[llvm-objcopy] Add --dump-section

Differential Revision: https://reviews.llvm.org/D49979

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@339358 91177308-0d34-0410-b5e6-96231b3b80d8

test/tools/llvm-objcopy/dump-section.test

@@ -1,9 +1,14 @@
 # RUN: yaml2obj %s > %t
 # RUN: llvm-objcopy -O binary -j .text %t %t2
 # RUN: llvm-objcopy -O binary -only-keep .text %t %t3
+# RUN: llvm-objcopy --dump-section .text=%t4 %t %t5
+# RUN: llvm-objcopy --dump-section .foo=%t6 %t %t7
+# RUN: not llvm-objcopy --dump-section .bar=%t8 %t %t9 2>&1 | FileCheck %s --check-prefix=NOBITS
 # RUN: od -t x1 %t2 | FileCheck %s
+# RUN: od -t x1 %t6 | FileCheck %s --check-prefix=NON-ALLOC
 # RUN: wc -c %t2 | FileCheck %s --check-prefix=SIZE
 # RUN: diff %t2 %t3
+# RUN: diff %t4 %t3
 
 !ELF
 FileHeader:
@@ -17,6 +22,13 @@ Sections:
     Flags:           [ SHF_ALLOC, SHF_EXECINSTR ]
     AddressAlign:    0x0000000000001000
     Content:         "DEADBEEF"
+  - Name:            .foo
+    Type:            SHT_PROGBITS
+    Flags:           [ SHF_WRITE ]
+    Content:         "CAFE"
+  - Name:            .bar
+    Type:            SHT_NOBITS
+    Flags:           [ SHF_WRITE ]
 ProgramHeaders:
 - Type: PT_LOAD
   Flags: [ PF_X, PF_R ]
@@ -25,4 +37,8 @@ ProgramHeaders:
 
 #CHECK: 0000000 de ad be ef
 
+#NON-ALLOC: 0000000 ca fe
+
 #SIZE: 4
+
+#NOBITS: Can't dump section ".bar": it has no contents

tools/llvm-objcopy/ObjcopyOpts.td

@@ -102,3 +102,6 @@ def strip_unneeded : Flag<["-", "--"], "strip-unneeded">,
                       HelpText<"Remove all symbols not needed by relocations">;
 def keep_file_symbols : Flag<["-", "--"], "keep-file-symbols">,
                       HelpText<"Do not remove file symbols">;
+defm dump_section : Eq<"dump-section">,
+                   MetaVarName<"section=file">,
+                   HelpText<"Dump contents of section named <section> into file <file>">;

tools/llvm-objcopy/Object.cpp

@@ -853,6 +853,9 @@ template <class ELFT> void ELFBuilder<ELFT>::readSectionHeaders() {
     Sec.Align = Shdr.sh_addralign;
     Sec.EntrySize = Shdr.sh_entsize;
     Sec.Index = Index++;
+    Sec.OriginalData =
+        ArrayRef<uint8_t>(ElfFile.base() + Shdr.sh_offset,
+                          (Shdr.sh_type == SHT_NOBITS) ? 0 : Shdr.sh_size);
   }
 
   // If a section index table exists we'll need to initialize it before we

tools/llvm-objcopy/Object.h

@@ -250,6 +250,7 @@ class SectionBase {
   uint64_t Offset = 0;
   uint64_t Size = 0;
   uint64_t Type = ELF::SHT_NULL;
+  ArrayRef<uint8_t> OriginalData;
 
   virtual ~SectionBase() = default;
 

tools/llvm-objcopy/llvm-objcopy.cpp

@@ -137,6 +137,7 @@ struct CopyConfig {
   std::vector<StringRef> Keep;
   std::vector<StringRef> OnlyKeep;
   std::vector<StringRef> AddSection;
+  std::vector<StringRef> DumpSection;
   std::vector<StringRef> SymbolsToLocalize;
   std::vector<StringRef> SymbolsToGlobalize;
   std::vector<StringRef> SymbolsToWeaken;
@@ -323,6 +324,30 @@ static void SplitDWOToFile(const CopyConfig &Config, const Reader &Reader,
   Writer->write();
 }
 
+static Error dumpSectionToFile(StringRef SecName, StringRef Filename,
+                               Object &Obj) {
+  for (auto &Sec : Obj.sections()) {
+    if (Sec.Name == SecName) {
+      if (Sec.OriginalData.size() == 0)
+        return make_error<StringError>("Can't dump section \"" + SecName +
+                                           "\": it has no contents",
+                                       object_error::parse_failed);
+      Expected<std::unique_ptr<FileOutputBuffer>> BufferOrErr =
+          FileOutputBuffer::create(Filename, Sec.OriginalData.size());
+      if (!BufferOrErr)
+        return BufferOrErr.takeError();
+      std::unique_ptr<FileOutputBuffer> Buf = std::move(*BufferOrErr);
+      std::copy(Sec.OriginalData.begin(), Sec.OriginalData.end(),
+                Buf->getBufferStart());
+      if (Error E = Buf->commit())
+        return E;
+      return Error::success();
+    }
+  }
+  return make_error<StringError>("Section not found",
+                                 object_error::parse_failed);
+}
+
 // This function handles the high level operations of GNU objcopy including
 // handling command line options. It's important to outline certain properties
 // we expect to hold of the command line operations. Any operation that "keeps"
@@ -555,6 +580,16 @@ static void HandleArgs(const CopyConfig &Config, Object &Obj,
     }
   }
 
+  if (!Config.DumpSection.empty()) {
+    for (const auto &Flag : Config.DumpSection) {
+      std::pair<StringRef, StringRef> SecPair = Flag.split("=");
+      StringRef SecName = SecPair.first;
+      StringRef File = SecPair.second;
+      if (Error E = dumpSectionToFile(SecName, File, Obj))
+        reportError(Config.InputFilename, std::move(E));
+    }
+  }
+
   if (!Config.AddGnuDebugLink.empty())
     Obj.addSection<GnuDebugLinkSection>(Config.AddGnuDebugLink);
 }
@@ -711,6 +746,8 @@ static CopyConfig ParseObjcopyOptions(ArrayRef<const char *> ArgsArr) {
     Config.OnlyKeep.push_back(Arg->getValue());
   for (auto Arg : InputArgs.filtered(OBJCOPY_add_section))
     Config.AddSection.push_back(Arg->getValue());
+  for (auto Arg : InputArgs.filtered(OBJCOPY_dump_section))
+    Config.DumpSection.push_back(Arg->getValue());
   Config.StripAll = InputArgs.hasArg(OBJCOPY_strip_all);
   Config.StripAllGNU = InputArgs.hasArg(OBJCOPY_strip_all_gnu);
   Config.StripDebug = InputArgs.hasArg(OBJCOPY_strip_debug);