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.
__jit_debug_register_code()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
readDebugObjectInfo(uint8_t * ArgData,uint64_t ArgSize)71 static std::pair<const char *, uint64_t> readDebugObjectInfo(uint8_t *ArgData,
72 uint64_t ArgSize) {
73 BinaryStreamReader ArgReader(ArrayRef<uint8_t>(ArgData, ArgSize),
74 support::endianness::big);
75 uint64_t Addr, Size;
76 cantFail(ArgReader.readInteger(Addr));
77 cantFail(ArgReader.readInteger(Size));
78
79 return std::make_pair(jitTargetAddressToPointer<const char *>(Addr), Size);
80 }
81
82 extern "C" orc::tpctypes::CWrapperFunctionResult
llvm_orc_registerJITLoaderGDBWrapper(uint8_t * Data,uint64_t Size)83 llvm_orc_registerJITLoaderGDBWrapper(uint8_t *Data, uint64_t Size) {
84 if (Size != sizeof(uint64_t) + sizeof(uint64_t))
85 return orc::tpctypes::WrapperFunctionResult::from(
86 "Invalid arguments to llvm_orc_registerJITLoaderGDBWrapper")
87 .release();
88
89 jit_code_entry *E = new jit_code_entry;
90 std::tie(E->symfile_addr, E->symfile_size) = readDebugObjectInfo(Data, Size);
91 E->prev_entry = nullptr;
92
93 std::lock_guard<std::mutex> Lock(*JITDebugLock);
94
95 // Insert this entry at the head of the list.
96 jit_code_entry *NextEntry = __jit_debug_descriptor.first_entry;
97 E->next_entry = NextEntry;
98 if (NextEntry) {
99 NextEntry->prev_entry = E;
100 }
101
102 __jit_debug_descriptor.first_entry = E;
103 __jit_debug_descriptor.relevant_entry = E;
104
105 // Run into the rendezvous breakpoint.
106 __jit_debug_descriptor.action_flag = JIT_REGISTER_FN;
107 __jit_debug_register_code();
108
109 return orc::tpctypes::WrapperFunctionResult().release();
110 }
111