46 lines
836 B
C
46 lines
836 B
C
// SPDX-License-Identifier: GPL-2.0
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/* Copyright (c) 2021 Google */
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#include "vmlinux.h"
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#include <bpf/bpf_helpers.h>
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extern const int bpf_prog_active __ksym; /* int type global var. */
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SEC("raw_tp/sys_enter")
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int handler1(const void *ctx)
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{
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int *active;
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__u32 cpu;
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cpu = bpf_get_smp_processor_id();
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active = (int *)bpf_per_cpu_ptr(&bpf_prog_active, cpu);
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if (active) {
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/* Kernel memory obtained from bpf_{per,this}_cpu_ptr
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* is read-only, should _not_ pass verification.
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*/
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/* WRITE_ONCE */
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*(volatile int *)active = -1;
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}
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return 0;
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}
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__noinline int write_active(int *p)
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{
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return p ? (*p = 42) : 0;
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}
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SEC("raw_tp/sys_enter")
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int handler2(const void *ctx)
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{
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int *active;
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__u32 cpu;
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active = bpf_this_cpu_ptr(&bpf_prog_active);
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write_active(active);
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return 0;
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}
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char _license[] SEC("license") = "GPL";
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