时间：2021-05-10 08:48:20 | 栏目：Shell | 点击：次
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。
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命令
readelf -S libxxx.so |grep debug