unwind-libdw.c

  1// SPDX-License-Identifier: GPL-2.0
  2#include <linux/compiler.h>
  3#include <elfutils/libdw.h>
  4#include <elfutils/libdwfl.h>
  5#include <inttypes.h>
  6#include <errno.h>
  7#include "debug.h"
  8#include "dso.h"
  9#include "unwind.h"
 10#include "unwind-libdw.h"
 11#include "machine.h"
 12#include "map.h"
 13#include "symbol.h"
 14#include "thread.h"
 15#include <linux/types.h>
 16#include <linux/zalloc.h>
 17#include "event.h"
 18#include "perf_regs.h"
 19#include "callchain.h"
 20#include "util/env.h"
 21
 22static char *debuginfo_path;
 23
 24static int __find_debuginfo(Dwfl_Module *mod __maybe_unused, void **userdata,
 25			    const char *modname __maybe_unused, Dwarf_Addr base __maybe_unused,
 26			    const char *file_name, const char *debuglink_file __maybe_unused,
 27			    GElf_Word debuglink_crc __maybe_unused, char **debuginfo_file_name)
 28{
 29	const struct dso *dso = *userdata;
 30
 31	assert(dso);
 32	if (dso__symsrc_filename(dso) && strcmp(file_name, dso__symsrc_filename(dso)))
 33		*debuginfo_file_name = strdup(dso__symsrc_filename(dso));
 34	return -1;
 35}
 36
 37static const Dwfl_Callbacks offline_callbacks = {
 38	.find_debuginfo		= __find_debuginfo,
 39	.debuginfo_path		= &debuginfo_path,
 40	.section_address	= dwfl_offline_section_address,
 41	// .find_elf is not set as we use dwfl_report_elf() instead.
 42};
 43
 44static int __report_module(struct addr_location *al, u64 ip,
 45			    struct unwind_info *ui)
 46{
 47	Dwfl_Module *mod;
 48	struct dso *dso = NULL;
 49	Dwarf_Addr base;
 50	/*
 51	 * Some callers will use al->sym, so we can't just use the
 52	 * cheaper thread__find_map() here.
 53	 */
 54	thread__find_symbol(ui->thread, PERF_RECORD_MISC_USER, ip, al);
 55
 56	if (al->map)
 57		dso = map__dso(al->map);
 58
 59	if (!dso)
 60		return 0;
 61
 62	/*
 63	 * The generated JIT DSO files only map the code segment without
 64	 * ELF headers.  Since JIT codes used to be packed in a memory
 65	 * segment, calculating the base address using pgoff falls into
 66	 * a different code in another DSO.  So just use the map->start
 67	 * directly to pick the correct one.
 68	 */
 69	if (!strncmp(dso__long_name(dso), "/tmp/jitted-", 12))
 70		base = map__start(al->map);
 71	else
 72		base = map__start(al->map) - map__pgoff(al->map);
 73
 74	mod = dwfl_addrmodule(ui->dwfl, ip);
 75	if (mod) {
 76		Dwarf_Addr s;
 77
 78		dwfl_module_info(mod, NULL, &s, NULL, NULL, NULL, NULL, NULL);
 79		if (s != base)
 80			mod = NULL;
 81	}
 82
 83	if (!mod) {
 84		char filename[PATH_MAX];
 85
 86		__symbol__join_symfs(filename, sizeof(filename), dso__long_name(dso));
 87		/* Don't hang up on device files like /dev/dri/renderD128. */
 88		if (is_regular_file(filename)) {
 89			mod = dwfl_report_elf(ui->dwfl, dso__short_name(dso), filename, -1,
 90					      base, false);
 91		}
 92	}
 93	if (!mod) {
 94		char filename[PATH_MAX];
 95
 96		if (dso__build_id_filename(dso, filename, sizeof(filename), false))
 97			mod = dwfl_report_elf(ui->dwfl, dso__short_name(dso), filename, -1,
 98					      base, false);
 99	}
100
101	if (mod) {
102		void **userdatap;
103
104		dwfl_module_info(mod, &userdatap, NULL, NULL, NULL, NULL, NULL, NULL);
105		*userdatap = dso;
106	}
107
108	return mod && dwfl_addrmodule(ui->dwfl, ip) == mod ? 0 : -1;
109}
110
111static int report_module(u64 ip, struct unwind_info *ui)
112{
113	struct addr_location al;
114	int res;
115
116	addr_location__init(&al);
117	res = __report_module(&al, ip, ui);
118	addr_location__exit(&al);
119	return res;
120}
121
122/*
123 * Store all entries within entries array,
124 * we will process it after we finish unwind.
125 */
126static int entry(u64 ip, struct unwind_info *ui)
127
128{
129	struct unwind_entry *e = &ui->entries[ui->idx++];
130	struct addr_location al;
131
132	addr_location__init(&al);
133	if (__report_module(&al, ip, ui)) {
134		addr_location__exit(&al);
135		return -1;
136	}
137
138	e->ip	  = ip;
139	e->ms.maps = maps__get(al.maps);
140	e->ms.map = map__get(al.map);
141	e->ms.sym = al.sym;
142
143	pr_debug("unwind: %s:ip = 0x%" PRIx64 " (0x%" PRIx64 ")\n",
144		 al.sym ? al.sym->name : "''",
145		 ip,
146		 al.map ? map__map_ip(al.map, ip) : (u64) 0);
147	addr_location__exit(&al);
148	return 0;
149}
150
151static pid_t next_thread(Dwfl *dwfl, void *arg, void **thread_argp)
152{
153	/* We want only single thread to be processed. */
154	if (*thread_argp != NULL)
155		return 0;
156
157	*thread_argp = arg;
158	return dwfl_pid(dwfl);
159}
160
161static int access_dso_mem(struct unwind_info *ui, Dwarf_Addr addr,
162			  Dwarf_Word *data)
163{
164	struct addr_location al;
165	ssize_t size;
166	struct dso *dso;
167
168	addr_location__init(&al);
169	if (!thread__find_map(ui->thread, PERF_RECORD_MISC_USER, addr, &al)) {
170		pr_debug("unwind: no map for %lx\n", (unsigned long)addr);
171		goto out_fail;
172	}
173	dso = map__dso(al.map);
174	if (!dso)
175		goto out_fail;
176
177	size = dso__data_read_addr(dso, al.map, ui->machine, addr, (u8 *) data, sizeof(*data));
178
179	addr_location__exit(&al);
180	return !(size == sizeof(*data));
181out_fail:
182	addr_location__exit(&al);
183	return -1;
184}
185
186static bool memory_read(Dwfl *dwfl __maybe_unused, Dwarf_Addr addr, Dwarf_Word *result,
187			void *arg)
188{
189	struct unwind_info *ui = arg;
190	const char *arch = perf_env__arch(ui->machine->env);
191	struct stack_dump *stack = &ui->sample->user_stack;
192	u64 start, end;
193	int offset;
194	int ret;
195
196	if (!ui->sample->user_regs)
197		return false;
198
199	ret = perf_reg_value(&start, ui->sample->user_regs,
200			     perf_arch_reg_sp(arch));
201	if (ret)
202		return false;
203
204	end = start + stack->size;
205
206	/* Check overflow. */
207	if (addr + sizeof(Dwarf_Word) < addr)
208		return false;
209
210	if (addr < start || addr + sizeof(Dwarf_Word) > end) {
211		ret = access_dso_mem(ui, addr, result);
212		if (ret) {
213			pr_debug("unwind: access_mem 0x%" PRIx64 " not inside range"
214				 " 0x%" PRIx64 "-0x%" PRIx64 "\n",
215				addr, start, end);
216			return false;
217		}
218		return true;
219	}
220
221	offset  = addr - start;
222	*result = *(Dwarf_Word *)&stack->data[offset];
223	pr_debug("unwind: access_mem addr 0x%" PRIx64 ", val %lx, offset %d\n",
224		 addr, (unsigned long)*result, offset);
225	return true;
226}
227
228static const Dwfl_Thread_Callbacks callbacks = {
229	.next_thread		= next_thread,
230	.memory_read		= memory_read,
231	.set_initial_registers	= libdw__arch_set_initial_registers,
232};
233
234static int
235frame_callback(Dwfl_Frame *state, void *arg)
236{
237	struct unwind_info *ui = arg;
238	Dwarf_Addr pc;
239	bool isactivation;
240
241	if (!dwfl_frame_pc(state, &pc, NULL)) {
242		if (!ui->best_effort)
243			pr_err("%s", dwfl_errmsg(-1));
244		return DWARF_CB_ABORT;
245	}
246
247	// report the module before we query for isactivation
248	report_module(pc, ui);
249
250	if (!dwfl_frame_pc(state, &pc, &isactivation)) {
251		if (!ui->best_effort)
252			pr_err("%s", dwfl_errmsg(-1));
253		return DWARF_CB_ABORT;
254	}
255
256	if (!isactivation)
257		--pc;
258
259	return entry(pc, ui) || !(--ui->max_stack) ?
260	       DWARF_CB_ABORT : DWARF_CB_OK;
261}
262
263int unwind__get_entries(unwind_entry_cb_t cb, void *arg,
264			struct thread *thread,
265			struct perf_sample *data,
266			int max_stack,
267			bool best_effort)
268{
269	struct unwind_info *ui, ui_buf = {
270		.sample		= data,
271		.thread		= thread,
272		.machine	= maps__machine((thread__maps(thread))),
273		.cb		= cb,
274		.arg		= arg,
275		.max_stack	= max_stack,
276		.best_effort    = best_effort
277	};
278	const char *arch = perf_env__arch(ui_buf.machine->env);
279	Dwarf_Word ip;
280	int err = -EINVAL, i;
281
282	if (!data->user_regs || !data->user_regs->regs)
283		return -EINVAL;
284
285	ui = zalloc(sizeof(ui_buf) + sizeof(ui_buf.entries[0]) * max_stack);
286	if (!ui)
287		return -ENOMEM;
288
289	*ui = ui_buf;
290
291	ui->dwfl = dwfl_begin(&offline_callbacks);
292	if (!ui->dwfl)
293		goto out;
294
295	err = perf_reg_value(&ip, data->user_regs, perf_arch_reg_ip(arch));
296	if (err)
297		goto out;
298
299	err = report_module(ip, ui);
300	if (err)
301		goto out;
302
303	err = !dwfl_attach_state(ui->dwfl, EM_NONE, thread__tid(thread), &callbacks, ui);
304	if (err)
305		goto out;
306
307	err = dwfl_getthread_frames(ui->dwfl, thread__tid(thread), frame_callback, ui);
308
309	if (err && ui->max_stack != max_stack)
310		err = 0;
311
312	/*
313	 * Display what we got based on the order setup.
314	 */
315	for (i = 0; i < ui->idx && !err; i++) {
316		int j = i;
317
318		if (callchain_param.order == ORDER_CALLER)
319			j = ui->idx - i - 1;
320
321		err = ui->entries[j].ip ? ui->cb(&ui->entries[j], ui->arg) : 0;
322	}
323
324 out:
325	if (err)
326		pr_debug("unwind: failed with '%s'\n", dwfl_errmsg(-1));
327
328	for (i = 0; i < ui->idx; i++)
329		map_symbol__exit(&ui->entries[i].ms);
330
331	dwfl_end(ui->dwfl);
332	free(ui);
333	return 0;
334}