// SPDX-License-Identifier: GPL-2.0
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// Copyright (c) 2018 Facebook
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#include <linux/bpf.h>
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#include "bpf_helpers.h"
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#ifndef PERF_MAX_STACK_DEPTH
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#define PERF_MAX_STACK_DEPTH 127
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#endif
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struct bpf_map_def SEC("maps") control_map = {
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.type = BPF_MAP_TYPE_ARRAY,
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.key_size = sizeof(__u32),
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.value_size = sizeof(__u32),
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.max_entries = 1,
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};
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struct bpf_map_def SEC("maps") stackid_hmap = {
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.type = BPF_MAP_TYPE_HASH,
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.key_size = sizeof(__u32),
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.value_size = sizeof(__u32),
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.max_entries = 16384,
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};
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struct bpf_map_def SEC("maps") stackmap = {
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.type = BPF_MAP_TYPE_STACK_TRACE,
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.key_size = sizeof(__u32),
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.value_size = sizeof(struct bpf_stack_build_id)
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* PERF_MAX_STACK_DEPTH,
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.max_entries = 128,
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.map_flags = BPF_F_STACK_BUILD_ID,
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};
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struct bpf_map_def SEC("maps") stack_amap = {
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.type = BPF_MAP_TYPE_ARRAY,
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.key_size = sizeof(__u32),
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.value_size = sizeof(struct bpf_stack_build_id)
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* PERF_MAX_STACK_DEPTH,
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.max_entries = 128,
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};
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/* taken from /sys/kernel/debug/tracing/events/random/urandom_read/format */
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struct random_urandom_args {
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unsigned long long pad;
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int got_bits;
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int pool_left;
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int input_left;
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};
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SEC("tracepoint/random/urandom_read")
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int oncpu(struct random_urandom_args *args)
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{
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__u32 max_len = sizeof(struct bpf_stack_build_id)
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* PERF_MAX_STACK_DEPTH;
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__u32 key = 0, val = 0, *value_p;
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void *stack_p;
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value_p = bpf_map_lookup_elem(&control_map, &key);
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if (value_p && *value_p)
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return 0; /* skip if non-zero *value_p */
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/* The size of stackmap and stackid_hmap should be the same */
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key = bpf_get_stackid(args, &stackmap, BPF_F_USER_STACK);
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if ((int)key >= 0) {
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bpf_map_update_elem(&stackid_hmap, &key, &val, 0);
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stack_p = bpf_map_lookup_elem(&stack_amap, &key);
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if (stack_p)
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bpf_get_stack(args, stack_p, max_len,
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BPF_F_USER_STACK | BPF_F_USER_BUILD_ID);
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}
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return 0;
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}
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char _license[] SEC("license") = "GPL";
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__u32 _version SEC("version") = 1; /* ignored by tracepoints, required by libbpf.a */
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