1// SPDX-License-Identifier: GPL-2.0
2#include <linux/compiler.h>
3#include <linux/types.h>
4#include <linux/zalloc.h>
5#include <inttypes.h>
6#include <limits.h>
7#include <unistd.h>
8#include "tests.h"
9#include "debug.h"
10#include "machine.h"
11#include "event.h"
12#include "../util/unwind.h"
13#include "perf_regs.h"
14#include "map.h"
15#include "symbol.h"
16#include "thread.h"
17#include "callchain.h"
18#include "util/synthetic-events.h"
19
20/* For bsearch. We try to unwind functions in shared object. */
21#include <stdlib.h>
22
23/*
24 * The test will assert frames are on the stack but tail call optimizations lose
25 * the frame of the caller. Clang can disable this optimization on a called
26 * function but GCC currently (11/2020) lacks this attribute. The barrier is
27 * used to inhibit tail calls in these cases.
28 */
29#ifdef __has_attribute
30#if __has_attribute(disable_tail_calls)
31#define NO_TAIL_CALL_ATTRIBUTE __attribute__((disable_tail_calls))
32#define NO_TAIL_CALL_BARRIER
33#endif
34#endif
35#ifndef NO_TAIL_CALL_ATTRIBUTE
36#define NO_TAIL_CALL_ATTRIBUTE
37#define NO_TAIL_CALL_BARRIER __asm__ __volatile__("" : : : "memory");
38#endif
39
40static int mmap_handler(struct perf_tool *tool __maybe_unused,
41			union perf_event *event,
42			struct perf_sample *sample,
43			struct machine *machine)
44{
45	return machine__process_mmap2_event(machine, event, sample);
46}
47
48static int init_live_machine(struct machine *machine)
49{
50	union perf_event event;
51	pid_t pid = getpid();
52
53	memset(&event, 0, sizeof(event));
54	return perf_event__synthesize_mmap_events(NULL, &event, pid, pid,
55						  mmap_handler, machine, true);
56}
57
58/*
59 * We need to keep these functions global, despite the
60 * fact that they are used only locally in this object,
61 * in order to keep them around even if the binary is
62 * stripped. If they are gone, the unwind check for
63 * symbol fails.
64 */
65int test_dwarf_unwind__thread(struct thread *thread);
66int test_dwarf_unwind__compare(void *p1, void *p2);
67int test_dwarf_unwind__krava_3(struct thread *thread);
68int test_dwarf_unwind__krava_2(struct thread *thread);
69int test_dwarf_unwind__krava_1(struct thread *thread);
70int test__dwarf_unwind(struct test_suite *test, int subtest);
71
72#define MAX_STACK 8
73
74static int unwind_entry(struct unwind_entry *entry, void *arg)
75{
76	unsigned long *cnt = (unsigned long *) arg;
77	char *symbol = entry->ms.sym ? entry->ms.sym->name : NULL;
78	static const char *funcs[MAX_STACK] = {
79		"test__arch_unwind_sample",
80		"test_dwarf_unwind__thread",
81		"test_dwarf_unwind__compare",
82		"bsearch",
83		"test_dwarf_unwind__krava_3",
84		"test_dwarf_unwind__krava_2",
85		"test_dwarf_unwind__krava_1",
86		"test__dwarf_unwind"
87	};
88	/*
89	 * The funcs[MAX_STACK] array index, based on the
90	 * callchain order setup.
91	 */
92	int idx = callchain_param.order == ORDER_CALLER ?
93		  MAX_STACK - *cnt - 1 : *cnt;
94
95	if (*cnt >= MAX_STACK) {
96		pr_debug("failed: crossed the max stack value %d\n", MAX_STACK);
97		return -1;
98	}
99
100	if (!symbol) {
101		pr_debug("failed: got unresolved address 0x%" PRIx64 "\n",
102			 entry->ip);
103		return -1;
104	}
105
106	(*cnt)++;
107	pr_debug("got: %s 0x%" PRIx64 ", expecting %s\n",
108		 symbol, entry->ip, funcs[idx]);
109	return strcmp((const char *) symbol, funcs[idx]);
110}
111
112NO_TAIL_CALL_ATTRIBUTE noinline int test_dwarf_unwind__thread(struct thread *thread)
113{
114	struct perf_sample sample;
115	unsigned long cnt = 0;
116	int err = -1;
117
118	memset(&sample, 0, sizeof(sample));
119
120	if (test__arch_unwind_sample(&sample, thread)) {
121		pr_debug("failed to get unwind sample\n");
122		goto out;
123	}
124
125	err = unwind__get_entries(unwind_entry, &cnt, thread,
126				  &sample, MAX_STACK, false);
127	if (err)
128		pr_debug("unwind failed\n");
129	else if (cnt != MAX_STACK) {
130		pr_debug("got wrong number of stack entries %lu != %d\n",
131			 cnt, MAX_STACK);
132		err = -1;
133	}
134
135 out:
136	zfree(&sample.user_stack.data);
137	zfree(&sample.user_regs.regs);
138	return err;
139}
140
141static int global_unwind_retval = -INT_MAX;
142
143NO_TAIL_CALL_ATTRIBUTE noinline int test_dwarf_unwind__compare(void *p1, void *p2)
144{
145	/* Any possible value should be 'thread' */
146	struct thread *thread = *(struct thread **)p1;
147
148	if (global_unwind_retval == -INT_MAX) {
149		/* Call unwinder twice for both callchain orders. */
150		callchain_param.order = ORDER_CALLER;
151
152		global_unwind_retval = test_dwarf_unwind__thread(thread);
153		if (!global_unwind_retval) {
154			callchain_param.order = ORDER_CALLEE;
155			global_unwind_retval = test_dwarf_unwind__thread(thread);
156		}
157	}
158
159	return p1 - p2;
160}
161
162NO_TAIL_CALL_ATTRIBUTE noinline int test_dwarf_unwind__krava_3(struct thread *thread)
163{
164	struct thread *array[2] = {thread, thread};
165	void *fp = &bsearch;
166	/*
167	 * make _bsearch a volatile function pointer to
168	 * prevent potential optimization, which may expand
169	 * bsearch and call compare directly from this function,
170	 * instead of libc shared object.
171	 */
172	void *(*volatile _bsearch)(void *, void *, size_t,
173			size_t, int (*)(void *, void *));
174
175	_bsearch = fp;
176	_bsearch(array, &thread, 2, sizeof(struct thread **),
177		 test_dwarf_unwind__compare);
178	return global_unwind_retval;
179}
180
181NO_TAIL_CALL_ATTRIBUTE noinline int test_dwarf_unwind__krava_2(struct thread *thread)
182{
183	int ret;
184
185	ret =  test_dwarf_unwind__krava_3(thread);
186	NO_TAIL_CALL_BARRIER;
187	return ret;
188}
189
190NO_TAIL_CALL_ATTRIBUTE noinline int test_dwarf_unwind__krava_1(struct thread *thread)
191{
192	int ret;
193
194	ret =  test_dwarf_unwind__krava_2(thread);
195	NO_TAIL_CALL_BARRIER;
196	return ret;
197}
198
199noinline int test__dwarf_unwind(struct test_suite *test __maybe_unused,
200				int subtest __maybe_unused)
201{
202	struct machine *machine;
203	struct thread *thread;
204	int err = -1;
205
206	machine = machine__new_host();
207	if (!machine) {
208		pr_err("Could not get machine\n");
209		return -1;
210	}
211
212	if (machine__create_kernel_maps(machine)) {
213		pr_err("Failed to create kernel maps\n");
214		return -1;
215	}
216
217	callchain_param.record_mode = CALLCHAIN_DWARF;
218	dwarf_callchain_users = true;
219
220	if (init_live_machine(machine)) {
221		pr_err("Could not init machine\n");
222		goto out;
223	}
224
225	if (verbose > 1)
226		machine__fprintf(machine, stderr);
227
228	thread = machine__find_thread(machine, getpid(), getpid());
229	if (!thread) {
230		pr_err("Could not get thread\n");
231		goto out;
232	}
233
234	err = test_dwarf_unwind__krava_1(thread);
235	thread__put(thread);
236
237 out:
238	machine__delete(machine);
239	return err;
240}
241
242DEFINE_SUITE("Test dwarf unwind", dwarf_unwind);
243