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Date: Sat, 28 Feb 2015 11:20:43 +0100 From: Peter Zijlstra <peterz@...radead.org> To: Alexei Starovoitov <ast@...mgrid.com> Cc: Ingo Molnar <mingo@...nel.org>, Steven Rostedt <rostedt@...dmis.org>, Namhyung Kim <namhyung@...nel.org>, Arnaldo Carvalho de Melo <acme@...radead.org>, Jiri Olsa <jolsa@...hat.com>, Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>, "David S. Miller" <davem@...emloft.net>, Daniel Borkmann <dborkman@...hat.com>, linux-api@...r.kernel.org, netdev@...r.kernel.org, linux-kernel@...r.kernel.org Subject: Re: [PATCH v4 tip 3/7] tracing: allow BPF programs to call ktime_get_ns() On Fri, Feb 27, 2015 at 04:08:51PM -0800, Alexei Starovoitov wrote: > bpf_ktime_get_ns() is used by programs to compue time delta between events > or as a timestamp > > Signed-off-by: Alexei Starovoitov <ast@...mgrid.com> > --- > include/uapi/linux/bpf.h | 1 + > kernel/trace/bpf_trace.c | 10 ++++++++++ > 2 files changed, 11 insertions(+) > > diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h > index 4486d36d2e9e..101e509d1001 100644 > --- a/include/uapi/linux/bpf.h > +++ b/include/uapi/linux/bpf.h > @@ -165,6 +165,7 @@ enum bpf_func_id { > BPF_FUNC_map_update_elem, /* int map_update_elem(&map, &key, &value, flags) */ > BPF_FUNC_map_delete_elem, /* int map_delete_elem(&map, &key) */ > BPF_FUNC_probe_read, /* int bpf_probe_read(void *dst, int size, void *src) */ > + BPF_FUNC_ktime_get_ns, /* u64 bpf_ktime_get_ns(void) */ > __BPF_FUNC_MAX_ID, > }; > > diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c > index bcce9b238dad..64b918488607 100644 > --- a/kernel/trace/bpf_trace.c > +++ b/kernel/trace/bpf_trace.c > @@ -36,6 +36,11 @@ static u64 bpf_probe_read(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5) > return probe_kernel_read(dst, unsafe_ptr, size); > } > > +static u64 bpf_ktime_get_ns(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5) > +{ > + return ktime_get_ns(); > +} Please use ktime_get_mono_fast_ns() instead. If you ever want to allow running BPF stuff from general tracepoints and the like you need to be NMI safe. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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