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Serenity Operating System
1/*
2 * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions are met:
7 *
8 * 1. Redistributions of source code must retain the above copyright notice, this
9 * list of conditions and the following disclaimer.
10 *
11 * 2. Redistributions in binary form must reproduce the above copyright notice,
12 * this list of conditions and the following disclaimer in the documentation
13 * and/or other materials provided with the distribution.
14 *
15 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
16 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
17 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
18 * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
19 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
20 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
21 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
22 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
23 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
24 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
25 */
26
27#include <assert.h>
28#include <dlfcn.h>
29#include <fcntl.h>
30#include <mman.h>
31#include <stdio.h>
32#include <stdlib.h>
33#include <sys/stat.h>
34
35#include <AK/FileSystemPath.h>
36#include <AK/HashMap.h>
37#include <AK/RefPtr.h>
38#include <AK/ScopeGuard.h>
39#include <AK/String.h>
40#include <AK/StringBuilder.h>
41#include <LibELF/ELFDynamicLoader.h>
42
43// NOTE: The string here should never include a trailing newline (according to POSIX)
44String g_dlerror_msg;
45
46HashMap<String, RefPtr<ELFDynamicLoader>> g_elf_objects;
47
48extern "C" {
49
50int dlclose(void*)
51{
52 g_dlerror_msg = "dlclose not implemented!";
53 return -1;
54}
55
56char* dlerror()
57{
58 return const_cast<char*>(g_dlerror_msg.characters());
59}
60
61void* dlopen(const char* filename, int flags)
62{
63 // FIXME: Create a global mutex/semaphore/lock for dlopen/dlclose/dlsym and (?) dlerror
64 // FIXME: refcount?
65
66 if (!filename) {
67 // FIXME: Return the handle for "the main executable"
68 // The Serenity Kernel will keep a mapping of the main elf binary resident in memory,
69 // But a future dynamic loader might have a different idea/way of letting us access this information
70 ASSERT_NOT_REACHED();
71 }
72
73 FileSystemPath file_path(filename);
74
75 auto existing_elf_object = g_elf_objects.get(file_path.basename());
76 if (existing_elf_object.has_value()) {
77 return const_cast<ELFDynamicLoader*>(existing_elf_object.value());
78 }
79
80 int fd = open(filename, O_RDONLY);
81 if (!fd) {
82 g_dlerror_msg = String::format("Unable to open file %s", filename);
83 return nullptr;
84 }
85
86 ScopeGuard close_fd_guard([fd]() { close(fd); });
87
88 struct stat file_stats{};
89
90 int ret = fstat(fd, &file_stats);
91 if (ret < 0) {
92 g_dlerror_msg = String::format("Unable to stat file %s", filename);
93 return nullptr;
94 }
95
96 auto loader = ELFDynamicLoader::construct(filename, fd, file_stats.st_size);
97
98 if (!loader->is_valid()) {
99 g_dlerror_msg = String::format("%s is not a valid ELF dynamic shared object!", filename);
100 return nullptr;
101 }
102
103 if (!loader->load_from_image(flags)) {
104 g_dlerror_msg = String::format("Failed to load ELF object %s", filename);
105 return nullptr;
106 }
107
108 g_elf_objects.set(file_path.basename(), move(loader));
109 g_dlerror_msg = "Successfully loaded ELF object.";
110
111 // we have one refcount already
112 return const_cast<ELFDynamicLoader*>(g_elf_objects.get(file_path.basename()).value());
113}
114
115void* dlsym(void* handle, const char* symbol_name)
116{
117 // FIXME: When called with a NULL handle we're supposed to search every dso in the process... that'll get expensive
118 ASSERT(handle);
119 auto* dso = reinterpret_cast<ELFDynamicLoader*>(handle);
120 void* symbol = dso->symbol_for_name(symbol_name);
121 if (!symbol) {
122 g_dlerror_msg = "Symbol not found";
123 return nullptr;
124 }
125 return symbol;
126}
127
128} // extern "C"