Linux map 文件解析

一、什么是Map文件

map文件就是通过编译器编译之后，生成的程序、数据及IO空间信息的一种映射文件，里面包含函数大小，入口地址等一些重要信息。从map文件我们可以了解到：

• 程序各区段的寻址是否正确
• 程序各区段的size，即目前存储器的使用量
• 程序中各个symbol的地址
• 各个symbol在存储器中的顺序关系（这在调试时很有用）
• 各个程序文件的存储用量

二、实例说明

1.简单的C 程序，生成map 文件

2. main.c
3. #include <stdio.h>
4. #include "add.h"
5. char* Hello="HelloWorld!";
6. char array[4]={0,1,2,3};
7. char array0[6];
8. int g_gloableInt;
9. double doubletest = 10;
10. char* testP = NULL;
11. int* pInt;
12. #define READ_SIZE (0x7A0)
13. void main(void)
14. {
15. int a = 5,b = 6,sum=0;
16. static int staticInt = 0;
17. char data[READ_SIZE]={0};
18. int ret = 0;
19. FILE* fp = fopen("abuf_apu_nbsm_o1_1_00720.mpg","r");
20. //FILE* fp_out = fopen("abuf_apu_nbsm_o1_1_00720_out.mpg","w+");
21. FILE* fp_out = fopen("abuf_apu_nbsm_o1_1_00720_out.mpg","w+");
22. if(!fp || !fp_out)
23. {
24. printf("NULL data file!");
25. return;
26. }
28. sum=math(a,b);
29. printf("sum is %d\n",sum);
30. staticInt += sum;
31. g_gloableInt =0;
32. printf("main=%016llx,math=%016llx,add=%016llx,sub=%016llx\ng_gloableInt=%016llx staticInt=%016llx Hello=%016llx\n",(long long)main,(long long)math,(long long)add,(long long)sub,(long long)&g_gloableInt,(long long)&staticInt,(long long)Hello);
33. printf("sizeof(doubletest)=%ld sizeof(testP)=%ld sizeof(array0)=%ld \n",sizeof(doubletest),sizeof(testP),sizeof(array0));
34. printf("&doubletest=%016llx,testP=%016llx array0=%016llx\n",(long long)&doubletest,(long long)testP,(long long)array0);
35. fseek(fp, 0, SEEK_SET);
36. fseek(fp_out, 0, SEEK_SET);
37. do
38. {
39. ret=fread(data,1,READ_SIZE,fp);
40. //printf("read %d byte data\n",ret);
41. fwrite((data+32),(ret-32),1,fp_out);
42. }while(ret==READ_SIZE);
43. fclose(fp);
44. fclose(fp_out);
45. return;
46. }
47. ---------------------------------------------------------------------------------------
48. add.c
49. #include "add.h"
50. int Min = 10;
51. int sub(int* v)
52. {
53. *v = (*v >Min)? (*v - Min):*v ;
54. return 0;
55. }
56. int add(int a, int b)
57. {
58. int sum = a+b;
59. sub(&sum);
60. return sum;
61. }
62. int math(int a,int b)
63. {
64. return add(a,b);
65. }
67. ---------------------------------------------------------------------------------------
68. #ifndef __ADD_H__
69. #define __ADD_H__
70. int math(int a, int b);
71. int add(int a, int b);
72. int sub(int* a);
73. #endif
75. --------------------------------------------------------------------------------------
76. dummy.c
77. #include "dummy.h"
79. int dummy_ver0(int dummmy)
80. {
81. return 0;
82. }
83. --------------------------------------------------------------------------------------
84. #ifndef __DUMMY_H__
85. #define __DUMMY_H__
86. int dummy_ver0(int dummmy);
87. #endif

复制代码

编译命令

gcc main.c add.c -Wl,-Map,add.map -o main   

生成的map 文件为：

1. Archive member included to satisfy reference by file (symbol) ==>included archive
3. /usr/lib/x86_64-linux-gnu/libc_nonshared.a(elf-init.oS)
4. /usr/lib/gcc/x86_64-linux-gnu/7/../../../x86_64-linux-gnu/Scrt1.o (__libc_csu_init)
6. As-needed library included to satisfy reference by file (symbol) ==>link 的lib
8. libc.so.6 /tmp/ccYQAtfU.o (fopen@@GLIBC_2.2.5)
10. Allocating common symbols
11. Common symbol size file
13. pInt 0x8 /tmp/ccYQAtfU.o
14. g_gloableInt 0x4 /tmp/ccYQAtfU.o
15. array0 0x6 /tmp/ccYQAtfU.o
17. Discarded input sections
19. .note.GNU-stack
20. 0x0000000000000000 0x0 /usr/lib/gcc/x86_64-linux-gnu/7/../../../x86_64-linux-gnu/Scrt1.o
21. .note.GNU-stack
22. 0x0000000000000000 0x0 /usr/lib/gcc/x86_64-linux-gnu/7/../../../x86_64-linux-gnu/crti.o
23. .note.GNU-stack
24. 0x0000000000000000 0x0 /usr/lib/gcc/x86_64-linux-gnu/7/crtbeginS.o
25. .note.GNU-stack
26. 0x0000000000000000 0x0 /tmp/ccYQAtfU.o ==>实际是main.o
27. .note.GNU-stack
28. 0x0000000000000000 0x0 /tmp/ccetcq5K.o ==>实际是add.o
29. .note.GNU-stack
30. 0x0000000000000000 0x0 /tmp/ccYNVa0B.o ==>实际是dummy.o
31. .note.GNU-stack
32. 0x0000000000000000 0x0 /usr/lib/x86_64-linux-gnu/libc_nonshared.a(elf-init.oS)
33. .note.GNU-stack
34. 0x0000000000000000 0x0 /usr/lib/gcc/x86_64-linux-gnu/7/crtendS.o
35. .note.GNU-stack
36. 0x0000000000000000 0x0 /usr/lib/gcc/x86_64-linux-gnu/7/../../../x86_64-linux-gnu/crtn.o
38. Memory Configuration
40. Name Origin Length Attributes
41. *default* 0x0000000000000000 0xffffffffffffffff
43. Linker script and memory map
45. LOAD /usr/lib/gcc/x86_64-linux-gnu/7/../../../x86_64-linux-gnu/Scrt1.o
46. LOAD /usr/lib/gcc/x86_64-linux-gnu/7/../../../x86_64-linux-gnu/crti.o
47. LOAD /usr/lib/gcc/x86_64-linux-gnu/7/crtbeginS.o
48. LOAD /tmp/ccYQAtfU.o
49. LOAD /tmp/ccetcq5K.o
50. LOAD /tmp/ccYNVa0B.o
51. LOAD /usr/lib/gcc/x86_64-linux-gnu/7/libgcc.a
52. LOAD /usr/lib/gcc/x86_64-linux-gnu/7/libgcc_s.so
53. START GROUP
54. LOAD /usr/lib/gcc/x86_64-linux-gnu/7/libgcc_s.so.1
55. LOAD /usr/lib/gcc/x86_64-linux-gnu/7/libgcc.a
56. END GROUP
57. LOAD /usr/lib/gcc/x86_64-linux-gnu/7/../../../x86_64-linux-gnu/libc.so
58. START GROUP
59. LOAD /lib/x86_64-linux-gnu/libc.so.6
60. LOAD /usr/lib/x86_64-linux-gnu/libc_nonshared.a
61. LOAD /lib/x86_64-linux-gnu/ld-linux-x86-64.so.2
62. END GROUP
63. LOAD /usr/lib/gcc/x86_64-linux-gnu/7/libgcc.a
64. LOAD /usr/lib/gcc/x86_64-linux-gnu/7/libgcc_s.so
65. START GROUP
66. LOAD /usr/lib/gcc/x86_64-linux-gnu/7/libgcc_s.so.1
67. LOAD /usr/lib/gcc/x86_64-linux-gnu/7/libgcc.a
68. END GROUP
69. LOAD /usr/lib/gcc/x86_64-linux-gnu/7/crtendS.o
70. LOAD /usr/lib/gcc/x86_64-linux-gnu/7/../../../x86_64-linux-gnu/crtn.o
71. [!provide] PROVIDE (__executable_start = SEGMENT_START ("text-segment", 0x0))
72. 0x0000000000000238 . = (SEGMENT_START ("text-segment", 0x0) + SIZEOF_HEADERS)
74. .interp 0x0000000000000238 0x1c
75. *(.interp)
76. .interp 0x0000000000000238 0x1c /usr/lib/gcc/x86_64-linux-gnu/7/../../../x86_64-linux-gnu/Scrt1.o
78. .note.ABI-tag 0x0000000000000254 0x20
79. .note.ABI-tag 0x0000000000000254 0x20 /usr/lib/gcc/x86_64-linux-gnu/7/../../../x86_64-linux-gnu/Scrt1.o
81. .note.gnu.build-id
82. 0x0000000000000274 0x24
83. *(.note.gnu.build-id)
84. .note.gnu.build-id
85. 0x0000000000000274 0x24 /usr/lib/gcc/x86_64-linux-gnu/7/../../../x86_64-linux-gnu/Scrt1.o
87. .hash
88. *(.hash)
90. .gnu.hash 0x0000000000000298 0x1c
91. *(.gnu.hash)
92. .gnu.hash 0x0000000000000298 0x1c /usr/lib/gcc/x86_64-linux-gnu/7/../../../x86_64-linux-gnu/Scrt1.o
94. .dynsym 0x00000000000002b8 0x138
95. *(.dynsym)
96. .dynsym 0x00000000000002b8 0x138 /usr/lib/gcc/x86_64-linux-gnu/7/../../../x86_64-linux-gnu/Scrt1.o
98. .dynstr 0x00000000000003f0 0xbf
99. *(.dynstr)
100. .dynstr 0x00000000000003f0 0xbf /usr/lib/gcc/x86_64-linux-gnu/7/../../../x86_64-linux-gnu/Scrt1.o
102. .gnu.version 0x00000000000004b0 0x1a
103. *(.gnu.version)
104. .gnu.version 0x00000000000004b0 0x1a /usr/lib/gcc/x86_64-linux-gnu/7/../../../x86_64-linux-gnu/Scrt1.o
106. .gnu.version_d 0x00000000000004d0 0x0
107. *(.gnu.version_d)
108. .gnu.version_d
109. 0x00000000000004d0 0x0 /usr/lib/gcc/x86_64-linux-gnu/7/../../../x86_64-linux-gnu/Scrt1.o
111. .gnu.version_r 0x00000000000004d0 0x30
112. *(.gnu.version_r)
113. .gnu.version_r
114. 0x00000000000004d0 0x30 /usr/lib/gcc/x86_64-linux-gnu/7/../../../x86_64-linux-gnu/Scrt1.o
116. .rela.dyn 0x0000000000000500 0xd8
117. *(.rela.init)
118. *(.rela.text .rela.text.* .rela.gnu.linkonce.t.*)
119. .rela.text 0x0000000000000500 0x0 /usr/lib/gcc/x86_64-linux-gnu/7/../../../x86_64-linux-gnu/Scrt1.o
120. *(.rela.fini)
121. *(.rela.rodata .rela.rodata.* .rela.gnu.linkonce.r.*)
122. *(.rela.data .rela.data.* .rela.gnu.linkonce.d.*)
123. .rela.data.rel.ro
124. 0x0000000000000500 0x0 /usr/lib/gcc/x86_64-linux-gnu/7/../../../x86_64-linux-gnu/Scrt1.o
125. .rela.data.rel.local
126. 0x0000000000000500 0x30 /usr/lib/gcc/x86_64-linux-gnu/7/../../../x86_64-linux-gnu/Scrt1.o
127. *(.rela.tdata .rela.tdata.* .rela.gnu.linkonce.td.*)
128. *(.rela.tbss .rela.tbss.* .rela.gnu.linkonce.tb.*)
129. *(.rela.ctors)
130. *(.rela.dtors)
131. *(.rela.got)
132. .rela.got 0x0000000000000530 0x78 /usr/lib/gcc/x86_64-linux-gnu/7/../../../x86_64-linux-gnu/Scrt1.o
133. *(.rela.bss .rela.bss.* .rela.gnu.linkonce.b.*)
134. .rela.bss 0x00000000000005a8 0x0 /usr/lib/gcc/x86_64-linux-gnu/7/../../../x86_64-linux-gnu/Scrt1.o
135. *(.rela.ldata .rela.ldata.* .rela.gnu.linkonce.l.*)
136. *(.rela.lbss .rela.lbss.* .rela.gnu.linkonce.lb.*)
137. *(.rela.lrodata .rela.lrodata.* .rela.gnu.linkonce.lr.*)
138. *(.rela.ifunc)
139. .rela.ifunc 0x00000000000005a8 0x0 /usr/lib/gcc/x86_64-linux-gnu/7/../../../x86_64-linux-gnu/Scrt1.o
140. .rela.fini_array
141. 0x00000000000005a8 0x18 /usr/lib/gcc/x86_64-linux-gnu/7/../../../x86_64-linux-gnu/Scrt1.o
142. .rela.init_array
143. 0x00000000000005c0 0x18 /usr/lib/gcc/x86_64-linux-gnu/7/../../../x86_64-linux-gnu/Scrt1.o
145. .rela.plt 0x00000000000005d8 0xa8
146. *(.rela.plt)
147. .rela.plt 0x00000000000005d8 0xa8 /usr/lib/gcc/x86_64-linux-gnu/7/../../../x86_64-linux-gnu/Scrt1.o
148. [!provide] PROVIDE (__rela_iplt_start = .)
149. *(.rela.iplt)
150. [!provide] PROVIDE (__rela_iplt_end = .)
152. .init 0x0000000000000680 0x17
153. *(SORT_NONE(.init))
154. .init 0x0000000000000680 0x12 /usr/lib/gcc/x86_64-linux-gnu/7/../../../x86_64-linux-gnu/crti.o
155. 0x0000000000000680 _init
156. .init 0x0000000000000692 0x5 /usr/lib/gcc/x86_64-linux-gnu/7/../../../x86_64-linux-gnu/crtn.o
158. .plt 0x00000000000006a0 0x80
159. *(.plt)
160. .plt 0x00000000000006a0 0x80 /usr/lib/gcc/x86_64-linux-gnu/7/../../../x86_64-linux-gnu/Scrt1.o
161. *(.iplt)
163. .plt.got 0x0000000000000720 0x8
164. *(.plt.got)
165. .plt.got 0x0000000000000720 0x8 /usr/lib/gcc/x86_64-linux-gnu/7/../../../x86_64-linux-gnu/Scrt1.o
167. .plt.sec
168. *(.plt.sec)
170. .text 0x0000000000000730 0x4c2
171. *(.text.unlikely .text.*_unlikely .text.unlikely.*)
172. *(.text.exit .text.exit.*)
173. *(.text.startup .text.startup.*)
174. *(.text.hot .text.hot.*)
175. *(.text .stub .text.* .gnu.linkonce.t.*)
176. .text 0x0000000000000730 0x2b /usr/lib/gcc/x86_64-linux-gnu/7/../../../x86_64-linux-gnu/Scrt1.o
177. 0x0000000000000730 _start
178. .text 0x000000000000075b 0x0 /usr/lib/gcc/x86_64-linux-gnu/7/../../../x86_64-linux-gnu/crti.o
179. *fill* 0x000000000000075b 0x5
180. .text 0x0000000000000760 0xda /usr/lib/gcc/x86_64-linux-gnu/7/crtbeginS.o
181. .text 0x000000000000083a 0x289 /tmp/ccYQAtfU.o
182. 0x000000000000083a main
183. .text 0x0000000000000ac3 0xa9 /tmp/ccetcq5K.o
184. 0x0000000000000ac3 sub
185. 0x0000000000000b00 add
186. 0x0000000000000b4d math
187. .text 0x0000000000000b6c 0xe /tmp/ccYNVa0B.o
188. 0x0000000000000b6c dummy_ver0
189. *fill* 0x0000000000000b7a 0x6
190. .text 0x0000000000000b80 0x72 /usr/lib/x86_64-linux-gnu/libc_nonshared.a(elf-init.oS)
191. 0x0000000000000b80 __libc_csu_init
192. 0x0000000000000bf0 __libc_csu_fini
193. .text 0x0000000000000bf2 0x0 /usr/lib/gcc/x86_64-linux-gnu/7/crtendS.o
194. .text 0x0000000000000bf2 0x0 /usr/lib/gcc/x86_64-linux-gnu/7/../../../x86_64-linux-gnu/crtn.o
195. *(.gnu.warning)
197. .fini 0x0000000000000bf4 0x9
198. *(SORT_NONE(.fini))
199. .fini 0x0000000000000bf4 0x4 /usr/lib/gcc/x86_64-linux-gnu/7/../../../x86_64-linux-gnu/crti.o
200. 0x0000000000000bf4 _fini
201. .fini 0x0000000000000bf8 0x5 /usr/lib/gcc/x86_64-linux-gnu/7/../../../x86_64-linux-gnu/crtn.o
202. [!provide] PROVIDE (__etext = .)
203. [!provide] PROVIDE (_etext = .)
204. [!provide] PROVIDE (etext = .)
206. .rodata 0x0000000000000c00 0x152
207. *(.rodata .rodata.* .gnu.linkonce.r.*)
208. .rodata.cst4 0x0000000000000c00 0x4 /usr/lib/gcc/x86_64-linux-gnu/7/../../../x86_64-linux-gnu/Scrt1.o
209. 0x0000000000000c00 _IO_stdin_used
210. *fill* 0x0000000000000c04 0x4
211. .rodata 0x0000000000000c08 0x14a /tmp/ccYQAtfU.o
213. .rodata1
214. *(.rodata1)
216. .eh_frame_hdr 0x0000000000000d54 0x5c
217. *(.eh_frame_hdr)
218. .eh_frame_hdr 0x0000000000000d54 0x5c /usr/lib/gcc/x86_64-linux-gnu/7/../../../x86_64-linux-gnu/Scrt1.o
219. 0x0000000000000d54 __GNU_EH_FRAME_HDR
220. *(.eh_frame_entry .eh_frame_entry.*)
222. .eh_frame 0x0000000000000db0 0x188
223. *(.eh_frame)
224. .eh_frame 0x0000000000000db0 0x30 /usr/lib/gcc/x86_64-linux-gnu/7/../../../x86_64-linux-gnu/Scrt1.o
225. 0x2c (size before relaxing)
226. *fill* 0x0000000000000de0 0x0
227. .eh_frame 0x0000000000000de0 0x40 /usr/lib/gcc/x86_64-linux-gnu/7/../../../x86_64-linux-gnu/Scrt1.o
228. .eh_frame 0x0000000000000e20 0x18 /usr/lib/gcc/x86_64-linux-gnu/7/../../../x86_64-linux-gnu/Scrt1.o
229. 0x30 (size before relaxing)
230. .eh_frame 0x0000000000000e38 0x20 /tmp/ccYQAtfU.o
231. 0x38 (size before relaxing)
232. .eh_frame 0x0000000000000e58 0x60 /tmp/ccetcq5K.o
233. 0x78 (size before relaxing)
234. .eh_frame 0x0000000000000eb8 0x20 /tmp/ccYNVa0B.o
235. 0x38 (size before relaxing)
236. .eh_frame 0x0000000000000ed8 0x5c /usr/lib/x86_64-linux-gnu/libc_nonshared.a(elf-init.oS)
237. 0x78 (size before relaxing)
238. .eh_frame 0x0000000000000f34 0x4 /usr/lib/gcc/x86_64-linux-gnu/7/crtendS.o
239. *(.eh_frame.*)
241. .gcc_except_table
242. *(.gcc_except_table .gcc_except_table.*)
244. .gnu_extab
245. *(.gnu_extab*)
247. .exception_ranges
248. *(.exception_ranges .exception_ranges*)
249. 0x0000000000201d88 . = DATA_SEGMENT_ALIGN (CONSTANT (MAXPAGESIZE), CONSTANT (COMMONPAGESIZE))
251. .eh_frame
252. *(.eh_frame)
253. *(.eh_frame.*)
255. .gnu_extab
256. *(.gnu_extab)
258. .gcc_except_table
259. *(.gcc_except_table .gcc_except_table.*)
261. .exception_ranges
262. *(.exception_ranges .exception_ranges*)
264. .tdata
265. *(.tdata .tdata.* .gnu.linkonce.td.*)
267. .tbss
268. *(.tbss .tbss.* .gnu.linkonce.tb.*)
269. *(.tcommon)
271. .preinit_array 0x0000000000201d88 0x0
272. [!provide] PROVIDE (__preinit_array_start = .)
273. *(.preinit_array)
274. [!provide] PROVIDE (__preinit_array_end = .)
276. .init_array 0x0000000000201d88 0x8
277. 0x0000000000201d88 PROVIDE (__init_array_start = .)
278. *(SORT_BY_INIT_PRIORITY(.init_array.*) SORT_BY_INIT_PRIORITY(.ctors.*))
279. *(.init_array EXCLUDE_FILE(*crtend?.o *crtend.o *crtbegin?.o *crtbegin.o) .ctors)
280. .init_array 0x0000000000201d88 0x8 /usr/lib/gcc/x86_64-linux-gnu/7/crtbeginS.o
281. 0x0000000000201d90 PROVIDE (__init_array_end = .)
283. .fini_array 0x0000000000201d90 0x8
284. [!provide] PROVIDE (__fini_array_start = .)
285. *(SORT_BY_INIT_PRIORITY(.fini_array.*) SORT_BY_INIT_PRIORITY(.dtors.*))
286. *(.fini_array EXCLUDE_FILE(*crtend?.o *crtend.o *crtbegin?.o *crtbegin.o) .dtors)
287. .fini_array 0x0000000000201d90 0x8 /usr/lib/gcc/x86_64-linux-gnu/7/crtbeginS.o
288. [!provide] PROVIDE (__fini_array_end = .)
290. .ctors
291. *crtbegin.o(.ctors)
292. *crtbegin?.o(.ctors)
293. *(EXCLUDE_FILE(*crtend?.o *crtend.o) .ctors)
294. *(SORT_BY_NAME(.ctors.*))
295. *(.ctors)
297. .dtors
298. *crtbegin.o(.dtors)
299. *crtbegin?.o(.dtors)
300. *(EXCLUDE_FILE(*crtend?.o *crtend.o) .dtors)
301. *(SORT_BY_NAME(.dtors.*))
302. *(.dtors)
304. .jcr
305. *(.jcr)
307. .data.rel.ro 0x0000000000201d98 0x0
308. *(.data.rel.ro.local* .gnu.linkonce.d.rel.ro.local.*)
309. *(.data.rel.ro .data.rel.ro.* .gnu.linkonce.d.rel.ro.*)
310. .data.rel.ro 0x0000000000201d98 0x0 /usr/lib/gcc/x86_64-linux-gnu/7/../../../x86_64-linux-gnu/Scrt1.o
312. .dynamic 0x0000000000201d98 0x1f0
313. *(.dynamic)
314. .dynamic 0x0000000000201d98 0x1f0 /usr/lib/gcc/x86_64-linux-gnu/7/../../../x86_64-linux-gnu/Scrt1.o
315. 0x0000000000201d98 _DYNAMIC
317. .got 0x0000000000201f88 0x78
318. *(.got.plt)
319. .got.plt 0x0000000000201f88 0x50 /usr/lib/gcc/x86_64-linux-gnu/7/../../../x86_64-linux-gnu/Scrt1.o
320. 0x0000000000201f88 _GLOBAL_OFFSET_TABLE_
321. *(.igot.plt)
322. *(.got)
323. .got 0x0000000000201fd8 0x28 /usr/lib/gcc/x86_64-linux-gnu/7/../../../x86_64-linux-gnu/Scrt1.o
324. *(.igot)
325. 0x0000000000202000 . = DATA_SEGMENT_RELRO_END (., 0x0)
327. .data 0x0000000000202000 0x2c
328. *(.data .data.* .gnu.linkonce.d.*)
329. .data 0x0000000000202000 0x4 /usr/lib/gcc/x86_64-linux-gnu/7/../../../x86_64-linux-gnu/Scrt1.o
330. 0x0000000000202000 data_start
331. 0x0000000000202000 __data_start
332. .data 0x0000000000202004 0x0 /usr/lib/gcc/x86_64-linux-gnu/7/../../../x86_64-linux-gnu/crti.o
333. .data 0x0000000000202004 0x0 /usr/lib/gcc/x86_64-linux-gnu/7/crtbeginS.o
334. *fill* 0x0000000000202004 0x4
335. .data.rel.local
336. 0x0000000000202008 0x8 /usr/lib/gcc/x86_64-linux-gnu/7/crtbeginS.o
337. 0x0000000000202008 __dso_handle
338. .data 0x0000000000202010 0x10 /tmp/ccYQAtfU.o
339. 0x0000000000202010 array
340. 0x0000000000202018 doubletest
341. .data.rel.local
342. 0x0000000000202020 0x8 /tmp/ccYQAtfU.o
343. 0x0000000000202020 Hello
344. .data 0x0000000000202028 0x4 /tmp/ccetcq5K.o
345. 0x0000000000202028 Min
346. .data 0x000000000020202c 0x0 /tmp/ccYNVa0B.o
347. .data 0x000000000020202c 0x0 /usr/lib/x86_64-linux-gnu/libc_nonshared.a(elf-init.oS)
348. .data 0x000000000020202c 0x0 /usr/lib/gcc/x86_64-linux-gnu/7/crtendS.o
349. .data 0x000000000020202c 0x0 /usr/lib/gcc/x86_64-linux-gnu/7/../../../x86_64-linux-gnu/crtn.o
351. .tm_clone_table
352. 0x0000000000202030 0x0
353. .tm_clone_table
354. 0x0000000000202030 0x0 /usr/lib/gcc/x86_64-linux-gnu/7/crtbeginS.o
355. .tm_clone_table
356. 0x0000000000202030 0x0 /usr/lib/gcc/x86_64-linux-gnu/7/crtendS.o
358. .data1
359. *(.data1)
360. 0x0000000000202030 _edata = .
361. [!provide] PROVIDE (edata = .)
362. 0x0000000000202030 . = .
363. 0x0000000000202030 __bss_start = .
365. .bss 0x0000000000202030 0x30
366. *(.dynbss)
367. .dynbss 0x0000000000202030 0x0 /usr/lib/gcc/x86_64-linux-gnu/7/../../../x86_64-linux-gnu/Scrt1.o
368. *(.bss .bss.* .gnu.linkonce.b.*)
369. .bss 0x0000000000202030 0x0 /usr/lib/gcc/x86_64-linux-gnu/7/../../../x86_64-linux-gnu/Scrt1.o
370. .bss 0x0000000000202030 0x0 /usr/lib/gcc/x86_64-linux-gnu/7/../../../x86_64-linux-gnu/crti.o
371. .bss 0x0000000000202030 0x1 /usr/lib/gcc/x86_64-linux-gnu/7/crtbeginS.o
372. *fill* 0x0000000000202031 0x7
373. .bss 0x0000000000202038 0xc /tmp/ccYQAtfU.o
374. 0x0000000000202038 testP
375. .bss 0x0000000000202044 0x0 /tmp/ccetcq5K.o
376. .bss 0x0000000000202044 0x0 /tmp/ccYNVa0B.o
377. .bss 0x0000000000202044 0x0 /usr/lib/x86_64-linux-gnu/libc_nonshared.a(elf-init.oS)
378. .bss 0x0000000000202044 0x0 /usr/lib/gcc/x86_64-linux-gnu/7/crtendS.o
379. .bss 0x0000000000202044 0x0 /usr/lib/gcc/x86_64-linux-gnu/7/../../../x86_64-linux-gnu/crtn.o
380. *(COMMON)
381. *fill* 0x0000000000202044 0x4
382. COMMON 0x0000000000202048 0x12 /tmp/ccYQAtfU.o
383. 0x0000000000202048 pInt
384. 0x0000000000202050 g_gloableInt
385. 0x0000000000202054 array0
386. 0x0000000000202060 . = ALIGN ((. != 0x0)?0x8:0x1)
387. *fill* 0x000000000020205a 0x6
389. .lbss
390. *(.dynlbss)
391. *(.lbss .lbss.* .gnu.linkonce.lb.*)
392. *(LARGE_COMMON)
393. 0x0000000000202060 . = ALIGN (0x8)
394. 0x0000000000202060 . = SEGMENT_START ("ldata-segment", .)
396. .lrodata
397. *(.lrodata .lrodata.* .gnu.linkonce.lr.*)
399. .ldata 0x0000000000602060 0x0
400. *(.ldata .ldata.* .gnu.linkonce.l.*)
401. 0x0000000000602060 . = ALIGN ((. != 0x0)?0x8:0x1)
402. 0x0000000000602060 . = ALIGN (0x8)
403. 0x0000000000602060 _end = .
404. [!provide] PROVIDE (end = .)
405. 0x0000000000602060 . = DATA_SEGMENT_END (.)
407. .stab
408. *(.stab)
410. .stabstr
411. *(.stabstr)
413. .stab.excl
414. *(.stab.excl)
416. .stab.exclstr
417. *(.stab.exclstr)
419. .stab.index
420. *(.stab.index)
422. .stab.indexstr
423. *(.stab.indexstr)
425. .comment 0x0000000000000000 0x29
426. *(.comment)
427. .comment 0x0000000000000000 0x29 /usr/lib/gcc/x86_64-linux-gnu/7/crtbeginS.o
428. 0x2a (size before relaxing)
429. .comment 0x0000000000000029 0x2a /tmp/ccYQAtfU.o
430. .comment 0x0000000000000029 0x2a /tmp/ccetcq5K.o
431. .comment 0x0000000000000029 0x2a /tmp/ccYNVa0B.o
432. .comment 0x0000000000000029 0x2a /usr/lib/gcc/x86_64-linux-gnu/7/crtendS.o
434. .debug
435. *(.debug)
437. .line
438. *(.line)
440. .debug_srcinfo
441. *(.debug_srcinfo)
443. .debug_sfnames
444. *(.debug_sfnames)
446. .debug_aranges
447. *(.debug_aranges)
449. .debug_pubnames
450. *(.debug_pubnames)
452. .debug_info
453. *(.debug_info .gnu.linkonce.wi.*)
455. .debug_abbrev
456. *(.debug_abbrev)
458. .debug_line
459. *(.debug_line .debug_line.* .debug_line_end)
461. .debug_frame
462. *(.debug_frame)
464. .debug_str
465. *(.debug_str)
467. .debug_loc
468. *(.debug_loc)
470. .debug_macinfo
471. *(.debug_macinfo)
473. .debug_weaknames
474. *(.debug_weaknames)
476. .debug_funcnames
477. *(.debug_funcnames)
479. .debug_typenames
480. *(.debug_typenames)
482. .debug_varnames
483. *(.debug_varnames)
485. .debug_pubtypes
486. *(.debug_pubtypes)
488. .debug_ranges
489. *(.debug_ranges)
491. .debug_macro
492. *(.debug_macro)
494. .debug_addr
495. *(.debug_addr)
497. .gnu.attributes
498. *(.gnu.attributes)
500. /DISCARD/
501. *(.note.GNU-stack)
502. *(.gnu_debuglink)
503. *(.gnu.lto_*)
504. OUTPUT(main elf64-x86-64)

复制代码

2.对比C 程序，读map 文件

tmp/testC$ ./main
sum is 1
main=000055854636e83a,math=000055854636eb4d,add=000055854636eb00,sub=000055854636eac3
g_gloableInt=0000558546570050 staticInt=0000558546570040 Hello=000055854636ec08
sizeof(doubletest)=8 sizeof(testP)=8 sizeof(array0)=6 
&doubletest=0000558546570018,testP=0000000000000000 array0=0000558546570054

1）首先是included archive file

Archive member included to satisfy reference by file (symbol) ==>included archive

/usr/lib/x86_64-linux-gnu/libc_nonshared.a(elf-init.oS)
                              /usr/lib/gcc/x86_64-linux-gnu/7/../../../x86_64-linux-gnu/Scrt1.o (__libc_csu_init)

解析：

> Scrt1.o 这个目标文件会调用到__libc_csu_init 这个函数

> __libc_csu_init 这个函数在elf-init.oS 目标文件中

> elf-init.oS 目标文件 被打包在libc_nonshared.a 这个archive file

2)然后是library included

As-needed library included to satisfy reference by file (symbol)  ==>link 的lib

libc.so.6                     /tmp/ccYQAtfU.o (fopen@@GLIBC_2.2.5)

解析：

> /tmp/ccYQAtfU.o（实际是main.0） 这个目标文件会调用到fopen 这个函数

> fopen这个函数在libc.so.6 这个lib 中

3)然后是common symbols

Allocating common symbols
Common symbol       size              file

pInt                0x8               /tmp/ccYQAtfU.o
g_gloableInt        0x4               /tmp/ccYQAtfU.o
array0              0x6               /tmp/ccYQAtfU.o

解析：

> /tmp/ccYQAtfU.o（实际是main.0）

> 上述3个变量都是main.c 文件中定义的全局变量，并且没有初始化

> 上述3个全局变量，可以被任何module 访问到，使用并且改变

> 实际写程序中，可以通过common symbols 列出的变量，来检查是否有必要写全局变量，如没有必要，则改成static.

4)Discarded input sections

Discarded input sections

 .note.GNU-stack
                0x0000000000000000        0x0 /usr/lib/gcc/x86_64-linux-gnu/7/../../../x86_64-linux-gnu/Scrt1.o
 .note.GNU-stack
                0x0000000000000000        0x0 /usr/lib/gcc/x86_64-linux-gnu/7/../../../x86_64-linux-gnu/crti.o
 .note.GNU-stack
                0x0000000000000000        0x0 /usr/lib/gcc/x86_64-linux-gnu/7/crtbeginS.o
 .note.GNU-stack
                0x0000000000000000        0x0 /tmp/ccYQAtfU.o ==>实际是main.o
 .note.GNU-stack
                0x0000000000000000        0x0 /tmp/ccetcq5K.o ==>实际是add.o
 .note.GNU-stack
                0x0000000000000000        0x0 /tmp/ccYNVa0B.o ==>实际是dummy.o
 .note.GNU-stack
                0x0000000000000000        0x0 /usr/lib/x86_64-linux-gnu/libc_nonshared.a(elf-init.oS)
 .note.GNU-stack
                0x0000000000000000        0x0 /usr/lib/gcc/x86_64-linux-gnu/7/crtendS.o
 .note.GNU-stack
                0x0000000000000000        0x0 /usr/lib/gcc/x86_64-linux-gnu/7/../../../x86_64-linux-gnu/crtn.o

解析：

> 原本以为测试程序dummy.c 这个文件中的function 没有被引用，只会把dummy.o 放在discarded input sections

> 实际测试结果，add.o （所有function和变量都被引用）也被放在了这里，有些不理解

5)Memory Configuration

Memory Configuration

Name             Origin             Length             Attributes
*default*        0x0000000000000000 0xffffffffffffffff

解析：

> 因为我是在linux pc 上编译，因此这部分没有特殊的memory 限制

6）Linker script and memory map

LOAD /usr/lib/gcc/x86_64-linux-gnu/7/../../../x86_64-linux-gnu/Scrt1.o
LOAD /usr/lib/gcc/x86_64-linux-gnu/7/../../../x86_64-linux-gnu/crti.o
LOAD /usr/lib/gcc/x86_64-linux-gnu/7/crtbeginS.o
LOAD /tmp/ccYQAtfU.o
LOAD /tmp/ccetcq5K.o
LOAD /tmp/ccYNVa0B.o
LOAD /usr/lib/gcc/x86_64-linux-gnu/7/libgcc.a
LOAD /usr/lib/gcc/x86_64-linux-gnu/7/libgcc_s.so
START GROUP
LOAD /usr/lib/gcc/x86_64-linux-gnu/7/libgcc_s.so.1
LOAD /usr/lib/gcc/x86_64-linux-gnu/7/libgcc.a
END GROUP

......

(.text start address is 0x0000000000000730, total size is x4c2)

.text           0x0000000000000730      0x4c2
 *(.text.unlikely .text.*_unlikely .text.unlikely.*)
 *(.text.exit .text.exit.*)
 *(.text.startup .text.startup.*)
 *(.text.hot .text.hot.*)
 *(.text .stub .text.* .gnu.linkonce.t.*)
 .text          0x0000000000000730       0x2b /usr/lib/gcc/x86_64-linux-gnu/7/../../../x86_64-linux-gnu/Scrt1.o
                0x0000000000000730                _start
 .text          0x000000000000075b        0x0 /usr/lib/gcc/x86_64-linux-gnu/7/../../../x86_64-linux-gnu/crti.o
 *fill*         0x000000000000075b        0x5 
 .text          0x0000000000000760       0xda /usr/lib/gcc/x86_64-linux-gnu/7/crtbeginS.o

(这里根据函数的调用关系，依次排列函数在memory 中的位置，先执行的先占memory)
 .text          0x000000000000083a      0x289 /tmp/ccYQAtfU.o(main.o)
                0x000000000000083a                main
 .text          0x0000000000000ac3       0xa9 /tmp/ccetcq5K.o(add.o)
                0x0000000000000ac3                sub(0xb00-0xac3=0x3D 表示sub函数占用的memory,不包含函数的data)
                0x0000000000000b00                add
                0x0000000000000b4d                math
 .text          0x0000000000000b6c        0xe /tmp/ccYNVa0B.o(dummy.o)
                0x0000000000000b6c                dummy_ver0
 *fill*         0x0000000000000b7a        0x6 
 .text          0x0000000000000b80       0x72 /usr/lib/x86_64-linux-gnu/libc_nonshared.a(elf-init.oS)
                0x0000000000000b80                __libc_csu_init
                0x0000000000000bf0                __libc_csu_fini
 .text          0x0000000000000bf2        0x0 /usr/lib/gcc/x86_64-linux-gnu/7/crtendS.o
 .text          0x0000000000000bf2        0x0 /usr/lib/gcc/x86_64-linux-gnu/7/../../../x86_64-linux-gnu/crtn.o
 *(.gnu.warning)

.fini           0x0000000000000bf4        0x9
 *(SORT_NONE(.fini))
 .fini          0x0000000000000bf4        0x4 /usr/lib/gcc/x86_64-linux-gnu/7/../../../x86_64-linux-gnu/crti.o
                0x0000000000000bf4                _fini
 .fini          0x0000000000000bf8        0x5 /usr/lib/gcc/x86_64-linux-gnu/7/../../../x86_64-linux-gnu/crtn.o
                [!provide]                        PROVIDE (__etext = .)
                [!provide]                        PROVIDE (_etext = .)
                [!provide]                        PROVIDE (etext = .)

（这里是read only data 区域，比如程序中的“helloWorld”就放在这里）

（这块区域start address 是0x0000000000000c00，total size is 0x152 ）

.rodata         0x0000000000000c00      0x152
 *(.rodata .rodata.* .gnu.linkonce.r.*)
 .rodata.cst4   0x0000000000000c00        0x4 /usr/lib/gcc/x86_64-linux-gnu/7/../../../x86_64-linux-gnu/Scrt1.o
                0x0000000000000c00                _IO_stdin_used
 *fill*         0x0000000000000c04        0x4 
 .rodata        0x0000000000000c08      0x14a /tmp/ccYQAtfU.o("helloWorld"?)

.rodata1
 *(.rodata1)

.eh_frame_hdr   0x0000000000000d54       0x5c
 *(.eh_frame_hdr)
 .eh_frame_hdr  0x0000000000000d54       0x5c /usr/lib/gcc/x86_64-linux-gnu/7/../../../x86_64-linux-gnu/Scrt1.o
                0x0000000000000d54                __GNU_EH_FRAME_HDR
 *(.eh_frame_entry .eh_frame_entry.*)

.eh_frame       0x0000000000000db0      0x188
 *(.eh_frame)
 .eh_frame      0x0000000000000db0       0x30 /usr/lib/gcc/x86_64-linux-gnu/7/../../../x86_64-linux-gnu/Scrt1.o
                                         0x2c (size before relaxing)
 *fill*         0x0000000000000de0        0x0 
 .eh_frame      0x0000000000000de0       0x40 /usr/lib/gcc/x86_64-linux-gnu/7/../../../x86_64-linux-gnu/Scrt1.o
 .eh_frame      0x0000000000000e20       0x18 /usr/lib/gcc/x86_64-linux-gnu/7/../../../x86_64-linux-gnu/Scrt1.o
                                         0x30 (size before relaxing)
 .eh_frame      0x0000000000000e38       0x20 /tmp/ccYQAtfU.o
                                         0x38 (size before relaxing)
 .eh_frame      0x0000000000000e58       0x60 /tmp/ccetcq5K.o
                                         0x78 (size before relaxing)
 .eh_frame      0x0000000000000eb8       0x20 /tmp/ccYNVa0B.o
                                         0x38 (size before relaxing)
 .eh_frame      0x0000000000000ed8       0x5c /usr/lib/x86_64-linux-gnu/libc_nonshared.a(elf-init.oS)
                                         0x78 (size before relaxing)
 .eh_frame      0x0000000000000f34        0x4 /usr/lib/gcc/x86_64-linux-gnu/7/crtendS.o
 *(.eh_frame.*)
 

6）.data 区域

（start address is 0x0000000000202000,total size is 0x2c）

.data           0x0000000000202000       0x2c
 *(.data .data.* .gnu.linkonce.d.*)
 .data          0x0000000000202000        0x4 /usr/lib/gcc/x86_64-linux-gnu/7/../../../x86_64-linux-gnu/Scrt1.o
                0x0000000000202000                data_start
                0x0000000000202000                __data_start
 .data          0x0000000000202004        0x0 /usr/lib/gcc/x86_64-linux-gnu/7/../../../x86_64-linux-gnu/crti.o
 .data          0x0000000000202004        0x0 /usr/lib/gcc/x86_64-linux-gnu/7/crtbeginS.o
 *fill*         0x0000000000202004        0x4 
 .data.rel.local
                0x0000000000202008        0x8 /usr/lib/gcc/x86_64-linux-gnu/7/crtbeginS.o
                0x0000000000202008                __dso_handle
 .data          0x0000000000202010       0x10 /tmp/ccYQAtfU.o
                0x0000000000202010                array(array 占用8byte,说明pointer 占用8byte，64bit 系统)
                0x0000000000202018                doubletest（double 类型占用8byte）
 .data.rel.local
                0x0000000000202020        0x8 /tmp/ccYQAtfU.o(Hello 字符指针占用8byte)
                0x0000000000202020                Hello
 .data          0x0000000000202028        0x4 /tmp/ccetcq5K.o（int 类型占用4byte）
                0x0000000000202028                Min
 .data          0x000000000020202c        0x0 /tmp/ccYNVa0B.o(没有全局变量，因此size 是0)
 .data          0x000000000020202c        0x0 /usr/lib/x86_64-linux-gnu/libc_nonshared.a(elf-init.oS)
 .data          0x000000000020202c        0x0 /usr/lib/gcc/x86_64-linux-gnu/7/crtendS.o
 .data          0x000000000020202c        0x0 /usr/lib/gcc/x86_64-linux-gnu/7/../../../x86_64-linux-gnu/crtn.o

解析：

> 初始化的全局变量，会放在这里

> 未初始化的全局变量，不会放在这里

> 如全局变量初始化为0，有的编译器会优化到.bss 。

6）.bss 区域

（start address is 0x0000000000202030,total size is 0x30）

.bss            0x0000000000202030       0x30
 *(.dynbss)
 .dynbss        0x0000000000202030        0x0 /usr/lib/gcc/x86_64-linux-gnu/7/../../../x86_64-linux-gnu/Scrt1.o
 *(.bss .bss.* .gnu.linkonce.b.*)
 .bss           0x0000000000202030        0x0 /usr/lib/gcc/x86_64-linux-gnu/7/../../../x86_64-linux-gnu/Scrt1.o
 .bss           0x0000000000202030        0x0 /usr/lib/gcc/x86_64-linux-gnu/7/../../../x86_64-linux-gnu/crti.o
 .bss           0x0000000000202030        0x1 /usr/lib/gcc/x86_64-linux-gnu/7/crtbeginS.o
 *fill*         0x0000000000202031        0x7 
 .bss           0x0000000000202038        0xc /tmp/ccYQAtfU.o(bss 中指针占12byte?No)
                0x0000000000202038                testP
 .bss           0x0000000000202044        0x0 /tmp/ccetcq5K.o
 .bss           0x0000000000202044        0x0 /tmp/ccYNVa0B.o
 .bss           0x0000000000202044        0x0 /usr/lib/x86_64-linux-gnu/libc_nonshared.a(elf-init.oS)
 .bss           0x0000000000202044        0x0 /usr/lib/gcc/x86_64-linux-gnu/7/crtendS.o
 .bss           0x0000000000202044        0x0 /usr/lib/gcc/x86_64-linux-gnu/7/../../../x86_64-linux-gnu/crtn.o
 *(COMMON)
 *fill*         0x0000000000202044        0x4 
 COMMON         0x0000000000202048       0x12 /tmp/ccYQAtfU.o
                0x0000000000202048                pInt(此处指针占8byte)
                0x0000000000202050                g_gloableInt（int 占4byte）
                0x0000000000202054                array0（占6byte=0x12-0x8-0x4）(正好对应其定义：char array0[6];)
                0x0000000000202060                . = ALIGN ((. != 0x0)?0x8:0x1)
 *fill*         0x000000000020205a        0x6 

.lbss
 *(.dynlbss)
 *(.lbss .lbss.* .gnu.linkonce.lb.*)
 *(LARGE_COMMON)
                0x0000000000202060                . = ALIGN (0x8)
                0x0000000000202060                . = SEGMENT_START ("ldata-segment", .)

.lrodata
 *(.lrodata .lrodata.* .gnu.linkonce.lr.*)

.ldata          0x0000000000602060        0x0
 *(.ldata .ldata.* .gnu.linkonce.l.*)
                0x0000000000602060                . = ALIGN ((. != 0x0)?0x8:0x1)
                0x0000000000602060                . = ALIGN (0x8)
                0x0000000000602060                _end = .
                [!provide]                        PROVIDE (end = .)
                0x0000000000602060                . = DATA_SEGMENT_END (.)

解析：

> 定义的未初始化全局变量放在bss 区域

6）_end

_end 可以体现main 可执行程序最终占用的memory 是 0x 2060 byte?

7）程序执行期间打印地址，以确认上述解读是否正确

$ ./main
sum is 1
main=000055854636e83a,math=000055854636eb4d,add=000055854636eb00,sub=000055854636eac3
g_gloableInt=0000558546570050 staticInt=0000558546570040 Hello=000055854636ec08
sizeof(doubletest)=8 sizeof(testP)=8 sizeof(array0)=6 
&doubletest=0000558546570018,testP=0000000000000000 array0=0000558546570054

解析：

> 程序执行期间打印的是虚拟地址

> 全局函数address 与map 文件一致（低12bit 相同）

> 未初始化全局变量 address 与map 文件一致（低8byte 相同）

> 初始化全局变量 address 与map 文件一致（低8byte 相同）

> Hello 指向的是存放“HelloWorld”的address 0x000055854636ec08,对应到map 文件的这里

 .rodata        0x0000000000000c08      0x14a /tmp/ccYQAtfU.o

基于以上分析，map 文件可以很准确反应程序的memory 使用情况。

8).comment

它存放的是编译器版本等信息。

9)总结

程序放在.text

常量字符串放在.rodata

全局初始化变量放在.data

全局未初始化变量放在.bss

static 函数，不体现在map 文件

static 全局变量（初始化/不初始化）都不体现在map 文件，located in .data

malloc 分配的memory 不在map 文件体现，实际在heap

可执行程序由.text / .data /.bss 3部分组成。

.text 和 .data 都存在可执行文件中，由系统从可执行文件中加载，.bss 不在可执行文件中，由系统初始化。

10）.data 与.bss 的区别

1. 初始化全局变量，放在data 区
2. char array[1024*1024]={0,1,2,3};

复制代码

 .data          0x0000000000202020   0x100008 /tmp/ccuT7WjH.o
                0x0000000000202020                array

编译后的exe size 为

1. testC$ ls -al main
2. -rwxrwxr-x 1 xa00000 xa00000 1061920 May 11 16:57 main

复制代码

1. 未初始化全局变量，放在bss 区
2. char array[1024*1024];

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.bss            0x0000000000202040   0x100050

......
 *(COMMON)
 *fill*         0x0000000000202058        0x8 
 COMMON         0x0000000000202060   0x10002a /tmp/ccKlvAPJ.o
                0x0000000000202060                malloc_ptr
                0x0000000000202068                pInt
                0x0000000000202080                array
                0x0000000000302080                g_gloableInt
                0x0000000000302084                array0

1. testC$ ls -al main
2. -rwxrwxr-x 1 xa00000 xa00000 13328 May 11 17:02 main

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1061920 - 13328=1048592 byte

结论：.bss size 不占用文件空间，只占用运行时的内存空间。

11)static 变量

1. main.c
2. static int tmpdata = 100;
3. static int tmpdata_uni = 100;
4. static void test_fun()
5. {
6. printf("test!");
7. }
8. void main(void)
9. {
10. int a = 5,b = 6,sum=0;
11. static int staticInt = 0;
12. char data[READ_SIZE]={0};
13. int ret = 0;
14. FILE* fp = fopen("abuf_apu_nbsm_o1_1_00720.mpg","r");
15. //FILE* fp_out = fopen("abuf_apu_nbsm_o1_1_00720_out.mpg","w+");
16. FILE* fp_out = fopen("abuf_apu_nbsm_o1_1_00720_out.mpg","w+");
17. static int tmpdata_2= 10;
18. static int tmpdata_2_uni= 10;
19. ......
20. }

复制代码

1. testC$ objdump -t main
3. main: file format elf64-x86-64
5. SYMBOL TABLE:
6. 0000000000000238 l d .interp 0000000000000000 .interp
7. 0000000000000254 l d .note.ABI-tag 0000000000000000 .note.ABI-tag
8. 0000000000000274 l d .note.gnu.build-id 0000000000000000 .note.gnu.build-id
9. 0000000000000298 l d .gnu.hash 0000000000000000 .gnu.hash
10. 00000000000002b8 l d .dynsym 0000000000000000 .dynsym
11. 0000000000000420 l d .dynstr 0000000000000000 .dynstr
12. 00000000000004ec l d .gnu.version 0000000000000000 .gnu.version
13. 0000000000000510 l d .gnu.version_r 0000000000000000 .gnu.version_r
14. 0000000000000540 l d .rela.dyn 0000000000000000 .rela.dyn
15. 0000000000000618 l d .rela.plt 0000000000000000 .rela.plt
16. 00000000000006f0 l d .init 0000000000000000 .init
17. 0000000000000710 l d .plt 0000000000000000 .plt
18. 00000000000007b0 l d .plt.got 0000000000000000 .plt.got
19. 00000000000007c0 l d .text 0000000000000000 .text
20. 0000000000000d04 l d .fini 0000000000000000 .fini
21. 0000000000000d10 l d .rodata 0000000000000000 .rodata
22. 0000000000000e84 l d .eh_frame_hdr 0000000000000000 .eh_frame_hdr
23. 0000000000000ee8 l d .eh_frame 0000000000000000 .eh_frame
24. 0000000000201d78 l d .init_array 0000000000000000 .init_array
25. 0000000000201d80 l d .fini_array 0000000000000000 .fini_array
26. 0000000000201d88 l d .dynamic 0000000000000000 .dynamic
27. 0000000000201f78 l d .got 0000000000000000 .got
28. 0000000000202000 l d .data 0000000000000000 .data
29. 0000000000202040 l d .bss 0000000000000000 .bss
30. 0000000000000000 l d .comment 0000000000000000 .comment
31. 0000000000000000 l df *ABS* 0000000000000000 crtstuff.c
32. 00000000000007f0 l F .text 0000000000000000 deregister_tm_clones
33. 0000000000000830 l F .text 0000000000000000 register_tm_clones
34. 0000000000000880 l F .text 0000000000000000 __do_global_dtors_aux
35. 0000000000202040 l O .bss 0000000000000001 completed.7698
36. 0000000000201d80 l O .fini_array 0000000000000000 __do_global_dtors_aux_fini_array_entry
37. 00000000000008c0 l F .text 0000000000000000 frame_dummy
38. 0000000000201d78 l O .init_array 0000000000000000 __frame_dummy_init_array_entry
39. 0000000000000000 l df *ABS* 0000000000000000 main.c
40. 0000000000202018 l O .data 0000000000000004 tmpdata
41. 000000000020201c l O .data 0000000000000004 tmpdata_uni
42. 00000000000008ca l F .text 0000000000000018 test_fun
43. 0000000000202050 l O .bss 0000000000000004 staticInt.2347
44. 0000000000202020 l O .data 0000000000000004 tmpdata_2_uni.2353
45. 0000000000202024 l O .data 0000000000000004 tmpdata_2.2352
46. 0000000000000000 l df *ABS* 0000000000000000 add.c
47. 0000000000000000 l df *ABS* 0000000000000000 dummy.c
48. 0000000000000000 l df *ABS* 0000000000000000 crtstuff.c
49. 000000000000108c l O .eh_frame 0000000000000000 __FRAME_END__
50. 0000000000000000 l df *ABS* 0000000000000000
51. 0000000000201d80 l .init_array 0000000000000000 __init_array_end
52. 0000000000201d88 l O .dynamic 0000000000000000 _DYNAMIC
53. 0000000000201d78 l .init_array 0000000000000000 __init_array_start
54. 0000000000000e84 l .eh_frame_hdr 0000000000000000 __GNU_EH_FRAME_HDR
55. 0000000000201f78 l O .got 0000000000000000 _GLOBAL_OFFSET_TABLE_
56. 0000000000000d00 g F .text 0000000000000002 __libc_csu_fini
57. 0000000000000000 F *UND* 0000000000000000 free@@GLIBC_2.2.5
58. 0000000000202060 g O .bss 0000000000000008 malloc_ptr
59. 0000000000202068 g O .bss 0000000000000008 pInt
60. 0000000000000000 w *UND* 0000000000000000 _ITM_deregisterTMCloneTable
61. 0000000000202000 w .data 0000000000000000 data_start
62. 0000000000000c10 g F .text 000000000000004d add
63. 0000000000000000 F *UND* 0000000000000000 fread@@GLIBC_2.2.5
64. 0000000000202080 g O .bss 0000000000100000 array
65. 0000000000302080 g O .bss 0000000000000004 g_gloableInt
66. 0000000000202034 g .data 0000000000000000 _edata
67. 0000000000202030 g O .data 0000000000000004 Min
68. 0000000000000000 F *UND* 0000000000000000 fclose@@GLIBC_2.2.5
69. 0000000000000d04 g F .fini 0000000000000000 _fini
70. 0000000000000000 F *UND* 0000000000000000 __stack_chk_fail@@GLIBC_2.4
71. 0000000000000000 F *UND* 0000000000000000 printf@@GLIBC_2.2.5
72. 0000000000000c7c g F .text 000000000000000e dummy_ver0
73. 0000000000000000 F *UND* 0000000000000000 __libc_start_main@@GLIBC_2.2.5
74. 0000000000202000 g .data 0000000000000000 __data_start
75. 0000000000000000 w *UND* 0000000000000000 __gmon_start__
76. 0000000000202008 g O .data 0000000000000000 .hidden __dso_handle
77. 0000000000000d10 g O .rodata 0000000000000004 _IO_stdin_used
78. 0000000000202028 g O .data 0000000000000008 Hello
79. 0000000000000c90 g F .text 0000000000000065 __libc_csu_init
80. 0000000000000000 F *UND* 0000000000000000 malloc@@GLIBC_2.2.5
81. 0000000000302084 g O .bss 0000000000000006 array0
82. 0000000000302090 g .bss 0000000000000000 _end
83. 00000000000007c0 g F .text 000000000000002b _start
84. 0000000000000000 F *UND* 0000000000000000 fseek@@GLIBC_2.2.5
85. 0000000000202034 g .bss 0000000000000000 __bss_start
86. 00000000000008e2 g F .text 00000000000002f1 main
87. 0000000000000000 F *UND* 0000000000000000 fopen@@GLIBC_2.2.5
88. 0000000000202010 g O .data 0000000000000008 doubletest
89. 0000000000000c5d g F .text 000000000000001f math
90. 0000000000202048 g O .bss 0000000000000008 testP
91. 0000000000000000 F *UND* 0000000000000000 fwrite@@GLIBC_2.2.5
92. 0000000000202038 g O .data 0000000000000000 .hidden __TMC_END__
93. 0000000000000000 w *UND* 0000000000000000 _ITM_registerTMCloneTable
94. 0000000000000bd3 g F .text 000000000000003d sub
95. 0000000000000000 w F *UND* 0000000000000000 __cxa_finalize@@GLIBC_2.2.5
96. 00000000000006f0 g F .init 0000000000000000 _init

复制代码

 objdump -t main

0000000000202018 l     O .data  0000000000000004              tmpdata
000000000020201c l     O .data  0000000000000004              tmpdata_uni
00000000000008ca l     F .text  0000000000000018              test_fun
0000000000202050 l     O .bss   0000000000000004              staticInt.2347
0000000000202020 l     O .data  0000000000000004              tmpdata_2_uni.2353
0000000000202024 l     O .data  0000000000000004              tmpdata_2.2352

conclusion:

static gloable (initialed or not-initialed) vars are located in .data

static non-gloable (initialed or not-initialed) vars are located in .data

三、reference

充分理解Linux GCC 链接生成的Map文件 - 知乎 (zhihu.com)