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[ELF][MIPS] Calculate combined addend for R_MIPS_GOT16 against local …
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…symbol

R_MIPS_GOT16 relocation against local symbol requires index of a local
GOT entry which contains page address corresponds to sum of the symbol
address and addend. The addend in that case is calculated using addends
from the R_MIPS_GOT16 and paired R_MIPS_LO16 relocations.

Differential Revision: http://reviews.llvm.org/D17610

llvm-svn: 261930
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@atanasyan
atanasyan committed Feb 25, 2016
1 parent ad9f53e commit 860fbf0
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Showing 2 changed files with 76 additions and 26 deletions.
53 changes: 38 additions & 15 deletions lld/ELF/InputSection.cpp
View file
Expand Up @@ -14,9 +14,12 @@
#include "OutputSections.h"
#include "Target.h"

#include "llvm/Support/Endian.h"

using namespace llvm;
using namespace llvm::ELF;
using namespace llvm::object;
using namespace llvm::support::endian;

using namespace lld;
using namespace lld::elf2;
Expand Down Expand Up @@ -141,6 +144,21 @@ void InputSection<ELFT>::copyRelocations(uint8_t *Buf,
}
}

static uint32_t getMipsPairedRelocType(uint32_t Type) {
if (Config->EMachine != EM_MIPS)
return R_MIPS_NONE;
switch (Type) {
case R_MIPS_HI16:
return R_MIPS_LO16;
case R_MIPS_PCHI16:
return R_MIPS_PCLO16;
case R_MICROMIPS_HI16:
return R_MICROMIPS_LO16;
default:
return R_MIPS_NONE;
}
}

template <class ELFT>
template <bool isRela>
uint8_t *
Expand All @@ -151,15 +169,7 @@ InputSectionBase<ELFT>::findMipsPairedReloc(uint8_t *Buf, uint32_t SymIndex,
// 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
if (isRela || Type == R_MIPS_NONE)
return nullptr;
for (const auto &RI : Rels) {
if (RI.getType(Config->Mips64EL) != Type)
Expand Down Expand Up @@ -225,20 +235,31 @@ void InputSectionBase<ELFT>::relocate(uint8_t *Buf, uint8_t *BufEnd,
uintX_t A = getAddend<ELFT>(RI);
if (!Body) {
uintX_t SymVA = getLocalRelTarget(*File, RI, A);
uint8_t *PairedLoc = nullptr;
if (Config->EMachine == EM_MIPS) {
if (Type == R_MIPS_GPREL16 || Type == R_MIPS_GPREL32)
// We need to adjust SymVA value in case of R_MIPS_GPREL16/32
// relocations because they use the following expression to calculate
// the relocation's result for local symbol: S + A + GP0 - G.
SymVA += File->getMipsGp0();
else if (Type == R_MIPS_GOT16)
else if (Type == R_MIPS_GOT16) {
// R_MIPS_GOT16 relocation against local symbol requires index of
// a local GOT entry which contains page address corresponds
// to the symbol address.
SymVA = Out<ELFT>::Got->getMipsLocalPageAddr(SymVA);
// to sum of the symbol address and addend. The addend in that case
// is calculated using addends from R_MIPS_GOT16 and paired
// R_MIPS_LO16 relocations.
const endianness E = ELFT::TargetEndianness;
uint8_t *LowLoc =
findMipsPairedReloc(Buf, SymIndex, R_MIPS_LO16, NextRelocs);
uint64_t AHL = read32<E>(BufLoc) << 16;
if (LowLoc)
AHL += SignExtend64<16>(read32<E>(LowLoc));
SymVA = Out<ELFT>::Got->getMipsLocalPageAddr(SymVA + AHL);
} else
PairedLoc = findMipsPairedReloc(
Buf, SymIndex, getMipsPairedRelocType(Type), NextRelocs);
}
Target->relocateOne(BufLoc, BufEnd, Type, AddrLoc, SymVA, 0,
findMipsPairedReloc(Buf, SymIndex, Type, NextRelocs));
Target->relocateOne(BufLoc, BufEnd, Type, AddrLoc, SymVA, 0, PairedLoc);
continue;
}

Expand Down Expand Up @@ -284,7 +305,9 @@ void InputSectionBase<ELFT>::relocate(uint8_t *Buf, uint8_t *BufEnd,
}
uintX_t Size = Body->getSize<ELFT>();
Target->relocateOne(BufLoc, BufEnd, Type, AddrLoc, SymVA + A, Size + A,
findMipsPairedReloc(Buf, SymIndex, Type, NextRelocs));
findMipsPairedReloc(Buf, SymIndex,
getMipsPairedRelocType(Type),
NextRelocs));
}
}

Expand Down
49 changes: 38 additions & 11 deletions lld/test/ELF/mips-got16.s
View file
Expand Up @@ -10,17 +10,21 @@
# CHECK: Disassembly of section .text:
# CHECK-NEXT: __start:
# CHECK-NEXT: 10000: 8f 88 80 18 lw $8, -32744($gp)
# CHECK-NEXT: 10004: 21 08 00 1c addi $8, $8, 28
# CHECK-NEXT: 10004: 21 08 00 2c addi $8, $8, 44
# CHECK-NEXT: 10008: 8f 88 80 1c lw $8, -32740($gp)
# CHECK-NEXT: 1000c: 21 08 00 00 addi $8, $8, 0
# CHECK-NEXT: 1000c: 21 08 90 00 addi $8, $8, -28672
# CHECK-NEXT: 10010: 8f 88 80 20 lw $8, -32736($gp)
# CHECK-NEXT: 10014: 21 08 00 04 addi $8, $8, 4
# CHECK-NEXT: 10018: 8f 88 80 24 lw $8, -32732($gp)
# CHECK-NEXT: 10014: 21 08 90 04 addi $8, $8, -28668
# CHECK-NEXT: 10018: 8f 88 80 20 lw $8, -32736($gp)
# CHECK-NEXT: 1001c: 21 08 10 04 addi $8, $8, 4100
# CHECK-NEXT: 10020: 8f 88 80 24 lw $8, -32732($gp)
# CHECK-NEXT: 10024: 21 08 10 08 addi $8, $8, 4104
# CHECK-NEXT: 10028: 8f 88 80 2c lw $8, -32724($gp)
#
# CHECK: SYMBOL TABLE:
# CHECK: 0001001c .text 00000000 $LC0
# CHECK: 00030000 .data 00000000 $LC1
# CHECK: 00030004 .data 00000000 .hidden bar
# CHECK: 0001002c .text 00000000 $LC0
# CHECK: 00039000 .data 00000000 $LC1
# CHECK: 00051008 .data 00000000 .hidden bar
# CHECK: 00000000 *UND* 00000000 foo

# GOT: Relocations [
Expand All @@ -47,22 +51,38 @@
# GOT-NEXT: Address: 0x20008
# GOT-NEXT: Access: -32744
# GOT-NEXT: Initial: 0x10000
# ^-- (0x1002c + 0x8000) & ~0xffff
# GOT-NEXT: }
# GOT-NEXT: Entry {
# GOT-NEXT: Address: 0x2000C
# GOT-NEXT: Access: -32740
# GOT-NEXT: Initial: 0x30000
# GOT-NEXT: Initial: 0x40000
# ^-- (0x39000 + 0x8000) & ~0xffff
# GOT-NEXT: }
# GOT-NEXT: Entry {
# GOT-NEXT: Address: 0x20010
# GOT-NEXT: Access: -32736
# GOT-NEXT: Initial: 0x30004
# GOT-NEXT: Initial: 0x50000
# ^-- (0x39000 + 0x10004 + 0x8000) & ~0xffff
# ^-- (0x39000 + 0x18004 + 0x8000) & ~0xffff
# GOT-NEXT: }
# GOT-NEXT: ]
# GOT-NEXT: Global entries [
# GOT-NEXT: Entry {
# GOT-NEXT: Address: 0x20014
# GOT-NEXT: Access: -32732
# GOT-NEXT: Initial: 0x51008
# ^-- 'bar' address
# GOT-NEXT: }
# GOT-NEXT: Entry {
# GOT-NEXT: Address: 0x20018
# GOT-NEXT: Access: -32728
# GOT-NEXT: Initial: 0x0
# ^-- redundant unused entry
# GOT-NEXT: }
# GOT-NEXT: ]
# GOT-NEXT: Global entries [
# GOT-NEXT: Entry {
# GOT-NEXT: Address: 0x2001C
# GOT-NEXT: Access: -32724
# GOT-NEXT: Initial: 0x0
# GOT-NEXT: Value: 0x0
# GOT-NEXT: Type: None
Expand All @@ -80,15 +100,22 @@ __start:
addi $t0,$t0,%lo($LC0)
lw $t0,%got($LC1)($gp)
addi $t0,$t0,%lo($LC1)
lw $t0,%got($LC1+0x10004)($gp)
addi $t0,$t0,%lo($LC1+0x10004)
lw $t0,%got($LC1+0x18004)($gp)
addi $t0,$t0,%lo($LC1+0x18004)
lw $t0,%got(bar)($gp)
addi $t0,$t0,%lo(bar)
lw $t0,%got(foo)($gp)
$LC0:
nop

.data
.space 0x9000
$LC1:
.word 0
.space 0x18000
.word 0
.global bar
.hidden bar
bar:
Expand Down

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