Subject: [PATCH 3/5] bpf: Add bpf_get_stackid_kfunc

From: Jiri Olsa <[email-masked]>
Date: Sun, 29 Dec 2019 15:37:38 +0100

Adding support to use bpf_get_stackid_kfunc in
BPF_TRACE_FENTRY/BPF_TRACE_FEXIT programs.

Signed-off-by: Jiri Olsa <[email-masked]>
---
 kernel/trace/bpf_trace.c | 28 ++++++++++++++++++++++++++++
 1 file changed, 28 insertions(+)

diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index 1b270bbd9016..c8e0709704f5 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -1203,12 +1203,40 @@ static const struct bpf_func_proto bpf_perf_event_output_proto_kfunc = {
 	.arg5_type	= ARG_CONST_SIZE_OR_ZERO,
 };
 
+BPF_CALL_3(bpf_get_stackid_kfunc, void*, args,
+	   struct bpf_map *, map, u64, flags)
+{
+	struct pt_regs *regs = get_bpf_kfunc_regs();
+	int ret;
+
+	if (IS_ERR(regs))
+		return PTR_ERR(regs);
+
+	perf_fetch_caller_regs(regs);
+	/* similar to bpf_perf_event_output_tp, but pt_regs fetched differently */
+	ret = bpf_get_stackid((unsigned long) regs, (unsigned long) map,
+			      flags, 0, 0);
+	put_bpf_kfunc_regs();
+	return ret;
+}
+
+static const struct bpf_func_proto bpf_get_stackid_proto_kfunc = {
+	.func		= bpf_get_stackid_kfunc,
+	.gpl_only	= true,
+	.ret_type	= RET_INTEGER,
+	.arg1_type	= ARG_PTR_TO_CTX,
+	.arg2_type	= ARG_CONST_MAP_PTR,
+	.arg3_type	= ARG_ANYTHING,
+};
+
 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;
+	case BPF_FUNC_get_stackid:
+		return &bpf_get_stackid_proto_kfunc;
 	default:
 		return tracing_func_proto(func_id, prog);
 	}
-- 
2.21.1