'perf top' crashes with the tunable 'kernel.kptr_restrict=2' set

Issue

• When issuing perf top with kernel.kptr_restrict=2 set, the application exits with a segfault.

# perf top
perf: Segmentation fault
-------- backtrace --------
perf[0x4ff3cb]
/lib64/libc.so.6(+0x35670)[0x7f706bc96670]
perf[0x4375e4]
perf(cmd_top+0xdbd)[0x43940d]
perf[0x471035]
perf(main+0x610)[0x41d270]
/lib64/libc.so.6(__libc_start_main+0xf5)[0x7f706bc82b15]
perf[0x41d389]