65 lines
1.6 KiB
C
65 lines
1.6 KiB
C
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// SPDX-License-Identifier: GPL-2.0
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/* Copyright (c) 2024 Meta Platforms, Inc. and affiliates. */
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#include <vmlinux.h>
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#include <bpf/bpf_tracing.h>
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#include <bpf/bpf_helpers.h>
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#include <bpf/bpf_core_read.h>
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#include "bpf_misc.h"
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#include "bpf_experimental.h"
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extern void bpf_rcu_read_lock(void) __ksym;
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extern void bpf_rcu_read_unlock(void) __ksym;
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#define private(name) SEC(".bss." #name) __hidden __attribute__((aligned(8)))
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private(A) struct bpf_spin_lock lock;
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struct {
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__uint(type, BPF_MAP_TYPE_PROG_ARRAY);
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__uint(max_entries, 3);
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__uint(key_size, sizeof(__u32));
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__uint(value_size, sizeof(__u32));
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} jmp_table SEC(".maps");
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SEC("?tc")
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__failure __msg("function calls are not allowed while holding a lock")
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int reject_tail_call_spin_lock(struct __sk_buff *ctx)
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{
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bpf_spin_lock(&lock);
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bpf_tail_call_static(ctx, &jmp_table, 0);
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return 0;
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}
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SEC("?tc")
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__failure __msg("tail_call cannot be used inside bpf_rcu_read_lock-ed region")
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int reject_tail_call_rcu_lock(struct __sk_buff *ctx)
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{
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bpf_rcu_read_lock();
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bpf_tail_call_static(ctx, &jmp_table, 0);
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bpf_rcu_read_unlock();
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return 0;
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}
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SEC("?tc")
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__failure __msg("tail_call cannot be used inside bpf_preempt_disable-ed region")
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int reject_tail_call_preempt_lock(struct __sk_buff *ctx)
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{
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bpf_guard_preempt();
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bpf_tail_call_static(ctx, &jmp_table, 0);
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return 0;
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}
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SEC("?tc")
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__failure __msg("tail_call would lead to reference leak")
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int reject_tail_call_ref(struct __sk_buff *ctx)
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{
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struct foo { int i; } *p;
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p = bpf_obj_new(typeof(*p));
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bpf_tail_call_static(ctx, &jmp_table, 0);
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return 0;
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}
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char _license[] SEC("license") = "GPL";
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