bpf: allow networking programs to use bpf_trace_printk() for debugging

bpf_trace_printk() is a helper function used to debug eBPF programs.
Let socket and TC programs use it as well.
Note, it's DEBUG ONLY helper. If it's used in the program,
the kernel will print warning banner to make sure users don't use
it in production.

Signed-off-by: Alexei Starovoitov <ast@plumgrid.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 16 insertions, 8 deletions

diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
index 1fc45cc83076..c5bedc82bc1c 100644
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -733,6 +733,10 @@ const struct bpf_func_proto bpf_ktime_get_ns_proto __weak;
 const struct bpf_func_proto bpf_get_current_pid_tgid_proto __weak;
 const struct bpf_func_proto bpf_get_current_uid_gid_proto __weak;
 const struct bpf_func_proto bpf_get_current_comm_proto __weak;
+const struct bpf_func_proto * __weak bpf_get_trace_printk_proto(void)
+{
+	return NULL;
+}
 
 /* Always built-in helper functions. */
 const struct bpf_func_proto bpf_tail_call_proto = {
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index 3a17638cdf46..4f9b5d41869b 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -147,6 +147,17 @@ static const struct bpf_func_proto bpf_trace_printk_proto = {
 	.arg2_type	= ARG_CONST_STACK_SIZE,
 };
 
+const struct bpf_func_proto *bpf_get_trace_printk_proto(void)
+{
+	/*
+	 * this program might be calling bpf_trace_printk,
+	 * so allocate per-cpu printk buffers
+	 */
+	trace_printk_init_buffers();
+
+	return &bpf_trace_printk_proto;
+}
+
 static const struct bpf_func_proto *kprobe_prog_func_proto(enum bpf_func_id func_id)
 {
 	switch (func_id) {
@@ -168,15 +179,8 @@ static const struct bpf_func_proto *kprobe_prog_func_proto(enum bpf_func_id func
 		return &bpf_get_current_uid_gid_proto;
 	case BPF_FUNC_get_current_comm:
 		return &bpf_get_current_comm_proto;
-
 	case BPF_FUNC_trace_printk:
-		/*
-		 * this program might be calling bpf_trace_printk,
-		 * so allocate per-cpu printk buffers
-		 */
-		trace_printk_init_buffers();
-
-		return &bpf_trace_printk_proto;
+		return bpf_get_trace_printk_proto();
 	default:
 		return NULL;
 	}