[llvm-objcopy] Add --strip-all option to llvm-objcopy

This change adds a slightly less extreme form of stripping. It should
remove any section that starts with ".debug" and should remove any
symbol table or relocations. In general this strips out most of the
stuff you don't need to execute but leaves a number of things around.
This behavior has been designed to be compatible with GNU strip/objcopy
--strip-all so that anywhere you currently use --strip-all you should be
able to use llvm-objcopy as a drop in replacement.

Differential Revision: https://reviews.llvm.org/D39769

llvm-svn: 318092

llvm/test/tools/llvm-objcopy/strip-all.test

@@ -0,0 +1,54 @@
+# RUN: yaml2obj %s > %t
+# RUN: llvm-objcopy --strip-all %t %t2
+# RUN: llvm-readobj -file-headers -sections %t2 | FileCheck %s
+
+!ELF
+FileHeader:
+  Class:           ELFCLASS64
+  Data:            ELFDATA2LSB
+  Type:            ET_REL
+  Machine:         EM_X86_64
+Sections:
+  - Name:            .dynstr
+    Type:            SHT_STRTAB
+    Flags:           [ SHF_ALLOC ]
+  - Name:            .symtab.dyn
+    Type:            SHT_SYMTAB
+    Flags:           [ SHF_ALLOC ]
+    Type:            SHT_NOBITS
+  - Name:            .text
+    Type:            SHT_PROGBITS
+    Flags:           [ SHF_ALLOC, SHF_EXECINSTR ]
+    Size:            4
+  - Name:            .debug_info
+    Type:            SHT_PROGBITS
+    Flags:           [ ]
+    AddressAlign:    0x1
+    Size:            4
+  - Name:            .debug_loc
+    Type:            SHT_PROGBITS
+    Flags:           [ SHF_ALLOC ]
+    AddressAlign:    0x1
+    Size:            4
+  - Name:            .comment
+    Type:            SHT_PROGBITS
+  - Name:            .random_section_name
+    Type:            SHT_PROGBITS
+  - Name:            .debug_not_a_real_debug_section
+    Type:            SHT_PROGBITS
+  - Name:            .rel.text
+    Type:            SHT_REL
+    Info:            .text
+  - Name:            .rela.text
+    Type:            SHT_RELA
+    Info:            .text
+
+# CHECK: SectionHeaderCount: 8
+
+# CHECK:      Name: .dynstr
+# CHECK:      Name: .symtab.dyn
+# CHECK:      Name: .text
+# CHECK:      Name: .debug_loc
+# CHECK:      Name: .comment
+# CHECK:      Name: .random_section_name
+# CHECK:      Name: .shstrtab

llvm/tools/llvm-objcopy/llvm-objcopy.cpp

@@ -81,6 +81,8 @@ static cl::list<std::string> ToRemove("remove-section",
                                       cl::desc("Remove a specific 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> StripSections("strip-sections",
                                    cl::desc("Remove all section headers"));
 static cl::opt<bool>
@@ -170,6 +172,24 @@ void CopyBinary(const ELFObjectFile<ELF64LE> &ObjFile) {
       return OnlyKeepDWOPred(*Obj, Sec) || RemovePred(Sec);
     };
 
+  if (StripAll)
+    RemovePred = [RemovePred, &Obj](const SectionBase &Sec) {
+      if (RemovePred(Sec))
+        return true;
+      if ((Sec.Flags & SHF_ALLOC) != 0)
+        return false;
+      if (&Sec == Obj->getSectionHeaderStrTab())
+        return false;
+      switch(Sec.Type) {
+      case SHT_SYMTAB:
+      case SHT_REL:
+      case SHT_RELA:
+      case SHT_STRTAB:
+        return true;
+      }
+      return Sec.Name.startswith(".debug");
+    };
+
   if (StripSections) {
     RemovePred = [RemovePred](const SectionBase &Sec) {
       return RemovePred(Sec) || (Sec.Flags & SHF_ALLOC) == 0;