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 two files */ 11 const volatile int my_tid __weak; 12 long syscall_id __weak; 13 14 int output_val1; 15 int output_ctx1; 16 int output_weak1; 17 18 /* same "subprog" name in all files, but it's ok because they all are static */ 19 static __noinline int subprog(int x) 20 { 21 /* but different formula */ 22 return x * 1; 23 } 24 25 /* Global functions can't be void */ 26 int set_output_val1(int x) 27 { 28 output_val1 = x + subprog(x); 29 return 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 */ 41 void set_output_ctx1(__u64 *ctx) 42 { 43 output_ctx1 = ctx[1]; /* long id, same as in BPF_PROG below */ 44 } 45 46 /* this weak instance should win because it's the first one */ 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 = bpf_core_type_size(struct task_struct); 55 __sink(whatever); 56 57 output_weak1 = x; 58 return x; 59 } 60 61 extern int set_output_val2(int x); 62 63 /* here we'll force set_output_ctx2() to be __hidden in the final obj file */ 64 __hidden extern void set_output_ctx2(__u64 *ctx); 65 66 SEC("?raw_tp/sys_enter") 67 int BPF_PROG(handler1, struct pt_regs *regs, long id) 68 { 69 static volatile int whatever; 70 71 if (my_tid != (u32)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_val2(1000); 79 set_output_ctx2(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 89 char LICENSE[] SEC("license") = "GPL"; 90