g++ -std=c++17 -fno-omit-frame-pointer -O0 -g3 -o main main.cpp
perf stat ./main 5
perf report
20.98% main [unknown] [k] 0xffffffffb1077f22 ◆
19.11% main main [.] func ▒
17.96% main libc-2.31.so [.] __memset_avx2_erms ▒
13.07% main [unknown] [k] 0xffffffffb067a936 ▒
5.75% main [unknown] [k] 0xffffffffb10e68e5 ▒
3.30% main main [.] std::min<int> ▒
1.72% main [unknown] [k] 0xffffffffb1077f25 ▒
1.58% main [unknown] [k] 0xffffffffb086f485 ▒
1.01% main main [.] std::max<int>
func is a symbol in main.cpp, so symbols in my source file have been resolved. I call std::max and memset, they have beed resolved, too. But what about 0xffffffffb1077f22, it is an address. And with nm main, I'm sure that it is not a symbol in main source file. What is it? I don't think it is a library function because memset and std::max can be resolved.
I run perf in ubuntu virtual machine of macos.
I did not give attention to the warning message of perf report.
It says:
WARNING: Kernel address maps (/proc/{kallsyms,modules}) are restricted,
check /proc/sys/kernel/kptr_restrict and /proc/sys/kernel/perf_event_paranoid.
So it seemed that I should set a proper value in /proc/sys/kernel/kptr_restrict.
echo 0 | sudo tee /proc/sys/kernel/kptr_restrict
Then the address can be resolved.