llvm/lib/ExecutionEngine/Orc/TargetProcess/JITLoaderGDB.cpp

   1 //===- JITLoaderGDB.h - Register objects via GDB JIT interface -*- C++ -*-===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8
   9 #include "llvm/ExecutionEngine/Orc/TargetProcess/JITLoaderGDB.h"
  10
  11 #include "llvm/ExecutionEngine/JITSymbol.h"
  12 #include "llvm/Support/BinaryStreamReader.h"
  13 #include "llvm/Support/ManagedStatic.h"
  14
  15 #include <cstdint>
  16 #include <mutex>
  17 #include <utility>
  18
  19 #define DEBUG_TYPE "orc"
  20
  21 // First version as landed in August 2009
  22 static constexpr uint32_t JitDescriptorVersion = 1;
  23
  24 // Keep in sync with gdb/gdb/jit.h
  25 extern "C" {
  26
  27 typedef enum {
  28   JIT_NOACTION = 0,
  29   JIT_REGISTER_FN,
  30   JIT_UNREGISTER_FN
  31 } jit_actions_t;
  32
  33 struct jit_code_entry {
  34   struct jit_code_entry *next_entry;
  35   struct jit_code_entry *prev_entry;
  36   const char *symfile_addr;
  37   uint64_t symfile_size;
  38 };
  39
  40 struct jit_descriptor {
  41   uint32_t version;
  42   // This should be jit_actions_t, but we want to be specific about the
  43   // bit-width.
  44   uint32_t action_flag;
  45   struct jit_code_entry *relevant_entry;
  46   struct jit_code_entry *first_entry;
  47 };
  48
  49 // We put information about the JITed function in this global, which the
  50 // debugger reads.  Make sure to specify the version statically, because the
  51 // debugger checks the version before we can set it during runtime.
  52 struct jit_descriptor __jit_debug_descriptor = {JitDescriptorVersion, 0,
  53                                                 nullptr, nullptr};
  54
  55 // Debuggers that implement the GDB JIT interface put a special breakpoint in
  56 // this function.
  57 LLVM_ATTRIBUTE_NOINLINE void __jit_debug_register_code() {
  58   // The noinline and the asm prevent calls to this function from being
  59   // optimized out.
  60 #if !defined(_MSC_VER)
  61   asm volatile("" ::: "memory");
  62 #endif
  63 }
  64 }
  65
  66 using namespace llvm;
  67
  68 // Serialize rendezvous with the debugger as well as access to shared data.
  69 ManagedStatic<std::mutex> JITDebugLock;
  70
  71 // Register debug object, return error message or null for success.
  72 static void registerJITLoaderGDBImpl(JITTargetAddress Addr, uint64_t Size) {
  73   jit_code_entry *E = new jit_code_entry;
  74   E->symfile_addr = jitTargetAddressToPointer<const char *>(Addr);
  75   E->symfile_size = Size;
  76   E->prev_entry = nullptr;
  77
  78   std::lock_guard<std::mutex> Lock(*JITDebugLock);
  79
  80   // Insert this entry at the head of the list.
  81   jit_code_entry *NextEntry = __jit_debug_descriptor.first_entry;
  82   E->next_entry = NextEntry;
  83   if (NextEntry) {
  84     NextEntry->prev_entry = E;
  85   }
  86
  87   __jit_debug_descriptor.first_entry = E;
  88   __jit_debug_descriptor.relevant_entry = E;
  89
  90   // Run into the rendezvous breakpoint.
  91   __jit_debug_descriptor.action_flag = JIT_REGISTER_FN;
  92   __jit_debug_register_code();
  93 }
  94
  95 extern "C" orc::shared::detail::CWrapperFunctionResult
  96 llvm_orc_registerJITLoaderGDBWrapper(const char *Data, uint64_t Size) {
  97   using namespace orc::shared;
  98   return WrapperFunction<void(SPSExecutorAddress, uint64_t)>::handle(
  99              Data, Size, registerJITLoaderGDBImpl)
 100       .release();
 101 }