bpf: introduce bpf_perf_event_output() helper
This helper is used to send raw data from eBPF program into
special PERF_TYPE_SOFTWARE/PERF_COUNT_SW_BPF_OUTPUT perf_event.
User space needs to perf_event_open() it (either for one or all cpus) and
store FD into perf_event_array (similar to bpf_perf_event_read() helper)
before eBPF program can send data into it.
Today the programs triggered by kprobe collect the data and either store
it into the maps or print it via bpf_trace_printk() where latter is the debug
facility and not suitable to stream the data. This new helper replaces
such bpf_trace_printk() usage and allows programs to have dedicated
channel into user space for post-processing of the raw data collected.
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index 0fe96c7..47febbe 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -215,6 +215,50 @@
.arg2_type = ARG_ANYTHING,
};
+static u64 bpf_perf_event_output(u64 r1, u64 r2, u64 index, u64 r4, u64 size)
+{
+ struct pt_regs *regs = (struct pt_regs *) (long) r1;
+ struct bpf_map *map = (struct bpf_map *) (long) r2;
+ struct bpf_array *array = container_of(map, struct bpf_array, map);
+ void *data = (void *) (long) r4;
+ struct perf_sample_data sample_data;
+ struct perf_event *event;
+ struct perf_raw_record raw = {
+ .size = size,
+ .data = data,
+ };
+
+ if (unlikely(index >= array->map.max_entries))
+ return -E2BIG;
+
+ event = (struct perf_event *)array->ptrs[index];
+ if (unlikely(!event))
+ return -ENOENT;
+
+ if (unlikely(event->attr.type != PERF_TYPE_SOFTWARE ||
+ event->attr.config != PERF_COUNT_SW_BPF_OUTPUT))
+ return -EINVAL;
+
+ if (unlikely(event->oncpu != smp_processor_id()))
+ return -EOPNOTSUPP;
+
+ perf_sample_data_init(&sample_data, 0, 0);
+ sample_data.raw = &raw;
+ perf_event_output(event, &sample_data, regs);
+ return 0;
+}
+
+static const struct bpf_func_proto bpf_perf_event_output_proto = {
+ .func = bpf_perf_event_output,
+ .gpl_only = false,
+ .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_STACK,
+ .arg5_type = ARG_CONST_STACK_SIZE,
+};
+
static const struct bpf_func_proto *kprobe_prog_func_proto(enum bpf_func_id func_id)
{
switch (func_id) {
@@ -242,6 +286,8 @@
return &bpf_get_smp_processor_id_proto;
case BPF_FUNC_perf_event_read:
return &bpf_perf_event_read_proto;
+ case BPF_FUNC_perf_event_output:
+ return &bpf_perf_event_output_proto;
default:
return NULL;
}