1 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
2 // -*- mode: C++ -*-
3 //
4 // Copyright 2022-2024 Google LLC
5 //
6 // Licensed under the Apache License v2.0 with LLVM Exceptions (the
7 // "License"); you may not use this file except in compliance with the
8 // License. You may obtain a copy of the License at
9 //
10 // https://llvm.org/LICENSE.txt
11 //
12 // Unless required by applicable law or agreed to in writing, software
13 // distributed under the License is distributed on an "AS IS" BASIS,
14 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
15 // See the License for the specific language governing permissions and
16 // limitations under the License.
17 //
18 // Author: Aleksei Vetrov
19
20 #include "elf_dwarf_handle.h"
21
22 #include <elfutils/libdw.h>
23 #include <elfutils/libdwfl.h>
24 #include <gelf.h>
25 #include <libelf.h>
26
27 #include <cstddef>
28 #include <functional>
29 #include <sstream>
30 #include <string>
31
32 #include "error.h"
33 #include "hex.h"
34
35 namespace stg {
36
37 namespace {
38
39 const Dwfl_Callbacks kDwflCallbacks = {
40 .find_elf = nullptr,
41 .find_debuginfo = dwfl_standard_find_debuginfo,
42 .section_address = dwfl_offline_section_address,
43 .debuginfo_path = nullptr};
44
45 constexpr int kReturnOk = 0;
46
GetDwflError(const char * caller)47 std::string GetDwflError(const char* caller) {
48 std::ostringstream result;
49 const int dwfl_error = dwfl_errno();
50 const char* errmsg = dwfl_errmsg(dwfl_error);
51 if (errmsg == nullptr) {
52 // There are some cases when DWFL fails to produce an error message.
53 result << caller << " returned error code " << Hex(dwfl_error);
54 } else {
55 result << caller << " returned error: " << errmsg;
56 }
57 return result.str();
58 }
59
CheckOrDwflError(bool condition,const char * caller)60 void CheckOrDwflError(bool condition, const char* caller) {
61 if (!condition) {
62 Die() << GetDwflError(caller);
63 }
64 }
65
66 } // namespace
67
ElfDwarfHandle(const char * module_name,const std::function<Dwfl_Module * ()> & add_module)68 ElfDwarfHandle::ElfDwarfHandle(
69 const char* module_name, const std::function<Dwfl_Module*()>& add_module) {
70 dwfl_ = DwflUniquePtr(dwfl_begin(&kDwflCallbacks));
71 CheckOrDwflError(dwfl_ != nullptr, "dwfl_begin");
72 // Add data to process to dwfl
73 dwfl_module_ = add_module();
74 CheckOrDwflError(dwfl_module_ != nullptr, module_name);
75 // Finish adding files to dwfl and process them
76 CheckOrDwflError(dwfl_report_end(dwfl_.get(), nullptr, nullptr) == kReturnOk,
77 "dwfl_report_end");
78 }
79
ElfDwarfHandle(const std::string & path)80 ElfDwarfHandle::ElfDwarfHandle(const std::string& path)
81 : ElfDwarfHandle("dwfl_report_offline", [&] {
82 return dwfl_report_offline(dwfl_.get(), path.c_str(), path.c_str(), -1);
83 }) {}
84
ElfDwarfHandle(char * data,size_t size)85 ElfDwarfHandle::ElfDwarfHandle(char* data, size_t size)
86 : ElfDwarfHandle("dwfl_report_offline_memory", [&] {
87 return dwfl_report_offline_memory(dwfl_.get(), "<memory>", "<memory>",
88 data, size);
89 }) {}
90
GetElf()91 Elf& ElfDwarfHandle::GetElf() {
92 GElf_Addr loadbase = 0; // output argument for dwfl, unused by us
93 Elf* elf = dwfl_module_getelf(dwfl_module_, &loadbase);
94 CheckOrDwflError(elf != nullptr, "dwfl_module_getelf");
95 return *elf;
96 }
97
GetDwarf()98 Dwarf* ElfDwarfHandle::GetDwarf() {
99 GElf_Addr loadbase = 0; // output argument for dwfl, unused by us
100 Dwarf* dwarf = dwfl_module_getdwarf(dwfl_module_, &loadbase);
101 if (dwarf == nullptr) {
102 Warn() << "No DWARF found: " << GetDwflError("dwfl_module_getdwarf");
103 }
104 return dwarf;
105 }
106
107 } // namespace stg
108