.elf格式内容
arm-linux-ld
可以将程序链接成我们arm平台下的可运行的程序
以之前使用过的led程序为例：
首先：
arm-linux-gcc -g -c led.S (-g是表示产生调试信息， -c是表示只编译不链接)
产生led.o文件
arm-linux-ld -Tled.lds -o led.elf led.o
产生.elf格式的文件
然后通过：
arm-linux-readelf命令：读出.elf的详细内容：
arm-linux-readelf -a led.elf（显示所有的log信息）
摘网上一幅图显示.elf格式的内容：
（该图片使用的是Linux C编程作者 宋劲斌的图片）
log信息：（红色的自己修改的）
ELF Header:
Magic: 7f 45 4c 46 01 01 01 00 00 00 00 00 00 00 00 00
Class: ELF32
Data: 2's complement, little endian（小端模式）
Version: 1 (current)
OS/ABI: UNIX - System V
ABI Version: 0
Type: EXEC (Executable file)
Machine: ARM（可运行在ARM平台上）
Version: 0x1
Entry point address: 0xd0020000
Start of program headers: 52 (bytes into file)
Start of section headers: 33192 (bytes into file)
Flags: 0x5000002, has entry point, Version5 EABI
Size of this header: 52 (bytes)
Size of program headers: 32 (bytes)
Number of program headers: 1
Size of section headers: 40 (bytes)
Number of section headers: 10
Section header string table index: 7
Section Headers:
[Nr] Name Type Addr Off Size ES Flg Lk Inf Al
[ 0] NULL 00000000 000000 000000 00 0 0 0
[ 1] .text PROGBITS d0020000 008000 00004c 00 AX 0 0 4
[ 2] .ARM.attributes ARM_ATTRIBUTES 00000000 00804c 000018 00 0 0 1
[ 3] .debug_line PROGBITS 00000000 008064 000045 00 0 0 1
[ 4] .debug_info PROGBITS 00000000 0080a9 000061 00 0 0 1
[ 5] .debug_abbrev PROGBITS 00000000 00810a 000014 00 0 0 1
[ 6] .debug_aranges PROGBITS 00000000 008120 000020 00 0 0 8
[ 7] .shstrtab STRTAB 00000000 008140 000066 00 0 0 1
[ 8] .symtab SYMTAB 00000000 008338 0000e0 10 9 11 4
[ 9] .strtab STRTAB 00000000 008418 000033 00 0 0 1
Key to Flags:
W (write), A (alloc), X (execute), M (merge), S (strings)
I (info), L (link order), G (group), 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 Align
LOAD 0x008000 0xd0020000 0xd0020000 0x0004c 0x0004c R E 0x8000
Section to Segment mapping:
Segment Sections...
00 .text
There is no dynamic section in this file.
There are no relocations in this file.
There are no unwind sections in this file.
Symbol table '.symtab' contains 14 entries:
Num: Value Size Type Bind Vis Ndx Name
0: 00000000 0 NOTYPE LOCAL DEFAULT UND
1: d0020000 0 SECTION LOCAL DEFAULT 1
2: 00000000 0 SECTION LOCAL DEFAULT 2
3: 00000000 0 SECTION LOCAL DEFAULT 3
4: 00000000 0 SECTION LOCAL DEFAULT 4
5: 00000000 0 SECTION LOCAL DEFAULT 5
6: 00000000 0 SECTION LOCAL DEFAULT 6
7: d0020000 0 NOTYPE LOCAL DEFAULT 1 $a
8: d0020008 0 NOTYPE LOCAL DEFAULT 1 led_debug
9: d0020004 0 NOTYPE LOCAL DEFAULT 1 MAIN_LOOP
10: d0020044 0 NOTYPE LOCAL DEFAULT 1 $d
11: d0020000 0 NOTYPE GLOBAL DEFAULT 1 _start
12: d002004c 0 NOTYPE GLOBAL DEFAULT ABS __bss_start
13: d002004c 0 NOTYPE GLOBAL DEFAULT ABS _end
No version information found in this file.
Attribute Section: aeabi
File Attributes
Tag_CPU_name: "4T"
Tag_CPU_arch: v4T
Tag_ARM_ISA_use: Yes
log信息：
Tag Type Name/Value
0x00000001 (NEEDED) Shared library: [libc.so.6]（这就是需要用到的库） 0x0000000c (INIT) 0x8274
0x0000000d (FINI) 0x841c
0x00000019 (INIT_ARRAY) 0x10448
0x0000001b (INIT_ARRAYSZ) 4 (bytes)
0x0000001a (FINI_ARRAY) 0x1044c
0x0000001c (FINI_ARRAYSZ) 4 (bytes)
0x00000004 (HASH) 0x8168
0x00000005 (STRTAB) 0x81e0
0x00000006 (SYMTAB) 0x8190
0x0000000a (STRSZ) 65 (bytes)
0x0000000b (SYMENT) 16 (bytes)
0x00000015 (DEBUG) 0x0
0x00000003 (PLTGOT) 0x1053c
0x00000002 (PLTRELSZ) 32 (bytes)
0x00000014 (PLTREL) REL
0x00000017 (JMPREL) 0x8254
0x00000011 (REL) 0x824c
0x00000012 (RELSZ) 8 (bytes)
0x00000013 (RELENT) 8 (bytes)
0x6ffffffe (VERNEED) 0x822c
0x6fffffff (VERNEEDNUM) 1
0x6ffffff0 (VERSYM) 0x8222
0x00000000 (NULL) 0x0