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samples/bpf: add error checking for perf ioctl calls in bpf loader 

load_bpf_file() should fail if ioctl with command
PERF_EVENT_IOC_ENABLE and PERF_EVENT_IOC_SET_BPF fails.
When they do fail, proper error messages are printed.

With this change, the below "syscall_tp" run shows that
the maximum number of bpf progs attaching to the same
perf tracepoint is indeed enforced.
  $ ./syscall_tp -i 64
  prog #0: map ids 4 5
  ...
  prog #63: map ids 382 383
  $ ./syscall_tp -i 65
  prog #0: map ids 4 5
  ...
  prog #64: map ids 388 389
  ioctl PERF_EVENT_IOC_SET_BPF failed err Argument list too long

Signed-off-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
This commit is contained in:
Yonghong Song 2017-11-30 13:47:55 -08:00 committed by Daniel Borkmann
parent c8c088ba0e
commit 0ec9552b43
1 changed files with 12 additions and 2 deletions
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14
samples/bpf/bpf_load.c
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@ -193,8 +193,18 @@ static int load_and_attach(const char *event, struct bpf_insn *prog, int size)
return -1;
}
event_fd[prog_cnt - 1] = efd;
ioctl(efd, PERF_EVENT_IOC_ENABLE, 0);
ioctl(efd, PERF_EVENT_IOC_SET_BPF, fd);
err = ioctl(efd, PERF_EVENT_IOC_ENABLE, 0);
if (err < 0) {
printf("ioctl PERF_EVENT_IOC_ENABLE failed err %s\n",
strerror(errno));
return -1;
}
err = ioctl(efd, PERF_EVENT_IOC_SET_BPF, fd);
if (err < 0) {
printf("ioctl PERF_EVENT_IOC_SET_BPF failed err %s\n",
strerror(errno));
return -1;
}
return 0;
}