llvm-objcopy: Implement --extract-partition and --extract-main-partition.

This implements the functionality described in
https://lld.llvm.org/Partitions.html. It works as follows:

- Reads the section headers using the ELF header at file offset 0;
- If extracting a loadable partition:
  - Finds the section containing the required partition ELF header by looking it up in the section table;
  - Reads the ELF and program headers from the section.
- If extracting the main partition:
  - Reads the ELF and program headers from file offset 0.
- Filters the section table according to which sections are in the program headers that it read:
  - If ParentSegment != nullptr or section is not SHF_ALLOC, then it goes in.
  - Sections containing partition ELF headers or program headers are excluded as there are no headers for these in ordinary ELF files.

Differential Revision: https://reviews.llvm.org/D62364

llvm-svn: 362818

1 files changed, 2 insertions, 0 deletions

diff --git a/llvm/tools/llvm-objcopy/CopyConfig.h b/llvm/tools/llvm-objcopy/CopyConfig.h
index 7607d3b34a3..06b3efddb5a 100644
--- a/llvm/tools/llvm-objcopy/CopyConfig.h
+++ b/llvm/tools/llvm-objcopy/CopyConfig.h
@@ -120,6 +120,7 @@ struct CopyConfig {
   StringRef BuildIdLinkDir;
   Optional<StringRef> BuildIdLinkInput;
   Optional<StringRef> BuildIdLinkOutput;
+  Optional<StringRef> ExtractPartition;
   StringRef SplitDWO;
   StringRef SymbolsPrefix;
   StringRef AllocSectionsPrefix;
@@ -155,6 +156,7 @@ struct CopyConfig {
   bool AllowBrokenLinks = false;
   bool DeterministicArchives = true;
   bool ExtractDWO = false;
+  bool ExtractMainPartition = false;
   bool KeepFileSymbols = false;
   bool LocalizeHidden = false;
   bool OnlyKeepDebug = false;