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
 21static char *debuginfo_path;
 22
 23static int __find_debuginfo(Dwfl_Module *mod __maybe_unused, void **userdata,
 24			    const char *modname __maybe_unused, Dwarf_Addr base __maybe_unused,
 25			    const char *file_name, const char *debuglink_file __maybe_unused,
 26			    GElf_Word debuglink_crc __maybe_unused, char **debuginfo_file_name)
 27{
 28	const struct dso *dso = *userdata;
 29
 30	assert(dso);
 31	if (dso->symsrc_filename && strcmp (file_name, dso->symsrc_filename))
 32		*debuginfo_file_name = strdup(dso->symsrc_filename);
 33	return -1;
 34}
 35
 36static const Dwfl_Callbacks offline_callbacks = {
 37	.find_debuginfo		= __find_debuginfo,
 38	.debuginfo_path		= &debuginfo_path,
 39	.section_address	= dwfl_offline_section_address,
 40	// .find_elf is not set as we use dwfl_report_elf() instead.
 41};
 42
 43static int __report_module(struct addr_location *al, u64 ip,
 44			    struct unwind_info *ui)
 45{
 46	Dwfl_Module *mod;
 47	struct dso *dso = NULL;
 48	/*
 49	 * Some callers will use al->sym, so we can't just use the
 50	 * cheaper thread__find_map() here.
 51	 */
 52	thread__find_symbol(ui->thread, PERF_RECORD_MISC_USER, ip, al);
 53
 54	if (al->map)
 55		dso = al->map->dso;
 56
 57	if (!dso)
 58		return 0;
 59
 60	mod = dwfl_addrmodule(ui->dwfl, ip);
 61	if (mod) {
 62		Dwarf_Addr s;
 63
 64		dwfl_module_info(mod, NULL, &s, NULL, NULL, NULL, NULL, NULL);
 65		if (s != al->map->start - al->map->pgoff)
 66			mod = 0;
 67	}
 68
 69	if (!mod)
 70		mod = dwfl_report_elf(ui->dwfl, dso->short_name, dso->long_name, -1,
 71				      al->map->start - al->map->pgoff, false);
 72	if (!mod) {
 73		char filename[PATH_MAX];
 74
 75		if (dso__build_id_filename(dso, filename, sizeof(filename), false))
 76			mod = dwfl_report_elf(ui->dwfl, dso->short_name, filename, -1,
 77					      al->map->start - al->map->pgoff, false);
 78	}
 79
 80	if (mod) {
 81		void **userdatap;
 82
 83		dwfl_module_info(mod, &userdatap, NULL, NULL, NULL, NULL, NULL, NULL);
 84		*userdatap = dso;
 85	}
 86
 87	return mod && dwfl_addrmodule(ui->dwfl, ip) == mod ? 0 : -1;
 88}
 89
 90static int report_module(u64 ip, struct unwind_info *ui)
 91{
 92	struct addr_location al;
 93
 94	return __report_module(&al, ip, ui);
 95}
 96
 97/*
 98 * Store all entries within entries array,
 99 * we will process it after we finish unwind.
100 */
101static int entry(u64 ip, struct unwind_info *ui)
102
103{
104	struct unwind_entry *e = &ui->entries[ui->idx++];
105	struct addr_location al;
106
107	if (__report_module(&al, ip, ui))
108		return -1;
109
110	e->ip	  = ip;
111	e->ms.maps = al.maps;
112	e->ms.map = al.map;
113	e->ms.sym = al.sym;
114
115	pr_debug("unwind: %s:ip = 0x%" PRIx64 " (0x%" PRIx64 ")\n",
116		 al.sym ? al.sym->name : "''",
117		 ip,
118		 al.map ? al.map->map_ip(al.map, ip) : (u64) 0);
119	return 0;
120}
121
122static pid_t next_thread(Dwfl *dwfl, void *arg, void **thread_argp)
123{
124	/* We want only single thread to be processed. */
125	if (*thread_argp != NULL)
126		return 0;
127
128	*thread_argp = arg;
129	return dwfl_pid(dwfl);
130}
131
132static int access_dso_mem(struct unwind_info *ui, Dwarf_Addr addr,
133			  Dwarf_Word *data)
134{
135	struct addr_location al;
136	ssize_t size;
137
138	if (!thread__find_map(ui->thread, PERF_RECORD_MISC_USER, addr, &al)) {
139		pr_debug("unwind: no map for %lx\n", (unsigned long)addr);
140		return -1;
141	}
142
143	if (!al.map->dso)
144		return -1;
145
146	size = dso__data_read_addr(al.map->dso, al.map, ui->machine,
147				   addr, (u8 *) data, sizeof(*data));
148
149	return !(size == sizeof(*data));
150}
151
152static bool memory_read(Dwfl *dwfl __maybe_unused, Dwarf_Addr addr, Dwarf_Word *result,
153			void *arg)
154{
155	struct unwind_info *ui = arg;
156	struct stack_dump *stack = &ui->sample->user_stack;
157	u64 start, end;
158	int offset;
159	int ret;
160
161	ret = perf_reg_value(&start, &ui->sample->user_regs, PERF_REG_SP);
162	if (ret)
163		return false;
164
165	end = start + stack->size;
166
167	/* Check overflow. */
168	if (addr + sizeof(Dwarf_Word) < addr)
169		return false;
170
171	if (addr < start || addr + sizeof(Dwarf_Word) > end) {
172		ret = access_dso_mem(ui, addr, result);
173		if (ret) {
174			pr_debug("unwind: access_mem 0x%" PRIx64 " not inside range"
175				 " 0x%" PRIx64 "-0x%" PRIx64 "\n",
176				addr, start, end);
177			return false;
178		}
179		return true;
180	}
181
182	offset  = addr - start;
183	*result = *(Dwarf_Word *)&stack->data[offset];
184	pr_debug("unwind: access_mem addr 0x%" PRIx64 ", val %lx, offset %d\n",
185		 addr, (unsigned long)*result, offset);
186	return true;
187}
188
189static const Dwfl_Thread_Callbacks callbacks = {
190	.next_thread		= next_thread,
191	.memory_read		= memory_read,
192	.set_initial_registers	= libdw__arch_set_initial_registers,
193};
194
195static int
196frame_callback(Dwfl_Frame *state, void *arg)
197{
198	struct unwind_info *ui = arg;
199	Dwarf_Addr pc;
200	bool isactivation;
201
202	if (!dwfl_frame_pc(state, &pc, NULL)) {
203		pr_err("%s", dwfl_errmsg(-1));
204		return DWARF_CB_ABORT;
205	}
206
207	// report the module before we query for isactivation
208	report_module(pc, ui);
209
210	if (!dwfl_frame_pc(state, &pc, &isactivation)) {
211		pr_err("%s", dwfl_errmsg(-1));
212		return DWARF_CB_ABORT;
213	}
214
215	if (!isactivation)
216		--pc;
217
218	return entry(pc, ui) || !(--ui->max_stack) ?
219	       DWARF_CB_ABORT : DWARF_CB_OK;
220}
221
222int unwind__get_entries(unwind_entry_cb_t cb, void *arg,
223			struct thread *thread,
224			struct perf_sample *data,
225			int max_stack)
226{
227	struct unwind_info *ui, ui_buf = {
228		.sample		= data,
229		.thread		= thread,
230		.machine	= thread->maps->machine,
231		.cb		= cb,
232		.arg		= arg,
233		.max_stack	= max_stack,
234	};
235	Dwarf_Word ip;
236	int err = -EINVAL, i;
237
238	if (!data->user_regs.regs)
239		return -EINVAL;
240
241	ui = zalloc(sizeof(ui_buf) + sizeof(ui_buf.entries[0]) * max_stack);
242	if (!ui)
243		return -ENOMEM;
244
245	*ui = ui_buf;
246
247	ui->dwfl = dwfl_begin(&offline_callbacks);
248	if (!ui->dwfl)
249		goto out;
250
251	err = perf_reg_value(&ip, &data->user_regs, PERF_REG_IP);
252	if (err)
253		goto out;
254
255	err = report_module(ip, ui);
256	if (err)
257		goto out;
258
259	err = !dwfl_attach_state(ui->dwfl, EM_NONE, thread->tid, &callbacks, ui);
260	if (err)
261		goto out;
262
263	err = dwfl_getthread_frames(ui->dwfl, thread->tid, frame_callback, ui);
264
265	if (err && ui->max_stack != max_stack)
266		err = 0;
267
268	/*
269	 * Display what we got based on the order setup.
270	 */
271	for (i = 0; i < ui->idx && !err; i++) {
272		int j = i;
273
274		if (callchain_param.order == ORDER_CALLER)
275			j = ui->idx - i - 1;
276
277		err = ui->entries[j].ip ? ui->cb(&ui->entries[j], ui->arg) : 0;
278	}
279
280 out:
281	if (err)
282		pr_debug("unwind: failed with '%s'\n", dwfl_errmsg(-1));
283
284	dwfl_end(ui->dwfl);
285	free(ui);
286	return 0;
287}