参考文章:
《程序员的自我修养——链接、转载与库》 P68
这里介绍两种方法,实现将将一张图片作为二进制可执行程序的一个段,其中第一种方法在我之前的博客中已经有所介绍,不过,那是采用的是交叉编译的方法,这次直接全部在PC机上完成;第二种方法是我在看上面的那本书的时候看到的,觉着也不错。
环境介绍: Win7 + VirtualBox + Debian6 + gcc version 4.4.5 (Debian 4.4.5-8)
第一种方法
- 目录结构
pengdl@debian:~/test/c/pic2$ tree -lh
. |-- [ 135] data.S |-- [ 811] main.c |-- [ 91] Makefile `-- [134K] peng.png0 directories, 4 files
- data.S
这里需要注意:
这段代码是我直接从Linux内核中拷贝出来的,并做了修改,源文件如下(arch/arm/boot/compressed/piggy.S):
但是上面的代码除了需要修改.incbin之外,第一行的段属性部分也需要修改,将"#alloc"修改为"a",意思是:这个段可以重定位。如果不加段属性"a",运行时会发生段错误:
1: pengdl@debian:~/test/c/pic2$ ./main
2: input_data = (nil)
3: input_data_end = 0x2187e
4: size = 0x2187e
5:
6: Segmentation fault
使用objdump工具可以看看为什么?
先看看data.o:
1: pengdl@debian:~/test/c/pic2$ objdump -ht data.o
2:
3: data.o: file format elf32-i386
4:
5: Sections:
6: Idx Name Size VMA LMA File off Algn
7: 0 .text 00000000 00000000 00000000 00000034 2**2
8: CONTENTS, ALLOC, LOAD, READONLY, CODE
9: 1 .data 00000000 00000000 00000000 00000034 2**2
10: CONTENTS, ALLOC, LOAD, DATA
11: 2 .bss 00000000 00000000 00000000 00000034 2**2
12: ALLOC
13: 3 .piggydata 0002187e 00000000 00000000 00000034 2**0
14: CONTENTS, READONLY
15: SYMBOL TABLE:
16: 00000000 l d .text 00000000 .text
17: 00000000 l d .data 00000000 .data
18: 00000000 l d .bss 00000000 .bss
19: 00000000 l d .piggydata 00000000 .piggydata
20: 00000000 g .piggydata 00000000 input_data
21: 0002187e g .piggydata 00000000 input_data_end
再看看main:
1: pengdl@debian:~/test/c/pic2$ objdump -ht main | grep input_data
2: 0002187e g .piggydata 00000000 input_data_end
3: 00000000 g .piggydata 00000000 input_data
从data.o的objdump信息可以看到,它的.piggydata是不能重定位的,再看看main的信息,input_data的地址直接就是0,在main.c中会发生访问0地址的段错误!!从main的运行打印信息中也可以看到:input_data = (nil)
把.piggydata的段属性重新设置为"a",再看看objdump信息:
1: pengdl@debian:~/test/c/pic2$ objdump -ht data.o
2:
3: data.o: file format elf32-i386
4:
5: Sections:
6: Idx Name Size VMA LMA File off Algn
7: 0 .text 00000000 00000000 00000000 00000034 2**2
8: CONTENTS, ALLOC, LOAD, READONLY, CODE
9: 1 .data 00000000 00000000 00000000 00000034 2**2
10: CONTENTS, ALLOC, LOAD, DATA
11: 2 .bss 00000000 00000000 00000000 00000034 2**2
12: ALLOC
13: 3 .piggydata 0002187e 00000000 00000000 00000034 2**0
14:CONTENTS, ALLOC, LOAD, READONLY, DATA
15: SYMBOL TABLE:
16: 00000000 l d .text 00000000 .text
17: 00000000 l d .data 00000000 .data
18: 00000000 l d .bss 00000000 .bss
19: 00000000 l d .piggydata 00000000 .piggydata
20: 00000000 g .piggydata 00000000 input_data
21: 0002187e g .piggydata 00000000 input_data_end
1: pengdl@debian:~/test/c/pic2$ objdump -ht main | grep input_data
2: 08069e63 g .piggydata 00000000 input_data_end
3: 080485e5 g .piggydata 00000000 input_data
可以看到,这下信息就正常了。
- main.c
1: #include
2:
3: int main(int argc, const char *argv[])
4: {
5: int i;
6:
7: extern const unsigned long input_data;
8: extern const unsigned long input_data_end;
9:
10: const unsigned char *start = (const unsigned char *)&input_data;
11: const unsigned char *end = (const unsigned char *)&input_data_end;
12: unsigned long size = end - start;
13:
14: printf("input_data = %p\n", &input_data);
15: printf("input_data_end = %p\n", &input_data_end);
16: printf("size = %#0x\n", size);
17:
18:
19:
20: for(i=0; i
21: {
22: if(i % 16 == 0)
23: {
24: printf("\n%0#x\t\t",i);
25: }
26: printf("%3x ",start[i]);
27: }
28:
29: printf("\n");
30:
31:
32: return 0;
33: }
需要注意的是:如何使用data.S中的标号。
- Makefile
1: main:main.o data.o
2: $(CC) $^ -o $@
3:
4: data.o:data.S
5:
6: main.c:main.o
7:
8:
9: clean:
10: $(RM) *.o main
- peng.png 就是一张普通的文件,与图片的格式无关。
下面是运行结果:
pengdl@debian:~/test/c/pic2$ ./main
input_data = 0x80485e5 // 数值跟main的objdump信息是一致的 input_data_end = 0x8069e63 size = 0x2187e //注意指针相减的含义00 89 50 4e 47 d a 1a a 0 0 0 d 49 48 44 52
0x10 0 0 1 28 0 0 1 89 8 2 0 0 0 b6 25 39 0x20 5 0 0 0 9 70 48 59 73 0 0 e c4 0 0 e 0x30 c4 1 95 2b e 1b 0 0 20 0 49 44 41 54 78 da 0x40 ec bd 67 5f 23 59 b2 af db 1f eb ee b3 a7 bb c 0x50 de a 79 21 bc 24 bc 40 de 23 ef bd f0 de 43 51 0x60 a6 ed 9c fb 1 ef 3f 56 64 2e a5 4 d5 33 67 df 0x70 17 73 5e 54 fe 9e d1 24 22 11 a2 2b 1f 45 c4 b2 0x80 3f 7d fe eb 4f f0 ed af bf 7a f8 e3 cf af bf ff 0x90 c1 e0 9c f9 f2 db ef 2f df 7e 7d 7c f9 fc f0 e9 0xa0 5 dc 3e 3e 5d dd dd 9f 5f df 9c 5e 5e 9d 5c 5c 0xb0 82 e3 cb cb a3 f3 ab c3 b3 cb 83 b3 b3 fd d3 53 0xc0 a6 7d 7c dc 3e 3c 68 1d ec b7 3a 6d d0 de ef b4下面是用winhex看到的:
第二种方法
使用objcopy工具
目录结构:
pengdl@debian:~/test/c/pic$ tree -lh
. |-- [ 999] main.c |-- [ 77] Makefile |-- [135K] peng.o `-- [134K] peng.png0 directories, 4 files
- peng.o
使用如下命令生成peng.o:
objdcopy –I binary –O elf32-i386 –B i386 peng.png peng.o
objdump –ht peng.o
参数解释:
-I --input-target <bfdname> Assume input file is in format <bfdname>
-O --output-target <bfdname> Create an output file in format <bfdname> -B --binary-architecture <arch> Set arch of output file, when input is binary-h, --[section-]headers Display the contents of the section headers
-t, --syms Display the contents of the symbol table(s)
1: pengdl@debian:~/test/c/pic$ objdump -ht peng.o
2:
3: peng.o: file format elf32-i386
4:
5: Sections:
6: Idx Name Size VMA LMA File off Algn
7: 0 .data 0002187e 00000000 00000000 00000034 2**0
8:CONTENTS, ALLOC, LOAD, DATA
9: SYMBOL TABLE:
10: 00000000 l d .data 00000000 .data
11: 00000000 g .data 00000000 _binary_peng_png_start
12: 0002187e g .data 00000000 _binary_peng_png_end
13: 0002187e g *ABS* 00000000 _binary_peng_png_size
符号“_binary_peng_png_start”、“_binary_peng_png_end”和“_binary_peng_png_size”分别表示该图片文件在内存中的起始地址、结束地址和大小。
可以看到,图片数据被放到了.data段。
- main.c
1: #include
2:
3: int main(int argc, const char *argv[])
4: {
5: int i;
6:
7: extern const unsigned long _binary_peng_png_start;
8: extern const unsigned long _binary_peng_png_size;
9: extern const unsigned long _binary_peng_png_end;
10:
11: const unsigned char *start = (const unsigned char *)&_binary_peng_png_start;
12: const unsigned long size = (const unsigned long)&_binary_peng_png_size;
13: const unsigned char *end = (const unsigned char *)&_binary_peng_png_end;
14:
15: printf("_binary_peng_png_start = %p\n", &_binary_peng_png_start);
16: printf("_binary_peng_png_size = %p\n", &_binary_peng_png_size);
17: printf("_binary_peng_png_end = %p\n", &_binary_peng_png_end);
18:
19:
20:
21: for(i=0; i
22: {
23: if(i % 16 == 0)
24: {
25: printf("\n%0#x\t\t",i);
26: }
27: printf("%3x ",start[i]);
28: }
29:
30: printf("\n");
31:
32:
33: return 0;
34: }
- Makefile
1: main:main.o peng.o
2: $(CC) $^ -o $@
3:
4: main.c:main.o
5:
6:
7: clean:
8: $(RM) *.o main
下面是运行结果:
pengdl@debian:~/test/c/pic$ ./main
_binary_peng_png_start = 0x80496f4 _binary_peng_png_size = 0x2187e _binary_peng_png_end = 0x806af720 89 50 4e 47 d a 1a a 0 0 0 d 49 48 44 52
0x10 0 0 1 28 0 0 1 89 8 2 0 0 0 b6 25 39 0x20 5 0 0 0 9 70 48 59 73 0 0 e c4 0 0 e 0x30 c4 1 95 2b e 1b 0 0 20 0 49 44 41 54 78 da 0x40 ec bd 67 5f 23 59 b2 af db 1f eb ee b3 a7 bb c 0x50 de a 79 21 bc 24 bc 40 de 23 ef bd f0 de 43 51 0x60 a6 ed 9c fb 1 ef 3f 56 64 2e a5 4 d5 33 67 df 0x70 17 73 5e 54 fe 9e d1 24 22 11 a2 2b 1f 45 c4 b2 0x80 3f 7d fe eb 4f f0 ed af bf 7a f8 e3 cf af bf ff 0x90 c1 e0 9c f9 f2 db ef 2f df 7e 7d 7c f9 fc f0 e9 0xa0 5 dc 3e 3e 5d dd dd 9f 5f df 9c 5e 5e 9d 5c 5c。。。。。。
完!!!