On 12/13/2017 08:42 AM, Yonghong Song wrote: > Commit f371b304f12e ("bpf/tracing: allow user space to > query prog array on the same tp") introduced a perf > ioctl command to query prog array attached to the > same perf tracepoint. The commit introduced a > compilation error when either CONFIG_BPF_SYSCALL or > CONFIG_EVENT_TRACING is not defined: > kernel/events/core.o: In function `perf_ioctl': > core.c:(.text+0x98c4): undefined reference to `bpf_event_query_prog_array' > > This patch fixed this error. > > Fixes: f371b304f12e ("bpf/tracing: allow user space to query prog array on > the same tp") > Reported-by: Stephen Rothwell <s...@canb.auug.org.au> > Signed-off-by: Yonghong Song <y...@fb.com>
Looking at _perf_ioctl(), we also have perf_event_set_bpf_prog() there. It's basically under CONFIG_EVENT_TRACING, which later calls perf_event_attach_bpf_prog() which is under CONFIG_BPF_EVENTS, so where we have the dummy handler returning -EOPNOTSUPP when BPF events is not set. bpf_trace.c is only built when CONFIG_BPF_EVENTS is set and that by itself depends on BPF_SYSCALL already. So it would be more correct to do the same thing here ... #if defined(CONFIG_EVENT_TRACING) && defined(CONFIG_BPF_EVENTS) [...] > --- > include/linux/bpf.h | 10 +++++++++- > 1 file changed, 9 insertions(+), 1 deletion(-) > > diff --git a/include/linux/bpf.h b/include/linux/bpf.h > index 93e15b9..8dbbfd7 100644 > --- a/include/linux/bpf.h > +++ b/include/linux/bpf.h > @@ -254,7 +254,6 @@ typedef unsigned long (*bpf_ctx_copy_t)(void *dst, const > void *src, > > u64 bpf_event_output(struct bpf_map *map, u64 flags, void *meta, u64 > meta_size, > void *ctx, u64 ctx_size, bpf_ctx_copy_t ctx_copy); > -int bpf_event_query_prog_array(struct perf_event *event, void __user *info); > > int bpf_prog_test_run_xdp(struct bpf_prog *prog, const union bpf_attr *kattr, > union bpf_attr __user *uattr); > @@ -558,6 +557,15 @@ static inline int sock_map_prog(struct bpf_map *map, > } > #endif > > +#if defined(CONFIG_EVENT_TRACING) && defined(CONFIG_BPF_SYSCALL) > +int bpf_event_query_prog_array(struct perf_event *event, void __user *info); > +#else > +static inline int bpf_event_query_prog_array(struct perf_event *event, void > __user *info) > +{ > + return -EOPNOTSUPP; > +} > +#endif > + > /* verifier prototypes for helper functions called from eBPF programs */ > extern const struct bpf_func_proto bpf_map_lookup_elem_proto; > extern const struct bpf_func_proto bpf_map_update_elem_proto; >