jcs.org
Serenity Operating System
1/*
2 * Copyright (c) 2019-2020, Andrew Kaster <andrewdkaster@gmail.com>
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#pragma once
28
29#include <AK/Assertions.h>
30#include <AK/OwnPtr.h>
31#include <AK/RefCounted.h>
32#include <AK/String.h>
33#include <LibELF/ELFDynamicObject.h>
34#include <LibELF/ELFImage.h>
35#include <LibELF/exec_elf.h>
36#include <sys/mman.h>
37
38#define ALIGN_ROUND_UP(x, align) ((((size_t)(x)) + align - 1) & (~(align - 1)))
39
40class ELFDynamicLoader : public RefCounted<ELFDynamicLoader> {
41public:
42 static NonnullRefPtr<ELFDynamicLoader> construct(const char* filename, int fd, size_t file_size);
43
44 ~ELFDynamicLoader();
45
46 bool is_valid() const { return m_valid; }
47
48 // Load a full ELF image from file into the current process and create an ELFDynamicObject
49 // from the SHT_DYNAMIC in the file.
50 bool load_from_image(unsigned flags);
51
52 // Stage 2 of loading: relocations and init functions
53 // Assumes that the program headers have been loaded and that m_dynamic_object is initialized
54 // Splitting loading like this allows us to use the same code to relocate a main executable as an elf binary
55 bool load_stage_2(unsigned flags);
56
57 // Intended for use by dlsym or other internal methods
58 void* symbol_for_name(const char*);
59
60 void dump();
61
62 // Will be called from _fixup_plt_entry, as part of the PLT trampoline
63 Elf32_Addr patch_plt_entry(u32 relocation_offset);
64
65private:
66 class ProgramHeaderRegion {
67 public:
68 void set_program_header(const Elf32_Phdr& header) { m_program_header = header; }
69
70 // Information from ELF Program header
71 u32 type() const { return m_program_header.p_type; }
72 u32 flags() const { return m_program_header.p_flags; }
73 u32 offset() const { return m_program_header.p_offset; }
74 VirtualAddress desired_load_address() const { return VirtualAddress(m_program_header.p_vaddr); }
75 u32 size_in_memory() const { return m_program_header.p_memsz; }
76 u32 size_in_image() const { return m_program_header.p_filesz; }
77 u32 alignment() const { return m_program_header.p_align; }
78 u32 mmap_prot() const;
79 bool is_readable() const { return flags() & PF_R; }
80 bool is_writable() const { return flags() & PF_W; }
81 bool is_executable() const { return flags() & PF_X; }
82 bool is_tls_template() const { return type() == PT_TLS; }
83 bool is_load() const { return type() == PT_LOAD; }
84 bool is_dynamic() const { return type() == PT_DYNAMIC; }
85
86 u32 required_load_size() { return ALIGN_ROUND_UP(m_program_header.p_memsz, m_program_header.p_align); }
87
88 private:
89 Elf32_Phdr m_program_header; // Explictly a copy of the PHDR in the image
90 };
91
92 explicit ELFDynamicLoader(const char* filename, int fd, size_t file_size);
93 explicit ELFDynamicLoader(Elf32_Dyn* dynamic_location, Elf32_Addr load_address);
94
95 // Stage 1
96 void load_program_headers(const ELFImage& elf_image);
97
98 // Stage 2
99 void do_relocations();
100 void setup_plt_trampoline();
101 void call_object_init_functions();
102
103 String m_filename;
104 size_t m_file_size { 0 };
105 int m_image_fd { -1 };
106 void* m_file_mapping { nullptr };
107 bool m_valid { true };
108
109 OwnPtr<ELFDynamicObject> m_dynamic_object;
110
111 VirtualAddress m_text_segment_load_address;
112 size_t m_text_segment_size;
113
114 VirtualAddress m_tls_segment_address;
115 VirtualAddress m_dynamic_section_address;
116};