Linux下查看.so和可执行文件是否debug编译的方法(必看)_Linux

今天同事问我，如何判断一个.so是否是debug编译的。

我记得以前自己是用file来查看一个.so，根据是否包含"not stripped"来判断该.so是否是debug编译的，于是就没做实验就回答。

然而，stripped/not stripped并不是debug/release编译的判断标准. 我对debug和release的.so运行file后，得出几乎相同的输出，都是not stripped. 所以我算是误导同事了。

根据<computers systems - a programmer's perspective>所言, debug/release的区别更多的表现在.so和可执行程序所拥有的段上。debug编译出来的。so和可执行程序拥有很多附加的段来包含哪些debug的信息。所以查看段信息是一种判断的方式。

我在ubuntu 11.04上分别对同一个开源软件进行debug和release编译，并且查看某个.so的段(readelf -s)，发现release编译的只有29个段：

there are 29 section headers, starting at offset 0x1b7d78:
section headers:
[nr] name type address offset
size entsize flags link info align
[ 0] null 0000000000000000 00000000
0000000000000000 0000000000000000 0 0 0
[ 1] .note.gnu.build-i note 00000000000001c8 000001c8
0000000000000024 0000000000000000 a 0 0 4
[ 2] .gnu.hash gnu_hash 00000000000001f0 000001f0
0000000000003430 0000000000000000 a 3 0 8
[ 3] .dynsym dynsym 0000000000003620 00003620
000000000000b400 0000000000000018 a 4 2 8
[ 4] .dynstr strtab 000000000000ea20 0000ea20
00000000000083e2 0000000000000000 a 0 0 1
[ 5] .gnu.version versym 0000000000016e02 00016e02
0000000000000f00 0000000000000002 a 3 0 2
[ 6] .gnu.version_r verneed 0000000000017d08 00017d08
0000000000000080 0000000000000000 a 4 2 8
[ 7] .rela.dyn rela 0000000000017d88 00017d88
0000000000009570 0000000000000018 a 3 0 8
[ 8] .rela.plt rela 00000000000212f8 000212f8
00000000000080d0 0000000000000018 a 3 10 8
[ 9] .init progbits 00000000000293c8 000293c8
0000000000000018 0000000000000000 ax 0 0 4
[10] .plt progbits 00000000000293e0 000293e0
00000000000055f0 0000000000000010 ax 0 0 4
[11] .text progbits 000000000002e9d0 0002e9d0
0000000000144658 0000000000000000 ax 0 0 16
[12] .fini progbits 0000000000173028 00173028
000000000000000e 0000000000000000 ax 0 0 4
[13] .rodata progbits 0000000000173040 00173040
000000000001e9a0 0000000000000000 a 0 0 32
[14] .eh_frame_hdr progbits 00000000001919e0 001919e0
000000000000427c 0000000000000000 a 0 0 4
[15] .eh_frame progbits 0000000000195c60 00195c60
0000000000017d7c 0000000000000000 a 0 0 8
[16] .ctors progbits 00000000003ae1e8 001ae1e8
0000000000000010 0000000000000000 wa 0 0 8
[17] .dtors progbits 00000000003ae1f8 001ae1f8
0000000000000010 0000000000000000 wa 0 0 8
[18] .jcr progbits 00000000003ae208 001ae208
0000000000000008 0000000000000000 wa 0 0 8
[19] .data.rel.ro progbits 00000000003ae220 001ae220
0000000000005b38 0000000000000000 wa 0 0 32
[20] .dynamic dynamic 00000000003b3d58 001b3d58
00000000000001a0 0000000000000010 wa 4 0 8
[21] .got progbits 00000000003b3ef8 001b3ef8
00000000000010e8 0000000000000008 wa 0 0 8
[22] .got.plt progbits 00000000003b4fe8 001b4fe8
0000000000002b08 0000000000000008 wa 0 0 8
[23] .data progbits 00000000003b7b00 001b7b00
0000000000000158 0000000000000000 wa 0 0 32
[24] .bss nobits 00000000003b7c58 001b7c58
0000000000000010 0000000000000000 wa 0 0 8
[25] .comment progbits 0000000000000000 001b7c58
000000000000002a 0000000000000001 ms 0 0 1
[26] .shstrtab strtab 0000000000000000 001b7c82
00000000000000f5 0000000000000000 0 0 1
[27] .symtab symtab 0000000000000000 001b84b8
000000000000fdb0 0000000000000018 28 788 8
[28] .strtab strtab 0000000000000000 001c8268
000000000000b8b0 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)

而debug编译的则有38个段, 且所有比release编译多出来的段,都是以.debug_作为开始字符串来命名的:

there are 38 section headers, starting at offset 0xdacc00:
section headers:
[nr] name type address offset
size entsize flags link info align
[ 0] null 0000000000000000 00000000
0000000000000000 0000000000000000 0 0 0
[ 1] .note.gnu.build-i note 00000000000001c8 000001c8
0000000000000024 0000000000000000 a 0 0 4
[ 2] .gnu.hash gnu_hash 00000000000001f0 000001f0
0000000000003620 0000000000000000 a 3 0 8
[ 3] .dynsym dynsym 0000000000003810 00003810
000000000000c000 0000000000000018 a 4 2 8
[ 4] .dynstr strtab 000000000000f810 0000f810
0000000000008ccb 0000000000000000 a 0 0 1
[ 5] .gnu.version versym 00000000000184dc 000184dc
0000000000001000 0000000000000002 a 3 0 2
[ 6] .gnu.version_r verneed 00000000000194e0 000194e0
0000000000000070 0000000000000000 a 4 2 8
[ 7] .rela.dyn rela 0000000000019550 00019550
0000000000009b40 0000000000000018 a 3 0 8
[ 8] .rela.plt rela 0000000000023090 00023090
0000000000008388 0000000000000018 a 3 10 8
[ 9] .init progbits 000000000002b418 0002b418
0000000000000018 0000000000000000 ax 0 0 4
[10] .plt progbits 000000000002b430 0002b430
00000000000057c0 0000000000000010 ax 0 0 4
[11] .text progbits 0000000000030bf0 00030bf0
00000000001d2428 0000000000000000 ax 0 0 16
[12] .fini progbits 0000000000203018 00203018
000000000000000e 0000000000000000 ax 0 0 4
[13] .rodata progbits 0000000000203040 00203040
00000000000276b8 0000000000000000 a 0 0 32
[14] .eh_frame_hdr progbits 000000000022a6f8 0022a6f8
00000000000059dc 0000000000000000 a 0 0 4
[15] .eh_frame progbits 00000000002300d8 002300d8
000000000001715c 0000000000000000 a 0 0 8
[16] .ctors progbits 0000000000448018 00248018
0000000000000010 0000000000000000 wa 0 0 8
[17] .dtors progbits 0000000000448028 00248028
0000000000000010 0000000000000000 wa 0 0 8
[18] .jcr progbits 0000000000448038 00248038
0000000000000008 0000000000000000 wa 0 0 8
[19] .data.rel.ro progbits 0000000000448040 00248040
0000000000005b38 0000000000000000 wa 0 0 32
[20] .dynamic dynamic 000000000044db78 0024db78
00000000000001a0 0000000000000010 wa 4 0 8
[21] .got progbits 000000000044dd18 0024dd18
00000000000012d0 0000000000000008 wa 0 0 8
[22] .got.plt progbits 000000000044efe8 0024efe8
0000000000002bf0 0000000000000008 wa 0 0 8
[23] .data progbits 0000000000451be0 00251be0
0000000000000160 0000000000000000 wa 0 0 32
[24] .bss nobits 0000000000451d40 00251d40
0000000000000040 0000000000000000 wa 0 0 16
[25] .comment progbits 0000000000000000 00251d40
0000000000000054 0000000000000001 ms 0 0 1
[26] .debug_aranges progbits 0000000000000000 00251d94
00000000000030c0 0000000000000000 0 0 1
[27] .debug_pubnames progbits 0000000000000000 00254e54
000000000000b8cb 0000000000000000 0 0 1
[28] .debug_info progbits 0000000000000000 0026071f
000000000097f69b 0000000000000000 0 0 1
[29] .debug_abbrev progbits 0000000000000000 00bdfdba
0000000000028211 0000000000000000 0 0 1
[30] .debug_line progbits 0000000000000000 00c07fcb
0000000000075fbf 0000000000000000 0 0 1
[31] .debug_str progbits 0000000000000000 00c7df8a
0000000000019789 0000000000000001 ms 0 0 1
[32] .debug_loc progbits 0000000000000000 00c97713
0000000000043528 0000000000000000 0 0 1
[33] .debug_pubtypes progbits 0000000000000000 00cdac3b
00000000000d1c97 0000000000000000 0 0 1
[34] .debug_ranges progbits 0000000000000000 00dac8d2
00000000000001c0 0000000000000000 0 0 1
[35] .shstrtab strtab 0000000000000000 00daca92
000000000000016e 0000000000000000 0 0 1
[36] .symtab symtab 0000000000000000 00dad580
0000000000014688 0000000000000018 37 1437 8
[37] .strtab strtab 0000000000000000 00dc1c08
000000000000e5a1 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)

对于可执行文件也有类似的区别。

所以这应当是判断debug/release的一个比较正确的方法了。

===================================

命令

readelf -s libxxx.so |grep debug

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