// SPDX-License-Identifier: GPL-2.0 /* Copyright (c) 2021 Facebook */ #include "vmlinux.h" #include <bpf/bpf_helpers.h> #include <bpf/bpf_tracing.h> #include <bpf/bpf_core_read.h> #include "bpf_misc.h" /* weak and shared between two files */ const volatile __u32 my_tid __weak; long syscall_id __weak; int output_val1; int output_ctx1; int output_weak1; /* same "subprog" name in all files, but it's ok because they all are static */ static __noinline int subprog(int x) { /* but different formula */ return x * 1; } /* Global functions can't be void */ int set_output_val1(int x) { output_val1 = x + subprog(x); return x; } /* This function can't be verified as global, as it assumes raw_tp/sys_enter * context and accesses syscall id (second argument). So we mark it as * __hidden, so that libbpf will mark it as static in the final object file, * right before verifying it in the kernel. * * But we don't mark it as __hidden here, rather at extern site. __hidden is * "contaminating" visibility, so it will get propagated from either extern or * actual definition (including from the losing __weak definition). */ void set_output_ctx1(__u64 *ctx) { output_ctx1 = ctx[1]; /* long id, same as in BPF_PROG below */ } /* this weak instance should win because it's the first one */ __weak int set_output_weak(int x) { static volatile int whatever; /* make sure we use CO-RE relocations in a weak function, this used to * cause problems for BPF static linker */ whatever = bpf_core_type_size(struct task_struct); __sink(whatever); output_weak1 = x; return x; } extern int set_output_val2(int x); /* here we'll force set_output_ctx2() to be __hidden in the final obj file */ __hidden extern void set_output_ctx2(__u64 *ctx); SEC("?raw_tp/sys_enter") int BPF_PROG(handler1, struct pt_regs *regs, long id) { static volatile int whatever; if (my_tid != (u32)bpf_get_current_pid_tgid() || id != syscall_id) return 0; /* make sure we have CO-RE relocations in main program */ whatever = bpf_core_type_size(struct task_struct); __sink(whatever); set_output_val2(1000); set_output_ctx2(ctx); /* ctx definition is hidden in BPF_PROG macro */ /* keep input value the same across both files to avoid dependency on * handler call order; differentiate by output_weak1 vs output_weak2. */ set_output_weak(42); return 0; } char LICENSE[] SEC("license") = "GPL";