Perf segfaults with --per-core

[ptosi]

Using the distributed perf binaries, I get a segfault when using the --per-core flag when perf stat tries to output the counters for the big cores:

$ perf stat -a -A --per-core -- sleep 1

 Performance counter stats for 'sleep 1':

S0-C0           1        1019.720314 task-clock                #    1.004 CPUs utilized            (100.00%)
S0-C0           1               1024 context-switches          #    0.001 M/sec                    (100.00%)
S0-C0           1                187 cpu-migrations            #    0.183 K/sec                    (100.00%)
S0-C0           1                152 page-faults               #    0.149 K/sec
S0-C0           1          237899272 cycles                    #    0.233 GHz                      (100.00%)
S0-C8           1    <not supported> stalled-cycles-frontend
S0-C8           1    <not supported> stalled-cycles-backend
S0-C0           1           40652336 instructions              #    0.25  insns per cycle          (100.00%)
S0-C8           1    <not supported> branches
S0-C0           1            1061322 branch-misses             #    1.040 M/sec
S0-C1           1        1019.717708 task-clock                #    1.004 CPUs utilized            (100.00%)
S0-C1           1                858 context-switches                                              (100.00%)
S0-C1           1                181 cpu-migrations                                                (100.00%)
S0-C1           1                315 page-faults
S0-C1           1          303381087 cycles                    #    0.000 GHz                      (100.00%)
S0-C8           1    <not supported> stalled-cycles-frontend
S0-C8           1    <not supported> stalled-cycles-backend
S0-C1           1           59281541 instructions              #    0.00  insns per cycle          (100.00%)
S0-C8           1    <not supported> branches
S0-C1           1            1425592 branch-misses
S0-C2           1        1019.983333 task-clock                #    1.004 CPUs utilized            (100.00%)
S0-C2           1                384 context-switches                                              (100.00%)
S0-C2           1                122 cpu-migrations                                                (100.00%)
S0-C2           1                258 page-faults
S0-C2           1          231191194 cycles                    #    0.000 GHz                      (100.00%)
S0-C8           1    <not supported> stalled-cycles-frontend
S0-C8           1    <not supported> stalled-cycles-backend
S0-C2           1           44800984 instructions              #    0.00  insns per cycle          (100.00%)
S0-C8           1    <not supported> branches
S0-C2           1             993487 branch-misses
S0-C3           1        1020.149480 task-clock                #    1.004 CPUs utilized            (100.00%)
S0-C3           1                553 context-switches                                              (100.00%)
S0-C3           1                137 cpu-migrations                                                (100.00%)
S0-C3           1                310 page-faults
S0-C3           1          212351971 cycles                    #    0.000 GHz                      (100.00%)
S0-C8           1    <not supported> stalled-cycles-frontend
S0-C8           1    <not supported> stalled-cycles-backend
S0-C3           1           49365014 instructions              #    0.00  insns per cycle          (100.00%)
S0-C8           1    <not supported> branches
S0-C3           1            1297067 branch-misses
S1-C0           1        1020.910417 task-clock                #    1.005 CPUs utilized            (100.00%)
S1-C0           1                148 context-switches         Segmentation fault

Tested on Pixel 2 (4.4.88-ga1592dc22912).

[marcbonnici]

This should be fixed by #396