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