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[ELF] MIPS paired R_MIPS_HI16/LO16 relocations support 

Some MIPS relocations including `R_MIPS_HI16/R_MIPS_LO16` use combined
addends. Such addend is calculated using addends of both paired relocations.
Each `R_MIPS_HI16` relocation is paired with the next `R_MIPS_LO16`
relocation. ABI requires to compute such combined addend in case of REL
relocation record format only.

For details see p. 4-17 at
ftp://www.linux-mips.org/pub/linux/mips/doc/ABI/mipsabi.pdf

This patch implements lookup of the next paired relocation suing new
`InputSectionBase::findPairedRelocLocation` method. The primary
disadvantage of this approach is that we put MIPS specific logic into
the common code. The next disadvantage is that we lookup `R_MIPS_LO16`
for each `R_MIPS_HI16` relocation, while in fact multiple `R_MIPS_HI16`
might be paired with the single `R_MIPS_LO16`. From the other side
this way allows us to keep `MipsTargetInfo` class stateless and implement
later relocation handling in parallel.

This patch does not support `R_MIPS_HI16/R_MIPS_LO16` relocations against
`_gp_disp` symbol. In that case the relocations use a special formula for
the calculation. That will be implemented later.

Differential Revision: http://reviews.llvm.org/D15112

llvm-svn: 254461
This commit is contained in:
Simon Atanasyan 2015-12-01 21:24:45 +00:00
parent b6f28ef2c9
commit 09b3e3685f
6 changed files with 157 additions and 21 deletions
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42
lld/ELF/InputSection.cpp
View File

@ -94,9 +94,38 @@ bool InputSection<ELFT>::classof(const InputSectionBase<ELFT> *S) {
template <class ELFT>
template <bool isRela>
void InputSectionBase<ELFT>::relocate(
uint8_t *Buf, uint8_t *BufEnd,
iterator_range<const Elf_Rel_Impl<ELFT, isRela> *> Rels) {
uint8_t *
InputSectionBase<ELFT>::findMipsPairedReloc(uint8_t *Buf, uint32_t Type,
RelIteratorRange<isRela> Rels) {
// Some MIPS relocations use addend calculated from addend of the relocation
// itself and addend of paired relocation. ABI requires to compute such
// combined addend in case of REL relocation record format only.
// See p. 4-17 at ftp://www.linux-mips.org/pub/linux/mips/doc/ABI/mipsabi.pdf
if (isRela || Config->EMachine != EM_MIPS)
return nullptr;
if (Type == R_MIPS_HI16)
Type = R_MIPS_LO16;
else if (Type == R_MIPS_PCHI16)
Type = R_MIPS_PCLO16;
else if (Type == R_MICROMIPS_HI16)
Type = R_MICROMIPS_LO16;
else
return nullptr;
for (const auto &RI : Rels) {
if (RI.getType(Config->Mips64EL) != Type)
continue;
uintX_t Offset = getOffset(RI.r_offset);
if (Offset == (uintX_t)-1)
return nullptr;
return Buf + Offset;
}
return nullptr;
}
template <class ELFT>
template <bool isRela>
void InputSectionBase<ELFT>::relocate(uint8_t *Buf, uint8_t *BufEnd,
RelIteratorRange<isRela> Rels) {
typedef Elf_Rel_Impl<ELFT, isRela> RelType;
size_t Num = Rels.end() - Rels.begin();
for (size_t I = 0; I < Num; ++I) {
@ -109,6 +138,7 @@ void InputSectionBase<ELFT>::relocate(
uint8_t *BufLoc = Buf + Offset;
uintX_t AddrLoc = OutSec->getVA() + Offset;
auto NextRelocs = llvm::make_range(&RI, Rels.end());
if (Target->isTlsLocalDynamicReloc(Type) &&
!Target->isTlsOptimized(Type, nullptr)) {
@ -123,7 +153,8 @@ void InputSectionBase<ELFT>::relocate(
const Elf_Shdr *SymTab = File->getSymbolTable();
if (SymIndex < SymTab->sh_info) {
uintX_t SymVA = getLocalRelTarget(*File, RI);
Target->relocateOne(BufLoc, BufEnd, Type, AddrLoc, SymVA);
Target->relocateOne(BufLoc, BufEnd, Type, AddrLoc, SymVA,
findMipsPairedReloc(Buf, Type, NextRelocs));
continue;
}
@ -161,7 +192,8 @@ void InputSectionBase<ELFT>::relocate(
continue;
}
Target->relocateOne(BufLoc, BufEnd, Type, AddrLoc,
SymVA + getAddend<ELFT>(RI));
SymVA + getAddend<ELFT>(RI),
findMipsPairedReloc(Buf, Type, NextRelocs));
}
}

13
lld/ELF/InputSection.h
View File

@ -76,9 +76,16 @@ public:
InputSectionBase<ELFT> *getRelocTarget(const Elf_Rela &Rel);
template <bool isRela>
void relocate(uint8_t *Buf, uint8_t *BufEnd,
llvm::iterator_range<
const llvm::object::Elf_Rel_Impl<ELFT, isRela> *> Rels);
using RelIteratorRange =
llvm::iterator_range<const llvm::object::Elf_Rel_Impl<ELFT, isRela> *>;
template <bool isRela>
void relocate(uint8_t *Buf, uint8_t *BufEnd, RelIteratorRange<isRela> Rels);
private:
template <bool isRela>
uint8_t *findMipsPairedReloc(uint8_t *Buf, uint32_t Type,
RelIteratorRange<isRela> Rels);
};
template <class ELFT>

45
lld/ELF/Target.cpp
View File

@ -87,7 +87,7 @@ public:
bool relocNeedsGot(uint32_t Type, const SymbolBody &S) const override;
bool relocNeedsPlt(uint32_t Type, const SymbolBody &S) const override;
void relocateOne(uint8_t *Loc, uint8_t *BufEnd, uint32_t Type, uint64_t P,
uint64_t SA) const override;
uint64_t SA, uint8_t *PairedLoc = nullptr) const override;
};
class X86_64TargetInfo final : public TargetInfo {
@ -106,7 +106,7 @@ public:
bool relocNeedsGot(uint32_t Type, const SymbolBody &S) const override;
bool relocNeedsPlt(uint32_t Type, const SymbolBody &S) const override;
void relocateOne(uint8_t *Loc, uint8_t *BufEnd, uint32_t Type, uint64_t P,
uint64_t SA) const override;
uint64_t SA, uint8_t *PairedLoc = nullptr) const override;
bool isRelRelative(uint32_t Type) const override;
bool isTlsOptimized(unsigned Type, const SymbolBody *S) const override;
unsigned relocateTlsOptimize(uint8_t *Loc, uint8_t *BufEnd, uint32_t Type,
@ -133,7 +133,7 @@ public:
bool relocNeedsGot(uint32_t Type, const SymbolBody &S) const override;
bool relocNeedsPlt(uint32_t Type, const SymbolBody &S) const override;
void relocateOne(uint8_t *Loc, uint8_t *BufEnd, uint32_t Type, uint64_t P,
uint64_t SA) const override;
uint64_t SA, uint8_t *PairedLoc = nullptr) const override;
bool isRelRelative(uint32_t Type) const override;
};
@ -150,7 +150,7 @@ public:
bool relocNeedsGot(uint32_t Type, const SymbolBody &S) const override;
bool relocNeedsPlt(uint32_t Type, const SymbolBody &S) const override;
void relocateOne(uint8_t *Loc, uint8_t *BufEnd, uint32_t Type, uint64_t P,
uint64_t SA) const override;
uint64_t SA, uint8_t *PairedLoc = nullptr) const override;
};
template <class ELFT> class MipsTargetInfo final : public TargetInfo {
@ -166,7 +166,7 @@ public:
bool relocNeedsGot(uint32_t Type, const SymbolBody &S) const override;
bool relocNeedsPlt(uint32_t Type, const SymbolBody &S) const override;
void relocateOne(uint8_t *Loc, uint8_t *BufEnd, uint32_t Type, uint64_t P,
uint64_t SA) const override;
uint64_t SA, uint8_t *PairedLoc = nullptr) const override;
};
} // anonymous namespace
@ -308,7 +308,8 @@ bool X86TargetInfo::relocNeedsPlt(uint32_t Type, const SymbolBody &S) const {
}
void X86TargetInfo::relocateOne(uint8_t *Loc, uint8_t *BufEnd, uint32_t Type,
uint64_t P, uint64_t SA) const {
uint64_t P, uint64_t SA,
uint8_t *PairedLoc) const {
switch (Type) {
case R_386_32:
add32le(Loc, SA);
@ -581,7 +582,8 @@ unsigned X86_64TargetInfo::relocateTlsOptimize(uint8_t *Loc, uint8_t *BufEnd,
}
void X86_64TargetInfo::relocateOne(uint8_t *Loc, uint8_t *BufEnd, uint32_t Type,
uint64_t P, uint64_t SA) const {
uint64_t P, uint64_t SA,
uint8_t *PairedLoc) const {
switch (Type) {
case R_X86_64_32:
checkUInt<32>(SA, Type);
@ -728,7 +730,8 @@ bool PPC64TargetInfo::isRelRelative(uint32_t Type) const {
}
void PPC64TargetInfo::relocateOne(uint8_t *Loc, uint8_t *BufEnd, uint32_t Type,
uint64_t P, uint64_t SA) const {
uint64_t P, uint64_t SA,
uint8_t *PairedLoc) const {
uint64_t TB = getPPC64TocBase();
// For a TOC-relative relocation, adjust the addend and proceed in terms of
@ -933,8 +936,8 @@ static uint64_t getAArch64Page(uint64_t Expr) {
}
void AArch64TargetInfo::relocateOne(uint8_t *Loc, uint8_t *BufEnd,
uint32_t Type, uint64_t P,
uint64_t SA) const {
uint32_t Type, uint64_t P, uint64_t SA,
uint8_t *PairedLoc) const {
switch (Type) {
case R_AARCH64_ABS16:
checkIntUInt<16>(SA, Type);
@ -1046,13 +1049,31 @@ bool MipsTargetInfo<ELFT>::relocNeedsPlt(uint32_t Type,
template <class ELFT>
void MipsTargetInfo<ELFT>::relocateOne(uint8_t *Loc, uint8_t *BufEnd,
uint32_t Type, uint64_t P,
uint64_t SA) const {
uint32_t Type, uint64_t P, uint64_t SA,
uint8_t *PairedLoc) const {
const endianness E = ELFT::TargetEndianness;
switch (Type) {
case R_MIPS_32:
add32<E>(Loc, SA);
break;
case R_MIPS_HI16: {
uint32_t Instr = read32<E>(Loc);
if (PairedLoc) {
uint64_t AHL = ((Instr & 0xffff) << 16) +
llvm::SignExtend64<16>(read32<E>(PairedLoc) & 0xffff);
write32<E>(Loc, (Instr & 0xffff0000) | (((SA + AHL) >> 16) & 0xffff));
} else {
warning("Can't find matching R_MIPS_LO16 relocation for R_MIPS_HI16");
write32<E>(Loc, (Instr & 0xffff0000) | ((SA >> 16) & 0xffff));
}
break;
}
case R_MIPS_LO16: {
uint32_t Instr = read32<E>(Loc);
int64_t AHL = llvm::SignExtend64<16>(Instr & 0xffff);
write32<E>(Loc, (Instr & 0xffff0000) | ((SA + AHL) & 0xffff));
break;
}
case R_MIPS_CALL16:
case R_MIPS_GOT16: {
int64_t V = SA - getMipsGpAddr<ELFT>();

3
lld/ELF/Target.h
View File

@ -57,7 +57,8 @@ public:
virtual bool relocNeedsGot(uint32_t Type, const SymbolBody &S) const = 0;
virtual bool relocNeedsPlt(uint32_t Type, const SymbolBody &S) const = 0;
virtual void relocateOne(uint8_t *Loc, uint8_t *BufEnd, uint32_t Type,
uint64_t P, uint64_t SA) const = 0;
uint64_t P, uint64_t SA,
uint8_t *PairedLoc = nullptr) const = 0;
virtual bool isTlsOptimized(unsigned Type, const SymbolBody *S) const;
virtual unsigned relocateTlsOptimize(uint8_t *Loc, uint8_t *BufEnd,
uint32_t Type, uint64_t P,

22
lld/test/ELF/mips-hilo-hi-only.s Normal file
View File

@ -0,0 +1,22 @@
# Check warning on orphaned R_MIPS_HI16 relocations.
# RUN: llvm-mc -filetype=obj -triple=mips-unknown-linux %s -o %t.o
# RUN: ld.lld %t.o -o %t.exe 2>&1 | FileCheck -check-prefix=WARN %s
# RUN: llvm-objdump -d -t %t.exe | FileCheck %s
# REQUIRES: mips
.text
.globl __start
__start:
lui $t0,%hi(__start+0x10000)
# WARN: Can't find matching R_MIPS_LO16 relocation for R_MIPS_HI16
# CHECK: Disassembly of section .text:
# CHECK-NEXT: __start:
# CHECK-NEXT: 20000: 3c 08 00 02 lui $8, 2
# ^-- %hi(__start) w/o addend
# CHECK: SYMBOL TABLE:
# CHECK: 0020000 .text 00000000 __start

53
lld/test/ELF/mips-hilo.s Normal file
View File

@ -0,0 +1,53 @@
# Check R_MIPS_HI16 / LO16 relocations calculation.
# RUN: llvm-mc -filetype=obj -triple=mips-unknown-linux %s -o %t.o
# RUN: ld.lld %t.o -o %t.exe
# RUN: llvm-objdump -d -t %t.exe | FileCheck %s
# REQUIRES: mips
.text
.globl __start
__start:
lui $t0,%hi(__start)
lui $t1,%hi(g1)
addi $t0,$t0,%lo(__start+4)
addi $t0,$t0,%lo(g1+8)
lui $t0,%hi(l1+0x10000)
lui $t1,%hi(l1+0x20000)
addi $t0,$t0,%lo(l1+(-4))
.data
.type l1,@object
.size l1,4
l1:
.word 0
.globl g1
.type g1,@object
.size g1,4
g1:
.word 0
# CHECK: Disassembly of section .text:
# CHECK-NEXT: __start:
# CHECK-NEXT: 20000: 3c 08 00 02 lui $8, 2
# ^-- %hi(__start+4)
# CHECK-NEXT: 20004: 3c 09 00 03 lui $9, 3
# ^-- %hi(g1+8)
# CHECK-NEXT: 20008: 21 08 00 04 addi $8, $8, 4
# ^-- %lo(__start+4)
# CHECK-NEXT: 2000c: 21 08 00 0c addi $8, $8, 12
# ^-- %lo(g1+8)
# CHECK-NEXT: 20010: 3c 08 00 03 lui $8, 3
# ^-- %hi(l1+0x10000-4)
# CHECK-NEXT: 20014: 3c 09 00 04 lui $9, 4
# ^-- %hi(l1+0x20000-4)
# CHECK-NEXT: 20018: 21 08 ff fc addi $8, $8, -4
# ^-- %lo(l1-4)
# CHECK: SYMBOL TABLE:
# CHECK: 0030000 l .data 00000004 l1
# CHECK: 0020000 .text 00000000 __start
# CHECK: 0030004 g .data 00000004 g1