[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
diff --git a/lld/ELF/InputSection.cpp b/lld/ELF/InputSection.cpp
index 2b75f8e..6c0bd52 100644
--- a/lld/ELF/InputSection.cpp
+++ b/lld/ELF/InputSection.cpp
@@ -94,9 +94,38 @@
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 @@
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 @@
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 @@
continue;
}
Target->relocateOne(BufLoc, BufEnd, Type, AddrLoc,
- SymVA + getAddend<ELFT>(RI));
+ SymVA + getAddend<ELFT>(RI),
+ findMipsPairedReloc(Buf, Type, NextRelocs));
}
}