add minimal support for aarch64 (#507)

Summary:
Pull Request resolved: #507

OI is currently completely incompatible with anything except `x86_64`. Changing that generally is a big effort, but `oilgen` should work on other architectures. Begin adding some support for `aarch64` architecture.

This change sets up a file structure for architecture support. It pulls the 2 functions needed to make `Descs.{h,cpp}` architecture agnostic into architecture specific files for `x86_64` and `aarch64`. This enables `oilgen` (the binary) to build. At this stage `oilgen` is unable to generate working code for `aarch64`, but at least this is a step in the right direction.

Differential Revision: D61661524

Author: JakeHillion

cmake/StandardProjectSettings.cmake

@@ -16,6 +16,8 @@ endif()
 
 # Generate compile_commands.json to make it easier to work with clang based tools
 set(CMAKE_EXPORT_COMPILE_COMMANDS ON)
+# Include implicit directories in the compile commands file
+set(CMAKE_CXX_STANDARD_INCLUDE_DIRECTORIES ${CMAKE_CXX_IMPLICIT_INCLUDE_DIRECTORIES})
 
 option(ENABLE_IPO "Enable Interprocedural Optimization, aka Link Time Optimization (LTO)" OFF)
 

oi/CMakeLists.txt

@@ -12,6 +12,8 @@ target_link_libraries(drgn_utils
 add_library(symbol_service
   Descs.cpp
   SymbolService.cpp
+  arch/aarch64.cpp
+  arch/x86_64.cpp
 )
 target_link_libraries(symbol_service
   drgn_utils

oi/Descs.cpp

@@ -38,18 +38,16 @@ std::ostream& operator<<(std::ostream& os, const FuncDesc::Range& r) {
  * location?).
  */
 std::optional<uintptr_t> FuncDesc::Arg::findAddress(
-    struct user_regs_struct* regs, uintptr_t pc) const {
-  auto prevRip = std::exchange(regs->rip, pc);
-  BOOST_SCOPE_EXIT_ALL(&) {
-    regs->rip = prevRip;
-  };
+    const user_regs_struct* regs, uintptr_t pc) const {
+  user_regs_struct modifiedRegs = *regs;
+  oi::detail::arch::setProgramCounter(modifiedRegs, pc);
 
   struct drgn_object object {};
   BOOST_SCOPE_EXIT_ALL(&) {
     drgn_object_deinit(&object);
   };
 
-  if (auto* err = drgn_object_locate(&locator, regs, &object)) {
+  if (auto* err = drgn_object_locate(&locator, &modifiedRegs, &object)) {
     LOG(ERROR) << "Error while finding address of argument: " << err->message;
     drgn_error_destroy(err);
     return std::nullopt;

oi/Descs.h

@@ -20,6 +20,8 @@
 #include <string>
 #include <vector>
 
+#include "oi/arch/Arch.h"
+
 extern "C" {
 #include <drgn.h>
 }
@@ -103,7 +105,7 @@ struct FuncDesc {
      * can be found at the given pc (what about if we don't have this
      * location?).
      */
-    virtual std::optional<uintptr_t> findAddress(struct user_regs_struct* regs,
+    virtual std::optional<uintptr_t> findAddress(const user_regs_struct* regs,
                                                  uintptr_t pc) const = 0;
   };
 
@@ -114,16 +116,16 @@ struct FuncDesc {
       drgn_object_locator_deinit(&locator);
     }
 
-    std::optional<uintptr_t> findAddress(struct user_regs_struct* regs,
+    std::optional<uintptr_t> findAddress(const user_regs_struct* regs,
                                          uintptr_t pc) const final;
   };
 
   struct Retval final : virtual TargetObject {
     ~Retval() final = default;
 
-    std::optional<uintptr_t> findAddress(struct user_regs_struct* regs,
+    std::optional<uintptr_t> findAddress(const user_regs_struct* regs,
                                          uintptr_t /* pc */) const final {
-      return regs->rax;
+      return oi::detail::arch::getReturnValueAddress(*regs);
     }
   };
 };

oi/OICompiler.cpp

@@ -88,8 +88,9 @@ static struct LLVMInitializer {
     llvm::InitializeNativeTargetAsmPrinter();
     llvm::InitializeNativeTargetDisassembler();
 
+    std::string triple = llvm::sys::getProcessTriple();
     disassemblerContext = LLVMCreateDisasm(
-        "x86_64-pc-linux", nullptr, 0, nullptr, symbolLookupCallback);
+        triple.c_str(), nullptr, 0, nullptr, symbolLookupCallback);
     if (!disassemblerContext) {
       throw std::runtime_error("Failed to initialize disassemblerContext");
     }

oi/arch/Arch.h

@@ -0,0 +1,29 @@
+/*
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+#pragma once
+
+#include <cstdint>
+#include <optional>
+
+struct user_regs_struct;
+
+namespace oi::detail::arch {
+
+void setProgramCounter(user_regs_struct& regs, uintptr_t pc);
+
+std::optional<uintptr_t> getReturnValueAddress(const user_regs_struct&);
+
+}  // namespace oi::detail::arch

oi/arch/aarch64.cpp

@@ -0,0 +1,36 @@
+/*
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+#ifdef __aarch64__
+
+extern "C" {
+#include <sys/user.h>
+}
+
+#include "Arch.h"
+
+namespace oi::detail::arch {
+
+std::optional<uintptr_t> getReturnValueAddress(const user_regs_struct& regs) {
+  return regs.regs[0];
+}
+
+void setProgramCounter(user_regs_struct& regs, uintptr_t pc) {
+  regs.pc = pc;
+}
+
+}  // namespace oi::detail::arch
+
+#endif

oi/arch/x86_64.cpp

@@ -0,0 +1,36 @@
+/*
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+#ifdef __x86_64__
+
+extern "C" {
+#include <sys/user.h>
+}
+
+#include "Arch.h"
+
+namespace oi::detail::arch {
+
+std::optional<uintptr_t> getReturnValueAddress(const user_regs_struct& regs) {
+  return regs.rax;
+}
+
+void setProgramCounter(user_regs_struct& regs, uintptr_t pc) {
+  regs.rip = pc;
+}
+
+}  // namespace oi::detail::arch
+
+#endif