[PATCH 2/5] bpf: Add bpf_perf_event_output_kfunc
From: Jiri Olsa <jolsa@kernel.org>
Date: 2019-12-29 14:37:57
Also in:
bpf
Subsystem:
bpf [general] (safe dynamic programs and tools), bpf [security & lsm] (security audit and enforcement using bpf), bpf [tracing], the rest, tracing · Maintainers:
Alexei Starovoitov, Daniel Borkmann, Andrii Nakryiko, Eduard Zingerman, Kumar Kartikeya Dwivedi, KP Singh, Matt Bobrowski, Song Liu, Linus Torvalds, Steven Rostedt, Masami Hiramatsu
Adding support to use perf_event_output in BPF_TRACE_FENTRY/BPF_TRACE_FEXIT programs. There are no pt_regs available in the trampoline, so getting one via bpf_kfunc_regs array. Signed-off-by: Jiri Olsa <jolsa@kernel.org> --- kernel/trace/bpf_trace.c | 67 ++++++++++++++++++++++++++++++++++++++++ 1 file changed, 67 insertions(+)
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index e5ef4ae9edb5..1b270bbd9016 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c@@ -1151,6 +1151,69 @@ raw_tp_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog) } } +struct bpf_kfunc_regs { + struct pt_regs regs[3]; +}; + +static DEFINE_PER_CPU(struct bpf_kfunc_regs, bpf_kfunc_regs); +static DEFINE_PER_CPU(int, bpf_kfunc_nest_level); + +static struct pt_regs *get_bpf_kfunc_regs(void) +{ + struct bpf_kfunc_regs *tp_regs = this_cpu_ptr(&bpf_kfunc_regs); + int nest_level = this_cpu_inc_return(bpf_kfunc_nest_level); + + if (WARN_ON_ONCE(nest_level > ARRAY_SIZE(tp_regs->regs))) { + this_cpu_dec(bpf_kfunc_nest_level); + return ERR_PTR(-EBUSY); + } + + return &tp_regs->regs[nest_level - 1]; +} + +static void put_bpf_kfunc_regs(void) +{ + this_cpu_dec(bpf_kfunc_nest_level); +} + +BPF_CALL_5(bpf_perf_event_output_kfunc, void *, ctx, struct bpf_map *, map, + u64, flags, void *, data, u64, size) +{ + struct pt_regs *regs = get_bpf_kfunc_regs(); + int ret; + + if (IS_ERR(regs)) + return PTR_ERR(regs); + + perf_fetch_caller_regs(regs); + ret = ____bpf_perf_event_output(regs, map, flags, data, size); + + put_bpf_kfunc_regs(); + return ret; +} + +static const struct bpf_func_proto bpf_perf_event_output_proto_kfunc = { + .func = bpf_perf_event_output_kfunc, + .gpl_only = true, + .ret_type = RET_INTEGER, + .arg1_type = ARG_PTR_TO_CTX, + .arg2_type = ARG_CONST_MAP_PTR, + .arg3_type = ARG_ANYTHING, + .arg4_type = ARG_PTR_TO_MEM, + .arg5_type = ARG_CONST_SIZE_OR_ZERO, +}; + +static const struct bpf_func_proto * +kfunc_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog) +{ + switch (func_id) { + case BPF_FUNC_perf_event_output: + return &bpf_perf_event_output_proto_kfunc; + default: + return tracing_func_proto(func_id, prog); + } +} + static const struct bpf_func_proto * tracing_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog) {
@@ -1160,6 +1223,10 @@ tracing_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog) return &bpf_skb_output_proto; #endif default: + if (prog->expected_attach_type == BPF_TRACE_FENTRY || + prog->expected_attach_type == BPF_TRACE_FEXIT) + return kfunc_prog_func_proto(func_id, prog); + return raw_tp_prog_func_proto(func_id, prog); } }
--
2.21.1