[llvm-objcopy][WebAssembly] Add dump/add/remove-section support

Add support for adding, removing, and dumping wasm sections to objcopy

Differential Revision: https://reviews.llvm.org/D70970

test/tools/llvm-objcopy/wasm/add-section.test

@@ -0,0 +1,83 @@
+## Test --add-section. This test dumps and removes the section first and checks
+## that adding it back doesn't change the result.
+# RUN: yaml2obj %s -o %t
+# RUN: llvm-objcopy --dump-section=producers=%t.sec --remove-section=producers %t %t2
+# RUN: llvm-objcopy --add-section=producers=%t.sec %t2 %t3
+# RUN: obj2yaml %t3 | FileCheck %s
+
+## Check that the producers section has been added back unchanged.
+# CHECK:      Name: producers
+# CHECK-NEXT: Tools:
+# CHECK-NEXT:  - Name:    clang
+# CHECK-NEXT:    Version: 9.0.0
+
+# Check that the section is replaced with new content in one invocation.
+# RUN: echo "123" > %t4
+# RUN: llvm-objcopy --remove-section=foo --add-section=foo=%t4 %t %t5
+# RUN: obj2yaml %t5 | FileCheck %s --check-prefix=REPLACE
+
+# REPLACE: - Type:  CUSTOM
+# REPLACE:   Name:    foo
+# REPLACE:   Payload: 3132330A
+
+--- !WASM
+FileHeader:
+  Version: 0x00000001
+Sections:
+  - Type: TYPE
+    Signatures:
+      - Index: 0
+        ParamTypes:
+          - I32
+        ReturnTypes:
+          - F32
+      - Index: 1
+        ParamTypes:
+          - I32
+          - I64
+        ReturnTypes: []
+  - Type: FUNCTION
+    FunctionTypes:
+      - 0
+      - 1
+  - Type: CODE
+    Relocations:
+      - Type: R_WASM_TABLE_INDEX_SLEB
+        Index: 0
+        Offset: 0x00000000
+      - Type: R_WASM_FUNCTION_INDEX_LEB
+        Index: 1
+        Offset: 0x0000000
+    Functions:
+      - Index: 0
+        Locals:
+         - Type: I32
+           Count: 3
+        Body: 010101010B
+      - Index: 1
+        Locals:
+         - Type:  I32
+           Count: 1
+        Body: 010101010B
+  - Type: CUSTOM
+    Name: linking
+    Version: 2
+    SymbolTable:
+      - Index:    0
+        Kind:     FUNCTION
+        Name:     func1
+        Flags:    [  ]
+        Function: 0
+      - Index:    1
+        Kind:     FUNCTION
+        Name:     func2
+        Flags:    [  ]
+        Function: 1
+  - Type: CUSTOM
+    Name: producers
+    Tools:
+      - Name:   clang
+        Version: 9.0.0
+  - Type: CUSTOM
+    Name: foo
+    Payload: ABC123

test/tools/llvm-objcopy/wasm/dump-section.test

@@ -0,0 +1,38 @@
+## Test the contents of a custom section dumped from a binary.
+# RUN: yaml2obj %s -o %t
+# RUN: llvm-objcopy --dump-section=producers=%t.sec %t
+# RUN: od -t x1 %t.sec | FileCheck %s
+
+# RUN: not llvm-objcopy --dump-section=nonexistent=%t.sec %t 2>&1 | FileCheck --check-prefix=NONEXISTENT %s
+# RUN: not llvm-objcopy --dump-section=producers=%t.dir/bar %t 2>&1 | FileCheck --check-prefix=DIROUT %s
+
+## Raw contents of the producers section.
+# CHECK: 0000000 01 0c 70 72 6f 63 65 73 73 65 64 2d 62 79 01 05
+# CHECK: 0000020 63 6c 61 6e 67 05 39 2e 30 2e 30
+
+# NONEXISTENT: section 'nonexistent' not found
+# DIROUT: error: {{.*}}/bar': {{[nN]}}o such file or directory
+
+## Check that dumping and removing a section works in the same invocation
+# RUN: llvm-objcopy --dump-section=producers=%t.sec --remove-section=producers %t %t2
+# RUN: od -t x1 %t.sec | FileCheck %s
+# RUN: obj2yaml %t2 | FileCheck --check-prefix=REMOVED %s
+
+# REMOVED-NOT: producers
+
+--- !WASM
+FileHeader:
+  Version: 0x00000001
+Sections:
+  - Type: TYPE
+    Signatures:
+      - Index: 0
+        ParamTypes:
+          - I32
+        ReturnTypes:
+          - F32
+  - Type: CUSTOM
+    Name: producers
+    Tools:
+      - Name:   clang
+        Version: 9.0.0

test/tools/llvm-objcopy/wasm/remove-section.test

@@ -0,0 +1,26 @@
+## Test the --remove-section flag.
+# RUN: yaml2obj %s -o %t
+# RUN: llvm-objcopy -R producers %t %t2
+# RUN: obj2yaml %t2 | FileCheck --implicit-check-not=producers %s
+## Check that the producers section has been removed, but not the type section.
+# CHECK: TYPE
+
+## Requests to remove nonexistent sections are silently ignored.
+# RUN: llvm-objcopy --remove-section=nonexistent=%t.sec %t 2&>1 | count 0
+
+--- !WASM
+FileHeader:
+  Version: 0x00000001
+Sections:
+  - Type: TYPE
+    Signatures:
+      - Index: 0
+        ParamTypes:
+          - I32
+        ReturnTypes:
+          - F32
+  - Type: CUSTOM
+    Name: producers
+    Tools:
+      - Name:   clang
+        Version: 9.0.0

tools/llvm-objcopy/CMakeLists.txt

@@ -33,6 +33,7 @@ add_llvm_tool(llvm-objcopy
   MachO/MachOWriter.cpp
   MachO/MachOLayoutBuilder.cpp
   MachO/Object.cpp
+  wasm/Object.cpp
   wasm/Reader.cpp
   wasm/Writer.cpp
   wasm/WasmObjcopy.cpp

tools/llvm-objcopy/wasm/Object.cpp

@@ -0,0 +1,36 @@
+//===- Object.cpp ---------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "Object.h"
+
+#include "llvm/Support/LEB128.h"
+#include "llvm/Support/raw_ostream.h"
+
+namespace llvm {
+namespace objcopy {
+namespace wasm {
+
+using namespace object;
+using namespace llvm::wasm;
+
+void Object::addSectionWithOwnedContents(
+    Section NewSection, std::unique_ptr<MemoryBuffer> &&Content) {
+  Sections.push_back(NewSection);
+  OwnedContents.emplace_back(std::move(Content));
+}
+
+void Object::removeSections(function_ref<bool(const Section &)> ToRemove) {
+  // TODO: remove reloc sections for the removed section, handle symbols, etc.
+  Sections.erase(
+      std::remove_if(std::begin(Sections), std::end(Sections), ToRemove),
+      std::end(Sections));
+}
+
+} // end namespace wasm
+} // end namespace objcopy
+} // end namespace llvm

tools/llvm-objcopy/wasm/Object.h

@@ -12,6 +12,7 @@
 #include "llvm/ADT/ArrayRef.h"
 #include "llvm/ADT/StringRef.h"
 #include "llvm/Object/Wasm.h"
+#include "llvm/Support/MemoryBuffer.h"
 #include <vector>
 
 namespace llvm {
@@ -30,6 +31,13 @@ struct Object {
   llvm::wasm::WasmObjectHeader Header;
   // For now don't discriminate between kinds of sections.
   std::vector<Section> Sections;
+
+  void addSectionWithOwnedContents(Section NewSection,
+                                   std::unique_ptr<MemoryBuffer> &&Content);
+  void removeSections(function_ref<bool(const Section &)> ToRemove);
+
+private:
+  std::vector<std::unique_ptr<MemoryBuffer>> OwnedContents;
 };
 
 } // end namespace wasm

tools/llvm-objcopy/wasm/WasmObjcopy.cpp

@@ -21,7 +21,58 @@ namespace wasm {
 
 using namespace object;
 
+static Error dumpSectionToFile(StringRef SecName, StringRef Filename,
+                               Object &Obj) {
+  for (const Section &Sec : Obj.Sections) {
+    if (Sec.Name == SecName) {
+      ArrayRef<uint8_t> Contents = Sec.Contents;
+      Expected<std::unique_ptr<FileOutputBuffer>> BufferOrErr =
+          FileOutputBuffer::create(Filename, Contents.size());
+      if (!BufferOrErr)
+        return BufferOrErr.takeError();
+      std::unique_ptr<FileOutputBuffer> Buf = std::move(*BufferOrErr);
+      std::copy(Contents.begin(), Contents.end(), Buf->getBufferStart());
+      if (Error E = Buf->commit())
+        return E;
+      return Error::success();
+    }
+  }
+  return createStringError(errc::invalid_argument, "section '%s' not found",
+                           SecName.str().c_str());
+}
 static Error handleArgs(const CopyConfig &Config, Object &Obj) {
+  // Only support AddSection, DumpSection, RemoveSection for now.
+  for (StringRef Flag : Config.DumpSection) {
+    StringRef SecName;
+    StringRef FileName;
+    std::tie(SecName, FileName) = Flag.split("=");
+    if (Error E = dumpSectionToFile(SecName, FileName, Obj))
+      return createFileError(FileName, std::move(E));
+  }
+
+  Obj.removeSections([&Config](const Section &Sec) {
+    if (Config.ToRemove.matches(Sec.Name))
+      return true;
+    return false;
+  });
+
+  for (StringRef Flag : Config.AddSection) {
+    StringRef SecName, FileName;
+    std::tie(SecName, FileName) = Flag.split("=");
+    ErrorOr<std::unique_ptr<MemoryBuffer>> BufOrErr =
+        MemoryBuffer::getFile(FileName);
+    if (!BufOrErr)
+      return createFileError(FileName, errorCodeToError(BufOrErr.getError()));
+    Section Sec;
+    Sec.SectionType = llvm::wasm::WASM_SEC_CUSTOM;
+    Sec.Name = SecName;
+    std::unique_ptr<MemoryBuffer> Buf = std::move(*BufOrErr);
+    Sec.Contents = makeArrayRef<uint8_t>(
+        reinterpret_cast<const uint8_t *>(Buf->getBufferStart()),
+        Buf->getBufferSize());
+    Obj.addSectionWithOwnedContents(Sec, std::move(Buf));
+  }
+
   if (!Config.AddGnuDebugLink.empty() || !Config.BuildIdLinkDir.empty() ||
       Config.BuildIdLinkInput || Config.BuildIdLinkOutput ||
       Config.ExtractPartition || !Config.SplitDWO.empty() ||
@@ -34,12 +85,10 @@ static Error handleArgs(const CopyConfig &Config, Object &Obj) {
       !Config.UnneededSymbolsToRemove.empty() ||
       !Config.SymbolsToWeaken.empty() || !Config.SymbolsToKeepGlobal.empty() ||
       !Config.SectionsToRename.empty() || !Config.SetSectionAlignment.empty() ||
-      !Config.SetSectionFlags.empty() || !Config.SymbolsToRename.empty() ||
-      !Config.ToRemove.empty() || !Config.DumpSection.empty() ||
-      !Config.AddSection.empty()) {
+      !Config.SetSectionFlags.empty() || !Config.SymbolsToRename.empty()) {
     return createStringError(
         llvm::errc::invalid_argument,
-        "no flags are supported yet, only basic copying is allowed");
+        "only add-section, dump-section, and remove-section are supported");
   }
   return Error::success();
 }
@@ -53,7 +102,7 @@ Error executeObjcopyOnBinary(const CopyConfig &Config,
   Object *Obj = ObjOrErr->get();
   assert(Obj && "Unable to deserialize Wasm object");
   if (Error E = handleArgs(Config, *Obj))
-    return createFileError(Config.InputFilename, std::move(E));
+    return E;
   Writer TheWriter(*Obj, Out);
   if (Error E = TheWriter.write())
     return createFileError(Config.OutputFilename, std::move(E));

utils/gn/secondary/llvm/tools/llvm-objcopy/BUILD.gn

@@ -72,6 +72,7 @@ executable("llvm-objcopy") {
     "MachO/MachOWriter.cpp",
     "MachO/Object.cpp",
     "llvm-objcopy.cpp",
+    "wasm/Object.cpp",
     "wasm/Reader.cpp",
     "wasm/WasmObjcopy.cpp",
     "wasm/Writer.cpp",