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 }
102