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, 9 insertions, 0 deletions

diff --git a/llvm/tools/llvm-objcopy/CopyConfig.cpp b/llvm/tools/llvm-objcopy/CopyConfig.cpp
index b138544..8500ff4 100644
--- a/llvm/tools/llvm-objcopy/CopyConfig.cpp
+++ b/llvm/tools/llvm-objcopy/CopyConfig.cpp
@@ -519,6 +519,8 @@ Expected<DriverConfig> parseObjcopyOptions(ArrayRef<const char *> ArgsArr) {
   Config.SymbolsPrefix = InputArgs.getLastArgValue(OBJCOPY_prefix_symbols);
   Config.AllocSectionsPrefix =
       InputArgs.getLastArgValue(OBJCOPY_prefix_alloc_sections);
+  if (auto Arg = InputArgs.getLastArg(OBJCOPY_extract_partition))
+    Config.ExtractPartition = Arg->getValue();
 
   for (auto Arg : InputArgs.filtered(OBJCOPY_redefine_symbol)) {
     if (!StringRef(Arg->getValue()).contains('='))
@@ -593,6 +595,8 @@ Expected<DriverConfig> parseObjcopyOptions(ArrayRef<const char *> ArgsArr) {
   Config.StripNonAlloc = InputArgs.hasArg(OBJCOPY_strip_non_alloc);
   Config.StripUnneeded = InputArgs.hasArg(OBJCOPY_strip_unneeded);
   Config.ExtractDWO = InputArgs.hasArg(OBJCOPY_extract_dwo);
+  Config.ExtractMainPartition =
+      InputArgs.hasArg(OBJCOPY_extract_main_partition);
   Config.LocalizeHidden = InputArgs.hasArg(OBJCOPY_localize_hidden);
   Config.Weaken = InputArgs.hasArg(OBJCOPY_weaken);
   if (InputArgs.hasArg(OBJCOPY_discard_all, OBJCOPY_discard_locals))
@@ -697,6 +701,11 @@ Expected<DriverConfig> parseObjcopyOptions(ArrayRef<const char *> ArgsArr) {
         errc::invalid_argument,
         "LLVM was not compiled with LLVM_ENABLE_ZLIB: cannot decompress");
 
+  if (Config.ExtractPartition && Config.ExtractMainPartition)
+    return createStringError(errc::invalid_argument,
+                             "cannot specify --extract-partition together with "
+                             "--extract-main-partition");
+
   DC.CopyConfigs.push_back(std::move(Config));
   return std::move(DC);
 }