[llvm-objcopy] Add --prefix-alloc-sections

This patch adds support for --prefix-alloc-sections, which adds a prefix
to every allocated section names.

It adds a prefix after renaming section names by --rename-section as GNU
objcopy does.

Fixes PR41266: https://bugs.llvm.org/show_bug.cgi?id=41266

Differential Revision: https://reviews.llvm.org/D60042

Patch by Seiya Nuta.

llvm-svn: 360233

1 files changed, 57 insertions, 1 deletions

diff --git a/llvm/tools/llvm-objcopy/ELF/ELFObjcopy.cpp b/llvm/tools/llvm-objcopy/ELF/ELFObjcopy.cpp
index 9b21190000e..bed2414559f 100644
--- a/llvm/tools/llvm-objcopy/ELF/ELFObjcopy.cpp
+++ b/llvm/tools/llvm-objcopy/ELF/ELFObjcopy.cpp
@@ -13,6 +13,7 @@
 #include "llvm-objcopy.h"
 
 #include "llvm/ADT/BitmaskEnum.h"
+#include "llvm/ADT/DenseSet.h"
 #include "llvm/ADT/Optional.h"
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/ADT/SmallVector.h"
@@ -580,7 +581,8 @@ static Error handleArgs(const CopyConfig &Config, Object &Obj,
   if (Error E = updateAndRemoveSymbols(Config, Obj))
     return E;
 
-  if (!Config.SectionsToRename.empty()) {
+  if (!Config.SectionsToRename.empty() || !Config.AllocSectionsPrefix.empty()) {
+    DenseSet<SectionBase *> PrefixedSections;
     for (auto &Sec : Obj.sections()) {
       const auto Iter = Config.SectionsToRename.find(Sec.Name);
       if (Iter != Config.SectionsToRename.end()) {
@@ -589,6 +591,60 @@ static Error handleArgs(const CopyConfig &Config, Object &Obj,
         if (SR.NewFlags.hasValue())
           setSectionFlagsAndType(Sec, SR.NewFlags.getValue());
       }
+
+      // Add a prefix to allocated sections and their relocation sections. This
+      // should be done after renaming the section by Config.SectionToRename to
+      // imitate the GNU objcopy behavior.
+      if (!Config.AllocSectionsPrefix.empty()) {
+        if (Sec.Flags & SHF_ALLOC) {
+          Sec.Name = (Config.AllocSectionsPrefix + Sec.Name).str();
+          PrefixedSections.insert(&Sec);
+
+        // Rename relocation sections associated to the allocated sections.
+        // For example, if we rename .text to .prefix.text, we also rename
+        // .rel.text to .rel.prefix.text.
+        //
+        // Dynamic relocation sections (SHT_REL[A] with SHF_ALLOC) are handled
+        // above, e.g., .rela.plt is renamed to .prefix.rela.plt, not
+        // .rela.prefix.plt since GNU objcopy does so.
+        } else if (auto *RelocSec = dyn_cast<RelocationSectionBase>(&Sec)) {
+          auto *TargetSec = RelocSec->getSection();
+          if (TargetSec && (TargetSec->Flags & SHF_ALLOC)) {
+            StringRef prefix;
+            switch (Sec.Type) {
+            case SHT_REL:
+              prefix = ".rel";
+              break;
+            case SHT_RELA:
+              prefix = ".rela";
+              break;
+            default:
+              continue;
+            }
+
+            // If the relocation section comes *after* the target section, we
+            // don't add Config.AllocSectionsPrefix because we've already added
+            // the prefix to TargetSec->Name. Otherwise, if the relocation
+            // section comes *before* the target section, we add the prefix.
+            if (PrefixedSections.count(TargetSec)) {
+              Sec.Name = (prefix + TargetSec->Name).str();
+            } else {
+              const auto Iter = Config.SectionsToRename.find(TargetSec->Name);
+              if (Iter != Config.SectionsToRename.end()) {
+                // Both `--rename-section` and `--prefix-alloc-sections` are
+                // given but the target section is not yet renamed.
+                Sec.Name =
+                    (prefix + Config.AllocSectionsPrefix + Iter->second.NewName)
+                        .str();
+              } else {
+                Sec.Name =
+                    (prefix + Config.AllocSectionsPrefix + TargetSec->Name)
+                        .str();
+              }
+            }
+          }
+        }
+      }
     }
   }