[llvm-objcopy][ELF] Disable huge section offset

By default, GNU objcopy issues a warning for large offsets in ELF files. To align with this behavior, we introduce an option to define a maximum file offset for a section. This allows us to skip creating excessively large files by specifying a threshold beyond which the file offset will trigger an error.
llvm · Sep 10, 2024 · ef2c3ba · ef2c3ba
1 parent b11a703
commit ef2c3ba
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Showing 7 changed files with 61 additions and 9 deletions.
diff --git a/llvm/include/llvm/ObjCopy/ELF/ELFConfig.h b/llvm/include/llvm/ObjCopy/ELF/ELFConfig.h
@@ -31,6 +31,7 @@ struct ELFConfig {
   bool KeepFileSymbols = false;
   bool LocalizeHidden = false;
   bool VerifyNoteSections = true;
+  std::optional<uint64_t> MaxHugeSectionOffset;
 };
 
 } // namespace objcopy

diff --git a/llvm/lib/ObjCopy/ELF/ELFObjcopy.cpp b/llvm/lib/ObjCopy/ELF/ELFObjcopy.cpp
@@ -176,11 +176,12 @@ static std::unique_ptr<Writer> createELFWriter(const CommonConfig &Config,
 }
 
 static std::unique_ptr<Writer> createWriter(const CommonConfig &Config,
+                                            const ELFConfig &ELFConfig,
                                             Object &Obj, raw_ostream &Out,
                                             ElfType OutputElfType) {
   switch (Config.OutputFormat) {
   case FileFormat::Binary:
-    return std::make_unique<BinaryWriter>(Obj, Out, Config);
+    return std::make_unique<BinaryWriter>(Obj, Out, Config, ELFConfig);
   case FileFormat::IHex:
     return std::make_unique<IHexWriter>(Obj, Out, Config.OutputFilename);
   case FileFormat::SREC:
@@ -926,10 +927,10 @@ static Error handleArgs(const CommonConfig &Config, const ELFConfig &ELFConfig,
   return Error::success();
 }
 
-static Error writeOutput(const CommonConfig &Config, Object &Obj,
-                         raw_ostream &Out, ElfType OutputElfType) {
+static Error writeOutput(const CommonConfig &Config, const ELFConfig &ELFConfig,
+                         Object &Obj, raw_ostream &Out, ElfType OutputElfType) {
   std::unique_ptr<Writer> Writer =
-      createWriter(Config, Obj, Out, OutputElfType);
+      createWriter(Config, ELFConfig, Obj, Out, OutputElfType);
   if (Error E = Writer->finalize())
     return E;
   return Writer->write();
@@ -947,7 +948,7 @@ Error objcopy::elf::executeObjcopyOnIHex(const CommonConfig &Config,
       getOutputElfType(Config.OutputArch.value_or(MachineInfo()));
   if (Error E = handleArgs(Config, ELFConfig, OutputElfType, **Obj))
     return E;
-  return writeOutput(Config, **Obj, Out, OutputElfType);
+  return writeOutput(Config, ELFConfig, **Obj, Out, OutputElfType);
 }
 
 Error objcopy::elf::executeObjcopyOnRawBinary(const CommonConfig &Config,
@@ -965,7 +966,7 @@ Error objcopy::elf::executeObjcopyOnRawBinary(const CommonConfig &Config,
       getOutputElfType(Config.OutputArch.value_or(MachineInfo()));
   if (Error E = handleArgs(Config, ELFConfig, OutputElfType, **Obj))
     return E;
-  return writeOutput(Config, **Obj, Out, OutputElfType);
+  return writeOutput(Config, ELFConfig, **Obj, Out, OutputElfType);
 }
 
 Error objcopy::elf::executeObjcopyOnBinary(const CommonConfig &Config,
@@ -985,7 +986,7 @@ Error objcopy::elf::executeObjcopyOnBinary(const CommonConfig &Config,
   if (Error E = handleArgs(Config, ELFConfig, OutputElfType, **Obj))
     return createFileError(Config.InputFilename, std::move(E));
 
-  if (Error E = writeOutput(Config, **Obj, Out, OutputElfType))
+  if (Error E = writeOutput(Config, ELFConfig, **Obj, Out, OutputElfType))
     return createFileError(Config.InputFilename, std::move(E));
 
   return Error::success();

diff --git a/llvm/lib/ObjCopy/ELF/ELFObject.cpp b/llvm/lib/ObjCopy/ELF/ELFObject.cpp
@@ -2744,6 +2744,13 @@ Error BinaryWriter::finalize() {
     if (Sec.Type != SHT_NOBITS && Sec.Size > 0) {
       Sec.Offset = Sec.Addr - MinAddr;
       TotalSize = std::max(TotalSize, Sec.Offset + Sec.Size);
+
+      if (MaxHugeSectionOffset) {
+        if (Sec.Offset > *MaxHugeSectionOffset)
+          return createStringError(errc::file_too_large,
+                                   "writing section " + Sec.Name +
+                                       " at huge file offset");
+      }
     }
 
   Buf = WritableMemoryBuffer::getNewMemBuffer(TotalSize);

diff --git a/llvm/lib/ObjCopy/ELF/ELFObject.h b/llvm/lib/ObjCopy/ELF/ELFObject.h
@@ -15,6 +15,7 @@
 #include "llvm/BinaryFormat/ELF.h"
 #include "llvm/MC/StringTableBuilder.h"
 #include "llvm/ObjCopy/CommonConfig.h"
+#include "llvm/ObjCopy/ELF/ELFConfig.h"
 #include "llvm/Object/ELFObjectFile.h"
 #include "llvm/Support/Errc.h"
 #include "llvm/Support/FileOutputBuffer.h"
@@ -366,12 +367,16 @@ class BinaryWriter : public Writer {
 
   uint64_t TotalSize = 0;
 
+  std::optional<uint64_t> MaxHugeSectionOffset;
+
 public:
   ~BinaryWriter() {}
   Error finalize() override;
   Error write() override;
-  BinaryWriter(Object &Obj, raw_ostream &Out, const CommonConfig &Config)
-      : Writer(Obj, Out), GapFill(Config.GapFill), PadTo(Config.PadTo) {}
+  BinaryWriter(Object &Obj, raw_ostream &Out, const CommonConfig &Config,
+               const ELFConfig &ELFConfig)
+      : Writer(Obj, Out), GapFill(Config.GapFill), PadTo(Config.PadTo),
+        MaxHugeSectionOffset(ELFConfig.MaxHugeSectionOffset) {}
 };
 
 // A base class for writing ascii hex formats such as srec and ihex.

diff --git a/llvm/test/tools/llvm-objcopy/ELF/disable-huge-section-offset.yaml b/llvm/test/tools/llvm-objcopy/ELF/disable-huge-section-offset.yaml
@@ -0,0 +1,27 @@
+# RUN: yaml2obj %s --docnum=1 -o %t
+# RUN: not llvm-objcopy -O binary %t %t2 --set-max-huge-section-offset=2000000000 2>&1 | FileCheck %s
+
+# CHECK: writing section .high_addr at huge file offset
+
+--- !ELF
+FileHeader:
+  Class:           ELFCLASS32
+  Data:            ELFDATA2LSB
+  Type:            ET_EXEC
+  Machine:         EM_MIPS
+Sections:
+  - Name:            .text
+    Type:            SHT_PROGBITS
+    Flags:           [ SHF_ALLOC, SHF_EXECINSTR ]
+    Address:         0x1000
+    Content:         "00112233445566778899AABBCCDDEEFF"
+  - Name:            .data
+    Type:            SHT_PROGBITS
+    Flags:           [ SHF_ALLOC, SHF_WRITE ]
+    Address:         0x2000
+    Content:         "112233445566778899AABBCCDDEEFF00"
+  - Name:            .high_addr
+    Type:            SHT_PROGBITS
+    Flags:           [ SHF_ALLOC, SHF_WRITE ]
+    Address:         0x80001000
+    Content:         "2233445566778899AABBCCDDEEFF0011"
diff --git a/llvm/tools/llvm-objcopy/ObjcopyOptions.cpp b/llvm/tools/llvm-objcopy/ObjcopyOptions.cpp
@@ -1054,6 +1054,11 @@ objcopy::parseObjcopyOptions(ArrayRef<const char *> RawArgsArr,
   Config.ExtractMainPartition =
       InputArgs.hasArg(OBJCOPY_extract_main_partition);
   ELFConfig.LocalizeHidden = InputArgs.hasArg(OBJCOPY_localize_hidden);
+
+  if (auto *Arg = InputArgs.getLastArg(OBJCOPY_set_max_huge_section_offset)) {
+    ELFConfig.MaxHugeSectionOffset = std::stoull(Arg->getValue());
+  }
+
   Config.Weaken = InputArgs.hasArg(OBJCOPY_weaken);
   if (auto *Arg =
           InputArgs.getLastArg(OBJCOPY_discard_all, OBJCOPY_discard_locals)) {

diff --git a/llvm/tools/llvm-objcopy/ObjcopyOpts.td b/llvm/tools/llvm-objcopy/ObjcopyOpts.td
@@ -146,6 +146,12 @@ def extract_main_partition
     : Flag<["--"], "extract-main-partition">,
       HelpText<"Extract main partition from the input file">;
 
+defm set_max_huge_section_offset
+    : Eq<"set-max-huge-section-offset",
+         "Emit an error if input section has a file offset greater than the "
+         "specified `offset`">,
+      MetaVarName<"offset">;
+
 def localize_hidden
     : Flag<["--"], "localize-hidden">,
       HelpText<