perf/bpf: Always use perf callchains if exist

If the perf_event has PERF_SAMPLE_CALLCHAIN, BPF can use it for stack trace.
The problematic cases like PEBS and IBS already handled in the PMU driver and
they filled the callchain info in the sample data.  For others, we can call
perf_callchain() before the BPF handler.

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20220908214104.3851807-2-namhyung@kernel.org

diff --git a/kernel/bpf/stackmap.c b/kernel/bpf/stackmap.c
index 1adbe67cdb95e1d18d084a57eb61f30991cb63a4..aecea7451b6103785203e32a832f2e9590b4abae 100644 (file)
--- a/kernel/bpf/stackmap.c
+++ b/kernel/bpf/stackmap.c
@@ -338,7 +338,7 @@ BPF_CALL_3(bpf_get_stackid_pe, struct bpf_perf_event_data_kern *, ctx,
        int ret;
 
        /* perf_sample_data doesn't have callchain, use bpf_get_stackid */
-       if (!(event->attr.sample_type & __PERF_SAMPLE_CALLCHAIN_EARLY))
+       if (!(event->attr.sample_type & PERF_SAMPLE_CALLCHAIN))
                return bpf_get_stackid((unsigned long)(ctx->regs),
                                       (unsigned long) map, flags, 0, 0);
 
@@ -506,7 +506,7 @@ BPF_CALL_4(bpf_get_stack_pe, struct bpf_perf_event_data_kern *, ctx,
        int err = -EINVAL;
        __u64 nr_kernel;
 
-       if (!(event->attr.sample_type & __PERF_SAMPLE_CALLCHAIN_EARLY))
+       if (!(event->attr.sample_type & PERF_SAMPLE_CALLCHAIN))
                return __bpf_get_stack(regs, NULL, NULL, buf, size, flags);
 
        if (unlikely(flags & ~(BPF_F_SKIP_FIELD_MASK | BPF_F_USER_STACK |

diff --git a/kernel/events/core.c b/kernel/events/core.c
index c98ecf3e09bab11639c568e25ef7861af9969ebb..7da5515082f9c266a68609892ba6ebb28e3f69b0 100644 (file)
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -10000,8 +10000,16 @@ static void bpf_overflow_handler(struct perf_event *event,
                goto out;
        rcu_read_lock();
        prog = READ_ONCE(event->prog);
-       if (prog)
+       if (prog) {
+               if (prog->call_get_stack &&
+                   (event->attr.sample_type & PERF_SAMPLE_CALLCHAIN) &&
+                   !(data->sample_flags & PERF_SAMPLE_CALLCHAIN)) {
+                       data->callchain = perf_callchain(event, regs);
+                       data->sample_flags |= PERF_SAMPLE_CALLCHAIN;
+               }
+
                ret = bpf_prog_run(prog, &ctx);
+       }
        rcu_read_unlock();
 out:
        __this_cpu_dec(bpf_prog_active);
@@ -10027,7 +10035,7 @@ static int perf_event_set_bpf_handler(struct perf_event *event,
 
        if (event->attr.precise_ip &&
            prog->call_get_stack &&
-           (!(event->attr.sample_type & __PERF_SAMPLE_CALLCHAIN_EARLY) ||
+           (!(event->attr.sample_type & PERF_SAMPLE_CALLCHAIN) ||
             event->attr.exclude_callchain_kernel ||
             event->attr.exclude_callchain_user)) {
                /*