Re: [PATCH, REPORT] bpf_trace: build error without PERF_EVENTS

From: Daniel Borkmann
Date: Tue Nov 10 2015 - 12:23:27 EST

On 11/10/2015 06:14 PM, Alexei Starovoitov wrote:
On Tue, Nov 10, 2015 at 09:25:01AM -0500, Steven Rostedt wrote:
On Tue, 10 Nov 2015 14:31:38 +0100
Daniel Borkmann <daniel@xxxxxxxxxxxxx> wrote:

On 11/10/2015 01:55 PM, Arnd Bergmann wrote:
In my ARM randconfig tests, I'm getting a build error for
newly added code in bpf_perf_event_read and bpf_perf_event_output
whenever CONFIG_PERF_EVENTS is disabled:

kernel/trace/bpf_trace.c: In function 'bpf_perf_event_read':
kernel/trace/bpf_trace.c:203:11: error: 'struct perf_event' has no member named 'oncpu'
if (event->oncpu != smp_processor_id() ||
kernel/trace/bpf_trace.c:204:11: error: 'struct perf_event' has no member named 'pmu'

This can happen when UPROBE_EVENT is enabled but KPROBE_EVENT
is disabled. I'm not sure if that is a configuration we care
about, otherwise we could prevent this case from occuring by
adding Kconfig dependencies.

I think that seems better than spreading #if IS_ENABLEDs into the code.
Probably enough to add a 'depends on PERF_EVENTS' to config BPF_EVENTS,
so it's also explicitly documented.

So just do the following then?

-- Steve

diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
index 8d6363f42169..f5aecff2d243 100644
--- a/kernel/trace/Kconfig
+++ b/kernel/trace/Kconfig
@@ -434,7 +434,7 @@ config UPROBE_EVENT

depends on BPF_SYSCALL

yeah that's definitely cleaner and avoids ifdef creep in the future.

Agreed, that's better.
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