diff mbox

[net-next,1/8] bpf: avoid excessive stack usage for perf_sample_data

Message ID 0839d8663c3d58cbaba010572c237286bdeae366.1497133948.git.daniel@iogearbox.net
State Accepted, archived
Delegated to: David Miller
Headers show

Commit Message

Daniel Borkmann June 10, 2017, 10:50 p.m. UTC 
perf_sample_data consumes 386 bytes on stack, reduce excessive stack
usage and move it to per cpu buffer. It's allowed due to preemption
being disabled for tracing, xdp and tc programs, thus at all times
only one program can run on a specific CPU and programs cannot run
from interrupt. We similarly also handle bpf_pt_regs.

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@kernel.org>
---
 kernel/trace/bpf_trace.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)
diff mbox

Patch

diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index 08eb072..051d7fc 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -266,14 +266,16 @@  const struct bpf_func_proto *bpf_get_trace_printk_proto(void)
 	.arg2_type	= ARG_ANYTHING,
 };
 
+static DEFINE_PER_CPU(struct perf_sample_data, bpf_sd);
+
 static __always_inline u64
 __bpf_perf_event_output(struct pt_regs *regs, struct bpf_map *map,
 			u64 flags, struct perf_raw_record *raw)
 {
 	struct bpf_array *array = container_of(map, struct bpf_array, map);
+	struct perf_sample_data *sd = this_cpu_ptr(&bpf_sd);
 	unsigned int cpu = smp_processor_id();
 	u64 index = flags & BPF_F_INDEX_MASK;
-	struct perf_sample_data sample_data;
 	struct bpf_event_entry *ee;
 	struct perf_event *event;
 
@@ -294,9 +296,9 @@  const struct bpf_func_proto *bpf_get_trace_printk_proto(void)
 	if (unlikely(event->oncpu != cpu))
 		return -EOPNOTSUPP;
 
-	perf_sample_data_init(&sample_data, 0, 0);
-	sample_data.raw = raw;
-	perf_event_output(event, &sample_data, regs);
+	perf_sample_data_init(sd, 0, 0);
+	sd->raw = raw;
+	perf_event_output(event, sd, regs);
 	return 0;
 }