From 098d2164e3441c252eaa28906d45e16b7bf1bd2b Mon Sep 17 00:00:00 2001 From: Wang Nan Date: Wed, 1 Jul 2015 02:13:49 +0000 Subject: [PATCH] bpf: Use correct #ifdef controller for trace_call_bpf() Commit e1abf2cc8d5d80b41c4419368ec743ccadbb131e ("bpf: Fix the build on BPF_SYSCALL=y && !CONFIG_TRACING kernels, make it more configurable") updated the building condition of bpf_trace.o from CONFIG_BPF_SYSCALL to CONFIG_BPF_EVENTS, but the corresponding #ifdef controller in trace_events.h for trace_call_bpf() was not changed. Which, in theory, is incorrect. With current Kconfigs, we can create a .config with CONFIG_BPF_SYSCALL=y and CONFIG_BPF_EVENTS=n by unselecting CONFIG_KPROBE_EVENT and selecting CONFIG_BPF_SYSCALL. With these options, trace_call_bpf() will be defined as an extern function, but if anyone calls it a symbol missing error will be triggered since bpf_trace.o was not built. This patch changes the #ifdef controller for trace_call_bpf() from CONFIG_BPF_SYSCALL to CONFIG_BPF_EVENTS. I'll show its correctness: Before this patch: BPF_SYSCALL BPF_EVENTS trace_call_bpf bpf_trace.o y y normal compiled n n inline not compiled y n normal not compiled (incorrect) n y impossible (BPF_EVENTS depends on BPF_SYSCALL) After this patch: BPF_SYSCALL BPF_EVENTS trace_call_bpf bpf_trace.o y y normal compiled n n inline not compiled y n inline not compiled (fixed) n y impossible (BPF_EVENTS depends on BPF_SYSCALL) So this patch doesn't break anything. QED. Signed-off-by: Wang Nan Cc: Alexei Starovoitov Cc: Brendan Gregg Cc: Daniel Borkmann Cc: David Ahern Cc: He Kuang Cc: Jiri Olsa Cc: Kaixu Xia Cc: Masami Hiramatsu Cc: Namhyung Kim Cc: Peter Zijlstra Cc: Zefan Li Cc: pi3orama@163.com Link: http://lkml.kernel.org/r/1435716878-189507-2-git-send-email-wangnan0@huawei.com Signed-off-by: Arnaldo Carvalho de Melo --- include/linux/trace_events.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/include/linux/trace_events.h b/include/linux/trace_events.h index 1063c850dbab..180dbf8720f9 100644 --- a/include/linux/trace_events.h +++ b/include/linux/trace_events.h @@ -542,7 +542,7 @@ event_trigger_unlock_commit_regs(struct trace_event_file *file, event_triggers_post_call(file, tt); } -#ifdef CONFIG_BPF_SYSCALL +#ifdef CONFIG_BPF_EVENTS unsigned int trace_call_bpf(struct bpf_prog *prog, void *ctx); #else static inline unsigned int trace_call_bpf(struct bpf_prog *prog, void *ctx) -- 2.30.2