perf symbols: Limit max callchain using max_stack on DWARF unwinding too

It was affecting only frame-pointer (fp) based callchain processing.

Usage example:

  perf top --call-graph dwarf,1024 --max-stack 2

Works for any tool that does callchain resolving and provides a
--max-stack option.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Waiman Long <Waiman.Long@hp.com>
Link: http://lkml.kernel.org/n/tip-eu45v8s3tq9ruay8tpfyon79@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/machine.c

@@ -1368,7 +1368,7 @@ int machine__resolve_callchain(struct machine *machine,
 
 	return unwind__get_entries(unwind_entry, &callchain_cursor, machine,
 				   thread, evsel->attr.sample_regs_user,
-				   sample);
+				   sample, max_stack);
 
 }
 

tools/perf/util/unwind.c

@@ -559,7 +559,7 @@ static unw_accessors_t accessors = {
 };
 
 static int get_entries(struct unwind_info *ui, unwind_entry_cb_t cb,
-		       void *arg)
+		       void *arg, int max_stack)
 {
 	unw_addr_space_t addr_space;
 	unw_cursor_t c;
@@ -575,7 +575,7 @@ static int get_entries(struct unwind_info *ui, unwind_entry_cb_t cb,
 	if (ret)
 		display_error(ret);
 
-	while (!ret && (unw_step(&c) > 0)) {
+	while (!ret && (unw_step(&c) > 0) && max_stack--) {
 		unw_word_t ip;
 
 		unw_get_reg(&c, UNW_REG_IP, &ip);
@@ -588,7 +588,8 @@ static int get_entries(struct unwind_info *ui, unwind_entry_cb_t cb,
 
 int unwind__get_entries(unwind_entry_cb_t cb, void *arg,
 			struct machine *machine, struct thread *thread,
-			u64 sample_uregs, struct perf_sample *data)
+			u64 sample_uregs, struct perf_sample *data,
+			int max_stack)
 {
 	unw_word_t ip;
 	struct unwind_info ui = {
@@ -610,5 +611,5 @@ int unwind__get_entries(unwind_entry_cb_t cb, void *arg,
 	if (ret)
 		return -ENOMEM;
 
-	return get_entries(&ui, cb, arg);
+	return get_entries(&ui, cb, arg, max_stack);
 }

tools/perf/util/unwind.h

@@ -18,7 +18,7 @@ int unwind__get_entries(unwind_entry_cb_t cb, void *arg,
 			struct machine *machine,
 			struct thread *thread,
 			u64 sample_uregs,
-			struct perf_sample *data);
+			struct perf_sample *data, int max_stack);
 int unwind__arch_reg_id(int regnum);
 #else
 static inline int
@@ -27,7 +27,8 @@ unwind__get_entries(unwind_entry_cb_t cb __maybe_unused,
 		    struct machine *machine __maybe_unused,
 		    struct thread *thread __maybe_unused,
 		    u64 sample_uregs __maybe_unused,
-		    struct perf_sample *data __maybe_unused)
+		    struct perf_sample *data __maybe_unused,
+		    int max_stack __maybe_unused)
 {
 	return 0;
 }