perf tools: Separate accounting of contexts and real addresses in a stack trace

The perf_sample->ip_callchain->nr value includes all the entries in the
ip_callchain->ip[] array, real addresses and PERF_CONTEXT_{KERNEL,USER,etc},
while what the user expects is that what is in the kernel.perf_event_max_stack
sysctl or in the upcoming per event perf_event_attr.sample_max_stack knob be
honoured in terms of IP addresses in the stack trace.

So match the kernel support and validate chain->nr taking into account
both kernel.perf_event_max_stack and kernel.perf_event_max_contexts_per_stack.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Brendan Gregg <brendan.d.gregg@gmail.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: He Kuang <hekuang@huawei.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Milian Wolff <milian.wolff@kdab.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Cc: Wang Nan <wangnan0@huawei.com>
Cc: Zefan Li <lizefan@huawei.com>
Link: http://lkml.kernel.org/n/tip-mgx0jpzfdq4uq4abfa40byu0@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

4 files changed, 24 insertions, 11 deletions

diff --git a/tools/perf/perf.c b/tools/perf/perf.c
index 797000842d40..15982cee5ef3 100644
--- a/tools/perf/perf.c
+++ b/tools/perf/perf.c
@@ -549,6 +549,9 @@ int main(int argc, const char **argv)
         if (sysctl__read_int("kernel/perf_event_max_stack", &value) == 0)
                 sysctl_perf_event_max_stack = value;
 
+        if (sysctl__read_int("kernel/perf_event_max_contexts_per_stack", &value) == 0)
+                sysctl_perf_event_max_contexts_per_stack = value;
+
         cmd = extract_argv0_path(argv[0]);
         if (!cmd)
                 cmd = "perf-help";
diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c
index 18dd96bdde05..7ba9fadb68af 100644
--- a/tools/perf/util/machine.c
+++ b/tools/perf/util/machine.c
@@ -1811,9 +1811,9 @@ static int thread__resolve_callchain_sample(struct thread *thread,
 {
         struct branch_stack *branch = sample->branch_stack;
         struct ip_callchain *chain = sample->callchain;
-        int chain_nr = min(max_stack, (int)chain->nr);
+        int chain_nr = chain->nr;
         u8 cpumode = PERF_RECORD_MISC_USER;
-        int i, j, err;
+        int i, j, err, nr_entries, nr_contexts;
         int skip_idx = -1;
         int first_call = 0;
 
@@ -1828,7 +1828,7 @@ 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 < sysctl_perf_event_max_stack)
+        if (chain_nr < sysctl_perf_event_max_stack)
                 skip_idx = arch_skip_callchain_idx(thread, chain);
 
         /*
@@ -1889,12 +1889,8 @@ static int thread__resolve_callchain_sample(struct thread *thread,
         }
 
 check_calls:
-        if (chain->nr > sysctl_perf_event_max_stack && (int)chain->nr > max_stack) {
-                pr_warning("corrupted callchain. skipping...\n");
-                return 0;
-        }
-
-        for (i = first_call; i < chain_nr; i++) {
+        for (i = first_call, nr_entries = 0, nr_contexts = 0;
+             i < chain_nr && nr_entries < max_stack; i++) {
                 u64 ip;
 
                 if (callchain_param.order == ORDER_CALLEE)
@@ -1908,6 +1904,14 @@ check_calls:
 #endif
                 ip = chain->ips[j];
 
+                if (ip >= PERF_CONTEXT_MAX) {
+                        if (++nr_contexts > sysctl_perf_event_max_contexts_per_stack)
+                                goto out_corrupted_callchain;
+                } else {
+                        if (++nr_entries > sysctl_perf_event_max_stack)
+                                goto out_corrupted_callchain;
+                }
+
                 err = add_callchain_ip(thread, cursor, parent, root_al, &cpumode, ip);
 
                 if (err)
@@ -1915,6 +1919,10 @@ check_calls:
         }
 
         return 0;
+
+out_corrupted_callchain:
+        pr_warning("corrupted callchain. skipping...\n");
+        return 0;
 }
 
 static int unwind_entry(struct unwind_entry *entry, void *arg)
diff --git a/tools/perf/util/util.c b/tools/perf/util/util.c
index eab077ad6ca9..23504ad5d6dd 100644
--- a/tools/perf/util/util.c
+++ b/tools/perf/util/util.c
@@ -33,7 +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;
+int sysctl_perf_event_max_stack = PERF_MAX_STACK_DEPTH;
+int sysctl_perf_event_max_contexts_per_stack = PERF_MAX_CONTEXTS_PER_STACK;
 
 bool test_attr__enabled;
 
diff --git a/tools/perf/util/util.h b/tools/perf/util/util.h
index 7651633a8dc7..1e8c3167b9fb 100644
--- a/tools/perf/util/util.h
+++ b/tools/perf/util/util.h
@@ -261,7 +261,8 @@ void sighandler_dump_stack(int sig);
 
 extern unsigned int page_size;
 extern int cacheline_size;
-extern unsigned int sysctl_perf_event_max_stack;
+extern int sysctl_perf_event_max_stack;
+extern int sysctl_perf_event_max_contexts_per_stack;
 
 struct parse_tag {
         char tag;