1// SPDX-License-Identifier: GPL-2.0 2/* Copyright (c) 2021 Facebook */ 3 4#include "vmlinux.h" 5#include <bpf/bpf_helpers.h> 6#include <bpf/bpf_tracing.h> 7#include <bpf/bpf_core_read.h> 8#include "bpf_misc.h" 9 10/* weak and shared between both files */ 11const volatile int my_tid __weak; 12long syscall_id __weak; 13 14int output_val2; 15int output_ctx2; 16int output_weak2; /* should stay zero */ 17 18/* same "subprog" name in all files, but it's ok because they all are static */ 19static __noinline int subprog(int x) 20{ 21 /* but different formula */ 22 return x * 2; 23} 24 25/* Global functions can't be void */ 26int set_output_val2(int x) 27{ 28 output_val2 = 2 * x + 2 * subprog(x); 29 return 2 * x; 30} 31 32/* This function can't be verified as global, as it assumes raw_tp/sys_enter 33 * context and accesses syscall id (second argument). So we mark it as 34 * __hidden, so that libbpf will mark it as static in the final object file, 35 * right before verifying it in the kernel. 36 * 37 * But we don't mark it as __hidden here, rather at extern site. __hidden is 38 * "contaminating" visibility, so it will get propagated from either extern or 39 * actual definition (including from the losing __weak definition). 40 */ 41void set_output_ctx2(__u64 *ctx) 42{ 43 output_ctx2 = ctx[1]; /* long id, same as in BPF_PROG below */ 44} 45 46/* this weak instance should lose, because it will be processed second */ 47__weak int set_output_weak(int x) 48{ 49 static volatile int whatever; 50 51 /* make sure we use CO-RE relocations in a weak function, this used to 52 * cause problems for BPF static linker 53 */ 54 whatever = 2 * bpf_core_type_size(struct task_struct); 55 __sink(whatever); 56 57 output_weak2 = x; 58 return 2 * x; 59} 60 61extern int set_output_val1(int x); 62 63/* here we'll force set_output_ctx1() to be __hidden in the final obj file */ 64__hidden extern void set_output_ctx1(__u64 *ctx); 65 66SEC("?raw_tp/sys_enter") 67int BPF_PROG(handler2, struct pt_regs *regs, long id) 68{ 69 static volatile int whatever; 70 71 if (my_tid != (s32)bpf_get_current_pid_tgid() || id != syscall_id) 72 return 0; 73 74 /* make sure we have CO-RE relocations in main program */ 75 whatever = bpf_core_type_size(struct task_struct); 76 __sink(whatever); 77 78 set_output_val1(2000); 79 set_output_ctx1(ctx); /* ctx definition is hidden in BPF_PROG macro */ 80 81 /* keep input value the same across both files to avoid dependency on 82 * handler call order; differentiate by output_weak1 vs output_weak2. 83 */ 84 set_output_weak(42); 85 86 return 0; 87} 88 89char LICENSE[] SEC("license") = "GPL"; 90