Subject: [PATCH 4/5] bpf: Add bpf_get_stack_kfunc

From: Jiri Olsa <[email-masked]>
Date: Sun, 29 Dec 2019 15:37:39 +0100

Adding support to use bpf_get_stack_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 c8e0709704f5..02979c5d6357 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -1229,6 +1229,32 @@ static const struct bpf_func_proto bpf_get_stackid_proto_kfunc = {
 	.arg3_type	= ARG_ANYTHING,
 };
 
+BPF_CALL_4(bpf_get_stack_kfunc, void*, args,
+	   void *, buf, u32, size, 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);
+	ret = bpf_get_stack((unsigned long) regs, (unsigned long) buf,
+			    (unsigned long) size, flags, 0);
+	put_bpf_kfunc_regs();
+	return ret;
+}
+
+static const struct bpf_func_proto bpf_get_stack_proto_kfunc = {
+	.func		= bpf_get_stack_raw_tp,
+	.gpl_only	= true,
+	.ret_type	= RET_INTEGER,
+	.arg1_type	= ARG_PTR_TO_CTX,
+	.arg2_type	= ARG_PTR_TO_MEM,
+	.arg3_type	= ARG_CONST_SIZE_OR_ZERO,
+	.arg4_type	= ARG_ANYTHING,
+};
+
 static const struct bpf_func_proto *
 kfunc_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
 {
@@ -1237,6 +1263,8 @@ kfunc_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
 		return &bpf_perf_event_output_proto_kfunc;
 	case BPF_FUNC_get_stackid:
 		return &bpf_get_stackid_proto_kfunc;
+	case BPF_FUNC_get_stack:
+		return &bpf_get_stack_proto_kfunc;
 	default:
 		return tracing_func_proto(func_id, prog);
 	}
-- 
2.21.1