perf intel_pt 无法解析 .plt 部分的符号

Question

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，但是那些 plt 符号无法解析。一个例子：

我的命令：

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。但是为什么没有解决呢？

Answer 1

我认为您还需要 wget 本身的 dbgsym 或使用 gcc -fno-plt 从源代码重新编译它，如上所述。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```