1 /*
2 Copyright (C) 2001-present by Serge Lamikhov-Center
3
4 Permission is hereby granted, free of charge, to any person obtaining a copy
5 of this software and associated documentation files (the "Software"), to deal
6 in the Software without restriction, including without limitation the rights
7 to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
8 copies of the Software, and to permit persons to whom the Software is
9 furnished to do so, subject to the following conditions:
10
11 The above copyright notice and this permission notice shall be included in
12 all copies or substantial portions of the Software.
13
14 THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
15 IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
16 FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
17 AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
18 LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
19 OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
20 THE SOFTWARE.
21 */
22
23 /*
24 * This example shows how to create ELF object file for Linux on x86
25 *
26 * Instructions:
27 * 1. Compile and link this file with ELFIO library
28 * g++ writer.cpp -o writer
29 * 2. Execute result file write_obj
30 * ./writer
31 * 3. Add executable flag to the output file
32 * chmod +x hello_x86_64
33 * 4. Run the result file:
34 * ./hello_x86_64
35 */
36
37 #include <elfio/elfio.hpp>
38
39 using namespace ELFIO;
40
41 const Elf64_Addr CODE_ADDR = 0x00401000;
42 const Elf_Xword PAGE_SIZE = 0x1000;
43 const Elf64_Addr DATA_ADDR = CODE_ADDR + PAGE_SIZE;
44
main(void)45 int main( void )
46 {
47 elfio writer;
48
49 // You can't proceed without this function call!
50 writer.create( ELFCLASS64, ELFDATA2LSB );
51
52 writer.set_os_abi( ELFOSABI_LINUX );
53 writer.set_type( ET_EXEC );
54 writer.set_machine( EM_X86_64 );
55
56 // Create code section
57 section* text_sec = writer.sections.add( ".text" );
58 text_sec->set_type( SHT_PROGBITS );
59 text_sec->set_flags( SHF_ALLOC | SHF_EXECINSTR );
60 text_sec->set_addr_align( 0x10 );
61
62 // Add data into it
63 char text[] = {
64 '\xB8', '\x04', '\x00', '\x00', '\x00', // mov eax, 4
65 '\xBB', '\x01', '\x00', '\x00', '\x00', // mov ebx, 1
66 '\xB9', '\x00', '\x00', '\x00', '\x00', // mov ecx, msg
67 '\xBA', '\x0E', '\x00', '\x00', '\x00', // mov edx, 14
68 '\xCD', '\x80', // int 0x80
69 '\xB8', '\x01', '\x00', '\x00', '\x00', // mov eax, 1
70 '\xCD', '\x80' // int 0x80
71 };
72 // Adjust data address for 'msg'
73 *(uint32_t*)( text + 11 ) = DATA_ADDR;
74
75 text_sec->set_data( text, sizeof( text ) );
76
77 // Create a loadable segment
78 segment* text_seg = writer.segments.add();
79 text_seg->set_type( PT_LOAD );
80 text_seg->set_virtual_address( CODE_ADDR );
81 text_seg->set_physical_address( CODE_ADDR );
82 text_seg->set_flags( PF_X | PF_R );
83 text_seg->set_align( PAGE_SIZE );
84
85 // Add code section into program segment
86 text_seg->add_section_index( text_sec->get_index(),
87 text_sec->get_addr_align() );
88
89 // Create data section
90 section* data_sec = writer.sections.add( ".data" );
91 data_sec->set_type( SHT_PROGBITS );
92 data_sec->set_flags( SHF_ALLOC | SHF_WRITE );
93 data_sec->set_addr_align( 0x4 );
94
95 char data[] = {
96 '\x48', '\x65', '\x6C', '\x6C', '\x6F', // msg: db 'Hello, World!', 10
97 '\x2C', '\x20', '\x57', '\x6F', '\x72',
98 '\x6C', '\x64', '\x21', '\x0A' };
99 data_sec->set_data( data, sizeof( data ) );
100
101 // Create a read/write segment
102 segment* data_seg = writer.segments.add();
103 data_seg->set_type( PT_LOAD );
104 data_seg->set_virtual_address( DATA_ADDR );
105 data_seg->set_physical_address( DATA_ADDR );
106 data_seg->set_flags( PF_W | PF_R );
107 data_seg->set_align( PAGE_SIZE );
108
109 // Add code section into program segment
110 data_seg->add_section_index( data_sec->get_index(),
111 data_sec->get_addr_align() );
112
113 // Add optional signature for the file producer
114 section* note_sec = writer.sections.add( ".note" );
115 note_sec->set_type( SHT_NOTE );
116 note_sec->set_addr_align( 1 );
117
118 note_section_accessor note_writer( writer, note_sec );
119 note_writer.add_note( 0x01, "Created by ELFIO", 0, 0 );
120 char descr[6] = { 0x31, 0x32, 0x33, 0x34, 0x35, 0x36 };
121 note_writer.add_note( 0x01, "Never easier!", descr, sizeof( descr ) );
122
123 // Setup entry point. Usually, a linker sets this address on base of
124 // ‘_start’ label.
125 // In this example, the code starts at the first address of the
126 // 'text_seg' segment. Therefore, the start address is set
127 // to be equal to the segment location
128 writer.set_entry( CODE_ADDR );
129
130 // Create ELF file
131 writer.save( "hello_x86_64" );
132
133 return 0;
134 }
135