前言
需求来自于 linux binary 的执行分析, 以及一些反编译工具的实现
比如 readelf, hopper disassemble 什么的
主要的目的是 更加详细了解 elf 的文件格式
为 后续的一些 理解做准备
elf 解析
elf 文件主要分为 四个部分
elfHeader, programHeaders, segments, segmentHeaders
我们这里查看的 elf 为一个 简单的 HelloWorld 生成的一个 elf 文件
#include "stdio.h"
int main(int argc, char** argv) {
int x = 2;
int y = 3;
int z = x + y;
printf(" x + y = %d\n ", z);
}
readelf 解析如下
root@ubuntu:~# readelf -a Test01Sum
ELF Header:
Magic: 7f 45 4c 46 02 01 01 00 00 00 00 00 00 00 00 00
Class: ELF64
Data: 2's complement, little endian
Version: 1 (current)
OS/ABI: UNIX - System V
ABI Version: 0
Type: EXEC (Executable file)
Machine: Advanced Micro Devices X86-64
Version: 0x1
Entry point address: 0x400430
Start of program headers: 64 (bytes into file)
Start of section headers: 6624 (bytes into file)
Flags: 0x0
Size of this header: 64 (bytes)
Size of program headers: 56 (bytes)
Number of program headers: 9
Size of section headers: 64 (bytes)
Number of section headers: 31
Section header string table index: 28
Section Headers:
[Nr] Name Type Address Offset
Size EntSize Flags Link Info Align
[ 0] NULL 0000000000000000 00000000
0000000000000000 0000000000000000 0 0 0
[ 1] .interp PROGBITS 0000000000400238 00000238
000000000000001c 0000000000000000 A 0 0 1
[ 2] .note.ABI-tag NOTE 0000000000400254 00000254
0000000000000020 0000000000000000 A 0 0 4
[ 3] .note.gnu.build-i NOTE 0000000000400274 00000274
0000000000000024 0000000000000000 A 0 0 4
[ 4] .gnu.hash GNU_HASH 0000000000400298 00000298
000000000000001c 0000000000000000 A 5 0 8
[ 5] .dynsym DYNSYM 00000000004002b8 000002b8
0000000000000060 0000000000000018 A 6 1 8
[ 6] .dynstr STRTAB 0000000000400318 00000318
000000000000003f 0000000000000000 A 0 0 1
[ 7] .gnu.version VERSYM 0000000000400358 00000358
0000000000000008 0000000000000002 A 5 0 2
[ 8] .gnu.version_r VERNEED 0000000000400360 00000360
0000000000000020 0000000000000000 A 6 1 8
[ 9] .rela.dyn RELA 0000000000400380 00000380
0000000000000018 0000000000000018 A 5 0 8
[10] .rela.plt RELA 0000000000400398 00000398
0000000000000030 0000000000000018 AI 5 24 8
[11] .init PROGBITS 00000000004003c8 000003c8
000000000000001a 0000000000000000 AX 0 0 4
[12] .plt PROGBITS 00000000004003f0 000003f0
0000000000000030 0000000000000010 AX 0 0 16
[13] .plt.got PROGBITS 0000000000400420 00000420
0000000000000008 0000000000000000 AX 0 0 8
[14] .text PROGBITS 0000000000400430 00000430
00000000000001b2 0000000000000000 AX 0 0 16
[15] .fini PROGBITS 00000000004005e4 000005e4
0000000000000009 0000000000000000 AX 0 0 4
[16] .rodata PROGBITS 00000000004005f0 000005f0
0000000000000012 0000000000000000 A 0 0 4
[17] .eh_frame_hdr PROGBITS 0000000000400604 00000604
0000000000000034 0000000000000000 A 0 0 4
[18] .eh_frame PROGBITS 0000000000400638 00000638
00000000000000f4 0000000000000000 A 0 0 8
[19] .init_array INIT_ARRAY 0000000000600e10 00000e10
0000000000000008 0000000000000000 WA 0 0 8
[20] .fini_array FINI_ARRAY 0000000000600e18 00000e18
0000000000000008 0000000000000000 WA 0 0 8
[21] .jcr PROGBITS 0000000000600e20 00000e20
0000000000000008 0000000000000000 WA 0 0 8
[22] .dynamic DYNAMIC 0000000000600e28 00000e28
00000000000001d0 0000000000000010 WA 6 0 8
[23] .got PROGBITS 0000000000600ff8 00000ff8
0000000000000008 0000000000000008 WA 0 0 8
[24] .got.plt PROGBITS 0000000000601000 00001000
0000000000000028 0000000000000008 WA 0 0 8
[25] .data PROGBITS 0000000000601028 00001028
0000000000000010 0000000000000000 WA 0 0 8
[26] .bss NOBITS 0000000000601038 00001038
0000000000000008 0000000000000000 WA 0 0 1
[27] .comment PROGBITS 0000000000000000 00001038
0000000000000035 0000000000000001 MS 0 0 1
[28] .shstrtab STRTAB 0000000000000000 000018d2
000000000000010c 0000000000000000 0 0 1
[29] .symtab SYMTAB 0000000000000000 00001070
0000000000000648 0000000000000018 30 47 8
[30] .strtab STRTAB 0000000000000000 000016b8
000000000000021a 0000000000000000 0 0 1
Key to Flags:
W (write), A (alloc), X (execute), M (merge), S (strings), l (large)
I (info), L (link order), G (group), T (TLS), E (exclude), x (unknown)
O (extra OS processing required) o (OS specific), p (processor specific)
There are no section groups in this file.
Program Headers:
Type Offset VirtAddr PhysAddr
FileSiz MemSiz Flags Align
PHDR 0x0000000000000040 0x0000000000400040 0x0000000000400040
0x00000000000001f8 0x00000000000001f8 R E 8
INTERP 0x0000000000000238 0x0000000000400238 0x0000000000400238
0x000000000000001c 0x000000000000001c R 1
[Requesting program interpreter: /lib64/ld-linux-x86-64.so.2]
LOAD 0x0000000000000000 0x0000000000400000 0x0000000000400000
0x000000000000072c 0x000000000000072c R E 200000
LOAD 0x0000000000000e10 0x0000000000600e10 0x0000000000600e10
0x0000000000000228 0x0000000000000230 RW 200000
DYNAMIC 0x0000000000000e28 0x0000000000600e28 0x0000000000600e28
0x00000000000001d0 0x00000000000001d0 RW 8
NOTE 0x0000000000000254 0x0000000000400254 0x0000000000400254
0x0000000000000044 0x0000000000000044 R 4
GNU_EH_FRAME 0x0000000000000604 0x0000000000400604 0x0000000000400604
0x0000000000000034 0x0000000000000034 R 4
GNU_STACK 0x0000000000000000 0x0000000000000000 0x0000000000000000
0x0000000000000000 0x0000000000000000 RW 10
GNU_RELRO 0x0000000000000e10 0x0000000000600e10 0x0000000000600e10
0x00000000000001f0 0x00000000000001f0 R 1
Section to Segment mapping:
Segment Sections...
00
01 .interp
02 .interp .note.ABI-tag .note.gnu.build-id .gnu.hash .dynsym .dynstr .gnu.version .gnu.version_r .rela.dyn .rela.plt .init .plt .plt.got .text .fini .rodata .eh_frame_hdr .eh_frame
03 .init_array .fini_array .jcr .dynamic .got .got.plt .data .bss
04 .dynamic
05 .note.ABI-tag .note.gnu.build-id
06 .eh_frame_hdr
07
08 .init_array .fini_array .jcr .dynamic .got
Dynamic section at offset 0xe28 contains 24 entries:
Tag Type Name/Value
0x0000000000000001 (NEEDED) Shared library: [libc.so.6]
0x000000000000000c (INIT) 0x4003c8
0x000000000000000d (FINI) 0x4005e4
0x0000000000000019 (INIT_ARRAY) 0x600e10
0x000000000000001b (INIT_ARRAYSZ) 8 (bytes)
0x000000000000001a (FINI_ARRAY) 0x600e18
0x000000000000001c (FINI_ARRAYSZ) 8 (bytes)
0x000000006ffffef5 (GNU_HASH) 0x400298
0x0000000000000005 (STRTAB) 0x400318
0x0000000000000006 (SYMTAB) 0x4002b8
0x000000000000000a (STRSZ) 63 (bytes)
0x000000000000000b (SYMENT) 24 (bytes)
0x0000000000000015 (DEBUG) 0x0
0x0000000000000003 (PLTGOT) 0x601000
0x0000000000000002 (PLTRELSZ) 48 (bytes)
0x0000000000000014 (PLTREL) RELA
0x0000000000000017 (JMPREL) 0x400398
0x0000000000000007 (RELA) 0x400380
0x0000000000000008 (RELASZ) 24 (bytes)
0x0000000000000009 (RELAENT) 24 (bytes)
0x000000006ffffffe (VERNEED) 0x400360
0x000000006fffffff (VERNEEDNUM) 1
0x000000006ffffff0 (VERSYM) 0x400358
0x0000000000000000 (NULL) 0x0
Relocation section '.rela.dyn' at offset 0x380 contains 1 entries:
Offset Info Type Sym. Value Sym. Name + Addend
000000600ff8 000300000006 R_X86_64_GLOB_DAT 0000000000000000 __gmon_start__ + 0
Relocation section '.rela.plt' at offset 0x398 contains 2 entries:
Offset Info Type Sym. Value Sym. Name + Addend
000000601018 000100000007 R_X86_64_JUMP_SLO 0000000000000000 printf@GLIBC_2.2.5 + 0
000000601020 000200000007 R_X86_64_JUMP_SLO 0000000000000000 __libc_start_main@GLIBC_2.2.5 + 0
The decoding of unwind sections for machine type Advanced Micro Devices X86-64 is not currently supported.
Symbol table '.dynsym' contains 4 entries:
Num: Value Size Type Bind Vis Ndx Name
0: 0000000000000000 0 NOTYPE LOCAL DEFAULT UND
1: 0000000000000000 0 FUNC GLOBAL DEFAULT UND printf@GLIBC_2.2.5 (2)
2: 0000000000000000 0 FUNC GLOBAL DEFAULT UND __libc_start_main@GLIBC_2.2.5 (2)
3: 0000000000000000 0 NOTYPE WEAK DEFAULT UND __gmon_start__
Symbol table '.symtab' contains 67 entries:
Num: Value Size Type Bind Vis Ndx Name
0: 0000000000000000 0 NOTYPE LOCAL DEFAULT UND
1: 0000000000400238 0 SECTION LOCAL DEFAULT 1
2: 0000000000400254 0 SECTION LOCAL DEFAULT 2
3: 0000000000400274 0 SECTION LOCAL DEFAULT 3
4: 0000000000400298 0 SECTION LOCAL DEFAULT 4
5: 00000000004002b8 0 SECTION LOCAL DEFAULT 5
6: 0000000000400318 0 SECTION LOCAL DEFAULT 6
7: 0000000000400358 0 SECTION LOCAL DEFAULT 7
8: 0000000000400360 0 SECTION LOCAL DEFAULT 8
9: 0000000000400380 0 SECTION LOCAL DEFAULT 9
10: 0000000000400398 0 SECTION LOCAL DEFAULT 10
11: 00000000004003c8 0 SECTION LOCAL DEFAULT 11
12: 00000000004003f0 0 SECTION LOCAL DEFAULT 12
13: 0000000000400420 0 SECTION LOCAL DEFAULT 13
14: 0000000000400430 0 SECTION LOCAL DEFAULT 14
15: 00000000004005e4 0 SECTION LOCAL DEFAULT 15
16: 00000000004005f0 0 SECTION LOCAL DEFAULT 16
17: 0000000000400604 0 SECTION LOCAL DEFAULT 17
18: 0000000000400638 0 SECTION LOCAL DEFAULT 18
19: 0000000000600e10 0 SECTION LOCAL DEFAULT 19
20: 0000000000600e18 0 SECTION LOCAL DEFAULT 20
21: 0000000000600e20 0 SECTION LOCAL DEFAULT 21
22: 0000000000600e28 0 SECTION LOCAL DEFAULT 22
23: 0000000000600ff8 0 SECTION LOCAL DEFAULT 23
24: 0000000000601000 0 SECTION LOCAL DEFAULT 24
25: 0000000000601028 0 SECTION LOCAL DEFAULT 25
26: 0000000000601038 0 SECTION LOCAL DEFAULT 26
27: 0000000000000000 0 SECTION LOCAL DEFAULT 27
28: 0000000000000000 0 FILE LOCAL DEFAULT ABS crtstuff.c
29: 0000000000600e20 0 OBJECT LOCAL DEFAULT 21 __JCR_LIST__
30: 0000000000400460 0 FUNC LOCAL DEFAULT 14 deregister_tm_clones
31: 00000000004004a0 0 FUNC LOCAL DEFAULT 14 register_tm_clones
32: 00000000004004e0 0 FUNC LOCAL DEFAULT 14 __do_global_dtors_aux
33: 0000000000601038 1 OBJECT LOCAL DEFAULT 26 completed.7594
34: 0000000000600e18 0 OBJECT LOCAL DEFAULT 20 __do_global_dtors_aux_fin
35: 0000000000400500 0 FUNC LOCAL DEFAULT 14 frame_dummy
36: 0000000000600e10 0 OBJECT LOCAL DEFAULT 19 __frame_dummy_init_array_
37: 0000000000000000 0 FILE LOCAL DEFAULT ABS Test01Sum.c
38: 0000000000000000 0 FILE LOCAL DEFAULT ABS crtstuff.c
39: 0000000000400728 0 OBJECT LOCAL DEFAULT 18 __FRAME_END__
40: 0000000000600e20 0 OBJECT LOCAL DEFAULT 21 __JCR_END__
41: 0000000000000000 0 FILE LOCAL DEFAULT ABS
42: 0000000000600e18 0 NOTYPE LOCAL DEFAULT 19 __init_array_end
43: 0000000000600e28 0 OBJECT LOCAL DEFAULT 22 _DYNAMIC
44: 0000000000600e10 0 NOTYPE LOCAL DEFAULT 19 __init_array_start
45: 0000000000400604 0 NOTYPE LOCAL DEFAULT 17 __GNU_EH_FRAME_HDR
46: 0000000000601000 0 OBJECT LOCAL DEFAULT 24 _GLOBAL_OFFSET_TABLE_
47: 00000000004005e0 2 FUNC GLOBAL DEFAULT 14 __libc_csu_fini
48: 0000000000000000 0 NOTYPE WEAK DEFAULT UND _ITM_deregisterTMCloneTab
49: 0000000000601028 0 NOTYPE WEAK DEFAULT 25 data_start
50: 0000000000601038 0 NOTYPE GLOBAL DEFAULT 25 _edata
51: 00000000004005e4 0 FUNC GLOBAL DEFAULT 15 _fini
52: 0000000000000000 0 FUNC GLOBAL DEFAULT UND printf@@GLIBC_2.2.5
53: 0000000000000000 0 FUNC GLOBAL DEFAULT UND __libc_start_main@@GLIBC_
54: 0000000000601028 0 NOTYPE GLOBAL DEFAULT 25 __data_start
55: 0000000000000000 0 NOTYPE WEAK DEFAULT UND __gmon_start__
56: 0000000000601030 0 OBJECT GLOBAL HIDDEN 25 __dso_handle
57: 00000000004005f0 4 OBJECT GLOBAL DEFAULT 16 _IO_stdin_used
58: 0000000000400570 101 FUNC GLOBAL DEFAULT 14 __libc_csu_init
59: 0000000000601040 0 NOTYPE GLOBAL DEFAULT 26 _end
60: 0000000000400430 42 FUNC GLOBAL DEFAULT 14 _start
61: 0000000000601038 0 NOTYPE GLOBAL DEFAULT 26 __bss_start
62: 0000000000400526 67 FUNC GLOBAL DEFAULT 14 main
63: 0000000000000000 0 NOTYPE WEAK DEFAULT UND _Jv_RegisterClasses
64: 0000000000601038 0 OBJECT GLOBAL HIDDEN 25 __TMC_END__
65: 0000000000000000 0 NOTYPE WEAK DEFAULT UND _ITM_registerTMCloneTable
66: 00000000004003c8 0 FUNC GLOBAL DEFAULT 11 _init
Version symbols section '.gnu.version' contains 4 entries:
Addr: 0000000000400358 Offset: 0x000358 Link: 5 (.dynsym)
000: 0 (*local*) 2 (GLIBC_2.2.5) 2 (GLIBC_2.2.5) 0 (*local*)
Version needs section '.gnu.version_r' contains 1 entries:
Addr: 0x0000000000400360 Offset: 0x000360 Link: 6 (.dynstr)
000000: Version: 1 File: libc.so.6 Cnt: 1
0x0010: Name: GLIBC_2.2.5 Flags: none Version: 2
Displaying notes found at file offset 0x00000254 with length 0x00000020:
Owner Data size Description
GNU 0x00000010 NT_GNU_ABI_TAG (ABI version tag)
OS: Linux, ABI: 2.6.32
Displaying notes found at file offset 0x00000274 with length 0x00000024:
Owner Data size Description
GNU 0x00000014 NT_GNU_BUILD_ID (unique build ID bitstring)
Build ID: 676de8fa9bce03059433028da409bb25c151f668
hopper disassemble 解析如下, 截取片段
相关实体
ElfFile
/**
* ElfFile
*
* @author Jerry.X.He <970655147@qq.com>
* @version 1.0
* @date 2022-09-25 11:08
*/
@Data
public class ElfFile implements Serializable {
private ElfHeader header;
private List<ElfProgramHeader> programHeaders;
private Integer[] sectionBytes;
private List<ElfSegment> segments;
private List<ElfSectionHeader> sectionHeaders;
@Field(sort = 0, name = "header", dataType = DataType.GENERIC_BEAN, desc = "header", version = {1})
public ElfHeader getHeader() {
return header;
}
@Field(sort = 10, name = "programHeaders", dataType = DataType.GENERIC_BEAN_COLLECTION, desc = "programHeaders", version = {1})
public List<ElfProgramHeader> getprogramHeaders() {
return programHeaders;
}
@Field(sort = 20, name = "sectionBytes", dataType = DataType.BYTE_ARRAY, desc = "sectionBytes", version = {1})
public Integer[] getSectionBytes() {
return sectionBytes;
}
public void setSegments(List<ElfSegment> segments) {
this.segments = segments;
}
@Field(sort = 30, name = "sectionHeaders", dataType = DataType.GENERIC_BEAN_COLLECTION, desc = "sectionHeaders", version = {1})
public List<ElfSectionHeader> getSectionHeaders() {
return sectionHeaders;
}
}
ElfHeader
/**
* ElfHeader
*
* @author Jerry.X.He <970655147@qq.com>
* @version 1.0
* @date 2022-09-25 11:08
*/
@Data
public class ElfHeader implements Serializable {
private String ident;
private Integer type;
private Integer machine;
private Integer version;
private Long entry;
private Long phoff;
private Long shoff;
private Integer flags;
private Integer ehsize;
private Integer phentsize;
private Integer phnum;
private Integer shentsize;
private Integer shnum;
private Integer shstrndx;
private Long offsetInFile;
@Field(sort = 0, name = "ident", dataType = DataType.CHARSET_ENCODING_WITH_FIXED_LEN_STRING, lengthInBytes = 16, desc = "ident", version = {1})
public String getIdent() {
return ident;
}
@Field(sort = 10, name = "type", dataType = DataType.UNSIGNED_WORD, desc = "type", bigEndian = false, version = {1})
public Integer getType() {
return type;
}
@Field(sort = 20, name = "machine", dataType = DataType.UNSIGNED_WORD, desc = "machine", bigEndian = false, version = {1})
public Integer getMachine() {
return machine;
}
@Field(sort = 30, name = "version", dataType = DataType.DWORD, desc = "version", bigEndian = false, version = {1})
public Integer getVersion() {
return version;
}
@Field(sort = 40, name = "entry", dataType = DataType.QWORD, desc = "entry", bigEndian = false, version = {1})
public Long getEntry() {
return entry;
}
@Field(sort = 50, name = "phoff", dataType = DataType.QWORD, desc = "phoff", bigEndian = false, version = {1})
public Long getPhoff() {
return phoff;
}
@Field(sort = 60, name = "shoff", dataType = DataType.QWORD, desc = "shoff", bigEndian = false, version = {1})
public Long getShoff() {
return shoff;
}
@Field(sort = 70, name = "flags", dataType = DataType.DWORD, desc = "flags", bigEndian = false, version = {1})
public Integer getFlags() {
return flags;
}
@Field(sort = 80, name = "ehsize", dataType = DataType.UNSIGNED_WORD, desc = "ehsize", bigEndian = false, version = {1})
public Integer getEhsize() {
return ehsize;
}
@Field(sort = 90, name = "phentsize", dataType = DataType.UNSIGNED_WORD, desc = "phentsize", bigEndian = false, version = {1})
public Integer getPhentsize() {
return phentsize;
}
@Field(sort = 100, name = "phnum", dataType = DataType.UNSIGNED_WORD, desc = "phnum", bigEndian = false, version = {1})
public Integer getPhnum() {
return phnum;
}
@Field(sort = 110, name = "shentsize", dataType = DataType.UNSIGNED_WORD, desc = "shentsize", bigEndian = false, version = {1})
public Integer getShentsize() {
return shentsize;
}
@Field(sort = 120, name = "shnum", dataType = DataType.UNSIGNED_WORD, desc = "shnum", bigEndian = false, version = {1})
public Integer getShnum() {
return shnum;
}
@Field(sort = 130, name = "shstrndx", dataType = DataType.UNSIGNED_WORD, desc = "shstrndx", bigEndian = false, version = {1})
public Integer getShstrndx() {
return shstrndx;
}
public JSONObject getHexRelated() {
JSONObject result = new JSONObject();
result.put("entry", "0x" + Long.toHexString(entry));
result.put("phoff", "0x" + Long.toHexString(phoff));
result.put("shoff", "0x" + Long.toHexString(shoff));
return result;
}
public String toString() {
return JSON.toJSONString(this);
}
}
ElfProgramHeader
/**
* ElfPhHeader
*
* @author Jerry.X.He
* @version 1.0
* @date 2022/9/27 10:18
*/
@Data
public class ElfProgramHeader implements Serializable {
private Integer type;
private Integer flags;
private Long offset;
private Long vaddr;
private Long paddr;
private Long fileSz;
private Long memSz;
private Long align;
private Long offsetInFile;
@Field(sort = 0, name = "type", dataType = DataType.DWORD, desc = "type", bigEndian = false, version = {1})
public Integer getType() {
return type;
}
@Field(sort = 10, name = "flags", dataType = DataType.DWORD, desc = "flags", bigEndian = false, version = {1})
public Integer getFlags() {
return flags;
}
@Field(sort = 20, name = "offset", dataType = DataType.QWORD, desc = "offset", bigEndian = false, version = {1})
public Long getOffset() {
return offset;
}
@Field(sort = 30, name = "vaddr", dataType = DataType.QWORD, desc = "vaddr", bigEndian = false, version = {1})
public Long getVaddr() {
return vaddr;
}
@Field(sort = 40, name = "paddr", dataType = DataType.QWORD, desc = "paddr", bigEndian = false, version = {1})
public Long getPaddr() {
return paddr;
}
@Field(sort = 50, name = "fileSz", dataType = DataType.QWORD, desc = "fileSz", bigEndian = false, version = {1})
public Long getFileSz() {
return fileSz;
}
@Field(sort = 60, name = "memSz", dataType = DataType.QWORD, desc = "memSz", bigEndian = false, version = {1})
public Long getMemSz() {
return memSz;
}
@Field(sort = 70, name = "align", dataType = DataType.QWORD, desc = "align", bigEndian = false, version = {1})
public Long getAlign() {
return align;
}
public JSONObject getHexRelated() {
JSONObject result = new JSONObject();
result.put("offset", "0x" + Long.toHexString(offset));
result.put("vaddr", "0x" + Long.toHexString(vaddr));
result.put("paddr", "0x" + Long.toHexString(paddr));
result.put("fileSz", "0x" + Long.toHexString(fileSz));
result.put("memSz", "0x" + Long.toHexString(memSz));
result.put("offsetInFile", "0x" + Long.toHexString(offsetInFile));
return result;
}
public String toString() {
return JSON.toJSONString(this);
}
}
ElfSegment
/**
* ElfSegment
*
* @author Jerry.X.He
* @version 1.0
* @date 2022/9/27 14:30
*/
@Data
public class ElfSegment implements Serializable {
protected String name;
protected Integer[] bytes;
protected Long offsetInFile;
@Override
public String toString() {
List<String> toStringNames = Arrays.asList(".comment", ".dynstr", ".shstrtab", ".strtab");
if (toStringNames.contains(name)) {
return name + " " + ElfFileCodec.formatOffset(getOffsetInFile()) + " " + new String(ElfFileCodec.transferBytes(bytes));
}
return name + " " + ElfFileCodec.formatOffset(getOffsetInFile()) + " " + ElfFileCodec.toString(bytes);
}
}
ElfSectionHeader
/**
* ElfPhHeader
*
* @author Jerry.X.He
* @version 1.0
* @date 2022/9/27 10:18
*/
@Data
public class ElfSectionHeader implements Serializable {
private Integer name;
private Integer type;
private Long flags;
private Long address;
private Long offset;
private Long size;
private Integer link;
private Integer info;
private Long addrAlign;
private Long entrySize;
@Field(sort = 0, name = "name", dataType = DataType.DWORD, desc = "name", bigEndian = false, version = {1})
public Integer getName() {
return name;
}
@Field(sort = 10, name = "type", dataType = DataType.DWORD, desc = "type", bigEndian = false, version = {1})
public Integer getType() {
return type;
}
@Field(sort = 20, name = "flags", dataType = DataType.QWORD, desc = "flags", bigEndian = false, version = {1})
public Long getFlags() {
return flags;
}
@Field(sort = 30, name = "address", dataType = DataType.QWORD, desc = "address", bigEndian = false, version = {1})
public Long getAddress() {
return address;
}
@Field(sort = 40, name = "offset", dataType = DataType.QWORD, desc = "offset", bigEndian = false, version = {1})
public Long getOffset() {
return offset;
}
@Field(sort = 50, name = "size", dataType = DataType.QWORD, desc = "size", bigEndian = false, version = {1})
public Long getSize() {
return size;
}
@Field(sort = 60, name = "link", dataType = DataType.DWORD, desc = "link", bigEndian = false, version = {1})
public Integer getLink() {
return link;
}
@Field(sort = 70, name = "info", dataType = DataType.DWORD, desc = "info", bigEndian = false, version = {1})
public Integer getInfo() {
return info;
}
@Field(sort = 80, name = "addrAlign", dataType = DataType.QWORD, desc = "addrAlign", bigEndian = false, version = {1})
public Long getAddrAlign() {
return addrAlign;
}
@Field(sort = 90, name = "entrySize", dataType = DataType.QWORD, desc = "entrySize", bigEndian = false, version = {1})
public Long getEntrySize() {
return entrySize;
}
public JSONObject getHexRelated() {
JSONObject result = new JSONObject();
result.put("address", "0x" + Long.toHexString(address));
result.put("offset", "0x" + Long.toHexString(offset));
result.put("size", "0x" + Long.toHexString(size));
result.put("entrySize", "0x" + Long.toHexString(entrySize));
return result;
}
public String toString() {
return JSON.toJSONString(this);
}
}
ElfSegment 有多类实现, 这里不一一列举
ElfNoteSegment
/**
* ElfInterpSegment
*
* @author Jerry.X.He
* @version 1.0
* @date 2022/9/27 14:31
*/
@Data
@ToString(callSuper = true)
public class ElfNoteSegment extends ElfSegment {
private Integer nameSize;
private Integer descSize;
private Integer type;
private String nameInNote;
private Integer[] desc;
}
ElfDynamicSymSegment
/**
* ElfDynamicSymSegment
*
* @author Jerry.X.He
* @version 1.0
* @date 2022/9/27 14:31
*/
@Data
@ToString(callSuper = true)
public class ElfDynamicSymSegment extends ElfSegment {
private List<ElfSymTabElement> list;
@Field(sort = 0, name = "list", dataType = DataType.GENERIC_BEAN_COLLECTION, desc = "list", version = {1})
public List<ElfSymTabElement> getList() {
return list;
}
}
/**
* ElfSymTabElement
*
* @author Jerry.X.He
* @version 1.0
* @date 2022/9/27 14:31
*/
@Data
public class ElfSymTabElement {
private String name;
// 4bytes
private Integer nameIdx;
// 1byte, bind + type
private Integer info;
// 1byte, 可见属性
private Integer other;
// segment idx
private Integer shNIdx;
// 8bytes
private Long value;
// 8bytes
private Long size;
@Field(sort = 0, name = "nameIdx", dataType = DataType.DWORD, desc = "nameIdx", bigEndian = false, version = {1})
public Integer getNameIdx() {
return nameIdx;
}
@Field(sort = 10, name = "info", dataType = DataType.BYTE, desc = "info", bigEndian = false, version = {1})
public Integer getInfo() {
return info;
}
@Field(sort = 20, name = "other", dataType = DataType.BYTE, desc = "other", bigEndian = false, version = {1})
public Integer getOther() {
return other;
}
@Field(sort = 30, name = "shNIdx", dataType = DataType.WORD, desc = "shNIdx", bigEndian = false, version = {1})
public Integer getShNIdx() {
return shNIdx;
}
@Field(sort = 40, name = "value", dataType = DataType.QWORD, desc = "value", bigEndian = false, version = {1})
public Long getValue() {
return value;
}
@Field(sort = 50, name = "size", dataType = DataType.QWORD, desc = "size", bigEndian = false, version = {1})
public Long getSize() {
return size;
}
@Override
public String toString() {
JSONObject result = new JSONObject();
result.put("name", name);
result.put("info", info);
result.put("other", other);
result.put("shNIdx", shNIdx);
result.put("value", Long.toHexString(value));
result.put("size", size);
return result.toString();
}
}
相关实体的编码解码如下
ElfFileCodec
/**
* ElfFileCodec
*
* @author Jerry.X.He
* @version 1.0
* @date 2022/9/27 10:23
*/
public class ElfFileCodec extends AbstractCodec<ElfFile, ElfFile> {
private AbstractCodec<ElfHeader, ElfHeader> headerCodec = CodecUtils.createCodecForClazz(ElfHeader.class, 1);
private AbstractCodec<ElfProgramHeader, ElfProgramHeader> phHeaderCodec = CodecUtils.createCodecForClazz(ElfProgramHeader.class, 1);
private AbstractCodec<ElfSectionHeader, ElfSectionHeader> sectionHeaderCodec = CodecUtils.createCodecForClazz(ElfSectionHeader.class, 1);
private ElfSegmentCodec segmentCodec = new ElfSegmentCodec();
@Override
public void encode(ElfFile entity, ByteBuf buf) {
}
@Override
public ElfFile decode(ByteBuf buf) {
debugCurrentBufReaderIdx(buf, "before elf header codec");
long offsetInFile = buf.readerIndex();
ElfHeader header = headerCodec.decode(buf);
header.setOffsetInFile(offsetInFile);
debugCurrentBufReaderIdx(buf, "after elf header codec");
int programNum = header.getPhnum(), sectionNum = header.getShnum();
int sectionHeaderSz = sectionHeaderCodec.length() * sectionNum;
debugCurrentBufReaderIdx(buf, "before program header codec");
List<ElfProgramHeader> programHeaders = new ArrayList<>();
for (int i = 0; i < programNum; i++) {
offsetInFile = buf.readerIndex();
ElfProgramHeader phHeader = phHeaderCodec.decode(buf);
phHeader.setOffsetInFile(offsetInFile);
programHeaders.add(phHeader);
}
debugCurrentBufReaderIdx(buf, "after program header codec");
debugCurrentBufReaderIdx(buf, "before sections codec");
int allRemaining = buf.readableBytes();
int sectionBytesSz = allRemaining - sectionHeaderSz;
ByteArrayWithExactlyLenCodec byteArrayCodec = new ByteArrayWithExactlyLenCodec(sectionBytesSz);
Integer[] sectionBytesInInteger = byteArrayCodec.decode(buf);
debugCurrentBufReaderIdx(buf, "after sections codec");
debugCurrentBufReaderIdx(buf, "before section header codec");
List<ElfSectionHeader> sectionHeaders = new ArrayList<>();
for (int i = 0; i < sectionNum; i++) {
sectionHeaders.add(sectionHeaderCodec.decode(buf));
}
debugCurrentBufReaderIdx(buf, "after section header codec");
// section headers
List<ElfSegment> segments = new ArrayList<>();
for (ElfSectionHeader secHeader : sectionHeaders) {
int sectionSize = secHeader.getSize().intValue();
ByteArrayWithExactlyLenCodec sectionByteArrayCodec = new ByteArrayWithExactlyLenCodec(sectionSize);
Integer[] sectionBytes = new Integer[]{};
if (secHeader.getOffset() > 0) {
buf.readerIndex(secHeader.getOffset().intValue());
sectionBytes = (sectionByteArrayCodec.decode(buf));
}
segmentCodec.setSecHeader(secHeader);
ElfSegment elfSegment = segmentCodec.decode(Unpooled.wrappedBuffer(transferBytes(sectionBytes)));
elfSegment.setBytes(sectionBytes);
elfSegment.setOffsetInFile(secHeader.getOffset());
segments.add(elfSegment);
}
// resolve xx names
resolveRelatedNames(header, sectionHeaders, segments);
ElfFile result = new ElfFile();
result.setHeader(header);
result.setProgramHeaders(programHeaders);
result.setSectionBytes(sectionBytesInInteger);
result.setSegments(segments);
result.setSectionHeaders(sectionHeaders);
return result;
}
private void resolveRelatedNames(ElfHeader header, List<ElfSectionHeader> sectionHeaders, List<ElfSegment> segments) {
ElfSegment segStrTab = segments.get(header.getShstrndx());
// fill segment name
for (int i = 0; i < segments.size(); i++) {
ElfSegment segment = segments.get(i);
ElfSectionHeader secHeader = sectionHeaders.get(i);
String segName = lookStringInStrTab(segStrTab.getBytes(), secHeader.getName());
segment.setName(segName);
}
ElfDynStrSegment strTab = (ElfDynStrSegment) lookUpSegment(segments, ".strtab");
ElfDynStrSegment dynStrTab = (ElfDynStrSegment) lookUpSegment(segments, ".dynstr");
// fill symtab name
ElfSymTabSegment symTab = (ElfSymTabSegment) lookUpSegment(segments, ".symtab");
for (int i = 0; i < symTab.getList().size(); i++) {
ElfSymTabElement symtabEle = symTab.getList().get(i);
String eleName = lookStringInStrTab(strTab.getBytes(), symtabEle.getNameIdx());
symtabEle.setName(eleName);
}
// fill dynsym name
ElfDynamicSymSegment dynSymTab = (ElfDynamicSymSegment) lookUpSegment(segments, ".dynsym");
for (int i = 0; i < dynSymTab.getList().size(); i++) {
ElfSymTabElement symtabEle = dynSymTab.getList().get(i);
String eleName = lookStringInStrTab(dynStrTab.getBytes(), symtabEle.getNameIdx());
symtabEle.setName(eleName);
}
// rela.dyn
ElfRelaSegment relaDynTab = (ElfRelaSegment) lookUpSegment(segments, ".rela.dyn");
for (int i = 0; i < relaDynTab.getList().size(); i++) {
ElfRelaElement symtabEle = relaDynTab.getList().get(i);
String eleName = dynStrTab.getList().get(symtabEle.getNameIdx());
symtabEle.setName(eleName);
}
// rela.plt
ElfRelaSegment relaPltTab = (ElfRelaSegment) lookUpSegment(segments, ".rela.plt");
for (int i = 0; i < relaPltTab.getList().size(); i++) {
ElfRelaElement symtabEle = relaPltTab.getList().get(i);
String eleName = dynStrTab.getList().get(symtabEle.getNameIdx());
symtabEle.setName(eleName);
}
}
public static ElfSegment lookUpSegment(List<ElfSegment> segments, String name) {
for (ElfSegment segment : segments) {
if (Objects.equals(name, segment.getName())) {
return segment;
}
}
return null;
}
public static byte[] transferBytes(Integer[] bytes) {
byte[] result = new byte[bytes.length];
int idx = 0;
for (Integer b : bytes) {
result[idx++] = b.byteValue();
}
return result;
}
public static String formatOffset(Long offset) {
return String.format("0x00%s", Long.toHexString(offset));
}
public static String toString(Integer[] bytes) {
StringBuilder sb = new StringBuilder();
for (int i = 0; i < bytes.length; i++) {
String part = ByteBufUtil.hexDump(
new byte[]{bytes[i].byteValue()}
);
sb.append(" ");
sb.append(part);
}
return sb.toString();
}
public static String toAddress(Integer[] bytes) {
StringBuilder sb = new StringBuilder();
sb.append("0x");
for (int i = bytes.length - 1; i >= 0; i--) {
String part = ByteBufUtil.hexDump(
new byte[]{bytes[i].byteValue()}
);
sb.append(" ");
sb.append(part);
}
return sb.toString();
}
public static String lookStringInStrTab(Integer[] bytes, int offset) {
StringBuilder sb = new StringBuilder();
for (int i = offset; i < bytes.length; i++) {
if (bytes[i] == 0x00) {
break;
}
sb.append((char) bytes[i].intValue());
}
return sb.toString();
}
@Override
public boolean isFixedLength() {
return false;
}
@Override
public int length() {
return 0;
}
public void debugCurrentBufReaderIdx(ByteBuf buf, String title) {
System.out.println(title + " -> " + buf.readerIndex() + " - 0x" + Integer.toHexString(buf.readerIndex()));
}
}
ElfSegment 有多类实现, 这里不一一列举
ElfNoteSegmentCodec
/**
* ElfAbiTagSegmentCodec
*
* @author Jerry.X.He
* @version 1.0
* @date 2022/9/27 14:34
*/
public class ElfNoteSegmentCodec extends AbstractCodec<ElfNoteSegment, ElfNoteSegment> {
private DWordCodec dWordCodec = new DWordCodec(ByteOrder.LITTLE_ENDIAN);
private CharsetEncodingStringCodec stringCodec = new CharsetEncodingStringCodec(Constants.CHARSET_UTF8);
@Override
public void encode(ElfNoteSegment entity, ByteBuf buf) {
}
@Override
public ElfNoteSegment decode(ByteBuf buf) {
Integer nameSize = dWordCodec.decode(buf);
Integer descSize = dWordCodec.decode(buf);
Integer type = dWordCodec.decode(buf);
CharsetEncodingStringWithFixedLenCodec nameCodec = new CharsetEncodingStringWithFixedLenCodec(nameSize);
String name = nameCodec.decode(buf);
ByteArrayWithFixedLenCodec descCodec = new ByteArrayWithFixedLenCodec(descSize);
Integer[] desc = descCodec.decode(buf);
ElfNoteSegment result = new ElfNoteSegment();
result.setNameSize(nameSize);
result.setDescSize(descSize);
result.setType(type);
result.setNameInNote(name);
result.setDesc(desc);
return result;
}
@Override
public boolean isFixedLength() {
return false;
}
@Override
public int length() {
return 0;
}
}
ElfDynamicSymSegmentCodec
/**
* ElfDynamicSymSegmentCodec
*
* @author Jerry.X.He
* @version 1.0
* @date 2022/9/27 14:34
*/
public class ElfDynamicSymSegmentCodec extends AbstractCodec<ElfDynamicSymSegment, ElfDynamicSymSegment> {
AbstractCodec<ElfDynamicSymSegment, ElfDynamicSymSegment> codec = CodecUtils.createCodecForClazz(ElfDynamicSymSegment.class, 1);
@Override
public void encode(ElfDynamicSymSegment entity, ByteBuf buf) {
}
@Override
public ElfDynamicSymSegment decode(ByteBuf buf) {
return codec.decode(buf);
}
@Override
public boolean isFixedLength() {
return false;
}
@Override
public int length() {
return 0;
}
}
解析结果
完
