Index: ELF/Config.h =================================================================== --- ELF/Config.h +++ ELF/Config.h @@ -10,6 +10,7 @@ #ifndef LLD_ELF_CONFIG_H #define LLD_ELF_CONFIG_H +#include "llvm/ADT/CachedHashString.h" #include "llvm/ADT/MapVector.h" #include "llvm/ADT/StringRef.h" #include "llvm/Support/ELF.h" @@ -71,6 +72,7 @@ struct Configuration { InputFile *FirstElf = nullptr; uint8_t OSABI = 0; + llvm::DenseMap SymbolOrderingFile; llvm::StringMap SectionStartMap; llvm::StringRef DynamicLinker; llvm::StringRef Entry; Index: ELF/Driver.cpp =================================================================== --- ELF/Driver.cpp +++ ELF/Driver.cpp @@ -577,6 +577,10 @@ if (Optional Buffer = readFile(Arg->getValue())) parseDynamicList(*Buffer); + if (auto *Arg = Args.getLastArg(OPT_symbol_ordering_file)) + if (Optional Buffer = readFile(Arg->getValue())) + parseSymbolOrderingList(*Buffer); + for (auto *Arg : Args.filtered(OPT_export_dynamic_symbol)) Config->DynamicList.push_back(Arg->getValue()); Index: ELF/Options.td =================================================================== --- ELF/Options.td +++ ELF/Options.td @@ -177,6 +177,9 @@ def strip_debug: F<"strip-debug">, HelpText<"Strip debugging information">; +def symbol_ordering_file: S<"symbol-ordering-file">, + HelpText<"Layout sections in the order specified by symbol file">; + def sysroot: J<"sysroot=">, HelpText<"Set the system root">; def target1_rel: F<"target1-rel">, HelpText<"Interpret R_ARM_TARGET1 as R_ARM_REL32">; Index: ELF/OutputSections.h =================================================================== --- ELF/OutputSections.h +++ ELF/OutputSections.h @@ -437,6 +437,7 @@ typedef typename ELFT::uint uintX_t; OutputSection(StringRef Name, uint32_t Type, uintX_t Flags); void addSection(InputSectionBase *C) override; + void sort(std::function *S)> Order); void sortInitFini(); void sortCtorsDtors(); void writeTo(uint8_t *Buf) override; Index: ELF/OutputSections.cpp =================================================================== --- ELF/OutputSections.cpp +++ ELF/OutputSections.cpp @@ -14,6 +14,7 @@ #include "LinkerScript.h" #include "Memory.h" #include "Strings.h" +#include "SymbolListFile.h" #include "SymbolTable.h" #include "Target.h" #include "lld/Core/Parallel.h" @@ -984,26 +985,32 @@ this->Header.sh_size = Off; } -// Sorts input sections by section name suffixes, so that .foo.N comes -// before .foo.M if N < M. Used to sort .{init,fini}_array.N sections. -// We want to keep the original order if the priorities are the same -// because the compiler keeps the original initialization order in a -// translation unit and we need to respect that. -// For more detail, read the section of the GCC's manual about init_priority. -template void OutputSection::sortInitFini() { - // Sort sections by priority. - typedef std::pair *> Pair; +template +void OutputSection::sort( + std::function *S)> Order) { + typedef std::pair *> Pair; auto Comp = [](const Pair &A, const Pair &B) { return A.first < B.first; }; std::vector V; for (InputSection *S : Sections) - V.push_back({getPriority(S->Name), S}); + V.push_back({Order(S), S}); std::stable_sort(V.begin(), V.end(), Comp); Sections.clear(); for (Pair &P : V) Sections.push_back(P.second); } +// Sorts input sections by section name suffixes, so that .foo.N comes +// before .foo.M if N < M. Used to sort .{init,fini}_array.N sections. +// We want to keep the original order if the priorities are the same +// because the compiler keeps the original initialization order in a +// translation unit and we need to respect that. +// For more detail, read the section of the GCC's manual about init_priority. +template void OutputSection::sortInitFini() { + // Sort sections by priority. + sort([](InputSection *S) { return getPriority(S->Name); }); +} + // Returns true if S matches /Filename.?\.o$/. static bool isCrtBeginEnd(StringRef S, StringRef Filename) { if (!S.endswith(".o")) Index: ELF/SymbolListFile.h =================================================================== --- ELF/SymbolListFile.h +++ ELF/SymbolListFile.h @@ -17,6 +17,7 @@ namespace elf { void parseDynamicList(MemoryBufferRef MB); +void parseSymbolOrderingList(MemoryBufferRef MB); } // namespace elf } // namespace lld Index: ELF/SymbolListFile.cpp =================================================================== --- ELF/SymbolListFile.cpp +++ ELF/SymbolListFile.cpp @@ -56,3 +56,24 @@ void elf::parseDynamicList(MemoryBufferRef MB) { DynamicListParser(MB.getBuffer()).run(); } + +// Parse the --symbol-ordering-file argument. File has form: +// symbolName1 +// [...] +// symbolNameN +void elf::parseSymbolOrderingList(MemoryBufferRef MB) { + StringRef List = MB.getBuffer(); + unsigned I = 0; + while (!List.empty()) { + size_t Pos = List.find('\n'); + if (Pos == StringRef::npos) { + Config->SymbolOrderingFile.insert( + {CachedHashStringRef(List.trim()), I++}); + break; + } + + StringRef Sym = List.take_front(Pos + 1).trim(); + Config->SymbolOrderingFile.insert({CachedHashStringRef(Sym), I++}); + List = List.drop_front(Pos + 1).trim(); + } +} Index: ELF/Writer.cpp =================================================================== --- ELF/Writer.cpp +++ ELF/Writer.cpp @@ -633,6 +633,41 @@ reinterpret_cast *>(S)->sortCtorsDtors(); } +// Sort input sections using list provided by --symbol-ordering-file option. +template +static void sortSectionsByOrder(ArrayRef *> V) { + if (Config->SymbolOrderingFile.empty()) + return; + + // Build sections order map from symbols list. + DenseMap *, unsigned> SectionsOrder; + for (elf::ObjectFile *File : Symtab::X->getObjectFiles()) { + for (SymbolBody *Body : File->getSymbols()) { + auto *D = dyn_cast>(Body); + if (!D || !D->Section) + continue; + + StringRef StrTab = File->getStringTable(); + StringRef SymName = + D->isLocal() ? (StrTab.data() + Body->getNameOffset()) : D->getName(); + + auto It = Config->SymbolOrderingFile.find(CachedHashString(SymName)); + if (It == Config->SymbolOrderingFile.end()) + continue; + SectionsOrder.insert({D->Section, It->second}); + } + } + + // Sort input sections by order of symbols specified in + // --symbol-ordering-file. + for (OutputSectionBase *Base : V) + if (OutputSection *Sec = dyn_cast>(Base)) + Sec->sort([&](InputSection *S) { + auto It = SectionsOrder.find(S); + return It == SectionsOrder.end() ? UINT32_MAX : It->second; + }); +} + template void Writer::forEachRelSec( std::function &, const typename ELFT::Shdr &)> @@ -684,6 +719,7 @@ for (InputSectionData *ID : F->getSections()) addInputSec(cast>(ID)); + sortSectionsByOrder(OutputSections); sortInitFini(findSection(".init_array")); sortInitFini(findSection(".fini_array")); sortCtorsDtors(findSection(".ctors")); Index: test/ELF/Inputs/symbol-ordering-file.s =================================================================== --- test/ELF/Inputs/symbol-ordering-file.s +++ test/ELF/Inputs/symbol-ordering-file.s @@ -0,0 +1,3 @@ +.section .text,"ax" +_text2: + .byte 0x55 Index: test/ELF/symbol-ordering-file.s =================================================================== --- test/ELF/symbol-ordering-file.s +++ test/ELF/symbol-ordering-file.s @@ -0,0 +1,37 @@ +# REQUIRES: x86 +# RUN: llvm-mc -filetype=obj -triple=x86_64-pc-linux %s -o %t.o +# RUN: llvm-mc -filetype=obj -triple=x86_64-pc-linux \ +# RUN: %S/Inputs/symbol-ordering-file.s -o %t2.o +# RUN: ld.lld %t.o %t2.o -o %t.out +# RUN: llvm-objdump -s %t.out| FileCheck %s --check-prefix=BEFORE + +# BEFORE: Contents of section .text: +# BEFORE-NEXT: 11000 11223344 55 + +# RUN: echo "_ccc " > %t_order.txt +# RUN: echo "_text2" >> %t_order.txt +# RUN: echo "_aaa" >> %t_order.txt +# RUN: echo " " >> %t_order.txt +# RUN: echo "_text1" >> %t_order.txt +# RUN: echo " _bbb" >> %t_order.txt +# RUN: ld.lld --symbol-ordering-file %t_order.txt %t.o %t2.o -o %t2.out +# RUN: llvm-objdump -s %t2.out| FileCheck %s --check-prefix=AFTER + +# AFTER: Contents of section .text: +# AFTER-NEXT: 11000 44000000 55220000 1133 + +.section .text,"ax" +_text1: + .byte 0x11 + +.section .text.aaa,"ax" +_aaa: + .byte 0x22 + +.section .text.bbb,"ax" +_bbb: + .byte 0x33 + +.section .text.ccc,"ax" +_ccc: + .byte 0x44