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// /sys/fs/bpf/tc/globals/perf_map
// records traces from BPF, using the snapshot_* functions, read by userland tcpdump-style;
// note this is implicitly per-CPU (the "size" of the perf map is the max number of CPUs)
DECLARE_GLOBAL_MAP(perf_map, BPF_MAP_TYPE_PERF_EVENT_ARRAY, sizeof(int), sizeof(u_int32_t), 8);
kfn void
_snapshot(int type, void *ctx, u_char *sp, void *ep, u_int16_t len) {
u_int64_t flags = BPF_F_CURRENT_CPU;
struct perf_meta_packet meta =
{
.magic = PP_MAGIC,
.type = type,
.flags = 0,
.len = (u_int16_t)((u_char *)ep - sp),
};
if(len == 0) {
len = meta.len;
}
if(len > meta.len) {
len = meta.len;
}
flags |= (u_int64_t)len << 32;
perf_event_output(ctx, &perf_map, flags, &meta, sizeof(meta));
}
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