From b63d71ef813d48a5d07b92c9d911635b3163facf Mon Sep 17 00:00:00 2001 From: Oliver Stannard Date: Mon, 3 Nov 2014 12:02:51 +0000 Subject: [PATCH] Emit .eh_frame with relocations to functions, rather than sections When LLVM emits DWARF call frame information, it currently creates a local, section-relative symbol in the code section, which is pointed to by a relocation on the .eh_frame section. However, for C++ we emit some functions in section groups, and the SysV ABI has some rules to make it easier to remove these sections (http://www.sco.com/developers/gabi/latest/ch4.sheader.html#section_group_rules): A symbol table entry with STB_LOCAL binding that is defined relative to one of a group's sections, and that is contained in a symbol table section that is not part of the group, must be discarded if the group members are discarded. References to this symbol table entry from outside the group are not allowed. This means that we need to use the function symbol for the relocation, not a temporary symbol. There was a comment in the code claiming that the local symbol was used to avoid creating a relocation, but a relocation must be created anyway as the code and CFI are in different sections. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@221150 91177308-0d34-0410-b5e6-96231b3b80d8 --- include/llvm/MC/MCObjectStreamer.h | 3 ++- include/llvm/MC/MCStreamer.h | 4 ++-- lib/CodeGen/AsmPrinter/ARMException.cpp | 2 +- lib/CodeGen/AsmPrinter/DwarfCFIException.cpp | 2 +- lib/MC/MCAsmStreamer.cpp | 6 ++++-- lib/MC/MCObjectStreamer.cpp | 11 +++++++---- lib/MC/MCParser/AsmParser.cpp | 11 +++++++++-- lib/MC/MCStreamer.cpp | 8 ++++---- test/DebugInfo/AArch64/eh_frame.s | 11 ++++++++++- test/DebugInfo/AArch64/eh_frame_personality.ll | 12 +++++++++++- 10 files changed, 51 insertions(+), 19 deletions(-) diff --git a/include/llvm/MC/MCObjectStreamer.h b/include/llvm/MC/MCObjectStreamer.h index 0866ff5a9fc..71354477b33 100644 --- a/include/llvm/MC/MCObjectStreamer.h +++ b/include/llvm/MC/MCObjectStreamer.h @@ -41,7 +41,8 @@ class MCObjectStreamer : public MCStreamer { SmallVector PendingLabels; virtual void EmitInstToData(const MCInst &Inst, const MCSubtargetInfo&) = 0; - void EmitCFIStartProcImpl(MCDwarfFrameInfo &Frame) override; + void EmitCFIStartProcImpl(MCDwarfFrameInfo &Frame, + MCSymbol *FuncSym) override; void EmitCFIEndProcImpl(MCDwarfFrameInfo &Frame) override; // If any labels have been emitted but not assigned fragments, ensure that diff --git a/include/llvm/MC/MCStreamer.h b/include/llvm/MC/MCStreamer.h index 5cded5cfff9..7303bc9dc6c 100644 --- a/include/llvm/MC/MCStreamer.h +++ b/include/llvm/MC/MCStreamer.h @@ -198,7 +198,7 @@ class MCStreamer { protected: MCStreamer(MCContext &Ctx); - virtual void EmitCFIStartProcImpl(MCDwarfFrameInfo &Frame); + virtual void EmitCFIStartProcImpl(MCDwarfFrameInfo &Frame, MCSymbol *FuncSym); virtual void EmitCFIEndProcImpl(MCDwarfFrameInfo &CurFrame); WinEH::FrameInfo *getCurrentWinFrameInfo() { @@ -661,7 +661,7 @@ public: virtual MCSymbol *getDwarfLineTableSymbol(unsigned CUID); virtual void EmitCFISections(bool EH, bool Debug); - void EmitCFIStartProc(bool IsSimple); + void EmitCFIStartProc(bool IsSimple, MCSymbol *FuncSym); void EmitCFIEndProc(); virtual void EmitCFIDefCfa(int64_t Register, int64_t Offset); virtual void EmitCFIDefCfaOffset(int64_t Offset); diff --git a/lib/CodeGen/AsmPrinter/ARMException.cpp b/lib/CodeGen/AsmPrinter/ARMException.cpp index 251f5effd6b..e79ede9a5ae 100644 --- a/lib/CodeGen/AsmPrinter/ARMException.cpp +++ b/lib/CodeGen/AsmPrinter/ARMException.cpp @@ -66,7 +66,7 @@ void ARMException::beginFunction(const MachineFunction *MF) { "non-EH CFI not yet supported in prologue with EHABI lowering"); if (MoveType == AsmPrinter::CFI_M_Debug) { shouldEmitCFI = true; - Asm->OutStreamer.EmitCFIStartProc(false); + Asm->OutStreamer.EmitCFIStartProc(false, Asm->CurrentFnSym); } } diff --git a/lib/CodeGen/AsmPrinter/DwarfCFIException.cpp b/lib/CodeGen/AsmPrinter/DwarfCFIException.cpp index 74215aa695d..b8051fee9fa 100644 --- a/lib/CodeGen/AsmPrinter/DwarfCFIException.cpp +++ b/lib/CodeGen/AsmPrinter/DwarfCFIException.cpp @@ -102,7 +102,7 @@ void DwarfCFIException::beginFunction(const MachineFunction *MF) { if (!shouldEmitPersonality && !shouldEmitMoves) return; - Asm->OutStreamer.EmitCFIStartProc(/*IsSimple=*/false); + Asm->OutStreamer.EmitCFIStartProc(/*IsSimple=*/false, Asm->CurrentFnSym); // Indicate personality routine, if any. if (!shouldEmitPersonality) diff --git a/lib/MC/MCAsmStreamer.cpp b/lib/MC/MCAsmStreamer.cpp index f60c7fc5041..9e100333e9b 100644 --- a/lib/MC/MCAsmStreamer.cpp +++ b/lib/MC/MCAsmStreamer.cpp @@ -54,7 +54,8 @@ private: unsigned UseDwarfDirectory : 1; void EmitRegisterName(int64_t Register); - void EmitCFIStartProcImpl(MCDwarfFrameInfo &Frame) override; + void EmitCFIStartProcImpl(MCDwarfFrameInfo &Frame, + MCSymbol *FuncSym) override; void EmitCFIEndProcImpl(MCDwarfFrameInfo &Frame) override; public: @@ -925,7 +926,8 @@ void MCAsmStreamer::EmitCFISections(bool EH, bool Debug) { EmitEOL(); } -void MCAsmStreamer::EmitCFIStartProcImpl(MCDwarfFrameInfo &Frame) { +void MCAsmStreamer::EmitCFIStartProcImpl(MCDwarfFrameInfo &Frame, + MCSymbol *FuncSym) { OS << "\t.cfi_startproc"; if (Frame.IsSimple) OS << " simple"; diff --git a/lib/MC/MCObjectStreamer.cpp b/lib/MC/MCObjectStreamer.cpp index 21e68678e75..17371a28508 100644 --- a/lib/MC/MCObjectStreamer.cpp +++ b/lib/MC/MCObjectStreamer.cpp @@ -128,10 +128,13 @@ void MCObjectStreamer::EmitValueImpl(const MCExpr *Value, unsigned Size, DF->getContents().resize(DF->getContents().size() + Size, 0); } -void MCObjectStreamer::EmitCFIStartProcImpl(MCDwarfFrameInfo &Frame) { - // We need to create a local symbol to avoid relocations. - Frame.Begin = getContext().CreateTempSymbol(); - EmitLabel(Frame.Begin); +void MCObjectStreamer::EmitCFIStartProcImpl(MCDwarfFrameInfo &Frame, + MCSymbol *FuncSym) { + if (!FuncSym) { + FuncSym = getContext().CreateTempSymbol(); + EmitLabel(FuncSym); + } + Frame.Begin = FuncSym; } void MCObjectStreamer::EmitCFIEndProcImpl(MCDwarfFrameInfo &Frame) { diff --git a/lib/MC/MCParser/AsmParser.cpp b/lib/MC/MCParser/AsmParser.cpp index de7d96129f1..5a56094a3c7 100644 --- a/lib/MC/MCParser/AsmParser.cpp +++ b/lib/MC/MCParser/AsmParser.cpp @@ -172,6 +172,9 @@ private: /// \brief Are we parsing ms-style inline assembly? bool ParsingInlineAsm; + /// \brief The last symbol we emitted, used for call frame information. + MCSymbol *LastFuncSymbol; + public: AsmParser(SourceMgr &SM, MCContext &Ctx, MCStreamer &Out, const MCAsmInfo &MAI); @@ -491,7 +494,8 @@ AsmParser::AsmParser(SourceMgr &_SM, MCContext &_Ctx, MCStreamer &_Out, : Lexer(_MAI), Ctx(_Ctx), Out(_Out), MAI(_MAI), SrcMgr(_SM), PlatformParser(nullptr), CurBuffer(_SM.getMainFileID()), MacrosEnabledFlag(true), HadError(false), CppHashLineNumber(0), - AssemblerDialect(~0U), IsDarwin(false), ParsingInlineAsm(false) { + AssemblerDialect(~0U), IsDarwin(false), ParsingInlineAsm(false), + LastFuncSymbol(nullptr) { // Save the old handler. SavedDiagHandler = SrcMgr.getDiagHandler(); SavedDiagContext = SrcMgr.getDiagContext(); @@ -1305,6 +1309,9 @@ bool AsmParser::parseStatement(ParseStatementInfo &Info, if (!ParsingInlineAsm) Out.EmitLabel(Sym); + // Record the symbol, so that it can be used for call frame information + LastFuncSymbol = Sym; + // If we are generating dwarf for assembly source files then gather the // info to make a dwarf label entry for this label if needed. if (getContext().getGenDwarfForAssembly()) @@ -2961,7 +2968,7 @@ bool AsmParser::parseDirectiveCFIStartProc() { if (parseIdentifier(Simple) || Simple != "simple") return TokError("unexpected token in .cfi_startproc directive"); - getStreamer().EmitCFIStartProc(!Simple.empty()); + getStreamer().EmitCFIStartProc(!Simple.empty(), LastFuncSymbol); return false; } diff --git a/lib/MC/MCStreamer.cpp b/lib/MC/MCStreamer.cpp index f11ee669b4b..23e816c24bf 100644 --- a/lib/MC/MCStreamer.cpp +++ b/lib/MC/MCStreamer.cpp @@ -211,14 +211,14 @@ void MCStreamer::EmitCFISections(bool EH, bool Debug) { assert(EH || Debug); } -void MCStreamer::EmitCFIStartProc(bool IsSimple) { +void MCStreamer::EmitCFIStartProc(bool IsSimple, MCSymbol *FuncSym) { MCDwarfFrameInfo *CurFrame = getCurrentDwarfFrameInfo(); if (CurFrame && !CurFrame->End) report_fatal_error("Starting a frame before finishing the previous one!"); MCDwarfFrameInfo Frame; Frame.IsSimple = IsSimple; - EmitCFIStartProcImpl(Frame); + EmitCFIStartProcImpl(Frame, FuncSym); const MCAsmInfo* MAI = Context.getAsmInfo(); if (MAI) { @@ -233,8 +233,8 @@ void MCStreamer::EmitCFIStartProc(bool IsSimple) { DwarfFrameInfos.push_back(Frame); } -void MCStreamer::EmitCFIStartProcImpl(MCDwarfFrameInfo &Frame) { -} +void MCStreamer::EmitCFIStartProcImpl(MCDwarfFrameInfo &Frame, + MCSymbol *FuncSym) {} void MCStreamer::EmitCFIEndProc() { EnsureValidDwarfFrame(); diff --git a/test/DebugInfo/AArch64/eh_frame.s b/test/DebugInfo/AArch64/eh_frame.s index 12a58961d71..75b036eac26 100644 --- a/test/DebugInfo/AArch64/eh_frame.s +++ b/test/DebugInfo/AArch64/eh_frame.s @@ -1,5 +1,6 @@ // RUN: llvm-mc -triple aarch64-none-linux-gnu -filetype=obj %s -o %t -// RUN: llvm-objdump -s %t | FileCheck %s +// RUN: llvm-objdump -s %t | FileCheck %s --check-prefix=CHECK +// RUN: llvm-readobj -r %t | FileCheck %s --check-prefix=RELOC .text .globl foo .type foo,@function @@ -46,3 +47,11 @@ foo: // 00000000: PC begin for this FDE is at 00000000 (relocation is applied here) // 04000000: FDE applies up to PC begin+0x14 // 00: Augmentation string length 0 for this FDE + + +// Check the relocations applied to the .eh_frame section. +// These must not contain section-relative relocations to a section which +// is part of a group, as it could be removed. +// RELOC: Section ({{[0-9]+}}) .rela.eh_frame { +// RELOC-NEXT: 0x{{[0-9A-F]+}} R_AARCH64_PREL32 foo 0x0 +// RELOC-NEXT: } diff --git a/test/DebugInfo/AArch64/eh_frame_personality.ll b/test/DebugInfo/AArch64/eh_frame_personality.ll index 51d6bf80b95..0cc53a810e9 100644 --- a/test/DebugInfo/AArch64/eh_frame_personality.ll +++ b/test/DebugInfo/AArch64/eh_frame_personality.ll @@ -1,5 +1,6 @@ ; RUN: llc -verify-machineinstrs -mtriple=aarch64-none-linux-gnu %s -filetype=obj -o %t -; RUN: llvm-objdump -s %t | FileCheck %s +; RUN: llvm-objdump -s %t | FileCheck %s --check-prefix=CHECK +; RUN: llvm-readobj -r %t | FileCheck %s --check-prefix=RELOC declare i32 @__gxx_personality_v0(...) @@ -44,3 +45,12 @@ clean: ; 00: Second part of aug (language-specific data): absolute pointer format used ; 1b: pointer format: pc-relative signed 4-byte. Just like GNU. ; 0c 1f 00: Initial instructions ("DW_CFA_def_cfa x31 ofs 0" in this case) + +; Check the relocations applied to the .eh_frame section. +; These must not contain section-relative relocations to a section which +; is part of a group, as it could be removed. +; RELOC: Section ({{[0-9]+}}) .rela.eh_frame { +; RELOC-NEXT: 0x{{[0-9A-F]+}} R_AARCH64_ABS64 __gxx_personality_v0 0x0 +; RELOC-NEXT: 0x{{[0-9A-F]+}} R_AARCH64_PREL32 foo 0x0 +; RELOC-NEXT: 0x{{[0-9A-F]+}} R_AARCH64_ABS64 .gcc_except_table 0x0 +; RELOC-NEXT: }