Hi Al, On Fri, Nov 02, 2018 at 12:08:04PM +0000, Al Grant wrote: > > Now I still don't understand how the dso/map support "/proc/kallsyms" and > > have no idea to fix this issue, though I spent some time to look into it. > > The way this is supported is that at record time, pseudo mmap records > are created for the kernel. But depending on permissions these might > not get created. This isn't just an ETM issue, it can happen on Intel too.
Agree, I also think this is not a specific issue only for Arm platform, this should be one common issue for how to parse kernel symbols with kallsyms file. > What do you see in "perf report -D", do you see a PERF_RECORD_MMAP > record for "[kernel.kallsyms]_text" and possibly some others for loadable > kernel modules in /lib/modules? Yes, I can see PERF_RECORD_MMAP for "[kernel.kallsyms]_text". 0x350 [0x50]: event: 1 . . ... raw event: size 80 bytes . 0000: 01 00 00 00 01 00 50 00 ff ff ff ff 00 00 00 00 ......P......... . 0010: 00 00 08 08 00 00 ff ff ff ff f7 f7 ff ff 00 00 ................ . 0020: 00 00 08 08 00 00 ff ff 5b 6b 65 72 6e 65 6c 2e ........[kernel. . 0030: 6b 61 6c 6c 73 79 6d 73 5d 5f 74 65 78 74 00 00 kallsyms]_text.. . 0040: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 0x350 [0x50]: PERF_RECORD_MMAP -1/0: [0xffff000008080000(0xfffff7f7ffff) @ 0xffff000008080000]: x [kernel.kallsyms]_text Below is the infor for checking buildid: root@debian:~/coresight_test# perf buildid-list 0242d9154c78df1d8fe1d0512c36a236d0861a18 [kernel.kallsyms] b8c89e8ba41a2ea486c66a50c29c60d38c34a759 /root/coresight_test/main 26b12a9d1a54ed2b0478cb0203435b76aabab3fb /usr/lib/aarch64-linux-gnu/ld-2.27.so 8fca7ed524c9469b065af83bc8a529fe72858f53 [vdso] 25829a59e21012cfde7850b30a310cd3a58f531c /root/coresight_test/libcstest.so 70512527439ef76c8802a7a2a546bde6a5a6e967 /usr/lib/aarch64-linux-gnu/libc-2.27.so root@debian:~/coresight_test# ls ~/.debug/\[kernel.kallsyms\]/0242d9154c78df1d8fe1d0512c36a236d0861a18/ kallsyms > Does it all work if you run perf record as sudo? Or if you do > > sudo sysctl kernel.kptr_restrict=0 > > before you run perf record? Yes, tested this on Juno board with Debian rootFS and logined in with 'root' user. I suspected the pointer permission issue so checked with below command: root@debian:~/coresight_test# cat /proc/sys/kernel/kptr_restrict 0 Thanks, Leo Yan
