llvm/lib/ObjCopy/wasm/WasmObjcopy.cpp

   1 //===- WasmObjcopy.cpp ----------------------------------------------------===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8
   9 #include "llvm/ObjCopy/wasm/WasmObjcopy.h"
  10 #include "WasmObject.h"
  11 #include "WasmReader.h"
  12 #include "WasmWriter.h"
  13 #include "llvm/ObjCopy/CommonConfig.h"
  14 #include "llvm/Support/Errc.h"
  15 #include "llvm/Support/FileOutputBuffer.h"
  16
  17 namespace llvm {
  18 namespace objcopy {
  19 namespace wasm {
  20
  21 using namespace object;
  22 using SectionPred = std::function<bool(const Section &Sec)>;
  23
  24 static bool isDebugSection(const Section &Sec) {
  25   return Sec.Name.starts_with(".debug") || Sec.Name.starts_with("reloc..debug");
  26 }
  27
  28 static bool isLinkerSection(const Section &Sec) {
  29   return Sec.Name.starts_with("reloc.") || Sec.Name == "linking";
  30 }
  31
  32 static bool isNameSection(const Section &Sec) { return Sec.Name == "name"; }
  33
  34 // Sections which are known to be "comments" or informational and do not affect
  35 // program semantics.
  36 static bool isCommentSection(const Section &Sec) {
  37   return Sec.Name == "producers";
  38 }
  39
  40 static Error dumpSectionToFile(StringRef SecName, StringRef Filename,
  41                                Object &Obj) {
  42   for (const Section &Sec : Obj.Sections) {
  43     if (Sec.Name == SecName) {
  44       ArrayRef<uint8_t> Contents = Sec.Contents;
  45       Expected<std::unique_ptr<FileOutputBuffer>> BufferOrErr =
  46           FileOutputBuffer::create(Filename, Contents.size());
  47       if (!BufferOrErr)
  48         return BufferOrErr.takeError();
  49       std::unique_ptr<FileOutputBuffer> Buf = std::move(*BufferOrErr);
  50       std::copy(Contents.begin(), Contents.end(), Buf->getBufferStart());
  51       if (Error E = Buf->commit())
  52         return E;
  53       return Error::success();
  54     }
  55   }
  56   return createStringError(errc::invalid_argument, "section '%s' not found",
  57                            SecName.str().c_str());
  58 }
  59
  60 static void removeSections(const CommonConfig &Config, Object &Obj) {
  61   SectionPred RemovePred = [](const Section &) { return false; };
  62
  63   // Explicitly-requested sections.
  64   if (!Config.ToRemove.empty()) {
  65     RemovePred = [&Config](const Section &Sec) {
  66       return Config.ToRemove.matches(Sec.Name);
  67     };
  68   }
  69
  70   if (Config.StripDebug) {
  71     RemovePred = [RemovePred](const Section &Sec) {
  72       return RemovePred(Sec) || isDebugSection(Sec);
  73     };
  74   }
  75
  76   if (Config.StripAll) {
  77     RemovePred = [RemovePred](const Section &Sec) {
  78       return RemovePred(Sec) || isDebugSection(Sec) || isLinkerSection(Sec) ||
  79              isNameSection(Sec) || isCommentSection(Sec);
  80     };
  81   }
  82
  83   if (Config.OnlyKeepDebug) {
  84     RemovePred = [&Config](const Section &Sec) {
  85       // Keep debug sections, unless explicitly requested to remove.
  86       // Remove everything else, including known sections.
  87       return Config.ToRemove.matches(Sec.Name) || !isDebugSection(Sec);
  88     };
  89   }
  90
  91   if (!Config.OnlySection.empty()) {
  92     RemovePred = [&Config](const Section &Sec) {
  93       // Explicitly keep these sections regardless of previous removes.
  94       // Remove everything else, inluding known sections.
  95       return !Config.OnlySection.matches(Sec.Name);
  96     };
  97   }
  98
  99   if (!Config.KeepSection.empty()) {
 100     RemovePred = [&Config, RemovePred](const Section &Sec) {
 101       // Explicitly keep these sections regardless of previous removes.
 102       if (Config.KeepSection.matches(Sec.Name))
 103         return false;
 104       // Otherwise defer to RemovePred.
 105       return RemovePred(Sec);
 106     };
 107   }
 108
 109   Obj.removeSections(RemovePred);
 110 }
 111
 112 static Error handleArgs(const CommonConfig &Config, Object &Obj) {
 113   // Only support AddSection, DumpSection, RemoveSection for now.
 114   for (StringRef Flag : Config.DumpSection) {
 115     StringRef SecName;
 116     StringRef FileName;
 117     std::tie(SecName, FileName) = Flag.split("=");
 118     if (Error E = dumpSectionToFile(SecName, FileName, Obj))
 119       return createFileError(FileName, std::move(E));
 120   }
 121
 122   removeSections(Config, Obj);
 123
 124   for (const NewSectionInfo &NewSection : Config.AddSection) {
 125     Section Sec;
 126     Sec.SectionType = llvm::wasm::WASM_SEC_CUSTOM;
 127     Sec.Name = NewSection.SectionName;
 128
 129     llvm::StringRef InputData =
 130         llvm::StringRef(NewSection.SectionData->getBufferStart(),
 131                         NewSection.SectionData->getBufferSize());
 132     std::unique_ptr<MemoryBuffer> BufferCopy = MemoryBuffer::getMemBufferCopy(
 133         InputData, NewSection.SectionData->getBufferIdentifier());
 134     Sec.Contents = ArrayRef<uint8_t>(
 135         reinterpret_cast<const uint8_t *>(BufferCopy->getBufferStart()),
 136         BufferCopy->getBufferSize());
 137
 138     Obj.addSectionWithOwnedContents(Sec, std::move(BufferCopy));
 139   }
 140
 141   return Error::success();
 142 }
 143
 144 Error executeObjcopyOnBinary(const CommonConfig &Config, const WasmConfig &,
 145                              object::WasmObjectFile &In, raw_ostream &Out) {
 146   Reader TheReader(In);
 147   Expected<std::unique_ptr<Object>> ObjOrErr = TheReader.create();
 148   if (!ObjOrErr)
 149     return createFileError(Config.InputFilename, ObjOrErr.takeError());
 150   Object *Obj = ObjOrErr->get();
 151   assert(Obj && "Unable to deserialize Wasm object");
 152   if (Error E = handleArgs(Config, *Obj))
 153     return E;
 154   Writer TheWriter(*Obj, Out);
 155   if (Error E = TheWriter.write())
 156     return createFileError(Config.OutputFilename, std::move(E));
 157   return Error::success();
 158 }
 159
 160 } // end namespace wasm
 161 } // end namespace objcopy
 162 } // end namespace llvm