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
22 static char *debuginfo_path;
23
__find_debuginfo(Dwfl_Module * mod __maybe_unused,void ** userdata,const char * modname __maybe_unused,Dwarf_Addr base __maybe_unused,const char * file_name,const char * debuglink_file __maybe_unused,GElf_Word debuglink_crc __maybe_unused,char ** debuginfo_file_name)24 static 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
37 static 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
__report_module(struct addr_location * al,u64 ip,struct unwind_info * ui)44 static 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
report_module(u64 ip,struct unwind_info * ui)111 static 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 */
entry(u64 ip,struct unwind_info * ui)126 static 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 = al.maps;
140 e->ms.map = 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
next_thread(Dwfl * dwfl,void * arg,void ** thread_argp)151 static 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
access_dso_mem(struct unwind_info * ui,Dwarf_Addr addr,Dwarf_Word * data)161 static 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));
181 out_fail:
182 addr_location__exit(&al);
183 return -1;
184 }
185
memory_read(Dwfl * dwfl __maybe_unused,Dwarf_Addr addr,Dwarf_Word * result,void * arg)186 static 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
228 static 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
234 static int
frame_callback(Dwfl_Frame * state,void * arg)235 frame_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
unwind__get_entries(unwind_entry_cb_t cb,void * arg,struct thread * thread,struct perf_sample * data,int max_stack,bool best_effort)263 int 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 dwfl_end(ui->dwfl);
329 free(ui);
330 return 0;
331 }
332