From 9667305c6374df8672be46bc496f52f040999531 Mon Sep 17 00:00:00 2001 From: Alexei Starovoitov Date: Mon, 31 Aug 2020 08:51:55 -0700 Subject: [PATCH] bpf: Fix build without BPF_SYSCALL, but with BPF_JIT. MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit When CONFIG_BPF_SYSCALL is not set, but CONFIG_BPF_JIT=y the kernel build fails: In file included from ../kernel/bpf/trampoline.c:11: ../kernel/bpf/trampoline.c: In function ‘bpf_trampoline_update’: ../kernel/bpf/trampoline.c:220:39: error: ‘call_rcu_tasks_trace’ undeclared ../kernel/bpf/trampoline.c: In function ‘__bpf_prog_enter_sleepable’: ../kernel/bpf/trampoline.c:411:2: error: implicit declaration of function ‘rcu_read_lock_trace’ ../kernel/bpf/trampoline.c: In function ‘__bpf_prog_exit_sleepable’: ../kernel/bpf/trampoline.c:416:2: error: implicit declaration of function ‘rcu_read_unlock_trace’ This is due to: obj-$(CONFIG_BPF_JIT) += trampoline.o obj-$(CONFIG_BPF_JIT) += dispatcher.o There is a number of functions that arch/x86/net/bpf_jit_comp.c is using from these two files, but none of them will be used when only cBPF is on (which is the case for BPF_SYSCALL=n BPF_JIT=y). Add rcu_trace functions to rcupdate_trace.h. The JITed code won't execute them and BPF trampoline logic won't be used without BPF_SYSCALL. Fixes: 1e6c62a88215 ("bpf: Introduce sleepable BPF programs") Reported-by: kernel test robot Signed-off-by: Alexei Starovoitov Signed-off-by: Daniel Borkmann Acked-by: Paul E. McKenney Link: https://lore.kernel.org/bpf/20200831155155.62754-1-alexei.starovoitov@gmail.com --- include/linux/rcupdate_trace.h | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/include/linux/rcupdate_trace.h b/include/linux/rcupdate_trace.h index d9015aac78c6..aaaac8ac927c 100644 --- a/include/linux/rcupdate_trace.h +++ b/include/linux/rcupdate_trace.h @@ -82,7 +82,14 @@ static inline void rcu_read_unlock_trace(void) void call_rcu_tasks_trace(struct rcu_head *rhp, rcu_callback_t func); void synchronize_rcu_tasks_trace(void); void rcu_barrier_tasks_trace(void); - +#else +/* + * The BPF JIT forms these addresses even when it doesn't call these + * functions, so provide definitions that result in runtime errors. + */ +static inline void call_rcu_tasks_trace(struct rcu_head *rhp, rcu_callback_t func) { BUG(); } +static inline void rcu_read_lock_trace(void) { BUG(); } +static inline void rcu_read_unlock_trace(void) { BUG(); } #endif /* #ifdef CONFIG_TASKS_TRACE_RCU */ #endif /* __LINUX_RCUPDATE_TRACE_H */