[llvm-objcopy] Add --remove-symbol-prefix

llvm/docs/CommandGuide/llvm-objcopy.rst

@@ -117,6 +117,11 @@ multiple file formats.
  If specified, symbol and section names specified by other switches are treated
  as extended POSIX regular expression patterns.
 
+.. option:: --remove-symbol-prefix <prefix>
+
+Remove ``<prefix>`` from the start of every symbol name. No-op for symbols that do
+not start with ``<prefix>``.
+
 .. option:: --remove-section <section>, -R
 
  Remove the specified section from the output. Can be specified multiple times

llvm/include/llvm/ObjCopy/CommonConfig.h

@@ -218,6 +218,7 @@ struct CommonConfig {
   uint64_t PadTo = 0;
   StringRef SplitDWO;
   StringRef SymbolsPrefix;
+  StringRef SymbolsPrefixRemove;
   StringRef AllocSectionsPrefix;
   DiscardType DiscardMode = DiscardType::None;
 

llvm/lib/ObjCopy/ConfigManager.cpp

@@ -15,6 +15,7 @@ namespace objcopy {
 
 Expected<const COFFConfig &> ConfigManager::getCOFFConfig() const {
   if (!Common.SplitDWO.empty() || !Common.SymbolsPrefix.empty() ||
+      !Common.SymbolsPrefixRemove.empty() ||
       !Common.AllocSectionsPrefix.empty() || !Common.KeepSection.empty() ||
       !Common.SymbolsToGlobalize.empty() || !Common.SymbolsToKeep.empty() ||
       !Common.SymbolsToLocalize.empty() || !Common.SymbolsToWeaken.empty() ||
@@ -33,6 +34,7 @@ Expected<const COFFConfig &> ConfigManager::getCOFFConfig() const {
 
 Expected<const MachOConfig &> ConfigManager::getMachOConfig() const {
   if (!Common.SplitDWO.empty() || !Common.SymbolsPrefix.empty() ||
+      !Common.SymbolsPrefixRemove.empty() ||
       !Common.AllocSectionsPrefix.empty() || !Common.KeepSection.empty() ||
       !Common.SymbolsToGlobalize.empty() || !Common.SymbolsToKeep.empty() ||
       !Common.SymbolsToLocalize.empty() ||
@@ -54,6 +56,7 @@ Expected<const MachOConfig &> ConfigManager::getMachOConfig() const {
 Expected<const WasmConfig &> ConfigManager::getWasmConfig() const {
   if (!Common.AddGnuDebugLink.empty() || Common.ExtractPartition ||
       !Common.SplitDWO.empty() || !Common.SymbolsPrefix.empty() ||
+      !Common.SymbolsPrefixRemove.empty() ||
       !Common.AllocSectionsPrefix.empty() ||
       Common.DiscardMode != DiscardType::None || !Common.SymbolsToAdd.empty() ||
       !Common.SymbolsToGlobalize.empty() || !Common.SymbolsToLocalize.empty() ||
@@ -74,6 +77,7 @@ Expected<const WasmConfig &> ConfigManager::getWasmConfig() const {
 Expected<const XCOFFConfig &> ConfigManager::getXCOFFConfig() const {
   if (!Common.AddGnuDebugLink.empty() || Common.ExtractPartition ||
       !Common.SplitDWO.empty() || !Common.SymbolsPrefix.empty() ||
+      !Common.SymbolsPrefixRemove.empty() ||
       !Common.AllocSectionsPrefix.empty() ||
       Common.DiscardMode != DiscardType::None || !Common.AddSection.empty() ||
       !Common.DumpSection.empty() || !Common.SymbolsToAdd.empty() ||

llvm/lib/ObjCopy/ELF/ELFObjcopy.cpp

@@ -329,6 +329,11 @@ static Error updateAndRemoveSymbols(const CommonConfig &Config,
     if (I != Config.SymbolsToRename.end())
       Sym.Name = std::string(I->getValue());
 
+    if (!Config.SymbolsPrefixRemove.empty() && Sym.Type != STT_SECTION)
+      if (Sym.Name.compare(0, Config.SymbolsPrefixRemove.size(),
+                           Config.SymbolsPrefixRemove) == 0)
+        Sym.Name = Sym.Name.substr(Config.SymbolsPrefixRemove.size());
+
     if (!Config.SymbolsPrefix.empty() && Sym.Type != STT_SECTION)
       Sym.Name = (Config.SymbolsPrefix + Sym.Name).str();
   });

llvm/test/tools/llvm-objcopy/ELF/prefix-symbols-remove.test

@@ -0,0 +1,65 @@
+# RUN: yaml2obj %s -o %t
+# RUN: llvm-objcopy --remove-symbol-prefix __pf_ %t %t2
+# RUN: llvm-readelf --symbols %t2 | FileCheck %s
+
+## Show that an empty string is permitted as the argument to
+## --remove-symbol-prefix.
+# RUN: llvm-objcopy --remove-symbol-prefix= %t2 %t3
+# RUN: cmp %t2 %t3
+
+## When both options are present, llvm-objcopy should remove
+## prefixes first, before adding prefixes.
+# RUN: llvm-objcopy --prefix-symbols=__1_ %t %t4
+# RUN: llvm-objcopy --prefix-symbols=__2_ %t %t5
+# RUN: llvm-objcopy --remove-symbol-prefix=__1_ --prefix-symbols=__2_ %t4 %t6
+# RUN: cmp %t5 %t6
+
+## Show that the last --remove-symbol-prefix option wins.
+# RUN: llvm-objcopy --remove-symbol-prefix=__pf_ --remove-symbol-prefix=__ %t %7
+# RUN: llvm-objcopy --remove-symbol-prefix=__ %t %8
+# RUN: cmp %7 %8
+
+!ELF
+FileHeader:
+  Class:           ELFCLASS64
+  Data:            ELFDATA2LSB
+  Type:            ET_REL
+  Machine:         EM_X86_64
+Sections:
+  - Name:            .text
+    Type:            SHT_PROGBITS
+    Flags:           [ SHF_ALLOC, SHF_EXECINSTR ]
+    Address:         0x1000
+    AddressAlign:    0x0000000000000010
+    Size:            64
+Symbols:
+  - Name:     __pf_foo
+    Type:     STT_SECTION
+    Section:  .text
+  - Name:     __pf_bar
+    Type:     STT_FILE
+    Section:  .text
+  - Name:     foobar
+    Type:     STT_FUNC
+    Section:  .text
+    Binding:  STB_GLOBAL
+  - Name:     foo__pf_bar1
+    Type:     STT_FUNC
+    Section:  .text
+    Binding:  STB_GLOBAL
+  - Name:     __pf_foo__pf_bar2
+    Type:     STT_FUNC
+    Section:  .text
+    Binding:  STB_GLOBAL
+  - Name:     undef
+    Binding:  STB_GLOBAL
+
+# CHECK:      Symbol table '.symtab' contains 7 entries:
+# CHECK-NEXT: Name
+# CHECK-NEXT: {{ $}}
+# CHECK-NEXT: __pf_foo
+# CHECK-NEXT: bar
+# CHECK-NEXT: foobar
+# CHECK-NEXT: foo__pf_bar1
+# CHECK-NEXT: foo__pf_bar2
+# CHECK-NEXT: undef

llvm/tools/llvm-objcopy/ObjcopyOptions.cpp

@@ -731,7 +731,11 @@ objcopy::parseObjcopyOptions(ArrayRef<const char *> RawArgsArr,
         llvm::crc32(arrayRefFromStringRef(Debug->getBuffer()));
   }
   Config.SplitDWO = InputArgs.getLastArgValue(OBJCOPY_split_dwo);
+
   Config.SymbolsPrefix = InputArgs.getLastArgValue(OBJCOPY_prefix_symbols);
+  Config.SymbolsPrefixRemove =
+      InputArgs.getLastArgValue(OBJCOPY_remove_symbol_prefix);
+
   Config.AllocSectionsPrefix =
       InputArgs.getLastArgValue(OBJCOPY_prefix_alloc_sections);
   if (auto Arg = InputArgs.getLastArg(OBJCOPY_extract_partition))

llvm/tools/llvm-objcopy/ObjcopyOpts.td

@@ -203,6 +203,11 @@ defm dump_section
 defm prefix_symbols
     : Eq<"prefix-symbols", "Add <prefix> to the start of every symbol name">,
       MetaVarName<"prefix">;
+defm remove_symbol_prefix
+    : Eq<"remove-symbol-prefix",
+         "Remove <prefix> from the start of every symbol name. No-op for symbols that do not start "
+         "with <prefix>">,
+      MetaVarName<"prefix">;
 
 defm prefix_alloc_sections
     : Eq<"prefix-alloc-sections", "Add <prefix> to the start of every allocated section name">,