1 // SPDX-License-Identifier: GPL-2.0 2 /* Copyright (c) 2024 Meta Platforms, Inc. and affiliates. */ 3 #include <vmlinux.h> 4 #include <bpf/bpf_tracing.h> 5 #include <bpf/bpf_helpers.h> 6 #include <bpf/bpf_core_read.h> 7 8 #include "bpf_misc.h" 9 #include "bpf_experimental.h" 10 11 extern void bpf_rcu_read_lock(void) __ksym; 12 extern void bpf_rcu_read_unlock(void) __ksym; 13 14 #define private(name) SEC(".bss." #name) __hidden __attribute__((aligned(8))) 15 16 private(A) struct bpf_spin_lock lock; 17 18 struct { 19 __uint(type, BPF_MAP_TYPE_PROG_ARRAY); 20 __uint(max_entries, 3); 21 __uint(key_size, sizeof(__u32)); 22 __uint(value_size, sizeof(__u32)); 23 } jmp_table SEC(".maps"); 24 25 SEC("?tc") 26 __failure __msg("function calls are not allowed while holding a lock") 27 int reject_tail_call_spin_lock(struct __sk_buff *ctx) 28 { 29 bpf_spin_lock(&lock); 30 bpf_tail_call_static(ctx, &jmp_table, 0); 31 return 0; 32 } 33 34 SEC("?tc") 35 __failure __msg("tail_call cannot be used inside bpf_rcu_read_lock-ed region") 36 int reject_tail_call_rcu_lock(struct __sk_buff *ctx) 37 { 38 bpf_rcu_read_lock(); 39 bpf_tail_call_static(ctx, &jmp_table, 0); 40 bpf_rcu_read_unlock(); 41 return 0; 42 } 43 44 SEC("?tc") 45 __failure __msg("tail_call cannot be used inside bpf_preempt_disable-ed region") 46 int reject_tail_call_preempt_lock(struct __sk_buff *ctx) 47 { 48 bpf_guard_preempt(); 49 bpf_tail_call_static(ctx, &jmp_table, 0); 50 return 0; 51 } 52 53 SEC("?tc") 54 __failure __msg("tail_call would lead to reference leak") 55 int reject_tail_call_ref(struct __sk_buff *ctx) 56 { 57 struct foo { int i; } *p; 58 59 p = bpf_obj_new(typeof(*p)); 60 bpf_tail_call_static(ctx, &jmp_table, 0); 61 return 0; 62 } 63 64 char _license[] SEC("license") = "GPL"; 65