net: bpf: Make bpf_ktime_get_ns() available to non GPL programs
authorMaciej Żenczykowski <maze@google.com>
Mon, 20 Apr 2020 18:47:50 +0000 (11:47 -0700)
committerAlexei Starovoitov <ast@kernel.org>
Sun, 26 Apr 2020 16:04:14 +0000 (09:04 -0700)
commit082b57e3eb09810d357083cca5ee2df02c16aec9
tree6fe7ed4372099c4dd297d3d4f580c575b7d78ced
parent6f3f65d80dac8f2bafce2213005821fccdce194c
net: bpf: Make bpf_ktime_get_ns() available to non GPL programs

The entire implementation is in kernel/bpf/helpers.c:

BPF_CALL_0(bpf_ktime_get_ns) {
       /* NMI safe access to clock monotonic */
       return ktime_get_mono_fast_ns();
}

const struct bpf_func_proto bpf_ktime_get_ns_proto = {
       .func           = bpf_ktime_get_ns,
       .gpl_only       = false,
       .ret_type       = RET_INTEGER,
};

and this was presumably marked GPL due to kernel/time/timekeeping.c:
  EXPORT_SYMBOL_GPL(ktime_get_mono_fast_ns);

and while that may make sense for kernel modules (although even that
is doubtful), there is currently AFAICT no other source of time
available to ebpf.

Furthermore this is really just equivalent to clock_gettime(CLOCK_MONOTONIC)
which is exposed to userspace (via vdso even to make it performant)...

As such, I see no reason to keep the GPL restriction.
(In the future I'd like to have access to time from Apache licensed ebpf code)

Signed-off-by: Maciej Żenczykowski <maze@google.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
kernel/bpf/helpers.c