[llvm-objcopy] Add --strip-all-gnu and change --strip-all

GNU's --strip-all doesn't strip as aggressively as it could in general.
Currently llvm-objcopy copies the exact behavoir of GNU's --strip-all.
eu-strip is used as a drop in replacement for GNU strip/objcopy in many many
places without issue. eu-strip removes non-allocated sections and keeps
.gnu.warning* sections. Because --strip-all will likely be the most widely
used stripping option we should make --strip-all as aggressive as it can safely
be. Since we have evidence from eu-strip that this is a safe option we should
allow it. For those that might still have an issue afterwards I've added
--strip-all-gnu as an exact drop in replacement for GNU's --strip-all as well.

llvm-svn: 319071

1 files changed, 19 insertions, 3 deletions

diff --git a/llvm/tools/llvm-objcopy/llvm-objcopy.cpp b/llvm/tools/llvm-objcopy/llvm-objcopy.cpp
index ee7785557b3..09553e85202 100644
--- a/llvm/tools/llvm-objcopy/llvm-objcopy.cpp
+++ b/llvm/tools/llvm-objcopy/llvm-objcopy.cpp
@@ -82,8 +82,13 @@ static cl::list<std::string> ToRemove("remove-section",
                                       cl::value_desc("section"));
 static cl::alias ToRemoveA("R", cl::desc("Alias for remove-section"),
                            cl::aliasopt(ToRemove));
-static cl::opt<bool> StripAll("strip-all",
-                              cl::desc("Removes symbol, relocation, and debug information"));
+static cl::opt<bool> StripAll(
+    "strip-all",
+    cl::desc(
+        "Removes non-allocated sections other than .gnu.warning* sections"));
+static cl::opt<bool>
+    StripAllGNU("strip-all-gnu",
+                cl::desc("Removes symbol, relocation, and debug information"));
 static cl::opt<bool> StripDebug("strip-debug",
                                 cl::desc("Removes all debug information"));
 static cl::opt<bool> StripSections("strip-sections",
@@ -178,7 +183,7 @@ void CopyBinary(const ELFObjectFile<ELFT> &ObjFile) {
       return OnlyKeepDWOPred(*Obj, Sec) || RemovePred(Sec);
     };
 
-  if (StripAll)
+  if (StripAllGNU)
     RemovePred = [RemovePred, &Obj](const SectionBase &Sec) {
       if (RemovePred(Sec))
         return true;
@@ -218,6 +223,17 @@ void CopyBinary(const ELFObjectFile<ELFT> &ObjFile) {
       return (Sec.Flags & SHF_ALLOC) == 0;
     };
 
+  if (StripAll)
+    RemovePred = [RemovePred, &Obj](const SectionBase &Sec) {
+      if (RemovePred(Sec))
+        return true;
+      if (&Sec == Obj->getSectionHeaderStrTab())
+        return false;
+      if (Sec.Name.startswith(".gnu.warning"))
+        return false;
+      return (Sec.Flags & SHF_ALLOC) == 0;
+    };
+
   Obj->removeSections(RemovePred);
   Obj->finalize();
   WriteObjectFile(*Obj, OutputFilename.getValue());