On 12/13/17 7:50 AM, Alexei Starovoitov wrote:
On 12/13/17 7:44 AM, Daniel Borkmann wrote:
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)
[...]
+1
#ifdef CONFIG_BPF_EVENTS
works, whereas CONFIG_EVENT_TRACING probably not, since kprobe
can be disabled independently which will turn off BPF_EVENTS
and body of bpf_event_query_prog_array() will be gone.
I tested to enable/disable uprobe/kprobe/both and my patch works.
But I did not test enable a non uprobe/kprobe tracing event
(e.g., CONFIG_FUNCTION_TRACER) where CONFIG_TRACING and
CONFIG_EVENT_TRACING is on but CONFIG_UPROBES_EVENT/CONFIG_KPROBES_EVENT
is off and then my patch breaks.
Looks like
#ifdef CONFIG_BPF_EVENTS
is suffice.
This config will enable to include bpf_trace.c with the real definition.
It will depend on KPROBE_EVENTS or UPROBE_EVENTS and either
of them will enable CONFIG_TRACING and then CONFIG_EVENT_TRACING.
Will resubmit the patch after testing.
