bpf: Add bpf_trace_vprintk helper
This helper is meant to be "bpf_trace_printk, but with proper vararg
support". Follow bpf_snprintf's example and take a u64 pseudo-vararg
array. Write to /sys/kernel/debug/tracing/trace_pipe using the same
mechanism as bpf_trace_printk. The functionality of this helper was
requested in the libbpf issue tracker [0].
[0] Closes: https://github.com/libbpf/libbpf/issues/315
Signed-off-by: Dave Marchevsky <davemarchevsky@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20210917182911.2426606-4-davemarchevsky@fb.com
diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index 8f9f392..2c604ff 100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -1435,6 +1435,8 @@ bpf_base_func_proto(enum bpf_func_id func_id)
return &bpf_snprintf_proto;
case BPF_FUNC_task_pt_regs:
return &bpf_task_pt_regs_proto;
+ case BPF_FUNC_trace_vprintk:
+ return bpf_get_trace_vprintk_proto();
default:
return NULL;
}