[RFC v1 09/14] krsi: Add a helper function for bpf_perf_event_output

[KP Singh <kpsingh@chromium.org>]

From: KP Singh <kpsingh@google.com>

This helper is mapped to the existing operation
BPF_FUNC_perf_event_output.

An example usage of this function would be:

#define BUF_SIZE 64;

struct bpf_map_def SEC("maps") perf_map = {
        .type = BPF_MAP_TYPE_PERF_EVENT_ARRAY,
        .key_size = sizeof(int),
        .value_size = sizeof(u32),
        .max_entries = MAX_CPUS,
};

SEC("krsi")
int bpf_prog1(void *ctx)
{
	char buf[BUF_SIZE];
	int len;
	u64 flags = BPF_F_CURRENT_CPU;

	/* some logic that fills up buf with len data*/
	len = fill_up_buf(buf);
	if (len < 0)
		return len;
	if (len > BU)
		return 0;

	bpf_perf_event_output(ctx, &perf_map, flags, buf len);
	return 0;
}

A sample program that showcases the use of bpf_perf_event_output is
added later.

Signed-off-by: KP Singh <kpsingh@google.com>
---
 security/krsi/ops.c | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/security/krsi/ops.c b/security/krsi/ops.c
index a61508b7018f..57bd304a03f4 100644
--- a/security/krsi/ops.c
+++ b/security/krsi/ops.c
@@ -111,6 +111,26 @@ static bool krsi_prog_is_valid_access(int off, int size,
 	return false;
 }
 
+BPF_CALL_5(krsi_event_output, void *, log,
+	   struct bpf_map *, map, u64, flags, void *, data, u64, size)
+{
+	if (unlikely(flags & ~(BPF_F_INDEX_MASK)))
+		return -EINVAL;
+
+	return bpf_event_output(map, flags, data, size, NULL, 0, NULL);
+}
+
+static const struct bpf_func_proto krsi_event_output_proto =  {
+	.func		= krsi_event_output,
+	.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 *krsi_prog_func_proto(enum bpf_func_id
 							 func_id,
 							 const struct bpf_prog
@@ -121,6 +141,8 @@ static const struct bpf_func_proto *krsi_prog_func_proto(enum bpf_func_id
 		return &bpf_map_lookup_elem_proto;
 	case BPF_FUNC_get_current_pid_tgid:
 		return &bpf_get_current_pid_tgid_proto;
+	case BPF_FUNC_perf_event_output:
+		return &krsi_event_output_proto;
 	default:
 		return NULL;
 	}
-- 
2.20.1