perf tools: Set the maximum allowed stack from /proc/sys/kernel/perf_event_max_stack

There is an upper limit to what tooling considers a valid callchain,
and it was tied to the hardcoded value in the kernel,
PERF_MAX_STACK_DEPTH (127), now that this can be tuned via a sysctl,
make it read it and use that as the upper limit, falling back to
PERF_MAX_STACK_DEPTH for kernels where this sysctl isn't present.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Brendan Gregg <brendan.d.gregg@gmail.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Milian Wolff <milian.wolff@kdab.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lkml.kernel.org/n/tip-yjqsd30nnkogvj5oyx9ghir9@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

4 files changed, 7 insertions, 4 deletions

diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c
index 656c1d7ee7d4..2cb95bbf9ea6 100644
--- a/tools/perf/util/machine.c
+++ b/tools/perf/util/machine.c
@@ -1764,7 +1764,7 @@ static int resolve_lbr_callchain_sample(struct thread *thread,
                  */
                 int mix_chain_nr = i + 1 + lbr_nr + 1;
 
-                if (mix_chain_nr > PERF_MAX_STACK_DEPTH + PERF_MAX_BRANCH_DEPTH) {
+                if (mix_chain_nr > (int)sysctl_perf_event_max_stack + PERF_MAX_BRANCH_DEPTH) {
                         pr_warning("corrupted callchain. skipping...\n");
                         return 0;
                 }
@@ -1825,7 +1825,7 @@ static int thread__resolve_callchain_sample(struct thread *thread,
          * Based on DWARF debug information, some architectures skip
          * a callchain entry saved by the kernel.
          */
-        if (chain->nr < PERF_MAX_STACK_DEPTH)
+        if (chain->nr < sysctl_perf_event_max_stack)
                 skip_idx = arch_skip_callchain_idx(thread, chain);
 
         /*
@@ -1886,7 +1886,7 @@ static int thread__resolve_callchain_sample(struct thread *thread,
         }
 
 check_calls:
-        if (chain->nr > PERF_MAX_STACK_DEPTH && (int)chain->nr > max_stack) {
+        if (chain->nr > sysctl_perf_event_max_stack && (int)chain->nr > max_stack) {
                 pr_warning("corrupted callchain. skipping...\n");
                 return 0;
         }
diff --git a/tools/perf/util/scripting-engines/trace-event-perl.c b/tools/perf/util/scripting-engines/trace-event-perl.c
index ae1cebc307c5..62c7f6988e0e 100644
--- a/tools/perf/util/scripting-engines/trace-event-perl.c
+++ b/tools/perf/util/scripting-engines/trace-event-perl.c
@@ -265,7 +265,7 @@ static SV *perl_process_callchain(struct perf_sample *sample,
 
         if (thread__resolve_callchain(al->thread, &callchain_cursor, evsel,
                                       sample, NULL, NULL,
-                                      PERF_MAX_STACK_DEPTH) != 0) {
+                                      sysctl_perf_event_max_stack) != 0) {
                 pr_err("Failed to resolve callchain. Skipping\n");
                 goto exit;
         }
diff --git a/tools/perf/util/util.c b/tools/perf/util/util.c
index 9473d46c00bb..619ba2061b62 100644
--- a/tools/perf/util/util.c
+++ b/tools/perf/util/util.c
@@ -33,6 +33,8 @@ struct callchain_param	callchain_param = {
 unsigned int page_size;
 int cacheline_size;
 
+unsigned int sysctl_perf_event_max_stack = PERF_MAX_STACK_DEPTH;
+
 bool test_attr__enabled;
 
 bool perf_host  = true;
diff --git a/tools/perf/util/util.h b/tools/perf/util/util.h
index 26a924651e7b..88f607af1f47 100644
--- a/tools/perf/util/util.h
+++ b/tools/perf/util/util.h
@@ -267,6 +267,7 @@ void sighandler_dump_stack(int sig);
 
 extern unsigned int page_size;
 extern int cacheline_size;
+extern unsigned int sysctl_perf_event_max_stack;
 
 struct parse_tag {
         char tag;