这个工具和objdump命令提供的功能类似，但是它显示的信息更为具体，并且它不依赖BFD库(BFD库是一个GNU项目，它的目标就是希望通过一种统一的接口来处理不同的目标文件）；
ELF文件类型
ELF(Executable and Linking Format)是一种对象文件的格式，用于定义不同类型的对象文件(Object files)中都放了什么东西、以及都以什么样的格式去放这些东西。它自最早在 System V 系统上出现后，被 xNIX 世界所广泛接受，作为缺省的二进制文件格式来使用。可以说，ELF是构成众多xNIX系统的基础之一。
ELF文件有三种类型：
可重定位的对象文件(Relocatable file)
由汇编器汇编生成的 .o 文件可执行的对象文件(Executable file)
可执行应用程序可被共享的对象文件(Shared object file)
动态库文件，也即 .so 文件 .text section 里装载了可执行代码；.data section 里面装载了被初始化的数据；.bss section 里面装载了未被初始化的数据；以 .rec 打头的 sections 里面装载了重定位条目；.symtab 或者 .dynsym section 里面装载了符号信息；.strtab 或者 .dynstr section 里面装载了字符串信息；
参数说明
-a --all 全部 Equivalent to: -h -l -S -s -r -d -V -A -I-h --file-header 文件头 Display the ELF file header-l --program-headers 程序 Display the program headers–segments An alias for --program-headers-S --section-headers 段头 Display the sections’ header–sections An alias for --section-headers-e --headers 全部头 Equivalent to: -h -l -S-s --syms 符号表 Display the symbol table–symbols An alias for --syms-n --notes 内核注释 Display the core notes (if present)-r --relocs 重定位 Display the relocations (if present)-u --unwind Display the unwind info (if present)-d --dynamic 动态段 Display the dynamic segment (if present)-V --version-info 版本 Display the version sections (if present)-A --arch-specific CPU构架 Display architecture specific information (if any).-D --use-dynamic 动态段 Use the dynamic section info when displaying symbols-x --hex-dump= 显示 段内内容Dump the contents of section -w[liaprmfFso] or-I --histogram Display histogram of bucket list lengths-W --wide 宽行输出 Allow output width to exceed 80 characters-H --help Display this information-v --version Display the version number of readelf示例
想知道一个应用程序的可运行的架构平台::
$readelf -h main| grep Machine
-h选项将显示文件头的概要信息，从里面可以看到，有很多有用的信息：
$readelf -h mainELF Header:Magic: 7f 45 4c 46 02 01 01 00 00 00 00 00 00 00 00 00Class: ELF64Data:2 s complement, little endianVersion: 1 (current)OS/ABI: UNIX - System VABI Version: 0Type:EXEC (Executable file)Machine: Advanced Micro Devices X86-64Version: 0x1Entry point address:0x400790Start of program headers:64 (bytes into file)Start of section headers:5224 (bytes into file)Flags: 0x0Size of this header:64 (bytes)Size of program headers: 56 (bytes)Number of program headers: 8Size of section headers: 64 (bytes)Number of section headers: 29Section header string table index: 26
一个编译好的应用程序，想知道其编译时是否使用了-g选项（加入调试信息）:
$readelf -S main| grep debug
用-S选项是显示所有段信息；如果编译时使用了-g选项，则会有debug段;
查看.o文件是否编入了调试信息（编译的时候是否加了-g)::
$readelf -S Shpos.o | grep debug
完整输出
readelf输出的完整内容:
$readelf -all a.outELF Header:Magic: 7f 45 4c 46 01 01 01 00 00 00 00 00 00 00 00 00 Class: ELF32Data:2's complement, little endianVersion: 1 (current)OS/ABI: UNIX - System VABI Version: 0Type:EXEC (Executable file)Machine: Intel 80386Version: 0x1Entry point address:0x8048330Start of program headers:52 (bytes into file)Start of section headers:4412 (bytes into file)Flags: 0x0Size of this header:52 (bytes)Size of program headers: 32 (bytes)Number of program headers: 9Size of section headers: 40 (bytes)Number of section headers: 30Section header string table index: 27Section Headers:[Nr] Name Type AddrOff Size ES Flg Lk Inf Al[ 0] NULL 00000000 000000 000000 000 0 0[ 1] .interp PROGBITS 08048154 000154 000013 00 A 0 0 1[ 2] .note.ABI-tagNOTE 08048168 000168 000020 00 A 0 0 4[ 3] .note.gnu.build-i NOTE 08048188 000188 000024 00 A 0 0 4[ 4] .gnu.hash GNU_HASH 080481ac 0001ac 000020 04 A 5 0 4[ 5] .dynsym DYNSYM080481cc 0001cc 000050 10 A 6 1 4[ 6] .dynstr STRTAB0804821c 00021c 00004c 00 A 0 0 1[ 7] .gnu.versionVERSYM08048268 000268 00000a 02 A 5 0 2[ 8] .gnu.version_r VERNEED 08048274 000274 000020 00 A 6 1 4[ 9] .rel.dynREL 08048294 000294 000008 08 A 5 0 4[10] .rel.pltREL 0804829c 00029c 000018 08 A 5 12 4[11] .init PROGBITS 080482b4 0002b4 00002e 00 AX 0 0 4[12] .plt PROGBITS 080482f0 0002f0 000040 04 AX 0 0 16[13] .text PROGBITS 08048330 000330 00018c 00 AX 0 0 16[14] .fini PROGBITS 080484bc 0004bc 00001a 00 AX 0 0 4[15] .rodata PROGBITS 080484d8 0004d8 000011 00 A 0 0 4[16] .eh_frame_hdrPROGBITS 080484ec 0004ec 000034 00 A 0 0 4[17] .eh_frame PROGBITS 08048520 000520 0000c4 00 A 0 0 4[18] .ctors PROGBITS 08049f14 000f14 000008 00 WA 0 0 4[19] .dtors PROGBITS 08049f1c 000f1c 000008 00 WA 0 0 4[20] .jcr PROGBITS 08049f24 000f24 000004 00 WA 0 0 4[21] .dynamicDYNAMIC 08049f28 000f28 0000c8 08 WA 6 0 4[22] .got PROGBITS 08049ff0 000ff0 000004 04 WA 0 0 4[23] .got.pltPROGBITS 08049ff4 000ff4 000018 04 WA 0 0 4[24] .data PROGBITS 0804a00c 00100c 000008 00 WA 0 0 4[25] .bss NOBITS0804a014 001014 000008 00 WA 0 0 4[26] .commentPROGBITS 00000000 001014 00002a 01 MS 0 0 1[27] .shstrtab STRTAB00000000 00103e 0000fc 000 0 1[28] .symtab SYMTAB00000000 0015ec 000410 1029 45 4[29] .strtab STRTAB00000000 0019fc 0001f9 000 0 1Key to Flags:W (write), A (alloc), X (execute), M (merge), S (strings)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 Flg AlignPHDR 0x000034 0x08048034 0x08048034 0x00120 0x00120 R E 0x4INTERP 0x000154 0x08048154 0x08048154 0x00013 0x00013 R 0x1[Requesting program interpreter: /lib/ld-linux.so.2]LOAD 0x000000 0x08048000 0x08048000 0x005e4 0x005e4 R E 0x1000LOAD 0x000f14 0x08049f14 0x08049f14 0x00100 0x00108 RW 0x1000DYNAMIC 0x000f28 0x08049f28 0x08049f28 0x000c8 0x000c8 RW 0x4NOTE 0x000168 0x08048168 0x08048168 0x00044 0x00044 R 0x4GNU_EH_FRAME 0x0004ec 0x080484ec 0x080484ec 0x00034 0x00034 R 0x4GNU_STACK0x000000 0x00000000 0x00000000 0x00000 0x00000 RW 0x4GNU_RELRO0x000f14 0x08049f14 0x08049f14 0x000ec 0x000ec R 0x1Section to Segment mapping:Segment Sections...0001.interp 02.interp .note.ABI-tag .note.gnu.build-id .gnu.hash .dynsym .dynstr .gnu.version .gnu.version_r .rel.dyn .rel.plt .init .plt .text .fini .rodata .eh_frame_hdr .eh_frame 03.ctors .dtors .jcr .dynamic .got .got.plt .data .bss 04.dynamic 05.note.ABI-tag .note.gnu.build-id 06.eh_frame_hdr 0708.ctors .dtors .jcr .dynamic .got Dynamic section at offset 0xf28 contains 20 entries:Tag TypeName/Value0x00000001 (NEEDED) Shared library: [libc.so.6]0x0000000c (INIT) 0x80482b40x0000000d (FINI) 0x80484bc0x6ffffef5 (GNU_HASH) 0x80481ac0x00000005 (STRTAB) 0x804821c0x00000006 (SYMTAB) 0x80481cc0x0000000a (STRSZ) 76 (bytes)0x0000000b (SYMENT) 16 (bytes)0x00000015 (DEBUG) 0x00x00000003 (PLTGOT) 0x8049ff40x00000002 (PLTRELSZ) 24 (bytes)0x00000014 (PLTREL) REL0x00000017 (JMPREL) 0x804829c0x00000011 (REL) 0x80482940x00000012 (RELSZ) 8 (bytes)0x00000013 (RELENT) 8 (bytes)0x6ffffffe (VERNEED)0x80482740x6fffffff (VERNEEDNUM) 10x6ffffff0 (VERSYM) 0x80482680x00000000 (NULL) 0x0Relocation section '.rel.dyn' at offset 0x294 contains 1 entries:OffsetInfo Type Sym.Value Sym. Name08049ff0 00000206 R_386_GLOB_DAT 00000000 __gmon_start__Relocation section '.rel.plt' at offset 0x29c contains 3 entries:OffsetInfo Type Sym.Value Sym. Name0804a000 00000107 R_386_JUMP_SLOT 00000000 printf0804a004 00000207 R_386_JUMP_SLOT 00000000 __gmon_start__0804a008 00000307 R_386_JUMP_SLOT 00000000 __libc_start_mainThere are no unwind sections in this file.Symbol table '.dynsym' contains 5 entries:Num: Value Size Type Bind VisNdx Name0: 000000000 NOTYPE LOCAL DEFAULT UND 1: 000000000 FUNC GLOBAL DEFAULT UND printf@GLIBC_2.0 (2)2: 000000000 NOTYPE WEAK DEFAULT UND __gmon_start__3: 000000000 FUNC GLOBAL DEFAULT UND __libc_start_main@GLIBC_2.0 (2)4: 080484dc4 OBJECT GLOBAL DEFAULT 15 _IO_stdin_usedSymbol table '.symtab' contains 65 entries:Num: Value Size Type Bind VisNdx Name0: 000000000 NOTYPE LOCAL DEFAULT UND 1: 080481540 SECTION LOCAL DEFAULT 1 2: 080481680 SECTION LOCAL DEFAULT 2 3: 080481880 SECTION LOCAL DEFAULT 3 4: 080481ac0 SECTION LOCAL DEFAULT 4 5: 080481cc0 SECTION LOCAL DEFAULT 5 6: 0804821c0 SECTION LOCAL DEFAULT 6 7: 080482680 SECTION LOCAL DEFAULT 7 8: 080482740 SECTION LOCAL DEFAULT 8 9: 080482940 SECTION LOCAL DEFAULT 9 10: 0804829c0 SECTION LOCAL DEFAULT 10 11: 080482b40 SECTION LOCAL DEFAULT 11 12: 080482f00 SECTION LOCAL DEFAULT 12 13: 080483300 SECTION LOCAL DEFAULT 13 14: 080484bc0 SECTION LOCAL DEFAULT 14 15: 080484d80 SECTION LOCAL DEFAULT 15 16: 080484ec0 SECTION LOCAL DEFAULT 16 17: 080485200 SECTION LOCAL DEFAULT 17 18: 08049f140 SECTION LOCAL DEFAULT 18 19: 08049f1c0 SECTION LOCAL DEFAULT 19 20: 08049f240 SECTION LOCAL DEFAULT 20 21: 08049f280 SECTION LOCAL DEFAULT 21 22: 08049ff00 SECTION LOCAL DEFAULT 22 23: 08049ff40 SECTION LOCAL DEFAULT 23 24: 0804a00c0 SECTION LOCAL DEFAULT 24 25: 0804a0140 SECTION LOCAL DEFAULT 25 26: 000000000 SECTION LOCAL DEFAULT 26 27: 000000000 FILE LOCAL DEFAULT ABS crtstuff.c28: 08049f140 OBJECT LOCAL DEFAULT 18 __CTOR_LIST__29: 08049f1c0 OBJECT LOCAL DEFAULT 19 __DTOR_LIST__30: 08049f240 OBJECT LOCAL DEFAULT 20 __JCR_LIST__31: 080483600 FUNC LOCAL DEFAULT 13 __do_global_dtors_aux32: 0804a0141 OBJECT LOCAL DEFAULT 25 completed.608633: 0804a0184 OBJECT LOCAL DEFAULT 25 dtor_idx.608834: 080483c00 FUNC LOCAL DEFAULT 13 frame_dummy35: 000000000 FILE LOCAL DEFAULT ABS crtstuff.c36: 08049f180 OBJECT LOCAL DEFAULT 18 __CTOR_END__37: 080485e00 OBJECT LOCAL DEFAULT 17 __FRAME_END__38: 08049f240 OBJECT LOCAL DEFAULT 20 __JCR_END__39: 080484900 FUNC LOCAL DEFAULT 13 __do_global_ctors_aux40: 000000000 FILE LOCAL DEFAULT ABS a.c41: 08049f140 NOTYPE LOCAL DEFAULT 18 __init_array_end42: 08049f280 OBJECT LOCAL DEFAULT 21 _DYNAMIC43: 08049f140 NOTYPE LOCAL DEFAULT 18 __init_array_start44: 08049ff40 OBJECT LOCAL DEFAULT 23 _GLOBAL_OFFSET_TABLE_45: 080484802 FUNC GLOBAL DEFAULT 13 __libc_csu_fini46: 080484820 FUNC GLOBAL HIDDEN 13 __i686.get_pc_thunk.bx47: 0804a00c0 NOTYPE WEAK DEFAULT 24 data_start48: 000000000 FUNC GLOBAL DEFAULT UND printf@@GLIBC_2.049: 0804a0140 NOTYPE GLOBAL DEFAULT ABS _edata50: 080484bc0 FUNC GLOBAL DEFAULT 14 _fini51: 08049f200 OBJECT GLOBAL HIDDEN 19 __DTOR_END__52: 0804a00c0 NOTYPE GLOBAL DEFAULT 24 __data_start53: 000000000 NOTYPE WEAK DEFAULT UND __gmon_start__54: 0804a0100 OBJECT GLOBAL HIDDEN 24 __dso_handle55: 080484dc4 OBJECT GLOBAL DEFAULT 15 _IO_stdin_used56: 000000000 FUNC GLOBAL DEFAULT UND __libc_start_main@@GLIBC_57: 08048410 97 FUNC GLOBAL DEFAULT 13 __libc_csu_init58: 0804a01c0 NOTYPE GLOBAL DEFAULT ABS _end59: 080483300 FUNC GLOBAL DEFAULT 13 _start60: 080484d84 OBJECT GLOBAL DEFAULT 15 _fp_hw61: 0804a0140 NOTYPE GLOBAL DEFAULT ABS __bss_start62: 080483e4 40 FUNC GLOBAL DEFAULT 13 main63: 000000000 NOTYPE WEAK DEFAULT UND _Jv_RegisterClasses64: 080482b40 FUNC GLOBAL DEFAULT 11 _initHistogram for `.gnu.hash' bucket list length (total of 2 buckets):Length Number% of total Coverage0 1( 50.0%)1 1( 50.0%) 100.0%Version symbols section '.gnu.version' contains 5 entries:Addr: 0000000008048268 Offset: 0x000268 Link: 5 (.dynsym)000: 0 (*local*) 2 (GLIBC_2.0)0 (*local*) 2 (GLIBC_2.0) 004: 1 (*global*) Version needs section '.gnu.version_r' contains 1 entries:Addr: 0x0000000008048274 Offset: 0x000274 Link: 6 (.dynstr)000000: Version: 1 File: libc.so.6 Cnt: 10x0010: Name: GLIBC_2.0 Flags: none Version: 2Notes at offset 0x00000168 with length 0x00000020:Owner Data sizeDescriptionGNU 0x00000010NT_GNU_ABI_TAG (ABI version tag)OS: Linux, ABI: 2.6.15Notes at offset 0x00000188 with length 0x00000024:Owner Data sizeDescriptionGNU 0x00000014NT_GNU_BUILD_ID (unique build ID bitstring)Build ID: 17fb9651029b6a8543bfafec9eea23bd16454e65
关于ELF文件格式的参考：/xmphoenix/archive//10/23/2221879.html
参考
https://linuxtools-rst.readthedocs.io/zh_CN/latest/tool/readelf.html
