QUAD commands store one, two, four, and eight bytes (respectively).
After storing the bytes, the location counter is incremented by the number of bytes
stored.
Previously our scripts handles these commands incorrectly. For example:
SECTIONS {
.foo : {
*(.foo.1)
BYTE(0x11)
...
We accepted the script above treating BYTE as input section description.
These commands are used in the wild though.
Differential revision: https://reviews.llvm.org/D24830
Added:
lld/trunk/test/ELF/linkerscript/data-commands.s
Modified:
lld/trunk/ELF/LinkerScript.cpp
lld/trunk/ELF/LinkerScript.h
lld/trunk/ELF/OutputSections.cpp
Modified: lld/trunk/ELF/LinkerScript.cpp
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/LinkerScript.cpp?rev=282429&r1=282428&r2=282429&view=diff
==============================================================================
--- lld/trunk/ELF/LinkerScript.cpp (original)
+++ lld/trunk/ELF/LinkerScript.cpp Mon Sep 26 14:22:50 2016
@@ -38,6 +38,7 @@
using namespace llvm;
using namespace llvm::ELF;
using namespace llvm::object;
+using namespace llvm::support::endian;
using namespace lld;
using namespace lld::elf;
@@ -94,6 +95,10 @@ bool AssertCommand::classof(const BaseCo
return C->Kind == AssertKind;
}
+bool BytesDataCommand::classof(const BaseCommand *C) {
+ return C->Kind == BytesDataKind;
+}
+
template <class ELFT> static bool isDiscarded(InputSectionBase<ELFT> *S) {
return !S || !S->Live;
}
@@ -408,6 +413,7 @@ void LinkerScript<ELFT>::switchTo(Output
}
template <class ELFT> void LinkerScript<ELFT>::process(BaseCommand &Base) {
+ // This handles the assignments to symbol or to a location counter (.)
if (auto *AssignCmd = dyn_cast<SymbolAssignment>(&Base)) {
if (AssignCmd->Name == ".") {
// Update to location counter means update to section size.
@@ -418,6 +424,18 @@ template <class ELFT> void LinkerScript<
assignSectionSymbol<ELFT>(AssignCmd, CurOutSec, Dot - CurOutSec->getVA());
return;
}
+
+ // Handle BYTE(), SHORT(), LONG(), or QUAD().
+ if (auto *DataCmd = dyn_cast<BytesDataCommand>(&Base)) {
+ DataCmd->Offset = Dot - CurOutSec->getVA();
+ Dot += DataCmd->Size;
+ CurOutSec->setSize(Dot - CurOutSec->getVA());
+ return;
+ }
+
+ // It handles single input section description command,
+ // calculates and assigns the offsets for each section and also
+ // updates the output section size.
auto &ICmd = cast<InputSectionDescription>(Base);
for (InputSectionData *ID : ICmd.Sections) {
auto *IB = static_cast<InputSectionBase<ELFT> *>(ID);
@@ -689,6 +707,41 @@ ArrayRef<uint8_t> LinkerScript<ELFT>::ge
return {};
}
+template <class ELFT>
+static void writeInt(uint8_t *Buf, uint64_t Data, uint64_t Size) {
+ const endianness E = ELFT::TargetEndianness;
+
+ switch (Size) {
+ case 1:
+ *Buf = (uint8_t)Data;
+ break;
+ case 2:
+ write16<E>(Buf, Data);
+ break;
+ case 4:
+ write32<E>(Buf, Data);
+ break;
+ case 8:
+ write64<E>(Buf, Data);
+ break;
+ default:
+ llvm_unreachable("unsupported Size argument");
+ }
+}
+
+template <class ELFT>
+void LinkerScript<ELFT>::writeDataBytes(StringRef Name, uint8_t *Buf) {
+ int I = getSectionIndex(Name);
+ if (I == INT_MAX)
+ return;
+
+ OutputSectionCommand *Cmd =
+ dyn_cast<OutputSectionCommand>(Opt.Commands[I].get());
+ for (const std::unique_ptr<BaseCommand> &Base2 : Cmd->Commands)
+ if (auto *DataCmd = dyn_cast<BytesDataCommand>(Base2.get()))
+ writeInt<ELFT>(&Buf[DataCmd->Offset], DataCmd->Data, DataCmd->Size);
+}
+
template <class ELFT> Expr LinkerScript<ELFT>::getLma(StringRef Name) {
for (const std::unique_ptr<BaseCommand> &Base : Opt.Commands)
if (auto *Cmd = dyn_cast<OutputSectionCommand>(Base.get()))
@@ -815,6 +868,7 @@ private:
void readVersionScriptCommand();
SymbolAssignment *readAssignment(StringRef Name);
+ BytesDataCommand *readBytesDataCommand(StringRef Tok);
std::vector<uint8_t> readFill();
OutputSectionCommand *readOutputSectionDescription(StringRef OutSec);
std::vector<uint8_t> readOutputSectionFiller(StringRef Tok);
@@ -1254,6 +1308,8 @@ ScriptParser::readOutputSectionDescripti
StringRef Tok = next();
if (SymbolAssignment *Assignment = readProvideOrAssignment(Tok, false))
Cmd->Commands.emplace_back(Assignment);
+ else if (BytesDataCommand *Data = readBytesDataCommand(Tok))
+ Cmd->Commands.emplace_back(Data);
else if (Tok == "FILL")
Cmd->Filler = readFill();
else if (Tok == "SORT")
@@ -1451,6 +1507,25 @@ static bool readInteger(StringRef Tok, u
return true;
}
+BytesDataCommand *ScriptParser::readBytesDataCommand(StringRef Tok) {
+ int Size = StringSwitch<unsigned>(Tok)
+ .Case("BYTE", 1)
+ .Case("SHORT", 2)
+ .Case("LONG", 4)
+ .Case("QUAD", 8)
+ .Default(-1);
+ if (Size == -1)
+ return nullptr;
+
+ expect("(");
+ uint64_t Val = 0;
+ StringRef S = next();
+ if (!readInteger(S, Val))
+ setError("unexpected value: " + S);
+ expect(")");
+ return new BytesDataCommand(Val, Size);
+}
+
Expr ScriptParser::readPrimary() {
if (peek() == "(")
return readParenExpr();
Modified: lld/trunk/ELF/LinkerScript.h
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/LinkerScript.h?rev=282429&r1=282428&r2=282429&view=diff
==============================================================================
--- lld/trunk/ELF/LinkerScript.h (original)
+++ lld/trunk/ELF/LinkerScript.h Mon Sep 26 14:22:50 2016
@@ -44,10 +44,11 @@ void readVersionScript(MemoryBufferRef M
// This enum is used to implement linker script SECTIONS command.
// https://sourceware.org/binutils/docs/ld/SECTIONS.html#SECTIONS
enum SectionsCommandKind {
- AssignmentKind,
+ AssignmentKind, // . = expr or <sym> = expr
OutputSectionKind,
InputSectionKind,
- AssertKind
+ AssertKind, // ASSERT(expr)
+ BytesDataKind // BYTE(expr), SHORT(expr), LONG(expr) or QUAD(expr)
};
struct BaseCommand {
@@ -138,6 +139,15 @@ struct AssertCommand : BaseCommand {
Expr Expression;
};
+struct BytesDataCommand : BaseCommand {
+ BytesDataCommand(uint64_t Data, unsigned Size)
+ : BaseCommand(BytesDataKind), Data(Data), Size(Size) {}
+ static bool classof(const BaseCommand *C);
+ uint64_t Data;
+ unsigned Offset;
+ unsigned Size;
+};
+
struct PhdrsCommand {
StringRef Name;
unsigned Type;
@@ -194,6 +204,7 @@ public:
bool ignoreInterpSection();
ArrayRef<uint8_t> getFiller(StringRef Name);
+ void writeDataBytes(StringRef Name, uint8_t *Buf);
Expr getLma(StringRef Name);
bool shouldKeep(InputSectionBase<ELFT> *S);
void assignOffsets(OutputSectionCommand *Cmd);
Modified: lld/trunk/ELF/OutputSections.cpp
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/OutputSections.cpp?rev=282429&r1=282428&r2=282429&view=diff
==============================================================================
--- lld/trunk/ELF/OutputSections.cpp (original)
+++ lld/trunk/ELF/OutputSections.cpp Mon Sep 26 14:22:50 2016
@@ -1005,6 +1005,9 @@ template <class ELFT> void OutputSection
for (InputSection<ELFT> *C : Sections)
C->writeTo(Buf);
}
+ // Linker scripts may have BYTE()-family commands with which you
+ // can write arbitrary bytes to the output. Process them if any.
+ Script<ELFT>::X->writeDataBytes(this->Name, Buf);
}
template <class ELFT>
Added: lld/trunk/test/ELF/linkerscript/data-commands.s
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/test/ELF/linkerscript/data-commands.s?rev=282429&view=auto
==============================================================================
--- lld/trunk/test/ELF/linkerscript/data-commands.s (added)
+++ lld/trunk/test/ELF/linkerscript/data-commands.s Mon Sep 26 14:22:50 2016
@@ -0,0 +1,40 @@
+# REQUIRES: x86,mips
+# RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %t.o
+# RUN: echo "SECTIONS \
+# RUN: { \
+# RUN: .foo : { \
+# RUN: *(.foo.1) \
+# RUN: BYTE(0x11) \
+# RUN: *(.foo.2) \
+# RUN: SHORT(0x1122) \
+# RUN: *(.foo.3) \
+# RUN: LONG(0x11223344) \
+# RUN: *(.foo.4) \
+# RUN: QUAD(0x1122334455667788) \
+# RUN: } \
+# RUN: }" > %t.script
+# RUN: ld.lld -o %t --script %t.script %t.o
+# RUN: llvm-objdump -s %t | FileCheck %s
+
+# CHECK: Contents of section .foo:
+# CHECK-NEXT: ff11ff22 11ff4433 2211ff88 77665544
+# CHECK-NEXT: 332211
+
+# RUN: llvm-mc -filetype=obj -triple=mips64-unknown-linux %s -o %tmips64be
+# RUN: ld.lld --script %t.script %tmips64be -o %t2
+# RUN: llvm-objdump -s %t2 | FileCheck %s --check-prefix=BE
+# BE: Contents of section .foo:
+# BE-NEXT: ff11ff11 22ff1122 3344ff11 22334455
+# BE-NEXT: 667788
+
+.section .foo.1, "a"
+ .byte 0xFF
+
+.section .foo.2, "a"
+ .byte 0xFF
+
+.section .foo.3, "a"
+ .byte 0xFF
+
+.section .foo.4, "a"
+ .byte 0xFF
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