问题描述
我尝试利用 perf 来记录二进制文件的执行流程以及调用堆栈。为了解析符号，我安装了所有必要的调试包（如 -dbg 和 dbgsym 包）。
现在 perf 可以解析二进制的符号，但是，无法解析那些 plt 符号。一个例子：
我的指挥官：
perf record -e intel_pt//u wget www.google.com
perf script --itrace=cri0ns -F+flags,+insn,+ip,+pid,+tid,+sym
wget 246443/246443 [006] 3733275.105775: 1 instructions:u: jcc 562233367dec xcalloc+0x1c (/usr/bin/wget) insn: 75 0f
wget 246443/246443 [006] 3733275.105775: 1 instructions:u: call 562233367dee xcalloc+0x1e (/usr/bin/wget) insn: e8 7d ff fb ff
wget 246443/246443 [006] 3733275.105775: 1 branches:u: call 562233367dee xcalloc+0x1e (/usr/bin/wget) insn: e8 7d ff fb ff
wget 246443/246443 [006] 3733275.105775: 1 instructions:u: 562233327d70 [unkNown] (/usr/bin/wget) insn: f3 0f 1e fa
wget 246443/246443 [006] 3733275.105775: 1 instructions:u: jmp 562233327d74 [unkNown] (/usr/bin/wget) insn: f2 ff 25 0d 50 07 00
wget 246443/246443 [006] 3733275.105775: 1 instructions:u: 7f73b9ec2c90 __libc_calloc+0x0 (/usr/lib/x86_64-linux-gnu/libc-2.31.so) insn: f3 0f 1e fa
wget 246443/246443 [006] 3733275.105775: 1 instructions:u: 7f73b9ec2c94 __libc_calloc+0x4 (/usr/lib/x86_64-linux-gnu/libc-2.31.so) insn: 41 55
wget 246443/246443 [006] 3733275.105775: 1 instructions:u: 7f73b9ec2c96 __libc_calloc+0x6 (/usr/lib/x86_64-linux-gnu/libc-2.31.so) insn: 48 89 f8
如您所见，那些 [unkNown] 符号代表 .plt 部分。但是为什么当时没有解决？
解决方法
我认为 wget 本身也需要 dbgsym，或者按照上面的建议使用 gcc -fno-plt 从源代码重新编译它。我自己用 dbg package 试了一下，我的 perf 脚本输出是这样的。
wget 30246/30246 [029] 8799199.428350: 1 instructions:u: 55a0e2150ae0 ptimer_new+0x0 (/usr/bin/wget) insn: 55
wget 30246/30246 [029] 8799199.428350: 1 instructions:u: 55a0e2150ae1 ptimer_new+0x1 (/usr/bin/wget) insn: bf 01 00 00 00
wget 30246/30246 [029] 8799199.428350: 1 instructions:u: 55a0e2150ae6 ptimer_new+0x6 (/usr/bin/wget) insn: be 20 00 00 00
wget 30246/30246 [029] 8799199.428350: 1 instructions:u: 55a0e2150aeb ptimer_new+0xb (/usr/bin/wget) insn: 53
wget 30246/30246 [029] 8799199.428350: 1 instructions:u: 55a0e2150aec ptimer_new+0xc (/usr/bin/wget) insn: 48 83 ec 28
wget 30246/30246 [029] 8799199.428350: 1 instructions:u: 55a0e2150af0 ptimer_new+0x10 (/usr/bin/wget) insn: 64 48 8b 04 25 28 00 00 00
wget 30246/30246 [029] 8799199.428350: 1 instructions:u: 55a0e2150af9 ptimer_new+0x19 (/usr/bin/wget) insn: 48 89 44 24 18
wget 30246/30246 [029] 8799199.428350: 1 instructions:u: 55a0e2150afe ptimer_new+0x1e (/usr/bin/wget) insn: 31 c0
wget 30246/30246 [029] 8799199.428350: 1 instructions:u: call 55a0e2150b00 ptimer_new+0x20 (/usr/bin/wget) insn: e8 7b 9e 01 00
wget 30246/30246 [029] 8799199.428350: 1 branches:u: call 55a0e2150b00 ptimer_new+0x20 (/usr/bin/wget) => 55a0e216a980 xcalloc+0x0 (/usr/bin/wget) insn: e8 7b 9e 01 00
wget 30246/30246 [029] 8799199.428350: 1 instructions:u: 55a0e216a980 xcalloc+0x0 (/usr/bin/wget) insn: 48 89 f8
wget 30246/30246 [029] 8799199.428350: 1 instructions:u: 55a0e216a983 xcalloc+0x3 (/usr/bin/wget) insn: 48 83 ec 08
wget 30246/30246 [029] 8799199.428350: 1 instructions:u: 55a0e216a987 xcalloc+0x7 (/usr/bin/wget) insn: 48 f7 e6
wget 30246/30246 [029] 8799199.428350: 1 instructions:u: 55a0e216a98a xcalloc+0xa (/usr/bin/wget) insn: 0f 90 c2
wget 30246/30246 [029] 8799199.428350: 1 instructions:u: 55a0e216a98d xcalloc+0xd (/usr/bin/wget) insn: 48 85 c0
wget 30246/30246 [029] 8799199.428350: 1 instructions:u: jcc 55a0e216a990 xcalloc+0x10 (/usr/bin/wget) insn: 78 17
wget 30246/30246 [029] 8799199.428350: 1 instructions:u: 55a0e216a992 xcalloc+0x12 (/usr/bin/wget) insn: 0f b6 d2
wget 30246/30246 [029] 8799199.428350: 1 instructions:u: 55a0e216a995 xcalloc+0x15 (/usr/bin/wget) insn: 48 85 d2
wget 30246/30246 [029] 8799199.428350: 1 instructions:u: jcc 55a0e216a998 xcalloc+0x18 (/usr/bin/wget) insn: 75 0f
wget 30246/30246 [029] 8799199.428350: 1 instructions:u: call 55a0e216a99a xcalloc+0x1a (/usr/bin/wget) insn: e8 41 11 fc ff
wget 30246/30246 [029] 8799199.428350: 1 branches:u: call 55a0e216a99a xcalloc+0x1a (/usr/bin/wget) => 55a0e212bae0 calloc@plt+0x0 (/usr/bin/wget) insn: e8 41 11 fc ff
wget 30246/30246 [029] 8799199.428350: 1 instructions:u: jmp 55a0e212bae0 calloc@plt+0x0 (/usr/bin/wget) insn: ff 25 ea 32 06 00
wget 30246/30246 [029] 8799199.428350: 1 instructions:u: 7fb6f386e120 __libc_calloc+0x0 (/usr/lib/x86_64-linux-gnu/libc-2.28.so) insn: 48 89 fa
wget 30246/30246 [029] 8799199.428350: 1 instructions:u: 7fb6f386e123 __libc_calloc+0x3 (/usr/lib/x86_64-linux-gnu/libc-2.28.so) insn: 41 56
wget 30246/30246 [029] 8799199.428350: 1 instructions:u: 7fb6f386e125 __libc_calloc+0x5 (/usr/lib/x86_64-linux-gnu/libc-2.28.so) insn: b8 ff ff ff ff
wget 30246/30246 [029] 8799199.428350: 1 instructions:u: 7fb6f386e12a __libc_calloc+0xa (/usr/lib/x86_64-linux-gnu/libc-2.28.so) insn: 41 55```