llvm/lib/MC
Daniel Sanders 134705a273 [mips] Correct the ordering of HI/LO pairs in the relocation table.
Summary:
There seems to have been a misunderstanding as to the meaning of 'offset' in
the rules laid down by our ABI. The previous code believed that 'offset' meant
the offset within the section that the relocation is applied to. However, it
should have meant the offset from the symbol used in the relocation expression.

This patch adds two fields to ELFRelocationEntry and uses them to correct the
order of relocations for MIPS. These fields contain:
* The original symbol before shouldRelocateWithSymbol() is considered. This
  ensures that R_MIPS_GOT16 is able to correctly distinguish between local and
  external symbols, allowing us to tell whether %got() requires a matching
  %lo() or not (local symbols require one, external symbols don't). It also
  prevents confusing cases where the fuzzy matching rules cause things like
  %hi(foo)/%lo(foo+3) and %hi(bar)/%lo(bar+1) to swap their %lo()'s.
* The original offset before shouldRelocateWithSymbol() is considered. The
  existing Addend field is always zero when the object uses in place addends
  (because it's already moved it to the encoding) but MIPS needs to use the
  original offset to ensure that the linker correctly calculates the carry-in
  bit for %hi() and %got().

IAS ensures that unmatchable %hi()/%got() relocations are placed at the end of
the table to ensure that the linker rejects the table (we're unable to report
such errors directly). The alternatives to this risk accidental matching
against inappropriate relocations which may silently compute incorrect values
due to an incorrect carry bit between the %lo() and %hi()/%got().

Reviewers: sdardis

Subscribers: dsanders, sdardis, rafael, llvm-commits

Differential Revision: http://reviews.llvm.org/D19718


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@268733 91177308-0d34-0410-b5e6-96231b3b80d8
2016-05-06 13:49:25 +00:00
..
MCDisassembler One more batch of self-containing headers. 2016-01-27 19:29:56 +00:00
MCParser ARM: put extern __thread stubs in a special section. 2016-04-25 21:12:04 +00:00
CMakeLists.txt Move ObjectYAML code to a new library. 2016-03-01 19:15:06 +00:00
ConstantPools.cpp
ELFObjectWriter.cpp [mips] Correct the ordering of HI/LO pairs in the relocation table. 2016-05-06 13:49:25 +00:00
LLVMBuild.txt
MachObjectWriter.cpp Reapply: "ARM: put correct symbol index on indirect pointers in __thread_ptr."" 2016-04-26 18:29:16 +00:00
MCAsmBackend.cpp MachO: enable .data_region directives everywhere 2016-04-21 23:00:17 +00:00
MCAsmInfo.cpp [MachO] Add MachO alt-entry directive support. 2016-03-15 01:43:05 +00:00
MCAsmInfoCOFF.cpp
MCAsmInfoDarwin.cpp ARM: put extern __thread stubs in a special section. 2016-04-25 21:12:04 +00:00
MCAsmInfoELF.cpp
MCAsmStreamer.cpp [MC] Create unique .pdata sections for every .text section 2016-05-02 23:22:18 +00:00
MCAssembler.cpp [MCAssembler] Allow backend to finalize layout post-relaxation. 2016-04-27 21:26:13 +00:00
MCCodeEmitter.cpp
MCCodeGenInfo.cpp
MCCodeView.cpp [codeview] Fix emission of file changes in inline line tables 2016-02-19 23:55:38 +00:00
MCContext.cpp [MC] Create unique .pdata sections for every .text section 2016-05-02 23:22:18 +00:00
MCDwarf.cpp Read discriminators correctly from object file. 2016-04-28 22:09:37 +00:00
MCELFObjectTargetWriter.cpp
MCELFStreamer.cpp [mips] Use MipsMCExpr instead of MCSymbolRefExpr for all relocations. 2016-05-03 13:35:44 +00:00
MCExpr.cpp [mips] Use MipsMCExpr instead of MCSymbolRefExpr for all relocations. 2016-05-03 13:35:44 +00:00
MCFragment.cpp [NFC] Header cleanup 2016-04-18 09:17:29 +00:00
MCInst.cpp Annotate dump() methods with LLVM_DUMP_METHOD, addressing Richard Smith r259192 post commit comment. 2016-01-29 20:50:44 +00:00
MCInstPrinter.cpp
MCInstrAnalysis.cpp
MCInstrDesc.cpp
MCLabel.cpp Annotate dump() methods with LLVM_DUMP_METHOD, addressing Richard Smith r259192 post commit comment. 2016-01-29 20:50:44 +00:00
MCLinkerOptimizationHint.cpp
MCMachObjectTargetWriter.cpp
MCMachOStreamer.cpp MachO: enable .data_region directives everywhere 2016-04-21 23:00:17 +00:00
MCNullStreamer.cpp
MCObjectFileInfo.cpp Add accidentally deleted "break" 2016-04-25 21:28:52 +00:00
MCObjectStreamer.cpp [MC] Add support for encoding CodeView variable definition ranges 2016-02-05 01:55:49 +00:00
MCObjectWriter.cpp
MCRegisterInfo.cpp [codeview] Bail on a DBG_VALUE register operand with no register 2016-02-16 21:49:26 +00:00
MCSchedule.cpp
MCSection.cpp Annotate dump() methods with LLVM_DUMP_METHOD, addressing Richard Smith r259192 post commit comment. 2016-01-29 20:50:44 +00:00
MCSectionCOFF.cpp
MCSectionELF.cpp
MCSectionMachO.cpp
MCStreamer.cpp [MC] Create unique .pdata sections for every .text section 2016-05-02 23:22:18 +00:00
MCSubtargetInfo.cpp
MCSymbol.cpp Annotate dump() methods with LLVM_DUMP_METHOD, addressing Richard Smith r259192 post commit comment. 2016-01-29 20:50:44 +00:00
MCSymbolELF.cpp
MCTargetOptions.cpp
MCValue.cpp Annotate dump() methods with LLVM_DUMP_METHOD, addressing Richard Smith r259192 post commit comment. 2016-01-29 20:50:44 +00:00
MCWin64EH.cpp [MC] Create unique .pdata sections for every .text section 2016-05-02 23:22:18 +00:00
MCWinEH.cpp [MC] Create unique .pdata sections for every .text section 2016-05-02 23:22:18 +00:00
StringTableBuilder.cpp Make StringTableBuilder to cache hash values. 2016-05-06 00:51:58 +00:00
SubtargetFeature.cpp [NFC] Header cleanup 2016-04-18 09:17:29 +00:00
WinCOFFObjectWriter.cpp [MC] Add support for encoding CodeView variable definition ranges 2016-02-05 01:55:49 +00:00
WinCOFFStreamer.cpp [Object] Make .alt_entry directive parsing MachO specific. 2016-04-11 18:33:45 +00:00