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[ARM] Implementation of R_ARM_TARGET1 relocation
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This patch provides implementation of R_ARM_TARGET1 relocation with
configuration of its behaviour from a command line. This patch provides
two command line options for GnuLd driver: --arm-target1-rel and
--arm-target1-abs (similar to ld option names with extra prefix 'arm-').
So user may choose which behaviour of R_ARM_TARGET1 is preferred for his
implementation of libc.

Differential Revision: http://reviews.llvm.org/D8707

llvm-svn: 234009
Leny Kholodov committed Apr 3, 2015
1 parent 8dba5da commit 95ed78b
Showing 7 changed files with 166 additions and 0 deletions.
5 changes: 5 additions & 0 deletions lld/include/lld/ReaderWriter/ELFLinkingContext.h
Original file line number Diff line number Diff line change
@@ -302,6 +302,10 @@ class ELFLinkingContext : public LinkingContext {
script::Sema &linkerScriptSema() { return _linkerScriptSema; }
const script::Sema &linkerScriptSema() const { return _linkerScriptSema; }

// Set R_ARM_TARGET1 relocation behaviour
bool armTarget1Rel() const { return _armTarget1Rel; }
void setArmTarget1Rel(bool value) { _armTarget1Rel = value; }

protected:
ELFLinkingContext(llvm::Triple triple, std::unique_ptr<TargetHandler> handler)
: _triple(triple), _targetHandler(std::move(handler)) {}
@@ -327,6 +331,7 @@ class ELFLinkingContext : public LinkingContext {
bool _stripSymbols = false;
bool _alignSegments = true;
bool _collectStats = false;
bool _armTarget1Rel = false;
uint64_t _maxPageSize = 0x1000;

OutputMagic _outputMagic;
19 changes: 19 additions & 0 deletions lld/lib/Driver/GnuLdDriver.cpp
Original file line number Diff line number Diff line change
@@ -543,6 +543,25 @@ bool GnuLdDriver::parse(int argc, const char *argv[],
if (auto *arg = parsedArgs->getLastArg(OPT_output_filetype))
ctx->setOutputFileType(arg->getValue());

// Process ELF/ARM specific options
bool hasArmTarget1Rel = parsedArgs->hasArg(OPT_arm_target1_rel);
bool hasArmTarget1Abs = parsedArgs->hasArg(OPT_arm_target1_abs);
if (triple.getArch() == llvm::Triple::arm) {
if (hasArmTarget1Rel && hasArmTarget1Abs) {
diag << "error: options --arm-target1-rel and --arm-target1-abs"
" can't be used together.\n";
return false;
} else if (hasArmTarget1Rel || hasArmTarget1Abs) {
ctx->setArmTarget1Rel(hasArmTarget1Rel && !hasArmTarget1Abs);
}
} else if (hasArmTarget1Rel) {
diag << "warning: ignoring unsupported ARM/ELF specific argument: "
<< "--arm-target1-rel\n";
} else if (hasArmTarget1Abs) {
diag << "warning: ignoring unsupported ARM/ELF specific argument: "
<< "--arm-target1-abs\n";
}

for (auto *arg : parsedArgs->filtered(OPT_L))
ctx->addSearchPath(arg->getValue());

10 changes: 10 additions & 0 deletions lld/lib/Driver/GnuLdOptions.td
Original file line number Diff line number Diff line change
@@ -312,6 +312,16 @@ def output_filetype: Separate<["--"], "output-filetype">,
def alias_output_filetype: Joined<["--"], "output-filetype=">,
Alias<output_filetype>;

//===----------------------------------------------------------------------===//
/// Target Specific Options
//===----------------------------------------------------------------------===//
def grp_targetopts : OptionGroup<"opts">,
HelpText<"ARCH SPECIFIC OPTIONS">;
def arm_target1_rel : Flag<["--"], "arm-target1-rel">,
Group<grp_targetopts>, HelpText<"Interpret R_ARM_TARGET1 as R_ARM_REL32">;
def arm_target1_abs : Flag<["--"], "arm-target1-abs">,
Group<grp_targetopts>, HelpText<"Interpret R_ARM_TARGET1 as R_ARM_ABS32">;

//===----------------------------------------------------------------------===//
/// Ignored options
//===----------------------------------------------------------------------===//
9 changes: 9 additions & 0 deletions lld/lib/ReaderWriter/ELF/ARM/ARMRelocationHandler.cpp
Original file line number Diff line number Diff line change
@@ -84,6 +84,7 @@ static Reference::Addend readAddend(const uint8_t *location,
switch (kindValue) {
case R_ARM_ABS32:
case R_ARM_REL32:
case R_ARM_TARGET1:
case R_ARM_GOT_BREL:
case R_ARM_BASE_PREL:
case R_ARM_TLS_IE32:
@@ -529,6 +530,14 @@ std::error_code ARMTargetRelocationHandler::applyRelocation(
relocR_ARM_REL32(location, relocVAddress, targetVAddress, addend,
addressesThumb);
break;
case R_ARM_TARGET1:
if (_armLayout.target1Rel())
relocR_ARM_REL32(location, relocVAddress, targetVAddress, addend,
addressesThumb);
else
relocR_ARM_ABS32(location, relocVAddress, targetVAddress, addend,
addressesThumb);
break;
case R_ARM_THM_CALL:
// TODO: consider adding bool variable to disable J1 & J2 for archs
// before ARMv6
2 changes: 2 additions & 0 deletions lld/lib/ReaderWriter/ELF/ARM/ARMTargetHandler.h
Original file line number Diff line number Diff line change
@@ -45,6 +45,8 @@ template <class ELFT> class ARMTargetLayout : public TargetLayout<ELFT> {
llvm_unreachable("TLS segment not found");
}

bool target1Rel() const { return _ctx.armTarget1Rel(); }

private:
// TCB block size of the TLS.
enum { TCB_SIZE = 0x8 };
116 changes: 116 additions & 0 deletions lld/test/elf/ARM/rel-arm-target1.test
Original file line number Diff line number Diff line change
@@ -0,0 +1,116 @@
# Check handling of R_ARM_TARGET1 relocation.
#
# 1. R_ARM_TARGET1 is equal to R_ARM_ABS32
# RUN: yaml2obj -format=elf -docnum 1 %s > %t-abs32.o
# RUN: lld -flavor gnu -target arm -m armelf_linux_eabi -Bstatic \
# RUN: --noinhibit-exec --arm-target1-abs %t-abs32.o -o %t-abs32
# RUN: llvm-objdump -s -t %t-abs32 | FileCheck -check-prefix=CHECK-ABS32 %s
#
# CHECK-ABS32: Contents of section .data:
# CHECK-ABS32-NEXT: 401000 84004000
# CHECK-ABS32: SYMBOL TABLE:
# CHECK-ABS32: 00400074 g F .text {{[0-9a-f]+}} main
# CHECK-ABS32: 00401000 g .data 00000004 data
#
# 2. R_ARM_TARGET1 is equal to R_ARM_REL32
# Check handling of R_ARM_REL32 relocation.
# RUN: yaml2obj -format=elf %s -docnum 2 > %t-rel32.o
# RUN: lld -flavor gnu -target arm -m armelf_linux_eabi -Bstatic \
# RUN: --noinhibit-exec --arm-target1-rel %t-rel32.o -o %t-rel32
# RUN: llvm-objdump -s -t %t-rel32 | FileCheck -check-prefix=CHECK-REL32 %s
#
# CHECK-REL32: Contents of section .text:
# CHECK-REL32-NEXT: 400074 {{[0-9a-f]+}} 880fff00
# CHECK-REL32: SYMBOL TABLE:
# CHECK-REL32: 00400074 g F .text {{[0-9a-f]+}} main
# CHECK-REL32: 00401000 g .bss {{[0-9a-f]+}} _myref

# abs32.o
---
FileHeader:
Class: ELFCLASS32
Data: ELFDATA2LSB
Type: ET_REL
Machine: EM_ARM
Flags: [ EF_ARM_EABI_VER5 ]
Sections:
- Name: .text
Type: SHT_PROGBITS
Flags: [ SHF_ALLOC, SHF_EXECINSTR ]
AddressAlign: 0x0000000000000004
Content: 04B02DE500B08DE20030A0E30300A0E100D04BE204B09DE41EFF2FE1
- Name: .data
Type: SHT_PROGBITS
Flags: [ SHF_WRITE, SHF_ALLOC ]
AddressAlign: 0x0000000000000004
Content: '10000000'
- Name: .rel.data
Type: SHT_REL
Link: .symtab
AddressAlign: 0x0000000000000004
Info: .data
Relocations:
- Offset: 0x0000000000000000
Symbol: main
Type: R_ARM_TARGET1
Addend: 0
- Name: .bss
Type: SHT_NOBITS
Flags: [ SHF_WRITE, SHF_ALLOC ]
AddressAlign: 0x0000000000000001
Content: ''
Symbols:
Global:
- Name: main
Type: STT_FUNC
Section: .text
Size: 0x000000000000001C
- Name: data
Type: STT_OBJECT
Section: .data
Size: 0x0000000000000004
# rel32.o
---
FileHeader:
Class: ELFCLASS32
Data: ELFDATA2LSB
Type: ET_REL
Machine: EM_ARM
Flags: [ EF_ARM_EABI_VER5 ]
Sections:
- Name: .text
Type: SHT_PROGBITS
Flags: [ SHF_ALLOC, SHF_EXECINSTR ]
AddressAlign: 0x0000000000000004
Content: 80B400AF0000FF0000231846BD465DF8047B7047
- Name: .rel.text
Type: SHT_REL
Link: .symtab
AddressAlign: 0x0000000000000004
Info: .text
Relocations:
- Offset: 0x0000000000000004
Symbol: _myref
Type: R_ARM_TARGET1
- Name: .data
Type: SHT_PROGBITS
Flags: [ SHF_WRITE, SHF_ALLOC ]
AddressAlign: 0x0000000000000001
Content: ''
- Name: .bss
Type: SHT_NOBITS
Flags: [ SHF_WRITE, SHF_ALLOC ]
AddressAlign: 0x0000000000000004
Content: ''
Symbols:
Global:
- Name: _myref
Type: STT_OBJECT
Section: .bss
Size: 0x0000000000000004
- Name: main
Type: STT_FUNC
Section: .text
Value: 0x0000000000000001
Size: 0x0000000000000014
...
5 changes: 5 additions & 0 deletions lld/test/elf/options/target-specific-args.test
Original file line number Diff line number Diff line change
@@ -0,0 +1,5 @@
# Test of target specific options
# RUN: lld -flavor gnu -target x86_64 --arm-target1-rel \
# RUN: %p/../Inputs/foo.o.x86-64 --noinhibit-exec -o %t 2>&1 | FileCheck %s

# CHECK: warning: ignoring unsupported ARM/ELF specific argument: --arm-target1-rel

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